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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/sched/core.c
4 *
5 * Core kernel scheduler code and related syscalls
6 *
7 * Copyright (C) 1991-2002 Linus Torvalds
8 */
9#include <linux/highmem.h>
10#include <linux/hrtimer_api.h>
11#include <linux/ktime_api.h>
12#include <linux/sched/signal.h>
13#include <linux/syscalls_api.h>
14#include <linux/debug_locks.h>
15#include <linux/prefetch.h>
16#include <linux/capability.h>
17#include <linux/pgtable_api.h>
18#include <linux/wait_bit.h>
19#include <linux/jiffies.h>
20#include <linux/spinlock_api.h>
21#include <linux/cpumask_api.h>
22#include <linux/lockdep_api.h>
23#include <linux/hardirq.h>
24#include <linux/softirq.h>
25#include <linux/refcount_api.h>
26#include <linux/topology.h>
27#include <linux/sched/clock.h>
28#include <linux/sched/cond_resched.h>
29#include <linux/sched/cputime.h>
30#include <linux/sched/debug.h>
31#include <linux/sched/hotplug.h>
32#include <linux/sched/init.h>
33#include <linux/sched/isolation.h>
34#include <linux/sched/loadavg.h>
35#include <linux/sched/mm.h>
36#include <linux/sched/nohz.h>
37#include <linux/sched/rseq_api.h>
38#include <linux/sched/rt.h>
39
40#include <linux/blkdev.h>
41#include <linux/context_tracking.h>
42#include <linux/cpuset.h>
43#include <linux/delayacct.h>
44#include <linux/init_task.h>
45#include <linux/interrupt.h>
46#include <linux/ioprio.h>
47#include <linux/kallsyms.h>
48#include <linux/kcov.h>
49#include <linux/kprobes.h>
50#include <linux/llist_api.h>
51#include <linux/mmu_context.h>
52#include <linux/mmzone.h>
53#include <linux/mutex_api.h>
54#include <linux/nmi.h>
55#include <linux/nospec.h>
56#include <linux/perf_event_api.h>
57#include <linux/profile.h>
58#include <linux/psi.h>
59#include <linux/rcuwait_api.h>
60#include <linux/rseq.h>
61#include <linux/sched/wake_q.h>
62#include <linux/scs.h>
63#include <linux/slab.h>
64#include <linux/syscalls.h>
65#include <linux/vtime.h>
66#include <linux/wait_api.h>
67#include <linux/workqueue_api.h>
68
69#ifdef CONFIG_PREEMPT_DYNAMIC
70# ifdef CONFIG_GENERIC_ENTRY
71# include <linux/entry-common.h>
72# endif
73#endif
74
75#include <uapi/linux/sched/types.h>
76
77#include <asm/irq_regs.h>
78#include <asm/switch_to.h>
79#include <asm/tlb.h>
80
81#define CREATE_TRACE_POINTS
82#include <linux/sched/rseq_api.h>
83#include <trace/events/sched.h>
84#include <trace/events/ipi.h>
85#undef CREATE_TRACE_POINTS
86
87#include "sched.h"
88#include "stats.h"
89
90#include "autogroup.h"
91#include "pelt.h"
92#include "smp.h"
93#include "stats.h"
94
95#include "../workqueue_internal.h"
96#include "../../io_uring/io-wq.h"
97#include "../smpboot.h"
98
99EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu);
100EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask);
101
102/*
103 * Export tracepoints that act as a bare tracehook (ie: have no trace event
104 * associated with them) to allow external modules to probe them.
105 */
106EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
107EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
108EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
109EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
110EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
111EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_thermal_tp);
112EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
113EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
114EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
115EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
116EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
117EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp);
118
119DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
120
121#ifdef CONFIG_SCHED_DEBUG
122/*
123 * Debugging: various feature bits
124 *
125 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
126 * sysctl_sched_features, defined in sched.h, to allow constants propagation
127 * at compile time and compiler optimization based on features default.
128 */
129#define SCHED_FEAT(name, enabled) \
130 (1UL << __SCHED_FEAT_##name) * enabled |
131const_debug unsigned int sysctl_sched_features =
132#include "features.h"
133 0;
134#undef SCHED_FEAT
135
136/*
137 * Print a warning if need_resched is set for the given duration (if
138 * LATENCY_WARN is enabled).
139 *
140 * If sysctl_resched_latency_warn_once is set, only one warning will be shown
141 * per boot.
142 */
143__read_mostly int sysctl_resched_latency_warn_ms = 100;
144__read_mostly int sysctl_resched_latency_warn_once = 1;
145#endif /* CONFIG_SCHED_DEBUG */
146
147/*
148 * Number of tasks to iterate in a single balance run.
149 * Limited because this is done with IRQs disabled.
150 */
151const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
152
153__read_mostly int scheduler_running;
154
155#ifdef CONFIG_SCHED_CORE
156
157DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);
158
159/* kernel prio, less is more */
160static inline int __task_prio(const struct task_struct *p)
161{
162 if (p->sched_class == &stop_sched_class) /* trumps deadline */
163 return -2;
164
165 if (rt_prio(p->prio)) /* includes deadline */
166 return p->prio; /* [-1, 99] */
167
168 if (p->sched_class == &idle_sched_class)
169 return MAX_RT_PRIO + NICE_WIDTH; /* 140 */
170
171 return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
172}
173
174/*
175 * l(a,b)
176 * le(a,b) := !l(b,a)
177 * g(a,b) := l(b,a)
178 * ge(a,b) := !l(a,b)
179 */
180
181/* real prio, less is less */
182static inline bool prio_less(const struct task_struct *a,
183 const struct task_struct *b, bool in_fi)
184{
185
186 int pa = __task_prio(a), pb = __task_prio(b);
187
188 if (-pa < -pb)
189 return true;
190
191 if (-pb < -pa)
192 return false;
193
194 if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
195 return !dl_time_before(a->dl.deadline, b->dl.deadline);
196
197 if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
198 return cfs_prio_less(a, b, in_fi);
199
200 return false;
201}
202
203static inline bool __sched_core_less(const struct task_struct *a,
204 const struct task_struct *b)
205{
206 if (a->core_cookie < b->core_cookie)
207 return true;
208
209 if (a->core_cookie > b->core_cookie)
210 return false;
211
212 /* flip prio, so high prio is leftmost */
213 if (prio_less(b, a, !!task_rq(a)->core->core_forceidle_count))
214 return true;
215
216 return false;
217}
218
219#define __node_2_sc(node) rb_entry((node), struct task_struct, core_node)
220
221static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b)
222{
223 return __sched_core_less(__node_2_sc(a), __node_2_sc(b));
224}
225
226static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node)
227{
228 const struct task_struct *p = __node_2_sc(node);
229 unsigned long cookie = (unsigned long)key;
230
231 if (cookie < p->core_cookie)
232 return -1;
233
234 if (cookie > p->core_cookie)
235 return 1;
236
237 return 0;
238}
239
240void sched_core_enqueue(struct rq *rq, struct task_struct *p)
241{
242 rq->core->core_task_seq++;
243
244 if (!p->core_cookie)
245 return;
246
247 rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less);
248}
249
250void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags)
251{
252 rq->core->core_task_seq++;
253
254 if (sched_core_enqueued(p)) {
255 rb_erase(&p->core_node, &rq->core_tree);
256 RB_CLEAR_NODE(&p->core_node);
257 }
258
259 /*
260 * Migrating the last task off the cpu, with the cpu in forced idle
261 * state. Reschedule to create an accounting edge for forced idle,
262 * and re-examine whether the core is still in forced idle state.
263 */
264 if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 &&
265 rq->core->core_forceidle_count && rq->curr == rq->idle)
266 resched_curr(rq);
267}
268
269static int sched_task_is_throttled(struct task_struct *p, int cpu)
270{
271 if (p->sched_class->task_is_throttled)
272 return p->sched_class->task_is_throttled(p, cpu);
273
274 return 0;
275}
276
277static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie)
278{
279 struct rb_node *node = &p->core_node;
280 int cpu = task_cpu(p);
281
282 do {
283 node = rb_next(node);
284 if (!node)
285 return NULL;
286
287 p = __node_2_sc(node);
288 if (p->core_cookie != cookie)
289 return NULL;
290
291 } while (sched_task_is_throttled(p, cpu));
292
293 return p;
294}
295
296/*
297 * Find left-most (aka, highest priority) and unthrottled task matching @cookie.
298 * If no suitable task is found, NULL will be returned.
299 */
300static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
301{
302 struct task_struct *p;
303 struct rb_node *node;
304
305 node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp);
306 if (!node)
307 return NULL;
308
309 p = __node_2_sc(node);
310 if (!sched_task_is_throttled(p, rq->cpu))
311 return p;
312
313 return sched_core_next(p, cookie);
314}
315
316/*
317 * Magic required such that:
318 *
319 * raw_spin_rq_lock(rq);
320 * ...
321 * raw_spin_rq_unlock(rq);
322 *
323 * ends up locking and unlocking the _same_ lock, and all CPUs
324 * always agree on what rq has what lock.
325 *
326 * XXX entirely possible to selectively enable cores, don't bother for now.
327 */
328
329static DEFINE_MUTEX(sched_core_mutex);
330static atomic_t sched_core_count;
331static struct cpumask sched_core_mask;
332
333static void sched_core_lock(int cpu, unsigned long *flags)
334{
335 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
336 int t, i = 0;
337
338 local_irq_save(*flags);
339 for_each_cpu(t, smt_mask)
340 raw_spin_lock_nested(&cpu_rq(t)->__lock, i++);
341}
342
343static void sched_core_unlock(int cpu, unsigned long *flags)
344{
345 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
346 int t;
347
348 for_each_cpu(t, smt_mask)
349 raw_spin_unlock(&cpu_rq(t)->__lock);
350 local_irq_restore(*flags);
351}
352
353static void __sched_core_flip(bool enabled)
354{
355 unsigned long flags;
356 int cpu, t;
357
358 cpus_read_lock();
359
360 /*
361 * Toggle the online cores, one by one.
362 */
363 cpumask_copy(&sched_core_mask, cpu_online_mask);
364 for_each_cpu(cpu, &sched_core_mask) {
365 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
366
367 sched_core_lock(cpu, &flags);
368
369 for_each_cpu(t, smt_mask)
370 cpu_rq(t)->core_enabled = enabled;
371
372 cpu_rq(cpu)->core->core_forceidle_start = 0;
373
374 sched_core_unlock(cpu, &flags);
375
376 cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask);
377 }
378
379 /*
380 * Toggle the offline CPUs.
381 */
382 for_each_cpu_andnot(cpu, cpu_possible_mask, cpu_online_mask)
383 cpu_rq(cpu)->core_enabled = enabled;
384
385 cpus_read_unlock();
386}
387
388static void sched_core_assert_empty(void)
389{
390 int cpu;
391
392 for_each_possible_cpu(cpu)
393 WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree));
394}
395
396static void __sched_core_enable(void)
397{
398 static_branch_enable(&__sched_core_enabled);
399 /*
400 * Ensure all previous instances of raw_spin_rq_*lock() have finished
401 * and future ones will observe !sched_core_disabled().
402 */
403 synchronize_rcu();
404 __sched_core_flip(true);
405 sched_core_assert_empty();
406}
407
408static void __sched_core_disable(void)
409{
410 sched_core_assert_empty();
411 __sched_core_flip(false);
412 static_branch_disable(&__sched_core_enabled);
413}
414
415void sched_core_get(void)
416{
417 if (atomic_inc_not_zero(&sched_core_count))
418 return;
419
420 mutex_lock(&sched_core_mutex);
421 if (!atomic_read(&sched_core_count))
422 __sched_core_enable();
423
424 smp_mb__before_atomic();
425 atomic_inc(&sched_core_count);
426 mutex_unlock(&sched_core_mutex);
427}
428
429static void __sched_core_put(struct work_struct *work)
430{
431 if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) {
432 __sched_core_disable();
433 mutex_unlock(&sched_core_mutex);
434 }
435}
436
437void sched_core_put(void)
438{
439 static DECLARE_WORK(_work, __sched_core_put);
440
441 /*
442 * "There can be only one"
443 *
444 * Either this is the last one, or we don't actually need to do any
445 * 'work'. If it is the last *again*, we rely on
446 * WORK_STRUCT_PENDING_BIT.
447 */
448 if (!atomic_add_unless(&sched_core_count, -1, 1))
449 schedule_work(&_work);
450}
451
452#else /* !CONFIG_SCHED_CORE */
453
454static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
455static inline void
456sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { }
457
458#endif /* CONFIG_SCHED_CORE */
459
460/*
461 * Serialization rules:
462 *
463 * Lock order:
464 *
465 * p->pi_lock
466 * rq->lock
467 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
468 *
469 * rq1->lock
470 * rq2->lock where: rq1 < rq2
471 *
472 * Regular state:
473 *
474 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
475 * local CPU's rq->lock, it optionally removes the task from the runqueue and
476 * always looks at the local rq data structures to find the most eligible task
477 * to run next.
478 *
479 * Task enqueue is also under rq->lock, possibly taken from another CPU.
480 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
481 * the local CPU to avoid bouncing the runqueue state around [ see
482 * ttwu_queue_wakelist() ]
483 *
484 * Task wakeup, specifically wakeups that involve migration, are horribly
485 * complicated to avoid having to take two rq->locks.
486 *
487 * Special state:
488 *
489 * System-calls and anything external will use task_rq_lock() which acquires
490 * both p->pi_lock and rq->lock. As a consequence the state they change is
491 * stable while holding either lock:
492 *
493 * - sched_setaffinity()/
494 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
495 * - set_user_nice(): p->se.load, p->*prio
496 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
497 * p->se.load, p->rt_priority,
498 * p->dl.dl_{runtime, deadline, period, flags, bw, density}
499 * - sched_setnuma(): p->numa_preferred_nid
500 * - sched_move_task(): p->sched_task_group
501 * - uclamp_update_active() p->uclamp*
502 *
503 * p->state <- TASK_*:
504 *
505 * is changed locklessly using set_current_state(), __set_current_state() or
506 * set_special_state(), see their respective comments, or by
507 * try_to_wake_up(). This latter uses p->pi_lock to serialize against
508 * concurrent self.
509 *
510 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
511 *
512 * is set by activate_task() and cleared by deactivate_task(), under
513 * rq->lock. Non-zero indicates the task is runnable, the special
514 * ON_RQ_MIGRATING state is used for migration without holding both
515 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
516 *
517 * p->on_cpu <- { 0, 1 }:
518 *
519 * is set by prepare_task() and cleared by finish_task() such that it will be
520 * set before p is scheduled-in and cleared after p is scheduled-out, both
521 * under rq->lock. Non-zero indicates the task is running on its CPU.
522 *
523 * [ The astute reader will observe that it is possible for two tasks on one
524 * CPU to have ->on_cpu = 1 at the same time. ]
525 *
526 * task_cpu(p): is changed by set_task_cpu(), the rules are:
527 *
528 * - Don't call set_task_cpu() on a blocked task:
529 *
530 * We don't care what CPU we're not running on, this simplifies hotplug,
531 * the CPU assignment of blocked tasks isn't required to be valid.
532 *
533 * - for try_to_wake_up(), called under p->pi_lock:
534 *
535 * This allows try_to_wake_up() to only take one rq->lock, see its comment.
536 *
537 * - for migration called under rq->lock:
538 * [ see task_on_rq_migrating() in task_rq_lock() ]
539 *
540 * o move_queued_task()
541 * o detach_task()
542 *
543 * - for migration called under double_rq_lock():
544 *
545 * o __migrate_swap_task()
546 * o push_rt_task() / pull_rt_task()
547 * o push_dl_task() / pull_dl_task()
548 * o dl_task_offline_migration()
549 *
550 */
551
552void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
553{
554 raw_spinlock_t *lock;
555
556 /* Matches synchronize_rcu() in __sched_core_enable() */
557 preempt_disable();
558 if (sched_core_disabled()) {
559 raw_spin_lock_nested(&rq->__lock, subclass);
560 /* preempt_count *MUST* be > 1 */
561 preempt_enable_no_resched();
562 return;
563 }
564
565 for (;;) {
566 lock = __rq_lockp(rq);
567 raw_spin_lock_nested(lock, subclass);
568 if (likely(lock == __rq_lockp(rq))) {
569 /* preempt_count *MUST* be > 1 */
570 preempt_enable_no_resched();
571 return;
572 }
573 raw_spin_unlock(lock);
574 }
575}
576
577bool raw_spin_rq_trylock(struct rq *rq)
578{
579 raw_spinlock_t *lock;
580 bool ret;
581
582 /* Matches synchronize_rcu() in __sched_core_enable() */
583 preempt_disable();
584 if (sched_core_disabled()) {
585 ret = raw_spin_trylock(&rq->__lock);
586 preempt_enable();
587 return ret;
588 }
589
590 for (;;) {
591 lock = __rq_lockp(rq);
592 ret = raw_spin_trylock(lock);
593 if (!ret || (likely(lock == __rq_lockp(rq)))) {
594 preempt_enable();
595 return ret;
596 }
597 raw_spin_unlock(lock);
598 }
599}
600
601void raw_spin_rq_unlock(struct rq *rq)
602{
603 raw_spin_unlock(rq_lockp(rq));
604}
605
606#ifdef CONFIG_SMP
607/*
608 * double_rq_lock - safely lock two runqueues
609 */
610void double_rq_lock(struct rq *rq1, struct rq *rq2)
611{
612 lockdep_assert_irqs_disabled();
613
614 if (rq_order_less(rq2, rq1))
615 swap(rq1, rq2);
616
617 raw_spin_rq_lock(rq1);
618 if (__rq_lockp(rq1) != __rq_lockp(rq2))
619 raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);
620
621 double_rq_clock_clear_update(rq1, rq2);
622}
623#endif
624
625/*
626 * __task_rq_lock - lock the rq @p resides on.
627 */
628struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
629 __acquires(rq->lock)
630{
631 struct rq *rq;
632
633 lockdep_assert_held(&p->pi_lock);
634
635 for (;;) {
636 rq = task_rq(p);
637 raw_spin_rq_lock(rq);
638 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
639 rq_pin_lock(rq, rf);
640 return rq;
641 }
642 raw_spin_rq_unlock(rq);
643
644 while (unlikely(task_on_rq_migrating(p)))
645 cpu_relax();
646 }
647}
648
649/*
650 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
651 */
652struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
653 __acquires(p->pi_lock)
654 __acquires(rq->lock)
655{
656 struct rq *rq;
657
658 for (;;) {
659 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
660 rq = task_rq(p);
661 raw_spin_rq_lock(rq);
662 /*
663 * move_queued_task() task_rq_lock()
664 *
665 * ACQUIRE (rq->lock)
666 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
667 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
668 * [S] ->cpu = new_cpu [L] task_rq()
669 * [L] ->on_rq
670 * RELEASE (rq->lock)
671 *
672 * If we observe the old CPU in task_rq_lock(), the acquire of
673 * the old rq->lock will fully serialize against the stores.
674 *
675 * If we observe the new CPU in task_rq_lock(), the address
676 * dependency headed by '[L] rq = task_rq()' and the acquire
677 * will pair with the WMB to ensure we then also see migrating.
678 */
679 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
680 rq_pin_lock(rq, rf);
681 return rq;
682 }
683 raw_spin_rq_unlock(rq);
684 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
685
686 while (unlikely(task_on_rq_migrating(p)))
687 cpu_relax();
688 }
689}
690
691/*
692 * RQ-clock updating methods:
693 */
694
695static void update_rq_clock_task(struct rq *rq, s64 delta)
696{
697/*
698 * In theory, the compile should just see 0 here, and optimize out the call
699 * to sched_rt_avg_update. But I don't trust it...
700 */
701 s64 __maybe_unused steal = 0, irq_delta = 0;
702
703#ifdef CONFIG_IRQ_TIME_ACCOUNTING
704 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
705
706 /*
707 * Since irq_time is only updated on {soft,}irq_exit, we might run into
708 * this case when a previous update_rq_clock() happened inside a
709 * {soft,}irq region.
710 *
711 * When this happens, we stop ->clock_task and only update the
712 * prev_irq_time stamp to account for the part that fit, so that a next
713 * update will consume the rest. This ensures ->clock_task is
714 * monotonic.
715 *
716 * It does however cause some slight miss-attribution of {soft,}irq
717 * time, a more accurate solution would be to update the irq_time using
718 * the current rq->clock timestamp, except that would require using
719 * atomic ops.
720 */
721 if (irq_delta > delta)
722 irq_delta = delta;
723
724 rq->prev_irq_time += irq_delta;
725 delta -= irq_delta;
726 psi_account_irqtime(rq->curr, irq_delta);
727 delayacct_irq(rq->curr, irq_delta);
728#endif
729#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
730 if (static_key_false((¶virt_steal_rq_enabled))) {
731 steal = paravirt_steal_clock(cpu_of(rq));
732 steal -= rq->prev_steal_time_rq;
733
734 if (unlikely(steal > delta))
735 steal = delta;
736
737 rq->prev_steal_time_rq += steal;
738 delta -= steal;
739 }
740#endif
741
742 rq->clock_task += delta;
743
744#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
745 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
746 update_irq_load_avg(rq, irq_delta + steal);
747#endif
748 update_rq_clock_pelt(rq, delta);
749}
750
751void update_rq_clock(struct rq *rq)
752{
753 s64 delta;
754
755 lockdep_assert_rq_held(rq);
756
757 if (rq->clock_update_flags & RQCF_ACT_SKIP)
758 return;
759
760#ifdef CONFIG_SCHED_DEBUG
761 if (sched_feat(WARN_DOUBLE_CLOCK))
762 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
763 rq->clock_update_flags |= RQCF_UPDATED;
764#endif
765
766 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
767 if (delta < 0)
768 return;
769 rq->clock += delta;
770 update_rq_clock_task(rq, delta);
771}
772
773#ifdef CONFIG_SCHED_HRTICK
774/*
775 * Use HR-timers to deliver accurate preemption points.
776 */
777
778static void hrtick_clear(struct rq *rq)
779{
780 if (hrtimer_active(&rq->hrtick_timer))
781 hrtimer_cancel(&rq->hrtick_timer);
782}
783
784/*
785 * High-resolution timer tick.
786 * Runs from hardirq context with interrupts disabled.
787 */
788static enum hrtimer_restart hrtick(struct hrtimer *timer)
789{
790 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
791 struct rq_flags rf;
792
793 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
794
795 rq_lock(rq, &rf);
796 update_rq_clock(rq);
797 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
798 rq_unlock(rq, &rf);
799
800 return HRTIMER_NORESTART;
801}
802
803#ifdef CONFIG_SMP
804
805static void __hrtick_restart(struct rq *rq)
806{
807 struct hrtimer *timer = &rq->hrtick_timer;
808 ktime_t time = rq->hrtick_time;
809
810 hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
811}
812
813/*
814 * called from hardirq (IPI) context
815 */
816static void __hrtick_start(void *arg)
817{
818 struct rq *rq = arg;
819 struct rq_flags rf;
820
821 rq_lock(rq, &rf);
822 __hrtick_restart(rq);
823 rq_unlock(rq, &rf);
824}
825
826/*
827 * Called to set the hrtick timer state.
828 *
829 * called with rq->lock held and irqs disabled
830 */
831void hrtick_start(struct rq *rq, u64 delay)
832{
833 struct hrtimer *timer = &rq->hrtick_timer;
834 s64 delta;
835
836 /*
837 * Don't schedule slices shorter than 10000ns, that just
838 * doesn't make sense and can cause timer DoS.
839 */
840 delta = max_t(s64, delay, 10000LL);
841 rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);
842
843 if (rq == this_rq())
844 __hrtick_restart(rq);
845 else
846 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
847}
848
849#else
850/*
851 * Called to set the hrtick timer state.
852 *
853 * called with rq->lock held and irqs disabled
854 */
855void hrtick_start(struct rq *rq, u64 delay)
856{
857 /*
858 * Don't schedule slices shorter than 10000ns, that just
859 * doesn't make sense. Rely on vruntime for fairness.
860 */
861 delay = max_t(u64, delay, 10000LL);
862 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
863 HRTIMER_MODE_REL_PINNED_HARD);
864}
865
866#endif /* CONFIG_SMP */
867
868static void hrtick_rq_init(struct rq *rq)
869{
870#ifdef CONFIG_SMP
871 INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq);
872#endif
873 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
874 rq->hrtick_timer.function = hrtick;
875}
876#else /* CONFIG_SCHED_HRTICK */
877static inline void hrtick_clear(struct rq *rq)
878{
879}
880
881static inline void hrtick_rq_init(struct rq *rq)
882{
883}
884#endif /* CONFIG_SCHED_HRTICK */
885
886/*
887 * cmpxchg based fetch_or, macro so it works for different integer types
888 */
889#define fetch_or(ptr, mask) \
890 ({ \
891 typeof(ptr) _ptr = (ptr); \
892 typeof(mask) _mask = (mask); \
893 typeof(*_ptr) _val = *_ptr; \
894 \
895 do { \
896 } while (!try_cmpxchg(_ptr, &_val, _val | _mask)); \
897 _val; \
898})
899
900#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
901/*
902 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
903 * this avoids any races wrt polling state changes and thereby avoids
904 * spurious IPIs.
905 */
906static inline bool set_nr_and_not_polling(struct task_struct *p)
907{
908 struct thread_info *ti = task_thread_info(p);
909 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
910}
911
912/*
913 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
914 *
915 * If this returns true, then the idle task promises to call
916 * sched_ttwu_pending() and reschedule soon.
917 */
918static bool set_nr_if_polling(struct task_struct *p)
919{
920 struct thread_info *ti = task_thread_info(p);
921 typeof(ti->flags) val = READ_ONCE(ti->flags);
922
923 do {
924 if (!(val & _TIF_POLLING_NRFLAG))
925 return false;
926 if (val & _TIF_NEED_RESCHED)
927 return true;
928 } while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED));
929
930 return true;
931}
932
933#else
934static inline bool set_nr_and_not_polling(struct task_struct *p)
935{
936 set_tsk_need_resched(p);
937 return true;
938}
939
940#ifdef CONFIG_SMP
941static inline bool set_nr_if_polling(struct task_struct *p)
942{
943 return false;
944}
945#endif
946#endif
947
948static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
949{
950 struct wake_q_node *node = &task->wake_q;
951
952 /*
953 * Atomically grab the task, if ->wake_q is !nil already it means
954 * it's already queued (either by us or someone else) and will get the
955 * wakeup due to that.
956 *
957 * In order to ensure that a pending wakeup will observe our pending
958 * state, even in the failed case, an explicit smp_mb() must be used.
959 */
960 smp_mb__before_atomic();
961 if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
962 return false;
963
964 /*
965 * The head is context local, there can be no concurrency.
966 */
967 *head->lastp = node;
968 head->lastp = &node->next;
969 return true;
970}
971
972/**
973 * wake_q_add() - queue a wakeup for 'later' waking.
974 * @head: the wake_q_head to add @task to
975 * @task: the task to queue for 'later' wakeup
976 *
977 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
978 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
979 * instantly.
980 *
981 * This function must be used as-if it were wake_up_process(); IOW the task
982 * must be ready to be woken at this location.
983 */
984void wake_q_add(struct wake_q_head *head, struct task_struct *task)
985{
986 if (__wake_q_add(head, task))
987 get_task_struct(task);
988}
989
990/**
991 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
992 * @head: the wake_q_head to add @task to
993 * @task: the task to queue for 'later' wakeup
994 *
995 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
996 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
997 * instantly.
998 *
999 * This function must be used as-if it were wake_up_process(); IOW the task
1000 * must be ready to be woken at this location.
1001 *
1002 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
1003 * that already hold reference to @task can call the 'safe' version and trust
1004 * wake_q to do the right thing depending whether or not the @task is already
1005 * queued for wakeup.
1006 */
1007void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
1008{
1009 if (!__wake_q_add(head, task))
1010 put_task_struct(task);
1011}
1012
1013void wake_up_q(struct wake_q_head *head)
1014{
1015 struct wake_q_node *node = head->first;
1016
1017 while (node != WAKE_Q_TAIL) {
1018 struct task_struct *task;
1019
1020 task = container_of(node, struct task_struct, wake_q);
1021 /* Task can safely be re-inserted now: */
1022 node = node->next;
1023 task->wake_q.next = NULL;
1024
1025 /*
1026 * wake_up_process() executes a full barrier, which pairs with
1027 * the queueing in wake_q_add() so as not to miss wakeups.
1028 */
1029 wake_up_process(task);
1030 put_task_struct(task);
1031 }
1032}
1033
1034/*
1035 * resched_curr - mark rq's current task 'to be rescheduled now'.
1036 *
1037 * On UP this means the setting of the need_resched flag, on SMP it
1038 * might also involve a cross-CPU call to trigger the scheduler on
1039 * the target CPU.
1040 */
1041void resched_curr(struct rq *rq)
1042{
1043 struct task_struct *curr = rq->curr;
1044 int cpu;
1045
1046 lockdep_assert_rq_held(rq);
1047
1048 if (test_tsk_need_resched(curr))
1049 return;
1050
1051 cpu = cpu_of(rq);
1052
1053 if (cpu == smp_processor_id()) {
1054 set_tsk_need_resched(curr);
1055 set_preempt_need_resched();
1056 return;
1057 }
1058
1059 if (set_nr_and_not_polling(curr))
1060 smp_send_reschedule(cpu);
1061 else
1062 trace_sched_wake_idle_without_ipi(cpu);
1063}
1064
1065void resched_cpu(int cpu)
1066{
1067 struct rq *rq = cpu_rq(cpu);
1068 unsigned long flags;
1069
1070 raw_spin_rq_lock_irqsave(rq, flags);
1071 if (cpu_online(cpu) || cpu == smp_processor_id())
1072 resched_curr(rq);
1073 raw_spin_rq_unlock_irqrestore(rq, flags);
1074}
1075
1076#ifdef CONFIG_SMP
1077#ifdef CONFIG_NO_HZ_COMMON
1078/*
1079 * In the semi idle case, use the nearest busy CPU for migrating timers
1080 * from an idle CPU. This is good for power-savings.
1081 *
1082 * We don't do similar optimization for completely idle system, as
1083 * selecting an idle CPU will add more delays to the timers than intended
1084 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
1085 */
1086int get_nohz_timer_target(void)
1087{
1088 int i, cpu = smp_processor_id(), default_cpu = -1;
1089 struct sched_domain *sd;
1090 const struct cpumask *hk_mask;
1091
1092 if (housekeeping_cpu(cpu, HK_TYPE_TIMER)) {
1093 if (!idle_cpu(cpu))
1094 return cpu;
1095 default_cpu = cpu;
1096 }
1097
1098 hk_mask = housekeeping_cpumask(HK_TYPE_TIMER);
1099
1100 guard(rcu)();
1101
1102 for_each_domain(cpu, sd) {
1103 for_each_cpu_and(i, sched_domain_span(sd), hk_mask) {
1104 if (cpu == i)
1105 continue;
1106
1107 if (!idle_cpu(i))
1108 return i;
1109 }
1110 }
1111
1112 if (default_cpu == -1)
1113 default_cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
1114
1115 return default_cpu;
1116}
1117
1118/*
1119 * When add_timer_on() enqueues a timer into the timer wheel of an
1120 * idle CPU then this timer might expire before the next timer event
1121 * which is scheduled to wake up that CPU. In case of a completely
1122 * idle system the next event might even be infinite time into the
1123 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
1124 * leaves the inner idle loop so the newly added timer is taken into
1125 * account when the CPU goes back to idle and evaluates the timer
1126 * wheel for the next timer event.
1127 */
1128static void wake_up_idle_cpu(int cpu)
1129{
1130 struct rq *rq = cpu_rq(cpu);
1131
1132 if (cpu == smp_processor_id())
1133 return;
1134
1135 /*
1136 * Set TIF_NEED_RESCHED and send an IPI if in the non-polling
1137 * part of the idle loop. This forces an exit from the idle loop
1138 * and a round trip to schedule(). Now this could be optimized
1139 * because a simple new idle loop iteration is enough to
1140 * re-evaluate the next tick. Provided some re-ordering of tick
1141 * nohz functions that would need to follow TIF_NR_POLLING
1142 * clearing:
1143 *
1144 * - On most archs, a simple fetch_or on ti::flags with a
1145 * "0" value would be enough to know if an IPI needs to be sent.
1146 *
1147 * - x86 needs to perform a last need_resched() check between
1148 * monitor and mwait which doesn't take timers into account.
1149 * There a dedicated TIF_TIMER flag would be required to
1150 * fetch_or here and be checked along with TIF_NEED_RESCHED
1151 * before mwait().
1152 *
1153 * However, remote timer enqueue is not such a frequent event
1154 * and testing of the above solutions didn't appear to report
1155 * much benefits.
1156 */
1157 if (set_nr_and_not_polling(rq->idle))
1158 smp_send_reschedule(cpu);
1159 else
1160 trace_sched_wake_idle_without_ipi(cpu);
1161}
1162
1163static bool wake_up_full_nohz_cpu(int cpu)
1164{
1165 /*
1166 * We just need the target to call irq_exit() and re-evaluate
1167 * the next tick. The nohz full kick at least implies that.
1168 * If needed we can still optimize that later with an
1169 * empty IRQ.
1170 */
1171 if (cpu_is_offline(cpu))
1172 return true; /* Don't try to wake offline CPUs. */
1173 if (tick_nohz_full_cpu(cpu)) {
1174 if (cpu != smp_processor_id() ||
1175 tick_nohz_tick_stopped())
1176 tick_nohz_full_kick_cpu(cpu);
1177 return true;
1178 }
1179
1180 return false;
1181}
1182
1183/*
1184 * Wake up the specified CPU. If the CPU is going offline, it is the
1185 * caller's responsibility to deal with the lost wakeup, for example,
1186 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
1187 */
1188void wake_up_nohz_cpu(int cpu)
1189{
1190 if (!wake_up_full_nohz_cpu(cpu))
1191 wake_up_idle_cpu(cpu);
1192}
1193
1194static void nohz_csd_func(void *info)
1195{
1196 struct rq *rq = info;
1197 int cpu = cpu_of(rq);
1198 unsigned int flags;
1199
1200 /*
1201 * Release the rq::nohz_csd.
1202 */
1203 flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu));
1204 WARN_ON(!(flags & NOHZ_KICK_MASK));
1205
1206 rq->idle_balance = idle_cpu(cpu);
1207 if (rq->idle_balance && !need_resched()) {
1208 rq->nohz_idle_balance = flags;
1209 raise_softirq_irqoff(SCHED_SOFTIRQ);
1210 }
1211}
1212
1213#endif /* CONFIG_NO_HZ_COMMON */
1214
1215#ifdef CONFIG_NO_HZ_FULL
1216static inline bool __need_bw_check(struct rq *rq, struct task_struct *p)
1217{
1218 if (rq->nr_running != 1)
1219 return false;
1220
1221 if (p->sched_class != &fair_sched_class)
1222 return false;
1223
1224 if (!task_on_rq_queued(p))
1225 return false;
1226
1227 return true;
1228}
1229
1230bool sched_can_stop_tick(struct rq *rq)
1231{
1232 int fifo_nr_running;
1233
1234 /* Deadline tasks, even if single, need the tick */
1235 if (rq->dl.dl_nr_running)
1236 return false;
1237
1238 /*
1239 * If there are more than one RR tasks, we need the tick to affect the
1240 * actual RR behaviour.
1241 */
1242 if (rq->rt.rr_nr_running) {
1243 if (rq->rt.rr_nr_running == 1)
1244 return true;
1245 else
1246 return false;
1247 }
1248
1249 /*
1250 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
1251 * forced preemption between FIFO tasks.
1252 */
1253 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
1254 if (fifo_nr_running)
1255 return true;
1256
1257 /*
1258 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
1259 * if there's more than one we need the tick for involuntary
1260 * preemption.
1261 */
1262 if (rq->nr_running > 1)
1263 return false;
1264
1265 /*
1266 * If there is one task and it has CFS runtime bandwidth constraints
1267 * and it's on the cpu now we don't want to stop the tick.
1268 * This check prevents clearing the bit if a newly enqueued task here is
1269 * dequeued by migrating while the constrained task continues to run.
1270 * E.g. going from 2->1 without going through pick_next_task().
1271 */
1272 if (sched_feat(HZ_BW) && __need_bw_check(rq, rq->curr)) {
1273 if (cfs_task_bw_constrained(rq->curr))
1274 return false;
1275 }
1276
1277 return true;
1278}
1279#endif /* CONFIG_NO_HZ_FULL */
1280#endif /* CONFIG_SMP */
1281
1282#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
1283 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
1284/*
1285 * Iterate task_group tree rooted at *from, calling @down when first entering a
1286 * node and @up when leaving it for the final time.
1287 *
1288 * Caller must hold rcu_lock or sufficient equivalent.
1289 */
1290int walk_tg_tree_from(struct task_group *from,
1291 tg_visitor down, tg_visitor up, void *data)
1292{
1293 struct task_group *parent, *child;
1294 int ret;
1295
1296 parent = from;
1297
1298down:
1299 ret = (*down)(parent, data);
1300 if (ret)
1301 goto out;
1302 list_for_each_entry_rcu(child, &parent->children, siblings) {
1303 parent = child;
1304 goto down;
1305
1306up:
1307 continue;
1308 }
1309 ret = (*up)(parent, data);
1310 if (ret || parent == from)
1311 goto out;
1312
1313 child = parent;
1314 parent = parent->parent;
1315 if (parent)
1316 goto up;
1317out:
1318 return ret;
1319}
1320
1321int tg_nop(struct task_group *tg, void *data)
1322{
1323 return 0;
1324}
1325#endif
1326
1327static void set_load_weight(struct task_struct *p, bool update_load)
1328{
1329 int prio = p->static_prio - MAX_RT_PRIO;
1330 struct load_weight *load = &p->se.load;
1331
1332 /*
1333 * SCHED_IDLE tasks get minimal weight:
1334 */
1335 if (task_has_idle_policy(p)) {
1336 load->weight = scale_load(WEIGHT_IDLEPRIO);
1337 load->inv_weight = WMULT_IDLEPRIO;
1338 return;
1339 }
1340
1341 /*
1342 * SCHED_OTHER tasks have to update their load when changing their
1343 * weight
1344 */
1345 if (update_load && p->sched_class == &fair_sched_class) {
1346 reweight_task(p, prio);
1347 } else {
1348 load->weight = scale_load(sched_prio_to_weight[prio]);
1349 load->inv_weight = sched_prio_to_wmult[prio];
1350 }
1351}
1352
1353#ifdef CONFIG_UCLAMP_TASK
1354/*
1355 * Serializes updates of utilization clamp values
1356 *
1357 * The (slow-path) user-space triggers utilization clamp value updates which
1358 * can require updates on (fast-path) scheduler's data structures used to
1359 * support enqueue/dequeue operations.
1360 * While the per-CPU rq lock protects fast-path update operations, user-space
1361 * requests are serialized using a mutex to reduce the risk of conflicting
1362 * updates or API abuses.
1363 */
1364static DEFINE_MUTEX(uclamp_mutex);
1365
1366/* Max allowed minimum utilization */
1367static unsigned int __maybe_unused sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
1368
1369/* Max allowed maximum utilization */
1370static unsigned int __maybe_unused sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
1371
1372/*
1373 * By default RT tasks run at the maximum performance point/capacity of the
1374 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
1375 * SCHED_CAPACITY_SCALE.
1376 *
1377 * This knob allows admins to change the default behavior when uclamp is being
1378 * used. In battery powered devices, particularly, running at the maximum
1379 * capacity and frequency will increase energy consumption and shorten the
1380 * battery life.
1381 *
1382 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
1383 *
1384 * This knob will not override the system default sched_util_clamp_min defined
1385 * above.
1386 */
1387static unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;
1388
1389/* All clamps are required to be less or equal than these values */
1390static struct uclamp_se uclamp_default[UCLAMP_CNT];
1391
1392/*
1393 * This static key is used to reduce the uclamp overhead in the fast path. It
1394 * primarily disables the call to uclamp_rq_{inc, dec}() in
1395 * enqueue/dequeue_task().
1396 *
1397 * This allows users to continue to enable uclamp in their kernel config with
1398 * minimum uclamp overhead in the fast path.
1399 *
1400 * As soon as userspace modifies any of the uclamp knobs, the static key is
1401 * enabled, since we have an actual users that make use of uclamp
1402 * functionality.
1403 *
1404 * The knobs that would enable this static key are:
1405 *
1406 * * A task modifying its uclamp value with sched_setattr().
1407 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
1408 * * An admin modifying the cgroup cpu.uclamp.{min, max}
1409 */
1410DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
1411
1412/* Integer rounded range for each bucket */
1413#define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
1414
1415#define for_each_clamp_id(clamp_id) \
1416 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
1417
1418static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
1419{
1420 return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1);
1421}
1422
1423static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
1424{
1425 if (clamp_id == UCLAMP_MIN)
1426 return 0;
1427 return SCHED_CAPACITY_SCALE;
1428}
1429
1430static inline void uclamp_se_set(struct uclamp_se *uc_se,
1431 unsigned int value, bool user_defined)
1432{
1433 uc_se->value = value;
1434 uc_se->bucket_id = uclamp_bucket_id(value);
1435 uc_se->user_defined = user_defined;
1436}
1437
1438static inline unsigned int
1439uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
1440 unsigned int clamp_value)
1441{
1442 /*
1443 * Avoid blocked utilization pushing up the frequency when we go
1444 * idle (which drops the max-clamp) by retaining the last known
1445 * max-clamp.
1446 */
1447 if (clamp_id == UCLAMP_MAX) {
1448 rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
1449 return clamp_value;
1450 }
1451
1452 return uclamp_none(UCLAMP_MIN);
1453}
1454
1455static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
1456 unsigned int clamp_value)
1457{
1458 /* Reset max-clamp retention only on idle exit */
1459 if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1460 return;
1461
1462 uclamp_rq_set(rq, clamp_id, clamp_value);
1463}
1464
1465static inline
1466unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
1467 unsigned int clamp_value)
1468{
1469 struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
1470 int bucket_id = UCLAMP_BUCKETS - 1;
1471
1472 /*
1473 * Since both min and max clamps are max aggregated, find the
1474 * top most bucket with tasks in.
1475 */
1476 for ( ; bucket_id >= 0; bucket_id--) {
1477 if (!bucket[bucket_id].tasks)
1478 continue;
1479 return bucket[bucket_id].value;
1480 }
1481
1482 /* No tasks -- default clamp values */
1483 return uclamp_idle_value(rq, clamp_id, clamp_value);
1484}
1485
1486static void __uclamp_update_util_min_rt_default(struct task_struct *p)
1487{
1488 unsigned int default_util_min;
1489 struct uclamp_se *uc_se;
1490
1491 lockdep_assert_held(&p->pi_lock);
1492
1493 uc_se = &p->uclamp_req[UCLAMP_MIN];
1494
1495 /* Only sync if user didn't override the default */
1496 if (uc_se->user_defined)
1497 return;
1498
1499 default_util_min = sysctl_sched_uclamp_util_min_rt_default;
1500 uclamp_se_set(uc_se, default_util_min, false);
1501}
1502
1503static void uclamp_update_util_min_rt_default(struct task_struct *p)
1504{
1505 if (!rt_task(p))
1506 return;
1507
1508 /* Protect updates to p->uclamp_* */
1509 guard(task_rq_lock)(p);
1510 __uclamp_update_util_min_rt_default(p);
1511}
1512
1513static inline struct uclamp_se
1514uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
1515{
1516 /* Copy by value as we could modify it */
1517 struct uclamp_se uc_req = p->uclamp_req[clamp_id];
1518#ifdef CONFIG_UCLAMP_TASK_GROUP
1519 unsigned int tg_min, tg_max, value;
1520
1521 /*
1522 * Tasks in autogroups or root task group will be
1523 * restricted by system defaults.
1524 */
1525 if (task_group_is_autogroup(task_group(p)))
1526 return uc_req;
1527 if (task_group(p) == &root_task_group)
1528 return uc_req;
1529
1530 tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
1531 tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
1532 value = uc_req.value;
1533 value = clamp(value, tg_min, tg_max);
1534 uclamp_se_set(&uc_req, value, false);
1535#endif
1536
1537 return uc_req;
1538}
1539
1540/*
1541 * The effective clamp bucket index of a task depends on, by increasing
1542 * priority:
1543 * - the task specific clamp value, when explicitly requested from userspace
1544 * - the task group effective clamp value, for tasks not either in the root
1545 * group or in an autogroup
1546 * - the system default clamp value, defined by the sysadmin
1547 */
1548static inline struct uclamp_se
1549uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
1550{
1551 struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
1552 struct uclamp_se uc_max = uclamp_default[clamp_id];
1553
1554 /* System default restrictions always apply */
1555 if (unlikely(uc_req.value > uc_max.value))
1556 return uc_max;
1557
1558 return uc_req;
1559}
1560
1561unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
1562{
1563 struct uclamp_se uc_eff;
1564
1565 /* Task currently refcounted: use back-annotated (effective) value */
1566 if (p->uclamp[clamp_id].active)
1567 return (unsigned long)p->uclamp[clamp_id].value;
1568
1569 uc_eff = uclamp_eff_get(p, clamp_id);
1570
1571 return (unsigned long)uc_eff.value;
1572}
1573
1574/*
1575 * When a task is enqueued on a rq, the clamp bucket currently defined by the
1576 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
1577 * updates the rq's clamp value if required.
1578 *
1579 * Tasks can have a task-specific value requested from user-space, track
1580 * within each bucket the maximum value for tasks refcounted in it.
1581 * This "local max aggregation" allows to track the exact "requested" value
1582 * for each bucket when all its RUNNABLE tasks require the same clamp.
1583 */
1584static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
1585 enum uclamp_id clamp_id)
1586{
1587 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1588 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1589 struct uclamp_bucket *bucket;
1590
1591 lockdep_assert_rq_held(rq);
1592
1593 /* Update task effective clamp */
1594 p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
1595
1596 bucket = &uc_rq->bucket[uc_se->bucket_id];
1597 bucket->tasks++;
1598 uc_se->active = true;
1599
1600 uclamp_idle_reset(rq, clamp_id, uc_se->value);
1601
1602 /*
1603 * Local max aggregation: rq buckets always track the max
1604 * "requested" clamp value of its RUNNABLE tasks.
1605 */
1606 if (bucket->tasks == 1 || uc_se->value > bucket->value)
1607 bucket->value = uc_se->value;
1608
1609 if (uc_se->value > uclamp_rq_get(rq, clamp_id))
1610 uclamp_rq_set(rq, clamp_id, uc_se->value);
1611}
1612
1613/*
1614 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
1615 * is released. If this is the last task reference counting the rq's max
1616 * active clamp value, then the rq's clamp value is updated.
1617 *
1618 * Both refcounted tasks and rq's cached clamp values are expected to be
1619 * always valid. If it's detected they are not, as defensive programming,
1620 * enforce the expected state and warn.
1621 */
1622static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
1623 enum uclamp_id clamp_id)
1624{
1625 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1626 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1627 struct uclamp_bucket *bucket;
1628 unsigned int bkt_clamp;
1629 unsigned int rq_clamp;
1630
1631 lockdep_assert_rq_held(rq);
1632
1633 /*
1634 * If sched_uclamp_used was enabled after task @p was enqueued,
1635 * we could end up with unbalanced call to uclamp_rq_dec_id().
1636 *
1637 * In this case the uc_se->active flag should be false since no uclamp
1638 * accounting was performed at enqueue time and we can just return
1639 * here.
1640 *
1641 * Need to be careful of the following enqueue/dequeue ordering
1642 * problem too
1643 *
1644 * enqueue(taskA)
1645 * // sched_uclamp_used gets enabled
1646 * enqueue(taskB)
1647 * dequeue(taskA)
1648 * // Must not decrement bucket->tasks here
1649 * dequeue(taskB)
1650 *
1651 * where we could end up with stale data in uc_se and
1652 * bucket[uc_se->bucket_id].
1653 *
1654 * The following check here eliminates the possibility of such race.
1655 */
1656 if (unlikely(!uc_se->active))
1657 return;
1658
1659 bucket = &uc_rq->bucket[uc_se->bucket_id];
1660
1661 SCHED_WARN_ON(!bucket->tasks);
1662 if (likely(bucket->tasks))
1663 bucket->tasks--;
1664
1665 uc_se->active = false;
1666
1667 /*
1668 * Keep "local max aggregation" simple and accept to (possibly)
1669 * overboost some RUNNABLE tasks in the same bucket.
1670 * The rq clamp bucket value is reset to its base value whenever
1671 * there are no more RUNNABLE tasks refcounting it.
1672 */
1673 if (likely(bucket->tasks))
1674 return;
1675
1676 rq_clamp = uclamp_rq_get(rq, clamp_id);
1677 /*
1678 * Defensive programming: this should never happen. If it happens,
1679 * e.g. due to future modification, warn and fixup the expected value.
1680 */
1681 SCHED_WARN_ON(bucket->value > rq_clamp);
1682 if (bucket->value >= rq_clamp) {
1683 bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
1684 uclamp_rq_set(rq, clamp_id, bkt_clamp);
1685 }
1686}
1687
1688static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
1689{
1690 enum uclamp_id clamp_id;
1691
1692 /*
1693 * Avoid any overhead until uclamp is actually used by the userspace.
1694 *
1695 * The condition is constructed such that a NOP is generated when
1696 * sched_uclamp_used is disabled.
1697 */
1698 if (!static_branch_unlikely(&sched_uclamp_used))
1699 return;
1700
1701 if (unlikely(!p->sched_class->uclamp_enabled))
1702 return;
1703
1704 for_each_clamp_id(clamp_id)
1705 uclamp_rq_inc_id(rq, p, clamp_id);
1706
1707 /* Reset clamp idle holding when there is one RUNNABLE task */
1708 if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
1709 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1710}
1711
1712static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
1713{
1714 enum uclamp_id clamp_id;
1715
1716 /*
1717 * Avoid any overhead until uclamp is actually used by the userspace.
1718 *
1719 * The condition is constructed such that a NOP is generated when
1720 * sched_uclamp_used is disabled.
1721 */
1722 if (!static_branch_unlikely(&sched_uclamp_used))
1723 return;
1724
1725 if (unlikely(!p->sched_class->uclamp_enabled))
1726 return;
1727
1728 for_each_clamp_id(clamp_id)
1729 uclamp_rq_dec_id(rq, p, clamp_id);
1730}
1731
1732static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p,
1733 enum uclamp_id clamp_id)
1734{
1735 if (!p->uclamp[clamp_id].active)
1736 return;
1737
1738 uclamp_rq_dec_id(rq, p, clamp_id);
1739 uclamp_rq_inc_id(rq, p, clamp_id);
1740
1741 /*
1742 * Make sure to clear the idle flag if we've transiently reached 0
1743 * active tasks on rq.
1744 */
1745 if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1746 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1747}
1748
1749static inline void
1750uclamp_update_active(struct task_struct *p)
1751{
1752 enum uclamp_id clamp_id;
1753 struct rq_flags rf;
1754 struct rq *rq;
1755
1756 /*
1757 * Lock the task and the rq where the task is (or was) queued.
1758 *
1759 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
1760 * price to pay to safely serialize util_{min,max} updates with
1761 * enqueues, dequeues and migration operations.
1762 * This is the same locking schema used by __set_cpus_allowed_ptr().
1763 */
1764 rq = task_rq_lock(p, &rf);
1765
1766 /*
1767 * Setting the clamp bucket is serialized by task_rq_lock().
1768 * If the task is not yet RUNNABLE and its task_struct is not
1769 * affecting a valid clamp bucket, the next time it's enqueued,
1770 * it will already see the updated clamp bucket value.
1771 */
1772 for_each_clamp_id(clamp_id)
1773 uclamp_rq_reinc_id(rq, p, clamp_id);
1774
1775 task_rq_unlock(rq, p, &rf);
1776}
1777
1778#ifdef CONFIG_UCLAMP_TASK_GROUP
1779static inline void
1780uclamp_update_active_tasks(struct cgroup_subsys_state *css)
1781{
1782 struct css_task_iter it;
1783 struct task_struct *p;
1784
1785 css_task_iter_start(css, 0, &it);
1786 while ((p = css_task_iter_next(&it)))
1787 uclamp_update_active(p);
1788 css_task_iter_end(&it);
1789}
1790
1791static void cpu_util_update_eff(struct cgroup_subsys_state *css);
1792#endif
1793
1794#ifdef CONFIG_SYSCTL
1795#ifdef CONFIG_UCLAMP_TASK
1796#ifdef CONFIG_UCLAMP_TASK_GROUP
1797static void uclamp_update_root_tg(void)
1798{
1799 struct task_group *tg = &root_task_group;
1800
1801 uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
1802 sysctl_sched_uclamp_util_min, false);
1803 uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
1804 sysctl_sched_uclamp_util_max, false);
1805
1806 guard(rcu)();
1807 cpu_util_update_eff(&root_task_group.css);
1808}
1809#else
1810static void uclamp_update_root_tg(void) { }
1811#endif
1812
1813static void uclamp_sync_util_min_rt_default(void)
1814{
1815 struct task_struct *g, *p;
1816
1817 /*
1818 * copy_process() sysctl_uclamp
1819 * uclamp_min_rt = X;
1820 * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
1821 * // link thread smp_mb__after_spinlock()
1822 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
1823 * sched_post_fork() for_each_process_thread()
1824 * __uclamp_sync_rt() __uclamp_sync_rt()
1825 *
1826 * Ensures that either sched_post_fork() will observe the new
1827 * uclamp_min_rt or for_each_process_thread() will observe the new
1828 * task.
1829 */
1830 read_lock(&tasklist_lock);
1831 smp_mb__after_spinlock();
1832 read_unlock(&tasklist_lock);
1833
1834 guard(rcu)();
1835 for_each_process_thread(g, p)
1836 uclamp_update_util_min_rt_default(p);
1837}
1838
1839static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
1840 void *buffer, size_t *lenp, loff_t *ppos)
1841{
1842 bool update_root_tg = false;
1843 int old_min, old_max, old_min_rt;
1844 int result;
1845
1846 guard(mutex)(&uclamp_mutex);
1847
1848 old_min = sysctl_sched_uclamp_util_min;
1849 old_max = sysctl_sched_uclamp_util_max;
1850 old_min_rt = sysctl_sched_uclamp_util_min_rt_default;
1851
1852 result = proc_dointvec(table, write, buffer, lenp, ppos);
1853 if (result)
1854 goto undo;
1855 if (!write)
1856 return 0;
1857
1858 if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
1859 sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE ||
1860 sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {
1861
1862 result = -EINVAL;
1863 goto undo;
1864 }
1865
1866 if (old_min != sysctl_sched_uclamp_util_min) {
1867 uclamp_se_set(&uclamp_default[UCLAMP_MIN],
1868 sysctl_sched_uclamp_util_min, false);
1869 update_root_tg = true;
1870 }
1871 if (old_max != sysctl_sched_uclamp_util_max) {
1872 uclamp_se_set(&uclamp_default[UCLAMP_MAX],
1873 sysctl_sched_uclamp_util_max, false);
1874 update_root_tg = true;
1875 }
1876
1877 if (update_root_tg) {
1878 static_branch_enable(&sched_uclamp_used);
1879 uclamp_update_root_tg();
1880 }
1881
1882 if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
1883 static_branch_enable(&sched_uclamp_used);
1884 uclamp_sync_util_min_rt_default();
1885 }
1886
1887 /*
1888 * We update all RUNNABLE tasks only when task groups are in use.
1889 * Otherwise, keep it simple and do just a lazy update at each next
1890 * task enqueue time.
1891 */
1892 return 0;
1893
1894undo:
1895 sysctl_sched_uclamp_util_min = old_min;
1896 sysctl_sched_uclamp_util_max = old_max;
1897 sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
1898 return result;
1899}
1900#endif
1901#endif
1902
1903static int uclamp_validate(struct task_struct *p,
1904 const struct sched_attr *attr)
1905{
1906 int util_min = p->uclamp_req[UCLAMP_MIN].value;
1907 int util_max = p->uclamp_req[UCLAMP_MAX].value;
1908
1909 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
1910 util_min = attr->sched_util_min;
1911
1912 if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
1913 return -EINVAL;
1914 }
1915
1916 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
1917 util_max = attr->sched_util_max;
1918
1919 if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
1920 return -EINVAL;
1921 }
1922
1923 if (util_min != -1 && util_max != -1 && util_min > util_max)
1924 return -EINVAL;
1925
1926 /*
1927 * We have valid uclamp attributes; make sure uclamp is enabled.
1928 *
1929 * We need to do that here, because enabling static branches is a
1930 * blocking operation which obviously cannot be done while holding
1931 * scheduler locks.
1932 */
1933 static_branch_enable(&sched_uclamp_used);
1934
1935 return 0;
1936}
1937
1938static bool uclamp_reset(const struct sched_attr *attr,
1939 enum uclamp_id clamp_id,
1940 struct uclamp_se *uc_se)
1941{
1942 /* Reset on sched class change for a non user-defined clamp value. */
1943 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) &&
1944 !uc_se->user_defined)
1945 return true;
1946
1947 /* Reset on sched_util_{min,max} == -1. */
1948 if (clamp_id == UCLAMP_MIN &&
1949 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1950 attr->sched_util_min == -1) {
1951 return true;
1952 }
1953
1954 if (clamp_id == UCLAMP_MAX &&
1955 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1956 attr->sched_util_max == -1) {
1957 return true;
1958 }
1959
1960 return false;
1961}
1962
1963static void __setscheduler_uclamp(struct task_struct *p,
1964 const struct sched_attr *attr)
1965{
1966 enum uclamp_id clamp_id;
1967
1968 for_each_clamp_id(clamp_id) {
1969 struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
1970 unsigned int value;
1971
1972 if (!uclamp_reset(attr, clamp_id, uc_se))
1973 continue;
1974
1975 /*
1976 * RT by default have a 100% boost value that could be modified
1977 * at runtime.
1978 */
1979 if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
1980 value = sysctl_sched_uclamp_util_min_rt_default;
1981 else
1982 value = uclamp_none(clamp_id);
1983
1984 uclamp_se_set(uc_se, value, false);
1985
1986 }
1987
1988 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
1989 return;
1990
1991 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1992 attr->sched_util_min != -1) {
1993 uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
1994 attr->sched_util_min, true);
1995 }
1996
1997 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1998 attr->sched_util_max != -1) {
1999 uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
2000 attr->sched_util_max, true);
2001 }
2002}
2003
2004static void uclamp_fork(struct task_struct *p)
2005{
2006 enum uclamp_id clamp_id;
2007
2008 /*
2009 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
2010 * as the task is still at its early fork stages.
2011 */
2012 for_each_clamp_id(clamp_id)
2013 p->uclamp[clamp_id].active = false;
2014
2015 if (likely(!p->sched_reset_on_fork))
2016 return;
2017
2018 for_each_clamp_id(clamp_id) {
2019 uclamp_se_set(&p->uclamp_req[clamp_id],
2020 uclamp_none(clamp_id), false);
2021 }
2022}
2023
2024static void uclamp_post_fork(struct task_struct *p)
2025{
2026 uclamp_update_util_min_rt_default(p);
2027}
2028
2029static void __init init_uclamp_rq(struct rq *rq)
2030{
2031 enum uclamp_id clamp_id;
2032 struct uclamp_rq *uc_rq = rq->uclamp;
2033
2034 for_each_clamp_id(clamp_id) {
2035 uc_rq[clamp_id] = (struct uclamp_rq) {
2036 .value = uclamp_none(clamp_id)
2037 };
2038 }
2039
2040 rq->uclamp_flags = UCLAMP_FLAG_IDLE;
2041}
2042
2043static void __init init_uclamp(void)
2044{
2045 struct uclamp_se uc_max = {};
2046 enum uclamp_id clamp_id;
2047 int cpu;
2048
2049 for_each_possible_cpu(cpu)
2050 init_uclamp_rq(cpu_rq(cpu));
2051
2052 for_each_clamp_id(clamp_id) {
2053 uclamp_se_set(&init_task.uclamp_req[clamp_id],
2054 uclamp_none(clamp_id), false);
2055 }
2056
2057 /* System defaults allow max clamp values for both indexes */
2058 uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
2059 for_each_clamp_id(clamp_id) {
2060 uclamp_default[clamp_id] = uc_max;
2061#ifdef CONFIG_UCLAMP_TASK_GROUP
2062 root_task_group.uclamp_req[clamp_id] = uc_max;
2063 root_task_group.uclamp[clamp_id] = uc_max;
2064#endif
2065 }
2066}
2067
2068#else /* CONFIG_UCLAMP_TASK */
2069static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
2070static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
2071static inline int uclamp_validate(struct task_struct *p,
2072 const struct sched_attr *attr)
2073{
2074 return -EOPNOTSUPP;
2075}
2076static void __setscheduler_uclamp(struct task_struct *p,
2077 const struct sched_attr *attr) { }
2078static inline void uclamp_fork(struct task_struct *p) { }
2079static inline void uclamp_post_fork(struct task_struct *p) { }
2080static inline void init_uclamp(void) { }
2081#endif /* CONFIG_UCLAMP_TASK */
2082
2083bool sched_task_on_rq(struct task_struct *p)
2084{
2085 return task_on_rq_queued(p);
2086}
2087
2088unsigned long get_wchan(struct task_struct *p)
2089{
2090 unsigned long ip = 0;
2091 unsigned int state;
2092
2093 if (!p || p == current)
2094 return 0;
2095
2096 /* Only get wchan if task is blocked and we can keep it that way. */
2097 raw_spin_lock_irq(&p->pi_lock);
2098 state = READ_ONCE(p->__state);
2099 smp_rmb(); /* see try_to_wake_up() */
2100 if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
2101 ip = __get_wchan(p);
2102 raw_spin_unlock_irq(&p->pi_lock);
2103
2104 return ip;
2105}
2106
2107static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
2108{
2109 if (!(flags & ENQUEUE_NOCLOCK))
2110 update_rq_clock(rq);
2111
2112 if (!(flags & ENQUEUE_RESTORE)) {
2113 sched_info_enqueue(rq, p);
2114 psi_enqueue(p, (flags & ENQUEUE_WAKEUP) && !(flags & ENQUEUE_MIGRATED));
2115 }
2116
2117 uclamp_rq_inc(rq, p);
2118 p->sched_class->enqueue_task(rq, p, flags);
2119
2120 if (sched_core_enabled(rq))
2121 sched_core_enqueue(rq, p);
2122}
2123
2124static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
2125{
2126 if (sched_core_enabled(rq))
2127 sched_core_dequeue(rq, p, flags);
2128
2129 if (!(flags & DEQUEUE_NOCLOCK))
2130 update_rq_clock(rq);
2131
2132 if (!(flags & DEQUEUE_SAVE)) {
2133 sched_info_dequeue(rq, p);
2134 psi_dequeue(p, flags & DEQUEUE_SLEEP);
2135 }
2136
2137 uclamp_rq_dec(rq, p);
2138 p->sched_class->dequeue_task(rq, p, flags);
2139}
2140
2141void activate_task(struct rq *rq, struct task_struct *p, int flags)
2142{
2143 if (task_on_rq_migrating(p))
2144 flags |= ENQUEUE_MIGRATED;
2145 if (flags & ENQUEUE_MIGRATED)
2146 sched_mm_cid_migrate_to(rq, p);
2147
2148 enqueue_task(rq, p, flags);
2149
2150 WRITE_ONCE(p->on_rq, TASK_ON_RQ_QUEUED);
2151 ASSERT_EXCLUSIVE_WRITER(p->on_rq);
2152}
2153
2154void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
2155{
2156 WRITE_ONCE(p->on_rq, (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING);
2157 ASSERT_EXCLUSIVE_WRITER(p->on_rq);
2158
2159 dequeue_task(rq, p, flags);
2160}
2161
2162static inline int __normal_prio(int policy, int rt_prio, int nice)
2163{
2164 int prio;
2165
2166 if (dl_policy(policy))
2167 prio = MAX_DL_PRIO - 1;
2168 else if (rt_policy(policy))
2169 prio = MAX_RT_PRIO - 1 - rt_prio;
2170 else
2171 prio = NICE_TO_PRIO(nice);
2172
2173 return prio;
2174}
2175
2176/*
2177 * Calculate the expected normal priority: i.e. priority
2178 * without taking RT-inheritance into account. Might be
2179 * boosted by interactivity modifiers. Changes upon fork,
2180 * setprio syscalls, and whenever the interactivity
2181 * estimator recalculates.
2182 */
2183static inline int normal_prio(struct task_struct *p)
2184{
2185 return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
2186}
2187
2188/*
2189 * Calculate the current priority, i.e. the priority
2190 * taken into account by the scheduler. This value might
2191 * be boosted by RT tasks, or might be boosted by
2192 * interactivity modifiers. Will be RT if the task got
2193 * RT-boosted. If not then it returns p->normal_prio.
2194 */
2195static int effective_prio(struct task_struct *p)
2196{
2197 p->normal_prio = normal_prio(p);
2198 /*
2199 * If we are RT tasks or we were boosted to RT priority,
2200 * keep the priority unchanged. Otherwise, update priority
2201 * to the normal priority:
2202 */
2203 if (!rt_prio(p->prio))
2204 return p->normal_prio;
2205 return p->prio;
2206}
2207
2208/**
2209 * task_curr - is this task currently executing on a CPU?
2210 * @p: the task in question.
2211 *
2212 * Return: 1 if the task is currently executing. 0 otherwise.
2213 */
2214inline int task_curr(const struct task_struct *p)
2215{
2216 return cpu_curr(task_cpu(p)) == p;
2217}
2218
2219/*
2220 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
2221 * use the balance_callback list if you want balancing.
2222 *
2223 * this means any call to check_class_changed() must be followed by a call to
2224 * balance_callback().
2225 */
2226static inline void check_class_changed(struct rq *rq, struct task_struct *p,
2227 const struct sched_class *prev_class,
2228 int oldprio)
2229{
2230 if (prev_class != p->sched_class) {
2231 if (prev_class->switched_from)
2232 prev_class->switched_from(rq, p);
2233
2234 p->sched_class->switched_to(rq, p);
2235 } else if (oldprio != p->prio || dl_task(p))
2236 p->sched_class->prio_changed(rq, p, oldprio);
2237}
2238
2239void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags)
2240{
2241 if (p->sched_class == rq->curr->sched_class)
2242 rq->curr->sched_class->wakeup_preempt(rq, p, flags);
2243 else if (sched_class_above(p->sched_class, rq->curr->sched_class))
2244 resched_curr(rq);
2245
2246 /*
2247 * A queue event has occurred, and we're going to schedule. In
2248 * this case, we can save a useless back to back clock update.
2249 */
2250 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
2251 rq_clock_skip_update(rq);
2252}
2253
2254static __always_inline
2255int __task_state_match(struct task_struct *p, unsigned int state)
2256{
2257 if (READ_ONCE(p->__state) & state)
2258 return 1;
2259
2260 if (READ_ONCE(p->saved_state) & state)
2261 return -1;
2262
2263 return 0;
2264}
2265
2266static __always_inline
2267int task_state_match(struct task_struct *p, unsigned int state)
2268{
2269 /*
2270 * Serialize against current_save_and_set_rtlock_wait_state(),
2271 * current_restore_rtlock_saved_state(), and __refrigerator().
2272 */
2273 guard(raw_spinlock_irq)(&p->pi_lock);
2274 return __task_state_match(p, state);
2275}
2276
2277/*
2278 * wait_task_inactive - wait for a thread to unschedule.
2279 *
2280 * Wait for the thread to block in any of the states set in @match_state.
2281 * If it changes, i.e. @p might have woken up, then return zero. When we
2282 * succeed in waiting for @p to be off its CPU, we return a positive number
2283 * (its total switch count). If a second call a short while later returns the
2284 * same number, the caller can be sure that @p has remained unscheduled the
2285 * whole time.
2286 *
2287 * The caller must ensure that the task *will* unschedule sometime soon,
2288 * else this function might spin for a *long* time. This function can't
2289 * be called with interrupts off, or it may introduce deadlock with
2290 * smp_call_function() if an IPI is sent by the same process we are
2291 * waiting to become inactive.
2292 */
2293unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
2294{
2295 int running, queued, match;
2296 struct rq_flags rf;
2297 unsigned long ncsw;
2298 struct rq *rq;
2299
2300 for (;;) {
2301 /*
2302 * We do the initial early heuristics without holding
2303 * any task-queue locks at all. We'll only try to get
2304 * the runqueue lock when things look like they will
2305 * work out!
2306 */
2307 rq = task_rq(p);
2308
2309 /*
2310 * If the task is actively running on another CPU
2311 * still, just relax and busy-wait without holding
2312 * any locks.
2313 *
2314 * NOTE! Since we don't hold any locks, it's not
2315 * even sure that "rq" stays as the right runqueue!
2316 * But we don't care, since "task_on_cpu()" will
2317 * return false if the runqueue has changed and p
2318 * is actually now running somewhere else!
2319 */
2320 while (task_on_cpu(rq, p)) {
2321 if (!task_state_match(p, match_state))
2322 return 0;
2323 cpu_relax();
2324 }
2325
2326 /*
2327 * Ok, time to look more closely! We need the rq
2328 * lock now, to be *sure*. If we're wrong, we'll
2329 * just go back and repeat.
2330 */
2331 rq = task_rq_lock(p, &rf);
2332 trace_sched_wait_task(p);
2333 running = task_on_cpu(rq, p);
2334 queued = task_on_rq_queued(p);
2335 ncsw = 0;
2336 if ((match = __task_state_match(p, match_state))) {
2337 /*
2338 * When matching on p->saved_state, consider this task
2339 * still queued so it will wait.
2340 */
2341 if (match < 0)
2342 queued = 1;
2343 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
2344 }
2345 task_rq_unlock(rq, p, &rf);
2346
2347 /*
2348 * If it changed from the expected state, bail out now.
2349 */
2350 if (unlikely(!ncsw))
2351 break;
2352
2353 /*
2354 * Was it really running after all now that we
2355 * checked with the proper locks actually held?
2356 *
2357 * Oops. Go back and try again..
2358 */
2359 if (unlikely(running)) {
2360 cpu_relax();
2361 continue;
2362 }
2363
2364 /*
2365 * It's not enough that it's not actively running,
2366 * it must be off the runqueue _entirely_, and not
2367 * preempted!
2368 *
2369 * So if it was still runnable (but just not actively
2370 * running right now), it's preempted, and we should
2371 * yield - it could be a while.
2372 */
2373 if (unlikely(queued)) {
2374 ktime_t to = NSEC_PER_SEC / HZ;
2375
2376 set_current_state(TASK_UNINTERRUPTIBLE);
2377 schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD);
2378 continue;
2379 }
2380
2381 /*
2382 * Ahh, all good. It wasn't running, and it wasn't
2383 * runnable, which means that it will never become
2384 * running in the future either. We're all done!
2385 */
2386 break;
2387 }
2388
2389 return ncsw;
2390}
2391
2392#ifdef CONFIG_SMP
2393
2394static void
2395__do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx);
2396
2397static int __set_cpus_allowed_ptr(struct task_struct *p,
2398 struct affinity_context *ctx);
2399
2400static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
2401{
2402 struct affinity_context ac = {
2403 .new_mask = cpumask_of(rq->cpu),
2404 .flags = SCA_MIGRATE_DISABLE,
2405 };
2406
2407 if (likely(!p->migration_disabled))
2408 return;
2409
2410 if (p->cpus_ptr != &p->cpus_mask)
2411 return;
2412
2413 /*
2414 * Violates locking rules! see comment in __do_set_cpus_allowed().
2415 */
2416 __do_set_cpus_allowed(p, &ac);
2417}
2418
2419void migrate_disable(void)
2420{
2421 struct task_struct *p = current;
2422
2423 if (p->migration_disabled) {
2424 p->migration_disabled++;
2425 return;
2426 }
2427
2428 guard(preempt)();
2429 this_rq()->nr_pinned++;
2430 p->migration_disabled = 1;
2431}
2432EXPORT_SYMBOL_GPL(migrate_disable);
2433
2434void migrate_enable(void)
2435{
2436 struct task_struct *p = current;
2437 struct affinity_context ac = {
2438 .new_mask = &p->cpus_mask,
2439 .flags = SCA_MIGRATE_ENABLE,
2440 };
2441
2442 if (p->migration_disabled > 1) {
2443 p->migration_disabled--;
2444 return;
2445 }
2446
2447 if (WARN_ON_ONCE(!p->migration_disabled))
2448 return;
2449
2450 /*
2451 * Ensure stop_task runs either before or after this, and that
2452 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
2453 */
2454 guard(preempt)();
2455 if (p->cpus_ptr != &p->cpus_mask)
2456 __set_cpus_allowed_ptr(p, &ac);
2457 /*
2458 * Mustn't clear migration_disabled() until cpus_ptr points back at the
2459 * regular cpus_mask, otherwise things that race (eg.
2460 * select_fallback_rq) get confused.
2461 */
2462 barrier();
2463 p->migration_disabled = 0;
2464 this_rq()->nr_pinned--;
2465}
2466EXPORT_SYMBOL_GPL(migrate_enable);
2467
2468static inline bool rq_has_pinned_tasks(struct rq *rq)
2469{
2470 return rq->nr_pinned;
2471}
2472
2473/*
2474 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
2475 * __set_cpus_allowed_ptr() and select_fallback_rq().
2476 */
2477static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
2478{
2479 /* When not in the task's cpumask, no point in looking further. */
2480 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
2481 return false;
2482
2483 /* migrate_disabled() must be allowed to finish. */
2484 if (is_migration_disabled(p))
2485 return cpu_online(cpu);
2486
2487 /* Non kernel threads are not allowed during either online or offline. */
2488 if (!(p->flags & PF_KTHREAD))
2489 return cpu_active(cpu) && task_cpu_possible(cpu, p);
2490
2491 /* KTHREAD_IS_PER_CPU is always allowed. */
2492 if (kthread_is_per_cpu(p))
2493 return cpu_online(cpu);
2494
2495 /* Regular kernel threads don't get to stay during offline. */
2496 if (cpu_dying(cpu))
2497 return false;
2498
2499 /* But are allowed during online. */
2500 return cpu_online(cpu);
2501}
2502
2503/*
2504 * This is how migration works:
2505 *
2506 * 1) we invoke migration_cpu_stop() on the target CPU using
2507 * stop_one_cpu().
2508 * 2) stopper starts to run (implicitly forcing the migrated thread
2509 * off the CPU)
2510 * 3) it checks whether the migrated task is still in the wrong runqueue.
2511 * 4) if it's in the wrong runqueue then the migration thread removes
2512 * it and puts it into the right queue.
2513 * 5) stopper completes and stop_one_cpu() returns and the migration
2514 * is done.
2515 */
2516
2517/*
2518 * move_queued_task - move a queued task to new rq.
2519 *
2520 * Returns (locked) new rq. Old rq's lock is released.
2521 */
2522static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
2523 struct task_struct *p, int new_cpu)
2524{
2525 lockdep_assert_rq_held(rq);
2526
2527 deactivate_task(rq, p, DEQUEUE_NOCLOCK);
2528 set_task_cpu(p, new_cpu);
2529 rq_unlock(rq, rf);
2530
2531 rq = cpu_rq(new_cpu);
2532
2533 rq_lock(rq, rf);
2534 WARN_ON_ONCE(task_cpu(p) != new_cpu);
2535 activate_task(rq, p, 0);
2536 wakeup_preempt(rq, p, 0);
2537
2538 return rq;
2539}
2540
2541struct migration_arg {
2542 struct task_struct *task;
2543 int dest_cpu;
2544 struct set_affinity_pending *pending;
2545};
2546
2547/*
2548 * @refs: number of wait_for_completion()
2549 * @stop_pending: is @stop_work in use
2550 */
2551struct set_affinity_pending {
2552 refcount_t refs;
2553 unsigned int stop_pending;
2554 struct completion done;
2555 struct cpu_stop_work stop_work;
2556 struct migration_arg arg;
2557};
2558
2559/*
2560 * Move (not current) task off this CPU, onto the destination CPU. We're doing
2561 * this because either it can't run here any more (set_cpus_allowed()
2562 * away from this CPU, or CPU going down), or because we're
2563 * attempting to rebalance this task on exec (sched_exec).
2564 *
2565 * So we race with normal scheduler movements, but that's OK, as long
2566 * as the task is no longer on this CPU.
2567 */
2568static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
2569 struct task_struct *p, int dest_cpu)
2570{
2571 /* Affinity changed (again). */
2572 if (!is_cpu_allowed(p, dest_cpu))
2573 return rq;
2574
2575 rq = move_queued_task(rq, rf, p, dest_cpu);
2576
2577 return rq;
2578}
2579
2580/*
2581 * migration_cpu_stop - this will be executed by a highprio stopper thread
2582 * and performs thread migration by bumping thread off CPU then
2583 * 'pushing' onto another runqueue.
2584 */
2585static int migration_cpu_stop(void *data)
2586{
2587 struct migration_arg *arg = data;
2588 struct set_affinity_pending *pending = arg->pending;
2589 struct task_struct *p = arg->task;
2590 struct rq *rq = this_rq();
2591 bool complete = false;
2592 struct rq_flags rf;
2593
2594 /*
2595 * The original target CPU might have gone down and we might
2596 * be on another CPU but it doesn't matter.
2597 */
2598 local_irq_save(rf.flags);
2599 /*
2600 * We need to explicitly wake pending tasks before running
2601 * __migrate_task() such that we will not miss enforcing cpus_ptr
2602 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
2603 */
2604 flush_smp_call_function_queue();
2605
2606 raw_spin_lock(&p->pi_lock);
2607 rq_lock(rq, &rf);
2608
2609 /*
2610 * If we were passed a pending, then ->stop_pending was set, thus
2611 * p->migration_pending must have remained stable.
2612 */
2613 WARN_ON_ONCE(pending && pending != p->migration_pending);
2614
2615 /*
2616 * If task_rq(p) != rq, it cannot be migrated here, because we're
2617 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
2618 * we're holding p->pi_lock.
2619 */
2620 if (task_rq(p) == rq) {
2621 if (is_migration_disabled(p))
2622 goto out;
2623
2624 if (pending) {
2625 p->migration_pending = NULL;
2626 complete = true;
2627
2628 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
2629 goto out;
2630 }
2631
2632 if (task_on_rq_queued(p)) {
2633 update_rq_clock(rq);
2634 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
2635 } else {
2636 p->wake_cpu = arg->dest_cpu;
2637 }
2638
2639 /*
2640 * XXX __migrate_task() can fail, at which point we might end
2641 * up running on a dodgy CPU, AFAICT this can only happen
2642 * during CPU hotplug, at which point we'll get pushed out
2643 * anyway, so it's probably not a big deal.
2644 */
2645
2646 } else if (pending) {
2647 /*
2648 * This happens when we get migrated between migrate_enable()'s
2649 * preempt_enable() and scheduling the stopper task. At that
2650 * point we're a regular task again and not current anymore.
2651 *
2652 * A !PREEMPT kernel has a giant hole here, which makes it far
2653 * more likely.
2654 */
2655
2656 /*
2657 * The task moved before the stopper got to run. We're holding
2658 * ->pi_lock, so the allowed mask is stable - if it got
2659 * somewhere allowed, we're done.
2660 */
2661 if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) {
2662 p->migration_pending = NULL;
2663 complete = true;
2664 goto out;
2665 }
2666
2667 /*
2668 * When migrate_enable() hits a rq mis-match we can't reliably
2669 * determine is_migration_disabled() and so have to chase after
2670 * it.
2671 */
2672 WARN_ON_ONCE(!pending->stop_pending);
2673 preempt_disable();
2674 task_rq_unlock(rq, p, &rf);
2675 stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
2676 &pending->arg, &pending->stop_work);
2677 preempt_enable();
2678 return 0;
2679 }
2680out:
2681 if (pending)
2682 pending->stop_pending = false;
2683 task_rq_unlock(rq, p, &rf);
2684
2685 if (complete)
2686 complete_all(&pending->done);
2687
2688 return 0;
2689}
2690
2691int push_cpu_stop(void *arg)
2692{
2693 struct rq *lowest_rq = NULL, *rq = this_rq();
2694 struct task_struct *p = arg;
2695
2696 raw_spin_lock_irq(&p->pi_lock);
2697 raw_spin_rq_lock(rq);
2698
2699 if (task_rq(p) != rq)
2700 goto out_unlock;
2701
2702 if (is_migration_disabled(p)) {
2703 p->migration_flags |= MDF_PUSH;
2704 goto out_unlock;
2705 }
2706
2707 p->migration_flags &= ~MDF_PUSH;
2708
2709 if (p->sched_class->find_lock_rq)
2710 lowest_rq = p->sched_class->find_lock_rq(p, rq);
2711
2712 if (!lowest_rq)
2713 goto out_unlock;
2714
2715 // XXX validate p is still the highest prio task
2716 if (task_rq(p) == rq) {
2717 deactivate_task(rq, p, 0);
2718 set_task_cpu(p, lowest_rq->cpu);
2719 activate_task(lowest_rq, p, 0);
2720 resched_curr(lowest_rq);
2721 }
2722
2723 double_unlock_balance(rq, lowest_rq);
2724
2725out_unlock:
2726 rq->push_busy = false;
2727 raw_spin_rq_unlock(rq);
2728 raw_spin_unlock_irq(&p->pi_lock);
2729
2730 put_task_struct(p);
2731 return 0;
2732}
2733
2734/*
2735 * sched_class::set_cpus_allowed must do the below, but is not required to
2736 * actually call this function.
2737 */
2738void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx)
2739{
2740 if (ctx->flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
2741 p->cpus_ptr = ctx->new_mask;
2742 return;
2743 }
2744
2745 cpumask_copy(&p->cpus_mask, ctx->new_mask);
2746 p->nr_cpus_allowed = cpumask_weight(ctx->new_mask);
2747
2748 /*
2749 * Swap in a new user_cpus_ptr if SCA_USER flag set
2750 */
2751 if (ctx->flags & SCA_USER)
2752 swap(p->user_cpus_ptr, ctx->user_mask);
2753}
2754
2755static void
2756__do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
2757{
2758 struct rq *rq = task_rq(p);
2759 bool queued, running;
2760
2761 /*
2762 * This here violates the locking rules for affinity, since we're only
2763 * supposed to change these variables while holding both rq->lock and
2764 * p->pi_lock.
2765 *
2766 * HOWEVER, it magically works, because ttwu() is the only code that
2767 * accesses these variables under p->pi_lock and only does so after
2768 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
2769 * before finish_task().
2770 *
2771 * XXX do further audits, this smells like something putrid.
2772 */
2773 if (ctx->flags & SCA_MIGRATE_DISABLE)
2774 SCHED_WARN_ON(!p->on_cpu);
2775 else
2776 lockdep_assert_held(&p->pi_lock);
2777
2778 queued = task_on_rq_queued(p);
2779 running = task_current(rq, p);
2780
2781 if (queued) {
2782 /*
2783 * Because __kthread_bind() calls this on blocked tasks without
2784 * holding rq->lock.
2785 */
2786 lockdep_assert_rq_held(rq);
2787 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
2788 }
2789 if (running)
2790 put_prev_task(rq, p);
2791
2792 p->sched_class->set_cpus_allowed(p, ctx);
2793
2794 if (queued)
2795 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
2796 if (running)
2797 set_next_task(rq, p);
2798}
2799
2800/*
2801 * Used for kthread_bind() and select_fallback_rq(), in both cases the user
2802 * affinity (if any) should be destroyed too.
2803 */
2804void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
2805{
2806 struct affinity_context ac = {
2807 .new_mask = new_mask,
2808 .user_mask = NULL,
2809 .flags = SCA_USER, /* clear the user requested mask */
2810 };
2811 union cpumask_rcuhead {
2812 cpumask_t cpumask;
2813 struct rcu_head rcu;
2814 };
2815
2816 __do_set_cpus_allowed(p, &ac);
2817
2818 /*
2819 * Because this is called with p->pi_lock held, it is not possible
2820 * to use kfree() here (when PREEMPT_RT=y), therefore punt to using
2821 * kfree_rcu().
2822 */
2823 kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu);
2824}
2825
2826static cpumask_t *alloc_user_cpus_ptr(int node)
2827{
2828 /*
2829 * See do_set_cpus_allowed() above for the rcu_head usage.
2830 */
2831 int size = max_t(int, cpumask_size(), sizeof(struct rcu_head));
2832
2833 return kmalloc_node(size, GFP_KERNEL, node);
2834}
2835
2836int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
2837 int node)
2838{
2839 cpumask_t *user_mask;
2840 unsigned long flags;
2841
2842 /*
2843 * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's
2844 * may differ by now due to racing.
2845 */
2846 dst->user_cpus_ptr = NULL;
2847
2848 /*
2849 * This check is racy and losing the race is a valid situation.
2850 * It is not worth the extra overhead of taking the pi_lock on
2851 * every fork/clone.
2852 */
2853 if (data_race(!src->user_cpus_ptr))
2854 return 0;
2855
2856 user_mask = alloc_user_cpus_ptr(node);
2857 if (!user_mask)
2858 return -ENOMEM;
2859
2860 /*
2861 * Use pi_lock to protect content of user_cpus_ptr
2862 *
2863 * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent
2864 * do_set_cpus_allowed().
2865 */
2866 raw_spin_lock_irqsave(&src->pi_lock, flags);
2867 if (src->user_cpus_ptr) {
2868 swap(dst->user_cpus_ptr, user_mask);
2869 cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
2870 }
2871 raw_spin_unlock_irqrestore(&src->pi_lock, flags);
2872
2873 if (unlikely(user_mask))
2874 kfree(user_mask);
2875
2876 return 0;
2877}
2878
2879static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p)
2880{
2881 struct cpumask *user_mask = NULL;
2882
2883 swap(p->user_cpus_ptr, user_mask);
2884
2885 return user_mask;
2886}
2887
2888void release_user_cpus_ptr(struct task_struct *p)
2889{
2890 kfree(clear_user_cpus_ptr(p));
2891}
2892
2893/*
2894 * This function is wildly self concurrent; here be dragons.
2895 *
2896 *
2897 * When given a valid mask, __set_cpus_allowed_ptr() must block until the
2898 * designated task is enqueued on an allowed CPU. If that task is currently
2899 * running, we have to kick it out using the CPU stopper.
2900 *
2901 * Migrate-Disable comes along and tramples all over our nice sandcastle.
2902 * Consider:
2903 *
2904 * Initial conditions: P0->cpus_mask = [0, 1]
2905 *
2906 * P0@CPU0 P1
2907 *
2908 * migrate_disable();
2909 * <preempted>
2910 * set_cpus_allowed_ptr(P0, [1]);
2911 *
2912 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes
2913 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region).
2914 * This means we need the following scheme:
2915 *
2916 * P0@CPU0 P1
2917 *
2918 * migrate_disable();
2919 * <preempted>
2920 * set_cpus_allowed_ptr(P0, [1]);
2921 * <blocks>
2922 * <resumes>
2923 * migrate_enable();
2924 * __set_cpus_allowed_ptr();
2925 * <wakes local stopper>
2926 * `--> <woken on migration completion>
2927 *
2928 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple
2929 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any
2930 * task p are serialized by p->pi_lock, which we can leverage: the one that
2931 * should come into effect at the end of the Migrate-Disable region is the last
2932 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask),
2933 * but we still need to properly signal those waiting tasks at the appropriate
2934 * moment.
2935 *
2936 * This is implemented using struct set_affinity_pending. The first
2937 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will
2938 * setup an instance of that struct and install it on the targeted task_struct.
2939 * Any and all further callers will reuse that instance. Those then wait for
2940 * a completion signaled at the tail of the CPU stopper callback (1), triggered
2941 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()).
2942 *
2943 *
2944 * (1) In the cases covered above. There is one more where the completion is
2945 * signaled within affine_move_task() itself: when a subsequent affinity request
2946 * occurs after the stopper bailed out due to the targeted task still being
2947 * Migrate-Disable. Consider:
2948 *
2949 * Initial conditions: P0->cpus_mask = [0, 1]
2950 *
2951 * CPU0 P1 P2
2952 * <P0>
2953 * migrate_disable();
2954 * <preempted>
2955 * set_cpus_allowed_ptr(P0, [1]);
2956 * <blocks>
2957 * <migration/0>
2958 * migration_cpu_stop()
2959 * is_migration_disabled()
2960 * <bails>
2961 * set_cpus_allowed_ptr(P0, [0, 1]);
2962 * <signal completion>
2963 * <awakes>
2964 *
2965 * Note that the above is safe vs a concurrent migrate_enable(), as any
2966 * pending affinity completion is preceded by an uninstallation of
2967 * p->migration_pending done with p->pi_lock held.
2968 */
2969static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf,
2970 int dest_cpu, unsigned int flags)
2971 __releases(rq->lock)
2972 __releases(p->pi_lock)
2973{
2974 struct set_affinity_pending my_pending = { }, *pending = NULL;
2975 bool stop_pending, complete = false;
2976
2977 /* Can the task run on the task's current CPU? If so, we're done */
2978 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
2979 struct task_struct *push_task = NULL;
2980
2981 if ((flags & SCA_MIGRATE_ENABLE) &&
2982 (p->migration_flags & MDF_PUSH) && !rq->push_busy) {
2983 rq->push_busy = true;
2984 push_task = get_task_struct(p);
2985 }
2986
2987 /*
2988 * If there are pending waiters, but no pending stop_work,
2989 * then complete now.
2990 */
2991 pending = p->migration_pending;
2992 if (pending && !pending->stop_pending) {
2993 p->migration_pending = NULL;
2994 complete = true;
2995 }
2996
2997 preempt_disable();
2998 task_rq_unlock(rq, p, rf);
2999 if (push_task) {
3000 stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
3001 p, &rq->push_work);
3002 }
3003 preempt_enable();
3004
3005 if (complete)
3006 complete_all(&pending->done);
3007
3008 return 0;
3009 }
3010
3011 if (!(flags & SCA_MIGRATE_ENABLE)) {
3012 /* serialized by p->pi_lock */
3013 if (!p->migration_pending) {
3014 /* Install the request */
3015 refcount_set(&my_pending.refs, 1);
3016 init_completion(&my_pending.done);
3017 my_pending.arg = (struct migration_arg) {
3018 .task = p,
3019 .dest_cpu = dest_cpu,
3020 .pending = &my_pending,
3021 };
3022
3023 p->migration_pending = &my_pending;
3024 } else {
3025 pending = p->migration_pending;
3026 refcount_inc(&pending->refs);
3027 /*
3028 * Affinity has changed, but we've already installed a
3029 * pending. migration_cpu_stop() *must* see this, else
3030 * we risk a completion of the pending despite having a
3031 * task on a disallowed CPU.
3032 *
3033 * Serialized by p->pi_lock, so this is safe.
3034 */
3035 pending->arg.dest_cpu = dest_cpu;
3036 }
3037 }
3038 pending = p->migration_pending;
3039 /*
3040 * - !MIGRATE_ENABLE:
3041 * we'll have installed a pending if there wasn't one already.
3042 *
3043 * - MIGRATE_ENABLE:
3044 * we're here because the current CPU isn't matching anymore,
3045 * the only way that can happen is because of a concurrent
3046 * set_cpus_allowed_ptr() call, which should then still be
3047 * pending completion.
3048 *
3049 * Either way, we really should have a @pending here.
3050 */
3051 if (WARN_ON_ONCE(!pending)) {
3052 task_rq_unlock(rq, p, rf);
3053 return -EINVAL;
3054 }
3055
3056 if (task_on_cpu(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) {
3057 /*
3058 * MIGRATE_ENABLE gets here because 'p == current', but for
3059 * anything else we cannot do is_migration_disabled(), punt
3060 * and have the stopper function handle it all race-free.
3061 */
3062 stop_pending = pending->stop_pending;
3063 if (!stop_pending)
3064 pending->stop_pending = true;
3065
3066 if (flags & SCA_MIGRATE_ENABLE)
3067 p->migration_flags &= ~MDF_PUSH;
3068
3069 preempt_disable();
3070 task_rq_unlock(rq, p, rf);
3071 if (!stop_pending) {
3072 stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
3073 &pending->arg, &pending->stop_work);
3074 }
3075 preempt_enable();
3076
3077 if (flags & SCA_MIGRATE_ENABLE)
3078 return 0;
3079 } else {
3080
3081 if (!is_migration_disabled(p)) {
3082 if (task_on_rq_queued(p))
3083 rq = move_queued_task(rq, rf, p, dest_cpu);
3084
3085 if (!pending->stop_pending) {
3086 p->migration_pending = NULL;
3087 complete = true;
3088 }
3089 }
3090 task_rq_unlock(rq, p, rf);
3091
3092 if (complete)
3093 complete_all(&pending->done);
3094 }
3095
3096 wait_for_completion(&pending->done);
3097
3098 if (refcount_dec_and_test(&pending->refs))
3099 wake_up_var(&pending->refs); /* No UaF, just an address */
3100
3101 /*
3102 * Block the original owner of &pending until all subsequent callers
3103 * have seen the completion and decremented the refcount
3104 */
3105 wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));
3106
3107 /* ARGH */
3108 WARN_ON_ONCE(my_pending.stop_pending);
3109
3110 return 0;
3111}
3112
3113/*
3114 * Called with both p->pi_lock and rq->lock held; drops both before returning.
3115 */
3116static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
3117 struct affinity_context *ctx,
3118 struct rq *rq,
3119 struct rq_flags *rf)
3120 __releases(rq->lock)
3121 __releases(p->pi_lock)
3122{
3123 const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
3124 const struct cpumask *cpu_valid_mask = cpu_active_mask;
3125 bool kthread = p->flags & PF_KTHREAD;
3126 unsigned int dest_cpu;
3127 int ret = 0;
3128
3129 update_rq_clock(rq);
3130
3131 if (kthread || is_migration_disabled(p)) {
3132 /*
3133 * Kernel threads are allowed on online && !active CPUs,
3134 * however, during cpu-hot-unplug, even these might get pushed
3135 * away if not KTHREAD_IS_PER_CPU.
3136 *
3137 * Specifically, migration_disabled() tasks must not fail the
3138 * cpumask_any_and_distribute() pick below, esp. so on
3139 * SCA_MIGRATE_ENABLE, otherwise we'll not call
3140 * set_cpus_allowed_common() and actually reset p->cpus_ptr.
3141 */
3142 cpu_valid_mask = cpu_online_mask;
3143 }
3144
3145 if (!kthread && !cpumask_subset(ctx->new_mask, cpu_allowed_mask)) {
3146 ret = -EINVAL;
3147 goto out;
3148 }
3149
3150 /*
3151 * Must re-check here, to close a race against __kthread_bind(),
3152 * sched_setaffinity() is not guaranteed to observe the flag.
3153 */
3154 if ((ctx->flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
3155 ret = -EINVAL;
3156 goto out;
3157 }
3158
3159 if (!(ctx->flags & SCA_MIGRATE_ENABLE)) {
3160 if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) {
3161 if (ctx->flags & SCA_USER)
3162 swap(p->user_cpus_ptr, ctx->user_mask);
3163 goto out;
3164 }
3165
3166 if (WARN_ON_ONCE(p == current &&
3167 is_migration_disabled(p) &&
3168 !cpumask_test_cpu(task_cpu(p), ctx->new_mask))) {
3169 ret = -EBUSY;
3170 goto out;
3171 }
3172 }
3173
3174 /*
3175 * Picking a ~random cpu helps in cases where we are changing affinity
3176 * for groups of tasks (ie. cpuset), so that load balancing is not
3177 * immediately required to distribute the tasks within their new mask.
3178 */
3179 dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, ctx->new_mask);
3180 if (dest_cpu >= nr_cpu_ids) {
3181 ret = -EINVAL;
3182 goto out;
3183 }
3184
3185 __do_set_cpus_allowed(p, ctx);
3186
3187 return affine_move_task(rq, p, rf, dest_cpu, ctx->flags);
3188
3189out:
3190 task_rq_unlock(rq, p, rf);
3191
3192 return ret;
3193}
3194
3195/*
3196 * Change a given task's CPU affinity. Migrate the thread to a
3197 * proper CPU and schedule it away if the CPU it's executing on
3198 * is removed from the allowed bitmask.
3199 *
3200 * NOTE: the caller must have a valid reference to the task, the
3201 * task must not exit() & deallocate itself prematurely. The
3202 * call is not atomic; no spinlocks may be held.
3203 */
3204static int __set_cpus_allowed_ptr(struct task_struct *p,
3205 struct affinity_context *ctx)
3206{
3207 struct rq_flags rf;
3208 struct rq *rq;
3209
3210 rq = task_rq_lock(p, &rf);
3211 /*
3212 * Masking should be skipped if SCA_USER or any of the SCA_MIGRATE_*
3213 * flags are set.
3214 */
3215 if (p->user_cpus_ptr &&
3216 !(ctx->flags & (SCA_USER | SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) &&
3217 cpumask_and(rq->scratch_mask, ctx->new_mask, p->user_cpus_ptr))
3218 ctx->new_mask = rq->scratch_mask;
3219
3220 return __set_cpus_allowed_ptr_locked(p, ctx, rq, &rf);
3221}
3222
3223int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
3224{
3225 struct affinity_context ac = {
3226 .new_mask = new_mask,
3227 .flags = 0,
3228 };
3229
3230 return __set_cpus_allowed_ptr(p, &ac);
3231}
3232EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
3233
3234/*
3235 * Change a given task's CPU affinity to the intersection of its current
3236 * affinity mask and @subset_mask, writing the resulting mask to @new_mask.
3237 * If user_cpus_ptr is defined, use it as the basis for restricting CPU
3238 * affinity or use cpu_online_mask instead.
3239 *
3240 * If the resulting mask is empty, leave the affinity unchanged and return
3241 * -EINVAL.
3242 */
3243static int restrict_cpus_allowed_ptr(struct task_struct *p,
3244 struct cpumask *new_mask,
3245 const struct cpumask *subset_mask)
3246{
3247 struct affinity_context ac = {
3248 .new_mask = new_mask,
3249 .flags = 0,
3250 };
3251 struct rq_flags rf;
3252 struct rq *rq;
3253 int err;
3254
3255 rq = task_rq_lock(p, &rf);
3256
3257 /*
3258 * Forcefully restricting the affinity of a deadline task is
3259 * likely to cause problems, so fail and noisily override the
3260 * mask entirely.
3261 */
3262 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
3263 err = -EPERM;
3264 goto err_unlock;
3265 }
3266
3267 if (!cpumask_and(new_mask, task_user_cpus(p), subset_mask)) {
3268 err = -EINVAL;
3269 goto err_unlock;
3270 }
3271
3272 return __set_cpus_allowed_ptr_locked(p, &ac, rq, &rf);
3273
3274err_unlock:
3275 task_rq_unlock(rq, p, &rf);
3276 return err;
3277}
3278
3279/*
3280 * Restrict the CPU affinity of task @p so that it is a subset of
3281 * task_cpu_possible_mask() and point @p->user_cpus_ptr to a copy of the
3282 * old affinity mask. If the resulting mask is empty, we warn and walk
3283 * up the cpuset hierarchy until we find a suitable mask.
3284 */
3285void force_compatible_cpus_allowed_ptr(struct task_struct *p)
3286{
3287 cpumask_var_t new_mask;
3288 const struct cpumask *override_mask = task_cpu_possible_mask(p);
3289
3290 alloc_cpumask_var(&new_mask, GFP_KERNEL);
3291
3292 /*
3293 * __migrate_task() can fail silently in the face of concurrent
3294 * offlining of the chosen destination CPU, so take the hotplug
3295 * lock to ensure that the migration succeeds.
3296 */
3297 cpus_read_lock();
3298 if (!cpumask_available(new_mask))
3299 goto out_set_mask;
3300
3301 if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask))
3302 goto out_free_mask;
3303
3304 /*
3305 * We failed to find a valid subset of the affinity mask for the
3306 * task, so override it based on its cpuset hierarchy.
3307 */
3308 cpuset_cpus_allowed(p, new_mask);
3309 override_mask = new_mask;
3310
3311out_set_mask:
3312 if (printk_ratelimit()) {
3313 printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n",
3314 task_pid_nr(p), p->comm,
3315 cpumask_pr_args(override_mask));
3316 }
3317
3318 WARN_ON(set_cpus_allowed_ptr(p, override_mask));
3319out_free_mask:
3320 cpus_read_unlock();
3321 free_cpumask_var(new_mask);
3322}
3323
3324static int
3325__sched_setaffinity(struct task_struct *p, struct affinity_context *ctx);
3326
3327/*
3328 * Restore the affinity of a task @p which was previously restricted by a
3329 * call to force_compatible_cpus_allowed_ptr().
3330 *
3331 * It is the caller's responsibility to serialise this with any calls to
3332 * force_compatible_cpus_allowed_ptr(@p).
3333 */
3334void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
3335{
3336 struct affinity_context ac = {
3337 .new_mask = task_user_cpus(p),
3338 .flags = 0,
3339 };
3340 int ret;
3341
3342 /*
3343 * Try to restore the old affinity mask with __sched_setaffinity().
3344 * Cpuset masking will be done there too.
3345 */
3346 ret = __sched_setaffinity(p, &ac);
3347 WARN_ON_ONCE(ret);
3348}
3349
3350void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
3351{
3352#ifdef CONFIG_SCHED_DEBUG
3353 unsigned int state = READ_ONCE(p->__state);
3354
3355 /*
3356 * We should never call set_task_cpu() on a blocked task,
3357 * ttwu() will sort out the placement.
3358 */
3359 WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq);
3360
3361 /*
3362 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
3363 * because schedstat_wait_{start,end} rebase migrating task's wait_start
3364 * time relying on p->on_rq.
3365 */
3366 WARN_ON_ONCE(state == TASK_RUNNING &&
3367 p->sched_class == &fair_sched_class &&
3368 (p->on_rq && !task_on_rq_migrating(p)));
3369
3370#ifdef CONFIG_LOCKDEP
3371 /*
3372 * The caller should hold either p->pi_lock or rq->lock, when changing
3373 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
3374 *
3375 * sched_move_task() holds both and thus holding either pins the cgroup,
3376 * see task_group().
3377 *
3378 * Furthermore, all task_rq users should acquire both locks, see
3379 * task_rq_lock().
3380 */
3381 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
3382 lockdep_is_held(__rq_lockp(task_rq(p)))));
3383#endif
3384 /*
3385 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
3386 */
3387 WARN_ON_ONCE(!cpu_online(new_cpu));
3388
3389 WARN_ON_ONCE(is_migration_disabled(p));
3390#endif
3391
3392 trace_sched_migrate_task(p, new_cpu);
3393
3394 if (task_cpu(p) != new_cpu) {
3395 if (p->sched_class->migrate_task_rq)
3396 p->sched_class->migrate_task_rq(p, new_cpu);
3397 p->se.nr_migrations++;
3398 rseq_migrate(p);
3399 sched_mm_cid_migrate_from(p);
3400 perf_event_task_migrate(p);
3401 }
3402
3403 __set_task_cpu(p, new_cpu);
3404}
3405
3406#ifdef CONFIG_NUMA_BALANCING
3407static void __migrate_swap_task(struct task_struct *p, int cpu)
3408{
3409 if (task_on_rq_queued(p)) {
3410 struct rq *src_rq, *dst_rq;
3411 struct rq_flags srf, drf;
3412
3413 src_rq = task_rq(p);
3414 dst_rq = cpu_rq(cpu);
3415
3416 rq_pin_lock(src_rq, &srf);
3417 rq_pin_lock(dst_rq, &drf);
3418
3419 deactivate_task(src_rq, p, 0);
3420 set_task_cpu(p, cpu);
3421 activate_task(dst_rq, p, 0);
3422 wakeup_preempt(dst_rq, p, 0);
3423
3424 rq_unpin_lock(dst_rq, &drf);
3425 rq_unpin_lock(src_rq, &srf);
3426
3427 } else {
3428 /*
3429 * Task isn't running anymore; make it appear like we migrated
3430 * it before it went to sleep. This means on wakeup we make the
3431 * previous CPU our target instead of where it really is.
3432 */
3433 p->wake_cpu = cpu;
3434 }
3435}
3436
3437struct migration_swap_arg {
3438 struct task_struct *src_task, *dst_task;
3439 int src_cpu, dst_cpu;
3440};
3441
3442static int migrate_swap_stop(void *data)
3443{
3444 struct migration_swap_arg *arg = data;
3445 struct rq *src_rq, *dst_rq;
3446
3447 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
3448 return -EAGAIN;
3449
3450 src_rq = cpu_rq(arg->src_cpu);
3451 dst_rq = cpu_rq(arg->dst_cpu);
3452
3453 guard(double_raw_spinlock)(&arg->src_task->pi_lock, &arg->dst_task->pi_lock);
3454 guard(double_rq_lock)(src_rq, dst_rq);
3455
3456 if (task_cpu(arg->dst_task) != arg->dst_cpu)
3457 return -EAGAIN;
3458
3459 if (task_cpu(arg->src_task) != arg->src_cpu)
3460 return -EAGAIN;
3461
3462 if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
3463 return -EAGAIN;
3464
3465 if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
3466 return -EAGAIN;
3467
3468 __migrate_swap_task(arg->src_task, arg->dst_cpu);
3469 __migrate_swap_task(arg->dst_task, arg->src_cpu);
3470
3471 return 0;
3472}
3473
3474/*
3475 * Cross migrate two tasks
3476 */
3477int migrate_swap(struct task_struct *cur, struct task_struct *p,
3478 int target_cpu, int curr_cpu)
3479{
3480 struct migration_swap_arg arg;
3481 int ret = -EINVAL;
3482
3483 arg = (struct migration_swap_arg){
3484 .src_task = cur,
3485 .src_cpu = curr_cpu,
3486 .dst_task = p,
3487 .dst_cpu = target_cpu,
3488 };
3489
3490 if (arg.src_cpu == arg.dst_cpu)
3491 goto out;
3492
3493 /*
3494 * These three tests are all lockless; this is OK since all of them
3495 * will be re-checked with proper locks held further down the line.
3496 */
3497 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
3498 goto out;
3499
3500 if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
3501 goto out;
3502
3503 if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
3504 goto out;
3505
3506 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
3507 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
3508
3509out:
3510 return ret;
3511}
3512#endif /* CONFIG_NUMA_BALANCING */
3513
3514/***
3515 * kick_process - kick a running thread to enter/exit the kernel
3516 * @p: the to-be-kicked thread
3517 *
3518 * Cause a process which is running on another CPU to enter
3519 * kernel-mode, without any delay. (to get signals handled.)
3520 *
3521 * NOTE: this function doesn't have to take the runqueue lock,
3522 * because all it wants to ensure is that the remote task enters
3523 * the kernel. If the IPI races and the task has been migrated
3524 * to another CPU then no harm is done and the purpose has been
3525 * achieved as well.
3526 */
3527void kick_process(struct task_struct *p)
3528{
3529 guard(preempt)();
3530 int cpu = task_cpu(p);
3531
3532 if ((cpu != smp_processor_id()) && task_curr(p))
3533 smp_send_reschedule(cpu);
3534}
3535EXPORT_SYMBOL_GPL(kick_process);
3536
3537/*
3538 * ->cpus_ptr is protected by both rq->lock and p->pi_lock
3539 *
3540 * A few notes on cpu_active vs cpu_online:
3541 *
3542 * - cpu_active must be a subset of cpu_online
3543 *
3544 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
3545 * see __set_cpus_allowed_ptr(). At this point the newly online
3546 * CPU isn't yet part of the sched domains, and balancing will not
3547 * see it.
3548 *
3549 * - on CPU-down we clear cpu_active() to mask the sched domains and
3550 * avoid the load balancer to place new tasks on the to be removed
3551 * CPU. Existing tasks will remain running there and will be taken
3552 * off.
3553 *
3554 * This means that fallback selection must not select !active CPUs.
3555 * And can assume that any active CPU must be online. Conversely
3556 * select_task_rq() below may allow selection of !active CPUs in order
3557 * to satisfy the above rules.
3558 */
3559static int select_fallback_rq(int cpu, struct task_struct *p)
3560{
3561 int nid = cpu_to_node(cpu);
3562 const struct cpumask *nodemask = NULL;
3563 enum { cpuset, possible, fail } state = cpuset;
3564 int dest_cpu;
3565
3566 /*
3567 * If the node that the CPU is on has been offlined, cpu_to_node()
3568 * will return -1. There is no CPU on the node, and we should
3569 * select the CPU on the other node.
3570 */
3571 if (nid != -1) {
3572 nodemask = cpumask_of_node(nid);
3573
3574 /* Look for allowed, online CPU in same node. */
3575 for_each_cpu(dest_cpu, nodemask) {
3576 if (is_cpu_allowed(p, dest_cpu))
3577 return dest_cpu;
3578 }
3579 }
3580
3581 for (;;) {
3582 /* Any allowed, online CPU? */
3583 for_each_cpu(dest_cpu, p->cpus_ptr) {
3584 if (!is_cpu_allowed(p, dest_cpu))
3585 continue;
3586
3587 goto out;
3588 }
3589
3590 /* No more Mr. Nice Guy. */
3591 switch (state) {
3592 case cpuset:
3593 if (cpuset_cpus_allowed_fallback(p)) {
3594 state = possible;
3595 break;
3596 }
3597 fallthrough;
3598 case possible:
3599 /*
3600 * XXX When called from select_task_rq() we only
3601 * hold p->pi_lock and again violate locking order.
3602 *
3603 * More yuck to audit.
3604 */
3605 do_set_cpus_allowed(p, task_cpu_possible_mask(p));
3606 state = fail;
3607 break;
3608 case fail:
3609 BUG();
3610 break;
3611 }
3612 }
3613
3614out:
3615 if (state != cpuset) {
3616 /*
3617 * Don't tell them about moving exiting tasks or
3618 * kernel threads (both mm NULL), since they never
3619 * leave kernel.
3620 */
3621 if (p->mm && printk_ratelimit()) {
3622 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
3623 task_pid_nr(p), p->comm, cpu);
3624 }
3625 }
3626
3627 return dest_cpu;
3628}
3629
3630/*
3631 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
3632 */
3633static inline
3634int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
3635{
3636 lockdep_assert_held(&p->pi_lock);
3637
3638 if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p))
3639 cpu = p->sched_class->select_task_rq(p, cpu, wake_flags);
3640 else
3641 cpu = cpumask_any(p->cpus_ptr);
3642
3643 /*
3644 * In order not to call set_task_cpu() on a blocking task we need
3645 * to rely on ttwu() to place the task on a valid ->cpus_ptr
3646 * CPU.
3647 *
3648 * Since this is common to all placement strategies, this lives here.
3649 *
3650 * [ this allows ->select_task() to simply return task_cpu(p) and
3651 * not worry about this generic constraint ]
3652 */
3653 if (unlikely(!is_cpu_allowed(p, cpu)))
3654 cpu = select_fallback_rq(task_cpu(p), p);
3655
3656 return cpu;
3657}
3658
3659void sched_set_stop_task(int cpu, struct task_struct *stop)
3660{
3661 static struct lock_class_key stop_pi_lock;
3662 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
3663 struct task_struct *old_stop = cpu_rq(cpu)->stop;
3664
3665 if (stop) {
3666 /*
3667 * Make it appear like a SCHED_FIFO task, its something
3668 * userspace knows about and won't get confused about.
3669 *
3670 * Also, it will make PI more or less work without too
3671 * much confusion -- but then, stop work should not
3672 * rely on PI working anyway.
3673 */
3674 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
3675
3676 stop->sched_class = &stop_sched_class;
3677
3678 /*
3679 * The PI code calls rt_mutex_setprio() with ->pi_lock held to
3680 * adjust the effective priority of a task. As a result,
3681 * rt_mutex_setprio() can trigger (RT) balancing operations,
3682 * which can then trigger wakeups of the stop thread to push
3683 * around the current task.
3684 *
3685 * The stop task itself will never be part of the PI-chain, it
3686 * never blocks, therefore that ->pi_lock recursion is safe.
3687 * Tell lockdep about this by placing the stop->pi_lock in its
3688 * own class.
3689 */
3690 lockdep_set_class(&stop->pi_lock, &stop_pi_lock);
3691 }
3692
3693 cpu_rq(cpu)->stop = stop;
3694
3695 if (old_stop) {
3696 /*
3697 * Reset it back to a normal scheduling class so that
3698 * it can die in pieces.
3699 */
3700 old_stop->sched_class = &rt_sched_class;
3701 }
3702}
3703
3704#else /* CONFIG_SMP */
3705
3706static inline int __set_cpus_allowed_ptr(struct task_struct *p,
3707 struct affinity_context *ctx)
3708{
3709 return set_cpus_allowed_ptr(p, ctx->new_mask);
3710}
3711
3712static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { }
3713
3714static inline bool rq_has_pinned_tasks(struct rq *rq)
3715{
3716 return false;
3717}
3718
3719static inline cpumask_t *alloc_user_cpus_ptr(int node)
3720{
3721 return NULL;
3722}
3723
3724#endif /* !CONFIG_SMP */
3725
3726static void
3727ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
3728{
3729 struct rq *rq;
3730
3731 if (!schedstat_enabled())
3732 return;
3733
3734 rq = this_rq();
3735
3736#ifdef CONFIG_SMP
3737 if (cpu == rq->cpu) {
3738 __schedstat_inc(rq->ttwu_local);
3739 __schedstat_inc(p->stats.nr_wakeups_local);
3740 } else {
3741 struct sched_domain *sd;
3742
3743 __schedstat_inc(p->stats.nr_wakeups_remote);
3744
3745 guard(rcu)();
3746 for_each_domain(rq->cpu, sd) {
3747 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
3748 __schedstat_inc(sd->ttwu_wake_remote);
3749 break;
3750 }
3751 }
3752 }
3753
3754 if (wake_flags & WF_MIGRATED)
3755 __schedstat_inc(p->stats.nr_wakeups_migrate);
3756#endif /* CONFIG_SMP */
3757
3758 __schedstat_inc(rq->ttwu_count);
3759 __schedstat_inc(p->stats.nr_wakeups);
3760
3761 if (wake_flags & WF_SYNC)
3762 __schedstat_inc(p->stats.nr_wakeups_sync);
3763}
3764
3765/*
3766 * Mark the task runnable.
3767 */
3768static inline void ttwu_do_wakeup(struct task_struct *p)
3769{
3770 WRITE_ONCE(p->__state, TASK_RUNNING);
3771 trace_sched_wakeup(p);
3772}
3773
3774static void
3775ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
3776 struct rq_flags *rf)
3777{
3778 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
3779
3780 lockdep_assert_rq_held(rq);
3781
3782 if (p->sched_contributes_to_load)
3783 rq->nr_uninterruptible--;
3784
3785#ifdef CONFIG_SMP
3786 if (wake_flags & WF_MIGRATED)
3787 en_flags |= ENQUEUE_MIGRATED;
3788 else
3789#endif
3790 if (p->in_iowait) {
3791 delayacct_blkio_end(p);
3792 atomic_dec(&task_rq(p)->nr_iowait);
3793 }
3794
3795 activate_task(rq, p, en_flags);
3796 wakeup_preempt(rq, p, wake_flags);
3797
3798 ttwu_do_wakeup(p);
3799
3800#ifdef CONFIG_SMP
3801 if (p->sched_class->task_woken) {
3802 /*
3803 * Our task @p is fully woken up and running; so it's safe to
3804 * drop the rq->lock, hereafter rq is only used for statistics.
3805 */
3806 rq_unpin_lock(rq, rf);
3807 p->sched_class->task_woken(rq, p);
3808 rq_repin_lock(rq, rf);
3809 }
3810
3811 if (rq->idle_stamp) {
3812 u64 delta = rq_clock(rq) - rq->idle_stamp;
3813 u64 max = 2*rq->max_idle_balance_cost;
3814
3815 update_avg(&rq->avg_idle, delta);
3816
3817 if (rq->avg_idle > max)
3818 rq->avg_idle = max;
3819
3820 rq->idle_stamp = 0;
3821 }
3822#endif
3823
3824 p->dl_server = NULL;
3825}
3826
3827/*
3828 * Consider @p being inside a wait loop:
3829 *
3830 * for (;;) {
3831 * set_current_state(TASK_UNINTERRUPTIBLE);
3832 *
3833 * if (CONDITION)
3834 * break;
3835 *
3836 * schedule();
3837 * }
3838 * __set_current_state(TASK_RUNNING);
3839 *
3840 * between set_current_state() and schedule(). In this case @p is still
3841 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
3842 * an atomic manner.
3843 *
3844 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
3845 * then schedule() must still happen and p->state can be changed to
3846 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
3847 * need to do a full wakeup with enqueue.
3848 *
3849 * Returns: %true when the wakeup is done,
3850 * %false otherwise.
3851 */
3852static int ttwu_runnable(struct task_struct *p, int wake_flags)
3853{
3854 struct rq_flags rf;
3855 struct rq *rq;
3856 int ret = 0;
3857
3858 rq = __task_rq_lock(p, &rf);
3859 if (task_on_rq_queued(p)) {
3860 if (!task_on_cpu(rq, p)) {
3861 /*
3862 * When on_rq && !on_cpu the task is preempted, see if
3863 * it should preempt the task that is current now.
3864 */
3865 update_rq_clock(rq);
3866 wakeup_preempt(rq, p, wake_flags);
3867 }
3868 ttwu_do_wakeup(p);
3869 ret = 1;
3870 }
3871 __task_rq_unlock(rq, &rf);
3872
3873 return ret;
3874}
3875
3876#ifdef CONFIG_SMP
3877void sched_ttwu_pending(void *arg)
3878{
3879 struct llist_node *llist = arg;
3880 struct rq *rq = this_rq();
3881 struct task_struct *p, *t;
3882 struct rq_flags rf;
3883
3884 if (!llist)
3885 return;
3886
3887 rq_lock_irqsave(rq, &rf);
3888 update_rq_clock(rq);
3889
3890 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
3891 if (WARN_ON_ONCE(p->on_cpu))
3892 smp_cond_load_acquire(&p->on_cpu, !VAL);
3893
3894 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
3895 set_task_cpu(p, cpu_of(rq));
3896
3897 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
3898 }
3899
3900 /*
3901 * Must be after enqueueing at least once task such that
3902 * idle_cpu() does not observe a false-negative -- if it does,
3903 * it is possible for select_idle_siblings() to stack a number
3904 * of tasks on this CPU during that window.
3905 *
3906 * It is ok to clear ttwu_pending when another task pending.
3907 * We will receive IPI after local irq enabled and then enqueue it.
3908 * Since now nr_running > 0, idle_cpu() will always get correct result.
3909 */
3910 WRITE_ONCE(rq->ttwu_pending, 0);
3911 rq_unlock_irqrestore(rq, &rf);
3912}
3913
3914/*
3915 * Prepare the scene for sending an IPI for a remote smp_call
3916 *
3917 * Returns true if the caller can proceed with sending the IPI.
3918 * Returns false otherwise.
3919 */
3920bool call_function_single_prep_ipi(int cpu)
3921{
3922 if (set_nr_if_polling(cpu_rq(cpu)->idle)) {
3923 trace_sched_wake_idle_without_ipi(cpu);
3924 return false;
3925 }
3926
3927 return true;
3928}
3929
3930/*
3931 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
3932 * necessary. The wakee CPU on receipt of the IPI will queue the task
3933 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
3934 * of the wakeup instead of the waker.
3935 */
3936static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3937{
3938 struct rq *rq = cpu_rq(cpu);
3939
3940 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
3941
3942 WRITE_ONCE(rq->ttwu_pending, 1);
3943 __smp_call_single_queue(cpu, &p->wake_entry.llist);
3944}
3945
3946void wake_up_if_idle(int cpu)
3947{
3948 struct rq *rq = cpu_rq(cpu);
3949
3950 guard(rcu)();
3951 if (is_idle_task(rcu_dereference(rq->curr))) {
3952 guard(rq_lock_irqsave)(rq);
3953 if (is_idle_task(rq->curr))
3954 resched_curr(rq);
3955 }
3956}
3957
3958bool cpus_share_cache(int this_cpu, int that_cpu)
3959{
3960 if (this_cpu == that_cpu)
3961 return true;
3962
3963 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
3964}
3965
3966/*
3967 * Whether CPUs are share cache resources, which means LLC on non-cluster
3968 * machines and LLC tag or L2 on machines with clusters.
3969 */
3970bool cpus_share_resources(int this_cpu, int that_cpu)
3971{
3972 if (this_cpu == that_cpu)
3973 return true;
3974
3975 return per_cpu(sd_share_id, this_cpu) == per_cpu(sd_share_id, that_cpu);
3976}
3977
3978static inline bool ttwu_queue_cond(struct task_struct *p, int cpu)
3979{
3980 /*
3981 * Do not complicate things with the async wake_list while the CPU is
3982 * in hotplug state.
3983 */
3984 if (!cpu_active(cpu))
3985 return false;
3986
3987 /* Ensure the task will still be allowed to run on the CPU. */
3988 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
3989 return false;
3990
3991 /*
3992 * If the CPU does not share cache, then queue the task on the
3993 * remote rqs wakelist to avoid accessing remote data.
3994 */
3995 if (!cpus_share_cache(smp_processor_id(), cpu))
3996 return true;
3997
3998 if (cpu == smp_processor_id())
3999 return false;
4000
4001 /*
4002 * If the wakee cpu is idle, or the task is descheduling and the
4003 * only running task on the CPU, then use the wakelist to offload
4004 * the task activation to the idle (or soon-to-be-idle) CPU as
4005 * the current CPU is likely busy. nr_running is checked to
4006 * avoid unnecessary task stacking.
4007 *
4008 * Note that we can only get here with (wakee) p->on_rq=0,
4009 * p->on_cpu can be whatever, we've done the dequeue, so
4010 * the wakee has been accounted out of ->nr_running.
4011 */
4012 if (!cpu_rq(cpu)->nr_running)
4013 return true;
4014
4015 return false;
4016}
4017
4018static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
4019{
4020 if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(p, cpu)) {
4021 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
4022 __ttwu_queue_wakelist(p, cpu, wake_flags);
4023 return true;
4024 }
4025
4026 return false;
4027}
4028
4029#else /* !CONFIG_SMP */
4030
4031static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
4032{
4033 return false;
4034}
4035
4036#endif /* CONFIG_SMP */
4037
4038static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
4039{
4040 struct rq *rq = cpu_rq(cpu);
4041 struct rq_flags rf;
4042
4043 if (ttwu_queue_wakelist(p, cpu, wake_flags))
4044 return;
4045
4046 rq_lock(rq, &rf);
4047 update_rq_clock(rq);
4048 ttwu_do_activate(rq, p, wake_flags, &rf);
4049 rq_unlock(rq, &rf);
4050}
4051
4052/*
4053 * Invoked from try_to_wake_up() to check whether the task can be woken up.
4054 *
4055 * The caller holds p::pi_lock if p != current or has preemption
4056 * disabled when p == current.
4057 *
4058 * The rules of saved_state:
4059 *
4060 * The related locking code always holds p::pi_lock when updating
4061 * p::saved_state, which means the code is fully serialized in both cases.
4062 *
4063 * For PREEMPT_RT, the lock wait and lock wakeups happen via TASK_RTLOCK_WAIT.
4064 * No other bits set. This allows to distinguish all wakeup scenarios.
4065 *
4066 * For FREEZER, the wakeup happens via TASK_FROZEN. No other bits set. This
4067 * allows us to prevent early wakeup of tasks before they can be run on
4068 * asymmetric ISA architectures (eg ARMv9).
4069 */
4070static __always_inline
4071bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
4072{
4073 int match;
4074
4075 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
4076 WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) &&
4077 state != TASK_RTLOCK_WAIT);
4078 }
4079
4080 *success = !!(match = __task_state_match(p, state));
4081
4082 /*
4083 * Saved state preserves the task state across blocking on
4084 * an RT lock or TASK_FREEZABLE tasks. If the state matches,
4085 * set p::saved_state to TASK_RUNNING, but do not wake the task
4086 * because it waits for a lock wakeup or __thaw_task(). Also
4087 * indicate success because from the regular waker's point of
4088 * view this has succeeded.
4089 *
4090 * After acquiring the lock the task will restore p::__state
4091 * from p::saved_state which ensures that the regular
4092 * wakeup is not lost. The restore will also set
4093 * p::saved_state to TASK_RUNNING so any further tests will
4094 * not result in false positives vs. @success
4095 */
4096 if (match < 0)
4097 p->saved_state = TASK_RUNNING;
4098
4099 return match > 0;
4100}
4101
4102/*
4103 * Notes on Program-Order guarantees on SMP systems.
4104 *
4105 * MIGRATION
4106 *
4107 * The basic program-order guarantee on SMP systems is that when a task [t]
4108 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
4109 * execution on its new CPU [c1].
4110 *
4111 * For migration (of runnable tasks) this is provided by the following means:
4112 *
4113 * A) UNLOCK of the rq(c0)->lock scheduling out task t
4114 * B) migration for t is required to synchronize *both* rq(c0)->lock and
4115 * rq(c1)->lock (if not at the same time, then in that order).
4116 * C) LOCK of the rq(c1)->lock scheduling in task
4117 *
4118 * Release/acquire chaining guarantees that B happens after A and C after B.
4119 * Note: the CPU doing B need not be c0 or c1
4120 *
4121 * Example:
4122 *
4123 * CPU0 CPU1 CPU2
4124 *
4125 * LOCK rq(0)->lock
4126 * sched-out X
4127 * sched-in Y
4128 * UNLOCK rq(0)->lock
4129 *
4130 * LOCK rq(0)->lock // orders against CPU0
4131 * dequeue X
4132 * UNLOCK rq(0)->lock
4133 *
4134 * LOCK rq(1)->lock
4135 * enqueue X
4136 * UNLOCK rq(1)->lock
4137 *
4138 * LOCK rq(1)->lock // orders against CPU2
4139 * sched-out Z
4140 * sched-in X
4141 * UNLOCK rq(1)->lock
4142 *
4143 *
4144 * BLOCKING -- aka. SLEEP + WAKEUP
4145 *
4146 * For blocking we (obviously) need to provide the same guarantee as for
4147 * migration. However the means are completely different as there is no lock
4148 * chain to provide order. Instead we do:
4149 *
4150 * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
4151 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
4152 *
4153 * Example:
4154 *
4155 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
4156 *
4157 * LOCK rq(0)->lock LOCK X->pi_lock
4158 * dequeue X
4159 * sched-out X
4160 * smp_store_release(X->on_cpu, 0);
4161 *
4162 * smp_cond_load_acquire(&X->on_cpu, !VAL);
4163 * X->state = WAKING
4164 * set_task_cpu(X,2)
4165 *
4166 * LOCK rq(2)->lock
4167 * enqueue X
4168 * X->state = RUNNING
4169 * UNLOCK rq(2)->lock
4170 *
4171 * LOCK rq(2)->lock // orders against CPU1
4172 * sched-out Z
4173 * sched-in X
4174 * UNLOCK rq(2)->lock
4175 *
4176 * UNLOCK X->pi_lock
4177 * UNLOCK rq(0)->lock
4178 *
4179 *
4180 * However, for wakeups there is a second guarantee we must provide, namely we
4181 * must ensure that CONDITION=1 done by the caller can not be reordered with
4182 * accesses to the task state; see try_to_wake_up() and set_current_state().
4183 */
4184
4185/**
4186 * try_to_wake_up - wake up a thread
4187 * @p: the thread to be awakened
4188 * @state: the mask of task states that can be woken
4189 * @wake_flags: wake modifier flags (WF_*)
4190 *
4191 * Conceptually does:
4192 *
4193 * If (@state & @p->state) @p->state = TASK_RUNNING.
4194 *
4195 * If the task was not queued/runnable, also place it back on a runqueue.
4196 *
4197 * This function is atomic against schedule() which would dequeue the task.
4198 *
4199 * It issues a full memory barrier before accessing @p->state, see the comment
4200 * with set_current_state().
4201 *
4202 * Uses p->pi_lock to serialize against concurrent wake-ups.
4203 *
4204 * Relies on p->pi_lock stabilizing:
4205 * - p->sched_class
4206 * - p->cpus_ptr
4207 * - p->sched_task_group
4208 * in order to do migration, see its use of select_task_rq()/set_task_cpu().
4209 *
4210 * Tries really hard to only take one task_rq(p)->lock for performance.
4211 * Takes rq->lock in:
4212 * - ttwu_runnable() -- old rq, unavoidable, see comment there;
4213 * - ttwu_queue() -- new rq, for enqueue of the task;
4214 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
4215 *
4216 * As a consequence we race really badly with just about everything. See the
4217 * many memory barriers and their comments for details.
4218 *
4219 * Return: %true if @p->state changes (an actual wakeup was done),
4220 * %false otherwise.
4221 */
4222int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
4223{
4224 guard(preempt)();
4225 int cpu, success = 0;
4226
4227 if (p == current) {
4228 /*
4229 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
4230 * == smp_processor_id()'. Together this means we can special
4231 * case the whole 'p->on_rq && ttwu_runnable()' case below
4232 * without taking any locks.
4233 *
4234 * In particular:
4235 * - we rely on Program-Order guarantees for all the ordering,
4236 * - we're serialized against set_special_state() by virtue of
4237 * it disabling IRQs (this allows not taking ->pi_lock).
4238 */
4239 if (!ttwu_state_match(p, state, &success))
4240 goto out;
4241
4242 trace_sched_waking(p);
4243 ttwu_do_wakeup(p);
4244 goto out;
4245 }
4246
4247 /*
4248 * If we are going to wake up a thread waiting for CONDITION we
4249 * need to ensure that CONDITION=1 done by the caller can not be
4250 * reordered with p->state check below. This pairs with smp_store_mb()
4251 * in set_current_state() that the waiting thread does.
4252 */
4253 scoped_guard (raw_spinlock_irqsave, &p->pi_lock) {
4254 smp_mb__after_spinlock();
4255 if (!ttwu_state_match(p, state, &success))
4256 break;
4257
4258 trace_sched_waking(p);
4259
4260 /*
4261 * Ensure we load p->on_rq _after_ p->state, otherwise it would
4262 * be possible to, falsely, observe p->on_rq == 0 and get stuck
4263 * in smp_cond_load_acquire() below.
4264 *
4265 * sched_ttwu_pending() try_to_wake_up()
4266 * STORE p->on_rq = 1 LOAD p->state
4267 * UNLOCK rq->lock
4268 *
4269 * __schedule() (switch to task 'p')
4270 * LOCK rq->lock smp_rmb();
4271 * smp_mb__after_spinlock();
4272 * UNLOCK rq->lock
4273 *
4274 * [task p]
4275 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
4276 *
4277 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4278 * __schedule(). See the comment for smp_mb__after_spinlock().
4279 *
4280 * A similar smp_rmb() lives in __task_needs_rq_lock().
4281 */
4282 smp_rmb();
4283 if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
4284 break;
4285
4286#ifdef CONFIG_SMP
4287 /*
4288 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
4289 * possible to, falsely, observe p->on_cpu == 0.
4290 *
4291 * One must be running (->on_cpu == 1) in order to remove oneself
4292 * from the runqueue.
4293 *
4294 * __schedule() (switch to task 'p') try_to_wake_up()
4295 * STORE p->on_cpu = 1 LOAD p->on_rq
4296 * UNLOCK rq->lock
4297 *
4298 * __schedule() (put 'p' to sleep)
4299 * LOCK rq->lock smp_rmb();
4300 * smp_mb__after_spinlock();
4301 * STORE p->on_rq = 0 LOAD p->on_cpu
4302 *
4303 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
4304 * __schedule(). See the comment for smp_mb__after_spinlock().
4305 *
4306 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
4307 * schedule()'s deactivate_task() has 'happened' and p will no longer
4308 * care about it's own p->state. See the comment in __schedule().
4309 */
4310 smp_acquire__after_ctrl_dep();
4311
4312 /*
4313 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
4314 * == 0), which means we need to do an enqueue, change p->state to
4315 * TASK_WAKING such that we can unlock p->pi_lock before doing the
4316 * enqueue, such as ttwu_queue_wakelist().
4317 */
4318 WRITE_ONCE(p->__state, TASK_WAKING);
4319
4320 /*
4321 * If the owning (remote) CPU is still in the middle of schedule() with
4322 * this task as prev, considering queueing p on the remote CPUs wake_list
4323 * which potentially sends an IPI instead of spinning on p->on_cpu to
4324 * let the waker make forward progress. This is safe because IRQs are
4325 * disabled and the IPI will deliver after on_cpu is cleared.
4326 *
4327 * Ensure we load task_cpu(p) after p->on_cpu:
4328 *
4329 * set_task_cpu(p, cpu);
4330 * STORE p->cpu = @cpu
4331 * __schedule() (switch to task 'p')
4332 * LOCK rq->lock
4333 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
4334 * STORE p->on_cpu = 1 LOAD p->cpu
4335 *
4336 * to ensure we observe the correct CPU on which the task is currently
4337 * scheduling.
4338 */
4339 if (smp_load_acquire(&p->on_cpu) &&
4340 ttwu_queue_wakelist(p, task_cpu(p), wake_flags))
4341 break;
4342
4343 /*
4344 * If the owning (remote) CPU is still in the middle of schedule() with
4345 * this task as prev, wait until it's done referencing the task.
4346 *
4347 * Pairs with the smp_store_release() in finish_task().
4348 *
4349 * This ensures that tasks getting woken will be fully ordered against
4350 * their previous state and preserve Program Order.
4351 */
4352 smp_cond_load_acquire(&p->on_cpu, !VAL);
4353
4354 cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU);
4355 if (task_cpu(p) != cpu) {
4356 if (p->in_iowait) {
4357 delayacct_blkio_end(p);
4358 atomic_dec(&task_rq(p)->nr_iowait);
4359 }
4360
4361 wake_flags |= WF_MIGRATED;
4362 psi_ttwu_dequeue(p);
4363 set_task_cpu(p, cpu);
4364 }
4365#else
4366 cpu = task_cpu(p);
4367#endif /* CONFIG_SMP */
4368
4369 ttwu_queue(p, cpu, wake_flags);
4370 }
4371out:
4372 if (success)
4373 ttwu_stat(p, task_cpu(p), wake_flags);
4374
4375 return success;
4376}
4377
4378static bool __task_needs_rq_lock(struct task_struct *p)
4379{
4380 unsigned int state = READ_ONCE(p->__state);
4381
4382 /*
4383 * Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when
4384 * the task is blocked. Make sure to check @state since ttwu() can drop
4385 * locks at the end, see ttwu_queue_wakelist().
4386 */
4387 if (state == TASK_RUNNING || state == TASK_WAKING)
4388 return true;
4389
4390 /*
4391 * Ensure we load p->on_rq after p->__state, otherwise it would be
4392 * possible to, falsely, observe p->on_rq == 0.
4393 *
4394 * See try_to_wake_up() for a longer comment.
4395 */
4396 smp_rmb();
4397 if (p->on_rq)
4398 return true;
4399
4400#ifdef CONFIG_SMP
4401 /*
4402 * Ensure the task has finished __schedule() and will not be referenced
4403 * anymore. Again, see try_to_wake_up() for a longer comment.
4404 */
4405 smp_rmb();
4406 smp_cond_load_acquire(&p->on_cpu, !VAL);
4407#endif
4408
4409 return false;
4410}
4411
4412/**
4413 * task_call_func - Invoke a function on task in fixed state
4414 * @p: Process for which the function is to be invoked, can be @current.
4415 * @func: Function to invoke.
4416 * @arg: Argument to function.
4417 *
4418 * Fix the task in it's current state by avoiding wakeups and or rq operations
4419 * and call @func(@arg) on it. This function can use ->on_rq and task_curr()
4420 * to work out what the state is, if required. Given that @func can be invoked
4421 * with a runqueue lock held, it had better be quite lightweight.
4422 *
4423 * Returns:
4424 * Whatever @func returns
4425 */
4426int task_call_func(struct task_struct *p, task_call_f func, void *arg)
4427{
4428 struct rq *rq = NULL;
4429 struct rq_flags rf;
4430 int ret;
4431
4432 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4433
4434 if (__task_needs_rq_lock(p))
4435 rq = __task_rq_lock(p, &rf);
4436
4437 /*
4438 * At this point the task is pinned; either:
4439 * - blocked and we're holding off wakeups (pi->lock)
4440 * - woken, and we're holding off enqueue (rq->lock)
4441 * - queued, and we're holding off schedule (rq->lock)
4442 * - running, and we're holding off de-schedule (rq->lock)
4443 *
4444 * The called function (@func) can use: task_curr(), p->on_rq and
4445 * p->__state to differentiate between these states.
4446 */
4447 ret = func(p, arg);
4448
4449 if (rq)
4450 rq_unlock(rq, &rf);
4451
4452 raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
4453 return ret;
4454}
4455
4456/**
4457 * cpu_curr_snapshot - Return a snapshot of the currently running task
4458 * @cpu: The CPU on which to snapshot the task.
4459 *
4460 * Returns the task_struct pointer of the task "currently" running on
4461 * the specified CPU. If the same task is running on that CPU throughout,
4462 * the return value will be a pointer to that task's task_struct structure.
4463 * If the CPU did any context switches even vaguely concurrently with the
4464 * execution of this function, the return value will be a pointer to the
4465 * task_struct structure of a randomly chosen task that was running on
4466 * that CPU somewhere around the time that this function was executing.
4467 *
4468 * If the specified CPU was offline, the return value is whatever it
4469 * is, perhaps a pointer to the task_struct structure of that CPU's idle
4470 * task, but there is no guarantee. Callers wishing a useful return
4471 * value must take some action to ensure that the specified CPU remains
4472 * online throughout.
4473 *
4474 * This function executes full memory barriers before and after fetching
4475 * the pointer, which permits the caller to confine this function's fetch
4476 * with respect to the caller's accesses to other shared variables.
4477 */
4478struct task_struct *cpu_curr_snapshot(int cpu)
4479{
4480 struct task_struct *t;
4481
4482 smp_mb(); /* Pairing determined by caller's synchronization design. */
4483 t = rcu_dereference(cpu_curr(cpu));
4484 smp_mb(); /* Pairing determined by caller's synchronization design. */
4485 return t;
4486}
4487
4488/**
4489 * wake_up_process - Wake up a specific process
4490 * @p: The process to be woken up.
4491 *
4492 * Attempt to wake up the nominated process and move it to the set of runnable
4493 * processes.
4494 *
4495 * Return: 1 if the process was woken up, 0 if it was already running.
4496 *
4497 * This function executes a full memory barrier before accessing the task state.
4498 */
4499int wake_up_process(struct task_struct *p)
4500{
4501 return try_to_wake_up(p, TASK_NORMAL, 0);
4502}
4503EXPORT_SYMBOL(wake_up_process);
4504
4505int wake_up_state(struct task_struct *p, unsigned int state)
4506{
4507 return try_to_wake_up(p, state, 0);
4508}
4509
4510/*
4511 * Perform scheduler related setup for a newly forked process p.
4512 * p is forked by current.
4513 *
4514 * __sched_fork() is basic setup used by init_idle() too:
4515 */
4516static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
4517{
4518 p->on_rq = 0;
4519
4520 p->se.on_rq = 0;
4521 p->se.exec_start = 0;
4522 p->se.sum_exec_runtime = 0;
4523 p->se.prev_sum_exec_runtime = 0;
4524 p->se.nr_migrations = 0;
4525 p->se.vruntime = 0;
4526 p->se.vlag = 0;
4527 p->se.slice = sysctl_sched_base_slice;
4528 INIT_LIST_HEAD(&p->se.group_node);
4529
4530#ifdef CONFIG_FAIR_GROUP_SCHED
4531 p->se.cfs_rq = NULL;
4532#endif
4533
4534#ifdef CONFIG_SCHEDSTATS
4535 /* Even if schedstat is disabled, there should not be garbage */
4536 memset(&p->stats, 0, sizeof(p->stats));
4537#endif
4538
4539 init_dl_entity(&p->dl);
4540
4541 INIT_LIST_HEAD(&p->rt.run_list);
4542 p->rt.timeout = 0;
4543 p->rt.time_slice = sched_rr_timeslice;
4544 p->rt.on_rq = 0;
4545 p->rt.on_list = 0;
4546
4547#ifdef CONFIG_PREEMPT_NOTIFIERS
4548 INIT_HLIST_HEAD(&p->preempt_notifiers);
4549#endif
4550
4551#ifdef CONFIG_COMPACTION
4552 p->capture_control = NULL;
4553#endif
4554 init_numa_balancing(clone_flags, p);
4555#ifdef CONFIG_SMP
4556 p->wake_entry.u_flags = CSD_TYPE_TTWU;
4557 p->migration_pending = NULL;
4558#endif
4559 init_sched_mm_cid(p);
4560}
4561
4562DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
4563
4564#ifdef CONFIG_NUMA_BALANCING
4565
4566int sysctl_numa_balancing_mode;
4567
4568static void __set_numabalancing_state(bool enabled)
4569{
4570 if (enabled)
4571 static_branch_enable(&sched_numa_balancing);
4572 else
4573 static_branch_disable(&sched_numa_balancing);
4574}
4575
4576void set_numabalancing_state(bool enabled)
4577{
4578 if (enabled)
4579 sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL;
4580 else
4581 sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED;
4582 __set_numabalancing_state(enabled);
4583}
4584
4585#ifdef CONFIG_PROC_SYSCTL
4586static void reset_memory_tiering(void)
4587{
4588 struct pglist_data *pgdat;
4589
4590 for_each_online_pgdat(pgdat) {
4591 pgdat->nbp_threshold = 0;
4592 pgdat->nbp_th_nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE);
4593 pgdat->nbp_th_start = jiffies_to_msecs(jiffies);
4594 }
4595}
4596
4597static int sysctl_numa_balancing(struct ctl_table *table, int write,
4598 void *buffer, size_t *lenp, loff_t *ppos)
4599{
4600 struct ctl_table t;
4601 int err;
4602 int state = sysctl_numa_balancing_mode;
4603
4604 if (write && !capable(CAP_SYS_ADMIN))
4605 return -EPERM;
4606
4607 t = *table;
4608 t.data = &state;
4609 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4610 if (err < 0)
4611 return err;
4612 if (write) {
4613 if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) &&
4614 (state & NUMA_BALANCING_MEMORY_TIERING))
4615 reset_memory_tiering();
4616 sysctl_numa_balancing_mode = state;
4617 __set_numabalancing_state(state);
4618 }
4619 return err;
4620}
4621#endif
4622#endif
4623
4624#ifdef CONFIG_SCHEDSTATS
4625
4626DEFINE_STATIC_KEY_FALSE(sched_schedstats);
4627
4628static void set_schedstats(bool enabled)
4629{
4630 if (enabled)
4631 static_branch_enable(&sched_schedstats);
4632 else
4633 static_branch_disable(&sched_schedstats);
4634}
4635
4636void force_schedstat_enabled(void)
4637{
4638 if (!schedstat_enabled()) {
4639 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
4640 static_branch_enable(&sched_schedstats);
4641 }
4642}
4643
4644static int __init setup_schedstats(char *str)
4645{
4646 int ret = 0;
4647 if (!str)
4648 goto out;
4649
4650 if (!strcmp(str, "enable")) {
4651 set_schedstats(true);
4652 ret = 1;
4653 } else if (!strcmp(str, "disable")) {
4654 set_schedstats(false);
4655 ret = 1;
4656 }
4657out:
4658 if (!ret)
4659 pr_warn("Unable to parse schedstats=\n");
4660
4661 return ret;
4662}
4663__setup("schedstats=", setup_schedstats);
4664
4665#ifdef CONFIG_PROC_SYSCTL
4666static int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
4667 size_t *lenp, loff_t *ppos)
4668{
4669 struct ctl_table t;
4670 int err;
4671 int state = static_branch_likely(&sched_schedstats);
4672
4673 if (write && !capable(CAP_SYS_ADMIN))
4674 return -EPERM;
4675
4676 t = *table;
4677 t.data = &state;
4678 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4679 if (err < 0)
4680 return err;
4681 if (write)
4682 set_schedstats(state);
4683 return err;
4684}
4685#endif /* CONFIG_PROC_SYSCTL */
4686#endif /* CONFIG_SCHEDSTATS */
4687
4688#ifdef CONFIG_SYSCTL
4689static struct ctl_table sched_core_sysctls[] = {
4690#ifdef CONFIG_SCHEDSTATS
4691 {
4692 .procname = "sched_schedstats",
4693 .data = NULL,
4694 .maxlen = sizeof(unsigned int),
4695 .mode = 0644,
4696 .proc_handler = sysctl_schedstats,
4697 .extra1 = SYSCTL_ZERO,
4698 .extra2 = SYSCTL_ONE,
4699 },
4700#endif /* CONFIG_SCHEDSTATS */
4701#ifdef CONFIG_UCLAMP_TASK
4702 {
4703 .procname = "sched_util_clamp_min",
4704 .data = &sysctl_sched_uclamp_util_min,
4705 .maxlen = sizeof(unsigned int),
4706 .mode = 0644,
4707 .proc_handler = sysctl_sched_uclamp_handler,
4708 },
4709 {
4710 .procname = "sched_util_clamp_max",
4711 .data = &sysctl_sched_uclamp_util_max,
4712 .maxlen = sizeof(unsigned int),
4713 .mode = 0644,
4714 .proc_handler = sysctl_sched_uclamp_handler,
4715 },
4716 {
4717 .procname = "sched_util_clamp_min_rt_default",
4718 .data = &sysctl_sched_uclamp_util_min_rt_default,
4719 .maxlen = sizeof(unsigned int),
4720 .mode = 0644,
4721 .proc_handler = sysctl_sched_uclamp_handler,
4722 },
4723#endif /* CONFIG_UCLAMP_TASK */
4724#ifdef CONFIG_NUMA_BALANCING
4725 {
4726 .procname = "numa_balancing",
4727 .data = NULL, /* filled in by handler */
4728 .maxlen = sizeof(unsigned int),
4729 .mode = 0644,
4730 .proc_handler = sysctl_numa_balancing,
4731 .extra1 = SYSCTL_ZERO,
4732 .extra2 = SYSCTL_FOUR,
4733 },
4734#endif /* CONFIG_NUMA_BALANCING */
4735 {}
4736};
4737static int __init sched_core_sysctl_init(void)
4738{
4739 register_sysctl_init("kernel", sched_core_sysctls);
4740 return 0;
4741}
4742late_initcall(sched_core_sysctl_init);
4743#endif /* CONFIG_SYSCTL */
4744
4745/*
4746 * fork()/clone()-time setup:
4747 */
4748int sched_fork(unsigned long clone_flags, struct task_struct *p)
4749{
4750 __sched_fork(clone_flags, p);
4751 /*
4752 * We mark the process as NEW here. This guarantees that
4753 * nobody will actually run it, and a signal or other external
4754 * event cannot wake it up and insert it on the runqueue either.
4755 */
4756 p->__state = TASK_NEW;
4757
4758 /*
4759 * Make sure we do not leak PI boosting priority to the child.
4760 */
4761 p->prio = current->normal_prio;
4762
4763 uclamp_fork(p);
4764
4765 /*
4766 * Revert to default priority/policy on fork if requested.
4767 */
4768 if (unlikely(p->sched_reset_on_fork)) {
4769 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
4770 p->policy = SCHED_NORMAL;
4771 p->static_prio = NICE_TO_PRIO(0);
4772 p->rt_priority = 0;
4773 } else if (PRIO_TO_NICE(p->static_prio) < 0)
4774 p->static_prio = NICE_TO_PRIO(0);
4775
4776 p->prio = p->normal_prio = p->static_prio;
4777 set_load_weight(p, false);
4778
4779 /*
4780 * We don't need the reset flag anymore after the fork. It has
4781 * fulfilled its duty:
4782 */
4783 p->sched_reset_on_fork = 0;
4784 }
4785
4786 if (dl_prio(p->prio))
4787 return -EAGAIN;
4788 else if (rt_prio(p->prio))
4789 p->sched_class = &rt_sched_class;
4790 else
4791 p->sched_class = &fair_sched_class;
4792
4793 init_entity_runnable_average(&p->se);
4794
4795
4796#ifdef CONFIG_SCHED_INFO
4797 if (likely(sched_info_on()))
4798 memset(&p->sched_info, 0, sizeof(p->sched_info));
4799#endif
4800#if defined(CONFIG_SMP)
4801 p->on_cpu = 0;
4802#endif
4803 init_task_preempt_count(p);
4804#ifdef CONFIG_SMP
4805 plist_node_init(&p->pushable_tasks, MAX_PRIO);
4806 RB_CLEAR_NODE(&p->pushable_dl_tasks);
4807#endif
4808 return 0;
4809}
4810
4811void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs)
4812{
4813 unsigned long flags;
4814
4815 /*
4816 * Because we're not yet on the pid-hash, p->pi_lock isn't strictly
4817 * required yet, but lockdep gets upset if rules are violated.
4818 */
4819 raw_spin_lock_irqsave(&p->pi_lock, flags);
4820#ifdef CONFIG_CGROUP_SCHED
4821 if (1) {
4822 struct task_group *tg;
4823 tg = container_of(kargs->cset->subsys[cpu_cgrp_id],
4824 struct task_group, css);
4825 tg = autogroup_task_group(p, tg);
4826 p->sched_task_group = tg;
4827 }
4828#endif
4829 rseq_migrate(p);
4830 /*
4831 * We're setting the CPU for the first time, we don't migrate,
4832 * so use __set_task_cpu().
4833 */
4834 __set_task_cpu(p, smp_processor_id());
4835 if (p->sched_class->task_fork)
4836 p->sched_class->task_fork(p);
4837 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4838}
4839
4840void sched_post_fork(struct task_struct *p)
4841{
4842 uclamp_post_fork(p);
4843}
4844
4845unsigned long to_ratio(u64 period, u64 runtime)
4846{
4847 if (runtime == RUNTIME_INF)
4848 return BW_UNIT;
4849
4850 /*
4851 * Doing this here saves a lot of checks in all
4852 * the calling paths, and returning zero seems
4853 * safe for them anyway.
4854 */
4855 if (period == 0)
4856 return 0;
4857
4858 return div64_u64(runtime << BW_SHIFT, period);
4859}
4860
4861/*
4862 * wake_up_new_task - wake up a newly created task for the first time.
4863 *
4864 * This function will do some initial scheduler statistics housekeeping
4865 * that must be done for every newly created context, then puts the task
4866 * on the runqueue and wakes it.
4867 */
4868void wake_up_new_task(struct task_struct *p)
4869{
4870 struct rq_flags rf;
4871 struct rq *rq;
4872
4873 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4874 WRITE_ONCE(p->__state, TASK_RUNNING);
4875#ifdef CONFIG_SMP
4876 /*
4877 * Fork balancing, do it here and not earlier because:
4878 * - cpus_ptr can change in the fork path
4879 * - any previously selected CPU might disappear through hotplug
4880 *
4881 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
4882 * as we're not fully set-up yet.
4883 */
4884 p->recent_used_cpu = task_cpu(p);
4885 rseq_migrate(p);
4886 __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK));
4887#endif
4888 rq = __task_rq_lock(p, &rf);
4889 update_rq_clock(rq);
4890 post_init_entity_util_avg(p);
4891
4892 activate_task(rq, p, ENQUEUE_NOCLOCK);
4893 trace_sched_wakeup_new(p);
4894 wakeup_preempt(rq, p, WF_FORK);
4895#ifdef CONFIG_SMP
4896 if (p->sched_class->task_woken) {
4897 /*
4898 * Nothing relies on rq->lock after this, so it's fine to
4899 * drop it.
4900 */
4901 rq_unpin_lock(rq, &rf);
4902 p->sched_class->task_woken(rq, p);
4903 rq_repin_lock(rq, &rf);
4904 }
4905#endif
4906 task_rq_unlock(rq, p, &rf);
4907}
4908
4909#ifdef CONFIG_PREEMPT_NOTIFIERS
4910
4911static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
4912
4913void preempt_notifier_inc(void)
4914{
4915 static_branch_inc(&preempt_notifier_key);
4916}
4917EXPORT_SYMBOL_GPL(preempt_notifier_inc);
4918
4919void preempt_notifier_dec(void)
4920{
4921 static_branch_dec(&preempt_notifier_key);
4922}
4923EXPORT_SYMBOL_GPL(preempt_notifier_dec);
4924
4925/**
4926 * preempt_notifier_register - tell me when current is being preempted & rescheduled
4927 * @notifier: notifier struct to register
4928 */
4929void preempt_notifier_register(struct preempt_notifier *notifier)
4930{
4931 if (!static_branch_unlikely(&preempt_notifier_key))
4932 WARN(1, "registering preempt_notifier while notifiers disabled\n");
4933
4934 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
4935}
4936EXPORT_SYMBOL_GPL(preempt_notifier_register);
4937
4938/**
4939 * preempt_notifier_unregister - no longer interested in preemption notifications
4940 * @notifier: notifier struct to unregister
4941 *
4942 * This is *not* safe to call from within a preemption notifier.
4943 */
4944void preempt_notifier_unregister(struct preempt_notifier *notifier)
4945{
4946 hlist_del(¬ifier->link);
4947}
4948EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
4949
4950static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
4951{
4952 struct preempt_notifier *notifier;
4953
4954 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4955 notifier->ops->sched_in(notifier, raw_smp_processor_id());
4956}
4957
4958static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4959{
4960 if (static_branch_unlikely(&preempt_notifier_key))
4961 __fire_sched_in_preempt_notifiers(curr);
4962}
4963
4964static void
4965__fire_sched_out_preempt_notifiers(struct task_struct *curr,
4966 struct task_struct *next)
4967{
4968 struct preempt_notifier *notifier;
4969
4970 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4971 notifier->ops->sched_out(notifier, next);
4972}
4973
4974static __always_inline void
4975fire_sched_out_preempt_notifiers(struct task_struct *curr,
4976 struct task_struct *next)
4977{
4978 if (static_branch_unlikely(&preempt_notifier_key))
4979 __fire_sched_out_preempt_notifiers(curr, next);
4980}
4981
4982#else /* !CONFIG_PREEMPT_NOTIFIERS */
4983
4984static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4985{
4986}
4987
4988static inline void
4989fire_sched_out_preempt_notifiers(struct task_struct *curr,
4990 struct task_struct *next)
4991{
4992}
4993
4994#endif /* CONFIG_PREEMPT_NOTIFIERS */
4995
4996static inline void prepare_task(struct task_struct *next)
4997{
4998#ifdef CONFIG_SMP
4999 /*
5000 * Claim the task as running, we do this before switching to it
5001 * such that any running task will have this set.
5002 *
5003 * See the smp_load_acquire(&p->on_cpu) case in ttwu() and
5004 * its ordering comment.
5005 */
5006 WRITE_ONCE(next->on_cpu, 1);
5007#endif
5008}
5009
5010static inline void finish_task(struct task_struct *prev)
5011{
5012#ifdef CONFIG_SMP
5013 /*
5014 * This must be the very last reference to @prev from this CPU. After
5015 * p->on_cpu is cleared, the task can be moved to a different CPU. We
5016 * must ensure this doesn't happen until the switch is completely
5017 * finished.
5018 *
5019 * In particular, the load of prev->state in finish_task_switch() must
5020 * happen before this.
5021 *
5022 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
5023 */
5024 smp_store_release(&prev->on_cpu, 0);
5025#endif
5026}
5027
5028#ifdef CONFIG_SMP
5029
5030static void do_balance_callbacks(struct rq *rq, struct balance_callback *head)
5031{
5032 void (*func)(struct rq *rq);
5033 struct balance_callback *next;
5034
5035 lockdep_assert_rq_held(rq);
5036
5037 while (head) {
5038 func = (void (*)(struct rq *))head->func;
5039 next = head->next;
5040 head->next = NULL;
5041 head = next;
5042
5043 func(rq);
5044 }
5045}
5046
5047static void balance_push(struct rq *rq);
5048
5049/*
5050 * balance_push_callback is a right abuse of the callback interface and plays
5051 * by significantly different rules.
5052 *
5053 * Where the normal balance_callback's purpose is to be ran in the same context
5054 * that queued it (only later, when it's safe to drop rq->lock again),
5055 * balance_push_callback is specifically targeted at __schedule().
5056 *
5057 * This abuse is tolerated because it places all the unlikely/odd cases behind
5058 * a single test, namely: rq->balance_callback == NULL.
5059 */
5060struct balance_callback balance_push_callback = {
5061 .next = NULL,
5062 .func = balance_push,
5063};
5064
5065static inline struct balance_callback *
5066__splice_balance_callbacks(struct rq *rq, bool split)
5067{
5068 struct balance_callback *head = rq->balance_callback;
5069
5070 if (likely(!head))
5071 return NULL;
5072
5073 lockdep_assert_rq_held(rq);
5074 /*
5075 * Must not take balance_push_callback off the list when
5076 * splice_balance_callbacks() and balance_callbacks() are not
5077 * in the same rq->lock section.
5078 *
5079 * In that case it would be possible for __schedule() to interleave
5080 * and observe the list empty.
5081 */
5082 if (split && head == &balance_push_callback)
5083 head = NULL;
5084 else
5085 rq->balance_callback = NULL;
5086
5087 return head;
5088}
5089
5090static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
5091{
5092 return __splice_balance_callbacks(rq, true);
5093}
5094
5095static void __balance_callbacks(struct rq *rq)
5096{
5097 do_balance_callbacks(rq, __splice_balance_callbacks(rq, false));
5098}
5099
5100static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
5101{
5102 unsigned long flags;
5103
5104 if (unlikely(head)) {
5105 raw_spin_rq_lock_irqsave(rq, flags);
5106 do_balance_callbacks(rq, head);
5107 raw_spin_rq_unlock_irqrestore(rq, flags);
5108 }
5109}
5110
5111#else
5112
5113static inline void __balance_callbacks(struct rq *rq)
5114{
5115}
5116
5117static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
5118{
5119 return NULL;
5120}
5121
5122static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
5123{
5124}
5125
5126#endif
5127
5128static inline void
5129prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
5130{
5131 /*
5132 * Since the runqueue lock will be released by the next
5133 * task (which is an invalid locking op but in the case
5134 * of the scheduler it's an obvious special-case), so we
5135 * do an early lockdep release here:
5136 */
5137 rq_unpin_lock(rq, rf);
5138 spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_);
5139#ifdef CONFIG_DEBUG_SPINLOCK
5140 /* this is a valid case when another task releases the spinlock */
5141 rq_lockp(rq)->owner = next;
5142#endif
5143}
5144
5145static inline void finish_lock_switch(struct rq *rq)
5146{
5147 /*
5148 * If we are tracking spinlock dependencies then we have to
5149 * fix up the runqueue lock - which gets 'carried over' from
5150 * prev into current:
5151 */
5152 spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_);
5153 __balance_callbacks(rq);
5154 raw_spin_rq_unlock_irq(rq);
5155}
5156
5157/*
5158 * NOP if the arch has not defined these:
5159 */
5160
5161#ifndef prepare_arch_switch
5162# define prepare_arch_switch(next) do { } while (0)
5163#endif
5164
5165#ifndef finish_arch_post_lock_switch
5166# define finish_arch_post_lock_switch() do { } while (0)
5167#endif
5168
5169static inline void kmap_local_sched_out(void)
5170{
5171#ifdef CONFIG_KMAP_LOCAL
5172 if (unlikely(current->kmap_ctrl.idx))
5173 __kmap_local_sched_out();
5174#endif
5175}
5176
5177static inline void kmap_local_sched_in(void)
5178{
5179#ifdef CONFIG_KMAP_LOCAL
5180 if (unlikely(current->kmap_ctrl.idx))
5181 __kmap_local_sched_in();
5182#endif
5183}
5184
5185/**
5186 * prepare_task_switch - prepare to switch tasks
5187 * @rq: the runqueue preparing to switch
5188 * @prev: the current task that is being switched out
5189 * @next: the task we are going to switch to.
5190 *
5191 * This is called with the rq lock held and interrupts off. It must
5192 * be paired with a subsequent finish_task_switch after the context
5193 * switch.
5194 *
5195 * prepare_task_switch sets up locking and calls architecture specific
5196 * hooks.
5197 */
5198static inline void
5199prepare_task_switch(struct rq *rq, struct task_struct *prev,
5200 struct task_struct *next)
5201{
5202 kcov_prepare_switch(prev);
5203 sched_info_switch(rq, prev, next);
5204 perf_event_task_sched_out(prev, next);
5205 rseq_preempt(prev);
5206 fire_sched_out_preempt_notifiers(prev, next);
5207 kmap_local_sched_out();
5208 prepare_task(next);
5209 prepare_arch_switch(next);
5210}
5211
5212/**
5213 * finish_task_switch - clean up after a task-switch
5214 * @prev: the thread we just switched away from.
5215 *
5216 * finish_task_switch must be called after the context switch, paired
5217 * with a prepare_task_switch call before the context switch.
5218 * finish_task_switch will reconcile locking set up by prepare_task_switch,
5219 * and do any other architecture-specific cleanup actions.
5220 *
5221 * Note that we may have delayed dropping an mm in context_switch(). If
5222 * so, we finish that here outside of the runqueue lock. (Doing it
5223 * with the lock held can cause deadlocks; see schedule() for
5224 * details.)
5225 *
5226 * The context switch have flipped the stack from under us and restored the
5227 * local variables which were saved when this task called schedule() in the
5228 * past. prev == current is still correct but we need to recalculate this_rq
5229 * because prev may have moved to another CPU.
5230 */
5231static struct rq *finish_task_switch(struct task_struct *prev)
5232 __releases(rq->lock)
5233{
5234 struct rq *rq = this_rq();
5235 struct mm_struct *mm = rq->prev_mm;
5236 unsigned int prev_state;
5237
5238 /*
5239 * The previous task will have left us with a preempt_count of 2
5240 * because it left us after:
5241 *
5242 * schedule()
5243 * preempt_disable(); // 1
5244 * __schedule()
5245 * raw_spin_lock_irq(&rq->lock) // 2
5246 *
5247 * Also, see FORK_PREEMPT_COUNT.
5248 */
5249 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
5250 "corrupted preempt_count: %s/%d/0x%x\n",
5251 current->comm, current->pid, preempt_count()))
5252 preempt_count_set(FORK_PREEMPT_COUNT);
5253
5254 rq->prev_mm = NULL;
5255
5256 /*
5257 * A task struct has one reference for the use as "current".
5258 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
5259 * schedule one last time. The schedule call will never return, and
5260 * the scheduled task must drop that reference.
5261 *
5262 * We must observe prev->state before clearing prev->on_cpu (in
5263 * finish_task), otherwise a concurrent wakeup can get prev
5264 * running on another CPU and we could rave with its RUNNING -> DEAD
5265 * transition, resulting in a double drop.
5266 */
5267 prev_state = READ_ONCE(prev->__state);
5268 vtime_task_switch(prev);
5269 perf_event_task_sched_in(prev, current);
5270 finish_task(prev);
5271 tick_nohz_task_switch();
5272 finish_lock_switch(rq);
5273 finish_arch_post_lock_switch();
5274 kcov_finish_switch(current);
5275 /*
5276 * kmap_local_sched_out() is invoked with rq::lock held and
5277 * interrupts disabled. There is no requirement for that, but the
5278 * sched out code does not have an interrupt enabled section.
5279 * Restoring the maps on sched in does not require interrupts being
5280 * disabled either.
5281 */
5282 kmap_local_sched_in();
5283
5284 fire_sched_in_preempt_notifiers(current);
5285 /*
5286 * When switching through a kernel thread, the loop in
5287 * membarrier_{private,global}_expedited() may have observed that
5288 * kernel thread and not issued an IPI. It is therefore possible to
5289 * schedule between user->kernel->user threads without passing though
5290 * switch_mm(). Membarrier requires a barrier after storing to
5291 * rq->curr, before returning to userspace, so provide them here:
5292 *
5293 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
5294 * provided by mmdrop_lazy_tlb(),
5295 * - a sync_core for SYNC_CORE.
5296 */
5297 if (mm) {
5298 membarrier_mm_sync_core_before_usermode(mm);
5299 mmdrop_lazy_tlb_sched(mm);
5300 }
5301
5302 if (unlikely(prev_state == TASK_DEAD)) {
5303 if (prev->sched_class->task_dead)
5304 prev->sched_class->task_dead(prev);
5305
5306 /* Task is done with its stack. */
5307 put_task_stack(prev);
5308
5309 put_task_struct_rcu_user(prev);
5310 }
5311
5312 return rq;
5313}
5314
5315/**
5316 * schedule_tail - first thing a freshly forked thread must call.
5317 * @prev: the thread we just switched away from.
5318 */
5319asmlinkage __visible void schedule_tail(struct task_struct *prev)
5320 __releases(rq->lock)
5321{
5322 /*
5323 * New tasks start with FORK_PREEMPT_COUNT, see there and
5324 * finish_task_switch() for details.
5325 *
5326 * finish_task_switch() will drop rq->lock() and lower preempt_count
5327 * and the preempt_enable() will end up enabling preemption (on
5328 * PREEMPT_COUNT kernels).
5329 */
5330
5331 finish_task_switch(prev);
5332 preempt_enable();
5333
5334 if (current->set_child_tid)
5335 put_user(task_pid_vnr(current), current->set_child_tid);
5336
5337 calculate_sigpending();
5338}
5339
5340/*
5341 * context_switch - switch to the new MM and the new thread's register state.
5342 */
5343static __always_inline struct rq *
5344context_switch(struct rq *rq, struct task_struct *prev,
5345 struct task_struct *next, struct rq_flags *rf)
5346{
5347 prepare_task_switch(rq, prev, next);
5348
5349 /*
5350 * For paravirt, this is coupled with an exit in switch_to to
5351 * combine the page table reload and the switch backend into
5352 * one hypercall.
5353 */
5354 arch_start_context_switch(prev);
5355
5356 /*
5357 * kernel -> kernel lazy + transfer active
5358 * user -> kernel lazy + mmgrab_lazy_tlb() active
5359 *
5360 * kernel -> user switch + mmdrop_lazy_tlb() active
5361 * user -> user switch
5362 *
5363 * switch_mm_cid() needs to be updated if the barriers provided
5364 * by context_switch() are modified.
5365 */
5366 if (!next->mm) { // to kernel
5367 enter_lazy_tlb(prev->active_mm, next);
5368
5369 next->active_mm = prev->active_mm;
5370 if (prev->mm) // from user
5371 mmgrab_lazy_tlb(prev->active_mm);
5372 else
5373 prev->active_mm = NULL;
5374 } else { // to user
5375 membarrier_switch_mm(rq, prev->active_mm, next->mm);
5376 /*
5377 * sys_membarrier() requires an smp_mb() between setting
5378 * rq->curr / membarrier_switch_mm() and returning to userspace.
5379 *
5380 * The below provides this either through switch_mm(), or in
5381 * case 'prev->active_mm == next->mm' through
5382 * finish_task_switch()'s mmdrop().
5383 */
5384 switch_mm_irqs_off(prev->active_mm, next->mm, next);
5385 lru_gen_use_mm(next->mm);
5386
5387 if (!prev->mm) { // from kernel
5388 /* will mmdrop_lazy_tlb() in finish_task_switch(). */
5389 rq->prev_mm = prev->active_mm;
5390 prev->active_mm = NULL;
5391 }
5392 }
5393
5394 /* switch_mm_cid() requires the memory barriers above. */
5395 switch_mm_cid(rq, prev, next);
5396
5397 prepare_lock_switch(rq, next, rf);
5398
5399 /* Here we just switch the register state and the stack. */
5400 switch_to(prev, next, prev);
5401 barrier();
5402
5403 return finish_task_switch(prev);
5404}
5405
5406/*
5407 * nr_running and nr_context_switches:
5408 *
5409 * externally visible scheduler statistics: current number of runnable
5410 * threads, total number of context switches performed since bootup.
5411 */
5412unsigned int nr_running(void)
5413{
5414 unsigned int i, sum = 0;
5415
5416 for_each_online_cpu(i)
5417 sum += cpu_rq(i)->nr_running;
5418
5419 return sum;
5420}
5421
5422/*
5423 * Check if only the current task is running on the CPU.
5424 *
5425 * Caution: this function does not check that the caller has disabled
5426 * preemption, thus the result might have a time-of-check-to-time-of-use
5427 * race. The caller is responsible to use it correctly, for example:
5428 *
5429 * - from a non-preemptible section (of course)
5430 *
5431 * - from a thread that is bound to a single CPU
5432 *
5433 * - in a loop with very short iterations (e.g. a polling loop)
5434 */
5435bool single_task_running(void)
5436{
5437 return raw_rq()->nr_running == 1;
5438}
5439EXPORT_SYMBOL(single_task_running);
5440
5441unsigned long long nr_context_switches_cpu(int cpu)
5442{
5443 return cpu_rq(cpu)->nr_switches;
5444}
5445
5446unsigned long long nr_context_switches(void)
5447{
5448 int i;
5449 unsigned long long sum = 0;
5450
5451 for_each_possible_cpu(i)
5452 sum += cpu_rq(i)->nr_switches;
5453
5454 return sum;
5455}
5456
5457/*
5458 * Consumers of these two interfaces, like for example the cpuidle menu
5459 * governor, are using nonsensical data. Preferring shallow idle state selection
5460 * for a CPU that has IO-wait which might not even end up running the task when
5461 * it does become runnable.
5462 */
5463
5464unsigned int nr_iowait_cpu(int cpu)
5465{
5466 return atomic_read(&cpu_rq(cpu)->nr_iowait);
5467}
5468
5469/*
5470 * IO-wait accounting, and how it's mostly bollocks (on SMP).
5471 *
5472 * The idea behind IO-wait account is to account the idle time that we could
5473 * have spend running if it were not for IO. That is, if we were to improve the
5474 * storage performance, we'd have a proportional reduction in IO-wait time.
5475 *
5476 * This all works nicely on UP, where, when a task blocks on IO, we account
5477 * idle time as IO-wait, because if the storage were faster, it could've been
5478 * running and we'd not be idle.
5479 *
5480 * This has been extended to SMP, by doing the same for each CPU. This however
5481 * is broken.
5482 *
5483 * Imagine for instance the case where two tasks block on one CPU, only the one
5484 * CPU will have IO-wait accounted, while the other has regular idle. Even
5485 * though, if the storage were faster, both could've ran at the same time,
5486 * utilising both CPUs.
5487 *
5488 * This means, that when looking globally, the current IO-wait accounting on
5489 * SMP is a lower bound, by reason of under accounting.
5490 *
5491 * Worse, since the numbers are provided per CPU, they are sometimes
5492 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
5493 * associated with any one particular CPU, it can wake to another CPU than it
5494 * blocked on. This means the per CPU IO-wait number is meaningless.
5495 *
5496 * Task CPU affinities can make all that even more 'interesting'.
5497 */
5498
5499unsigned int nr_iowait(void)
5500{
5501 unsigned int i, sum = 0;
5502
5503 for_each_possible_cpu(i)
5504 sum += nr_iowait_cpu(i);
5505
5506 return sum;
5507}
5508
5509#ifdef CONFIG_SMP
5510
5511/*
5512 * sched_exec - execve() is a valuable balancing opportunity, because at
5513 * this point the task has the smallest effective memory and cache footprint.
5514 */
5515void sched_exec(void)
5516{
5517 struct task_struct *p = current;
5518 struct migration_arg arg;
5519 int dest_cpu;
5520
5521 scoped_guard (raw_spinlock_irqsave, &p->pi_lock) {
5522 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC);
5523 if (dest_cpu == smp_processor_id())
5524 return;
5525
5526 if (unlikely(!cpu_active(dest_cpu)))
5527 return;
5528
5529 arg = (struct migration_arg){ p, dest_cpu };
5530 }
5531 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
5532}
5533
5534#endif
5535
5536DEFINE_PER_CPU(struct kernel_stat, kstat);
5537DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
5538
5539EXPORT_PER_CPU_SYMBOL(kstat);
5540EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
5541
5542/*
5543 * The function fair_sched_class.update_curr accesses the struct curr
5544 * and its field curr->exec_start; when called from task_sched_runtime(),
5545 * we observe a high rate of cache misses in practice.
5546 * Prefetching this data results in improved performance.
5547 */
5548static inline void prefetch_curr_exec_start(struct task_struct *p)
5549{
5550#ifdef CONFIG_FAIR_GROUP_SCHED
5551 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
5552#else
5553 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
5554#endif
5555 prefetch(curr);
5556 prefetch(&curr->exec_start);
5557}
5558
5559/*
5560 * Return accounted runtime for the task.
5561 * In case the task is currently running, return the runtime plus current's
5562 * pending runtime that have not been accounted yet.
5563 */
5564unsigned long long task_sched_runtime(struct task_struct *p)
5565{
5566 struct rq_flags rf;
5567 struct rq *rq;
5568 u64 ns;
5569
5570#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
5571 /*
5572 * 64-bit doesn't need locks to atomically read a 64-bit value.
5573 * So we have a optimization chance when the task's delta_exec is 0.
5574 * Reading ->on_cpu is racy, but this is ok.
5575 *
5576 * If we race with it leaving CPU, we'll take a lock. So we're correct.
5577 * If we race with it entering CPU, unaccounted time is 0. This is
5578 * indistinguishable from the read occurring a few cycles earlier.
5579 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
5580 * been accounted, so we're correct here as well.
5581 */
5582 if (!p->on_cpu || !task_on_rq_queued(p))
5583 return p->se.sum_exec_runtime;
5584#endif
5585
5586 rq = task_rq_lock(p, &rf);
5587 /*
5588 * Must be ->curr _and_ ->on_rq. If dequeued, we would
5589 * project cycles that may never be accounted to this
5590 * thread, breaking clock_gettime().
5591 */
5592 if (task_current(rq, p) && task_on_rq_queued(p)) {
5593 prefetch_curr_exec_start(p);
5594 update_rq_clock(rq);
5595 p->sched_class->update_curr(rq);
5596 }
5597 ns = p->se.sum_exec_runtime;
5598 task_rq_unlock(rq, p, &rf);
5599
5600 return ns;
5601}
5602
5603#ifdef CONFIG_SCHED_DEBUG
5604static u64 cpu_resched_latency(struct rq *rq)
5605{
5606 int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
5607 u64 resched_latency, now = rq_clock(rq);
5608 static bool warned_once;
5609
5610 if (sysctl_resched_latency_warn_once && warned_once)
5611 return 0;
5612
5613 if (!need_resched() || !latency_warn_ms)
5614 return 0;
5615
5616 if (system_state == SYSTEM_BOOTING)
5617 return 0;
5618
5619 if (!rq->last_seen_need_resched_ns) {
5620 rq->last_seen_need_resched_ns = now;
5621 rq->ticks_without_resched = 0;
5622 return 0;
5623 }
5624
5625 rq->ticks_without_resched++;
5626 resched_latency = now - rq->last_seen_need_resched_ns;
5627 if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
5628 return 0;
5629
5630 warned_once = true;
5631
5632 return resched_latency;
5633}
5634
5635static int __init setup_resched_latency_warn_ms(char *str)
5636{
5637 long val;
5638
5639 if ((kstrtol(str, 0, &val))) {
5640 pr_warn("Unable to set resched_latency_warn_ms\n");
5641 return 1;
5642 }
5643
5644 sysctl_resched_latency_warn_ms = val;
5645 return 1;
5646}
5647__setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
5648#else
5649static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
5650#endif /* CONFIG_SCHED_DEBUG */
5651
5652/*
5653 * This function gets called by the timer code, with HZ frequency.
5654 * We call it with interrupts disabled.
5655 */
5656void scheduler_tick(void)
5657{
5658 int cpu = smp_processor_id();
5659 struct rq *rq = cpu_rq(cpu);
5660 struct task_struct *curr = rq->curr;
5661 struct rq_flags rf;
5662 unsigned long thermal_pressure;
5663 u64 resched_latency;
5664
5665 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5666 arch_scale_freq_tick();
5667
5668 sched_clock_tick();
5669
5670 rq_lock(rq, &rf);
5671
5672 update_rq_clock(rq);
5673 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
5674 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
5675 curr->sched_class->task_tick(rq, curr, 0);
5676 if (sched_feat(LATENCY_WARN))
5677 resched_latency = cpu_resched_latency(rq);
5678 calc_global_load_tick(rq);
5679 sched_core_tick(rq);
5680 task_tick_mm_cid(rq, curr);
5681
5682 rq_unlock(rq, &rf);
5683
5684 if (sched_feat(LATENCY_WARN) && resched_latency)
5685 resched_latency_warn(cpu, resched_latency);
5686
5687 perf_event_task_tick();
5688
5689 if (curr->flags & PF_WQ_WORKER)
5690 wq_worker_tick(curr);
5691
5692#ifdef CONFIG_SMP
5693 rq->idle_balance = idle_cpu(cpu);
5694 trigger_load_balance(rq);
5695#endif
5696}
5697
5698#ifdef CONFIG_NO_HZ_FULL
5699
5700struct tick_work {
5701 int cpu;
5702 atomic_t state;
5703 struct delayed_work work;
5704};
5705/* Values for ->state, see diagram below. */
5706#define TICK_SCHED_REMOTE_OFFLINE 0
5707#define TICK_SCHED_REMOTE_OFFLINING 1
5708#define TICK_SCHED_REMOTE_RUNNING 2
5709
5710/*
5711 * State diagram for ->state:
5712 *
5713 *
5714 * TICK_SCHED_REMOTE_OFFLINE
5715 * | ^
5716 * | |
5717 * | | sched_tick_remote()
5718 * | |
5719 * | |
5720 * +--TICK_SCHED_REMOTE_OFFLINING
5721 * | ^
5722 * | |
5723 * sched_tick_start() | | sched_tick_stop()
5724 * | |
5725 * V |
5726 * TICK_SCHED_REMOTE_RUNNING
5727 *
5728 *
5729 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
5730 * and sched_tick_start() are happy to leave the state in RUNNING.
5731 */
5732
5733static struct tick_work __percpu *tick_work_cpu;
5734
5735static void sched_tick_remote(struct work_struct *work)
5736{
5737 struct delayed_work *dwork = to_delayed_work(work);
5738 struct tick_work *twork = container_of(dwork, struct tick_work, work);
5739 int cpu = twork->cpu;
5740 struct rq *rq = cpu_rq(cpu);
5741 int os;
5742
5743 /*
5744 * Handle the tick only if it appears the remote CPU is running in full
5745 * dynticks mode. The check is racy by nature, but missing a tick or
5746 * having one too much is no big deal because the scheduler tick updates
5747 * statistics and checks timeslices in a time-independent way, regardless
5748 * of when exactly it is running.
5749 */
5750 if (tick_nohz_tick_stopped_cpu(cpu)) {
5751 guard(rq_lock_irq)(rq);
5752 struct task_struct *curr = rq->curr;
5753
5754 if (cpu_online(cpu)) {
5755 update_rq_clock(rq);
5756
5757 if (!is_idle_task(curr)) {
5758 /*
5759 * Make sure the next tick runs within a
5760 * reasonable amount of time.
5761 */
5762 u64 delta = rq_clock_task(rq) - curr->se.exec_start;
5763 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
5764 }
5765 curr->sched_class->task_tick(rq, curr, 0);
5766
5767 calc_load_nohz_remote(rq);
5768 }
5769 }
5770
5771 /*
5772 * Run the remote tick once per second (1Hz). This arbitrary
5773 * frequency is large enough to avoid overload but short enough
5774 * to keep scheduler internal stats reasonably up to date. But
5775 * first update state to reflect hotplug activity if required.
5776 */
5777 os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
5778 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
5779 if (os == TICK_SCHED_REMOTE_RUNNING)
5780 queue_delayed_work(system_unbound_wq, dwork, HZ);
5781}
5782
5783static void sched_tick_start(int cpu)
5784{
5785 int os;
5786 struct tick_work *twork;
5787
5788 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5789 return;
5790
5791 WARN_ON_ONCE(!tick_work_cpu);
5792
5793 twork = per_cpu_ptr(tick_work_cpu, cpu);
5794 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
5795 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
5796 if (os == TICK_SCHED_REMOTE_OFFLINE) {
5797 twork->cpu = cpu;
5798 INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
5799 queue_delayed_work(system_unbound_wq, &twork->work, HZ);
5800 }
5801}
5802
5803#ifdef CONFIG_HOTPLUG_CPU
5804static void sched_tick_stop(int cpu)
5805{
5806 struct tick_work *twork;
5807 int os;
5808
5809 if (housekeeping_cpu(cpu, HK_TYPE_TICK))
5810 return;
5811
5812 WARN_ON_ONCE(!tick_work_cpu);
5813
5814 twork = per_cpu_ptr(tick_work_cpu, cpu);
5815 /* There cannot be competing actions, but don't rely on stop-machine. */
5816 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
5817 WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
5818 /* Don't cancel, as this would mess up the state machine. */
5819}
5820#endif /* CONFIG_HOTPLUG_CPU */
5821
5822int __init sched_tick_offload_init(void)
5823{
5824 tick_work_cpu = alloc_percpu(struct tick_work);
5825 BUG_ON(!tick_work_cpu);
5826 return 0;
5827}
5828
5829#else /* !CONFIG_NO_HZ_FULL */
5830static inline void sched_tick_start(int cpu) { }
5831static inline void sched_tick_stop(int cpu) { }
5832#endif
5833
5834#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
5835 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
5836/*
5837 * If the value passed in is equal to the current preempt count
5838 * then we just disabled preemption. Start timing the latency.
5839 */
5840static inline void preempt_latency_start(int val)
5841{
5842 if (preempt_count() == val) {
5843 unsigned long ip = get_lock_parent_ip();
5844#ifdef CONFIG_DEBUG_PREEMPT
5845 current->preempt_disable_ip = ip;
5846#endif
5847 trace_preempt_off(CALLER_ADDR0, ip);
5848 }
5849}
5850
5851void preempt_count_add(int val)
5852{
5853#ifdef CONFIG_DEBUG_PREEMPT
5854 /*
5855 * Underflow?
5856 */
5857 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
5858 return;
5859#endif
5860 __preempt_count_add(val);
5861#ifdef CONFIG_DEBUG_PREEMPT
5862 /*
5863 * Spinlock count overflowing soon?
5864 */
5865 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
5866 PREEMPT_MASK - 10);
5867#endif
5868 preempt_latency_start(val);
5869}
5870EXPORT_SYMBOL(preempt_count_add);
5871NOKPROBE_SYMBOL(preempt_count_add);
5872
5873/*
5874 * If the value passed in equals to the current preempt count
5875 * then we just enabled preemption. Stop timing the latency.
5876 */
5877static inline void preempt_latency_stop(int val)
5878{
5879 if (preempt_count() == val)
5880 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
5881}
5882
5883void preempt_count_sub(int val)
5884{
5885#ifdef CONFIG_DEBUG_PREEMPT
5886 /*
5887 * Underflow?
5888 */
5889 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
5890 return;
5891 /*
5892 * Is the spinlock portion underflowing?
5893 */
5894 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
5895 !(preempt_count() & PREEMPT_MASK)))
5896 return;
5897#endif
5898
5899 preempt_latency_stop(val);
5900 __preempt_count_sub(val);
5901}
5902EXPORT_SYMBOL(preempt_count_sub);
5903NOKPROBE_SYMBOL(preempt_count_sub);
5904
5905#else
5906static inline void preempt_latency_start(int val) { }
5907static inline void preempt_latency_stop(int val) { }
5908#endif
5909
5910static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
5911{
5912#ifdef CONFIG_DEBUG_PREEMPT
5913 return p->preempt_disable_ip;
5914#else
5915 return 0;
5916#endif
5917}
5918
5919/*
5920 * Print scheduling while atomic bug:
5921 */
5922static noinline void __schedule_bug(struct task_struct *prev)
5923{
5924 /* Save this before calling printk(), since that will clobber it */
5925 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
5926
5927 if (oops_in_progress)
5928 return;
5929
5930 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
5931 prev->comm, prev->pid, preempt_count());
5932
5933 debug_show_held_locks(prev);
5934 print_modules();
5935 if (irqs_disabled())
5936 print_irqtrace_events(prev);
5937 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
5938 pr_err("Preemption disabled at:");
5939 print_ip_sym(KERN_ERR, preempt_disable_ip);
5940 }
5941 check_panic_on_warn("scheduling while atomic");
5942
5943 dump_stack();
5944 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5945}
5946
5947/*
5948 * Various schedule()-time debugging checks and statistics:
5949 */
5950static inline void schedule_debug(struct task_struct *prev, bool preempt)
5951{
5952#ifdef CONFIG_SCHED_STACK_END_CHECK
5953 if (task_stack_end_corrupted(prev))
5954 panic("corrupted stack end detected inside scheduler\n");
5955
5956 if (task_scs_end_corrupted(prev))
5957 panic("corrupted shadow stack detected inside scheduler\n");
5958#endif
5959
5960#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5961 if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) {
5962 printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
5963 prev->comm, prev->pid, prev->non_block_count);
5964 dump_stack();
5965 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5966 }
5967#endif
5968
5969 if (unlikely(in_atomic_preempt_off())) {
5970 __schedule_bug(prev);
5971 preempt_count_set(PREEMPT_DISABLED);
5972 }
5973 rcu_sleep_check();
5974 SCHED_WARN_ON(ct_state() == CONTEXT_USER);
5975
5976 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
5977
5978 schedstat_inc(this_rq()->sched_count);
5979}
5980
5981static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
5982 struct rq_flags *rf)
5983{
5984#ifdef CONFIG_SMP
5985 const struct sched_class *class;
5986 /*
5987 * We must do the balancing pass before put_prev_task(), such
5988 * that when we release the rq->lock the task is in the same
5989 * state as before we took rq->lock.
5990 *
5991 * We can terminate the balance pass as soon as we know there is
5992 * a runnable task of @class priority or higher.
5993 */
5994 for_class_range(class, prev->sched_class, &idle_sched_class) {
5995 if (class->balance(rq, prev, rf))
5996 break;
5997 }
5998#endif
5999
6000 put_prev_task(rq, prev);
6001}
6002
6003/*
6004 * Pick up the highest-prio task:
6005 */
6006static inline struct task_struct *
6007__pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6008{
6009 const struct sched_class *class;
6010 struct task_struct *p;
6011
6012 /*
6013 * Optimization: we know that if all tasks are in the fair class we can
6014 * call that function directly, but only if the @prev task wasn't of a
6015 * higher scheduling class, because otherwise those lose the
6016 * opportunity to pull in more work from other CPUs.
6017 */
6018 if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) &&
6019 rq->nr_running == rq->cfs.h_nr_running)) {
6020
6021 p = pick_next_task_fair(rq, prev, rf);
6022 if (unlikely(p == RETRY_TASK))
6023 goto restart;
6024
6025 /* Assume the next prioritized class is idle_sched_class */
6026 if (!p) {
6027 put_prev_task(rq, prev);
6028 p = pick_next_task_idle(rq);
6029 }
6030
6031 /*
6032 * This is the fast path; it cannot be a DL server pick;
6033 * therefore even if @p == @prev, ->dl_server must be NULL.
6034 */
6035 if (p->dl_server)
6036 p->dl_server = NULL;
6037
6038 return p;
6039 }
6040
6041restart:
6042 put_prev_task_balance(rq, prev, rf);
6043
6044 /*
6045 * We've updated @prev and no longer need the server link, clear it.
6046 * Must be done before ->pick_next_task() because that can (re)set
6047 * ->dl_server.
6048 */
6049 if (prev->dl_server)
6050 prev->dl_server = NULL;
6051
6052 for_each_class(class) {
6053 p = class->pick_next_task(rq);
6054 if (p)
6055 return p;
6056 }
6057
6058 BUG(); /* The idle class should always have a runnable task. */
6059}
6060
6061#ifdef CONFIG_SCHED_CORE
6062static inline bool is_task_rq_idle(struct task_struct *t)
6063{
6064 return (task_rq(t)->idle == t);
6065}
6066
6067static inline bool cookie_equals(struct task_struct *a, unsigned long cookie)
6068{
6069 return is_task_rq_idle(a) || (a->core_cookie == cookie);
6070}
6071
6072static inline bool cookie_match(struct task_struct *a, struct task_struct *b)
6073{
6074 if (is_task_rq_idle(a) || is_task_rq_idle(b))
6075 return true;
6076
6077 return a->core_cookie == b->core_cookie;
6078}
6079
6080static inline struct task_struct *pick_task(struct rq *rq)
6081{
6082 const struct sched_class *class;
6083 struct task_struct *p;
6084
6085 for_each_class(class) {
6086 p = class->pick_task(rq);
6087 if (p)
6088 return p;
6089 }
6090
6091 BUG(); /* The idle class should always have a runnable task. */
6092}
6093
6094extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi);
6095
6096static void queue_core_balance(struct rq *rq);
6097
6098static struct task_struct *
6099pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6100{
6101 struct task_struct *next, *p, *max = NULL;
6102 const struct cpumask *smt_mask;
6103 bool fi_before = false;
6104 bool core_clock_updated = (rq == rq->core);
6105 unsigned long cookie;
6106 int i, cpu, occ = 0;
6107 struct rq *rq_i;
6108 bool need_sync;
6109
6110 if (!sched_core_enabled(rq))
6111 return __pick_next_task(rq, prev, rf);
6112
6113 cpu = cpu_of(rq);
6114
6115 /* Stopper task is switching into idle, no need core-wide selection. */
6116 if (cpu_is_offline(cpu)) {
6117 /*
6118 * Reset core_pick so that we don't enter the fastpath when
6119 * coming online. core_pick would already be migrated to
6120 * another cpu during offline.
6121 */
6122 rq->core_pick = NULL;
6123 return __pick_next_task(rq, prev, rf);
6124 }
6125
6126 /*
6127 * If there were no {en,de}queues since we picked (IOW, the task
6128 * pointers are all still valid), and we haven't scheduled the last
6129 * pick yet, do so now.
6130 *
6131 * rq->core_pick can be NULL if no selection was made for a CPU because
6132 * it was either offline or went offline during a sibling's core-wide
6133 * selection. In this case, do a core-wide selection.
6134 */
6135 if (rq->core->core_pick_seq == rq->core->core_task_seq &&
6136 rq->core->core_pick_seq != rq->core_sched_seq &&
6137 rq->core_pick) {
6138 WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq);
6139
6140 next = rq->core_pick;
6141 if (next != prev) {
6142 put_prev_task(rq, prev);
6143 set_next_task(rq, next);
6144 }
6145
6146 rq->core_pick = NULL;
6147 goto out;
6148 }
6149
6150 put_prev_task_balance(rq, prev, rf);
6151
6152 smt_mask = cpu_smt_mask(cpu);
6153 need_sync = !!rq->core->core_cookie;
6154
6155 /* reset state */
6156 rq->core->core_cookie = 0UL;
6157 if (rq->core->core_forceidle_count) {
6158 if (!core_clock_updated) {
6159 update_rq_clock(rq->core);
6160 core_clock_updated = true;
6161 }
6162 sched_core_account_forceidle(rq);
6163 /* reset after accounting force idle */
6164 rq->core->core_forceidle_start = 0;
6165 rq->core->core_forceidle_count = 0;
6166 rq->core->core_forceidle_occupation = 0;
6167 need_sync = true;
6168 fi_before = true;
6169 }
6170
6171 /*
6172 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
6173 *
6174 * @task_seq guards the task state ({en,de}queues)
6175 * @pick_seq is the @task_seq we did a selection on
6176 * @sched_seq is the @pick_seq we scheduled
6177 *
6178 * However, preemptions can cause multiple picks on the same task set.
6179 * 'Fix' this by also increasing @task_seq for every pick.
6180 */
6181 rq->core->core_task_seq++;
6182
6183 /*
6184 * Optimize for common case where this CPU has no cookies
6185 * and there are no cookied tasks running on siblings.
6186 */
6187 if (!need_sync) {
6188 next = pick_task(rq);
6189 if (!next->core_cookie) {
6190 rq->core_pick = NULL;
6191 /*
6192 * For robustness, update the min_vruntime_fi for
6193 * unconstrained picks as well.
6194 */
6195 WARN_ON_ONCE(fi_before);
6196 task_vruntime_update(rq, next, false);
6197 goto out_set_next;
6198 }
6199 }
6200
6201 /*
6202 * For each thread: do the regular task pick and find the max prio task
6203 * amongst them.
6204 *
6205 * Tie-break prio towards the current CPU
6206 */
6207 for_each_cpu_wrap(i, smt_mask, cpu) {
6208 rq_i = cpu_rq(i);
6209
6210 /*
6211 * Current cpu always has its clock updated on entrance to
6212 * pick_next_task(). If the current cpu is not the core,
6213 * the core may also have been updated above.
6214 */
6215 if (i != cpu && (rq_i != rq->core || !core_clock_updated))
6216 update_rq_clock(rq_i);
6217
6218 p = rq_i->core_pick = pick_task(rq_i);
6219 if (!max || prio_less(max, p, fi_before))
6220 max = p;
6221 }
6222
6223 cookie = rq->core->core_cookie = max->core_cookie;
6224
6225 /*
6226 * For each thread: try and find a runnable task that matches @max or
6227 * force idle.
6228 */
6229 for_each_cpu(i, smt_mask) {
6230 rq_i = cpu_rq(i);
6231 p = rq_i->core_pick;
6232
6233 if (!cookie_equals(p, cookie)) {
6234 p = NULL;
6235 if (cookie)
6236 p = sched_core_find(rq_i, cookie);
6237 if (!p)
6238 p = idle_sched_class.pick_task(rq_i);
6239 }
6240
6241 rq_i->core_pick = p;
6242
6243 if (p == rq_i->idle) {
6244 if (rq_i->nr_running) {
6245 rq->core->core_forceidle_count++;
6246 if (!fi_before)
6247 rq->core->core_forceidle_seq++;
6248 }
6249 } else {
6250 occ++;
6251 }
6252 }
6253
6254 if (schedstat_enabled() && rq->core->core_forceidle_count) {
6255 rq->core->core_forceidle_start = rq_clock(rq->core);
6256 rq->core->core_forceidle_occupation = occ;
6257 }
6258
6259 rq->core->core_pick_seq = rq->core->core_task_seq;
6260 next = rq->core_pick;
6261 rq->core_sched_seq = rq->core->core_pick_seq;
6262
6263 /* Something should have been selected for current CPU */
6264 WARN_ON_ONCE(!next);
6265
6266 /*
6267 * Reschedule siblings
6268 *
6269 * NOTE: L1TF -- at this point we're no longer running the old task and
6270 * sending an IPI (below) ensures the sibling will no longer be running
6271 * their task. This ensures there is no inter-sibling overlap between
6272 * non-matching user state.
6273 */
6274 for_each_cpu(i, smt_mask) {
6275 rq_i = cpu_rq(i);
6276
6277 /*
6278 * An online sibling might have gone offline before a task
6279 * could be picked for it, or it might be offline but later
6280 * happen to come online, but its too late and nothing was
6281 * picked for it. That's Ok - it will pick tasks for itself,
6282 * so ignore it.
6283 */
6284 if (!rq_i->core_pick)
6285 continue;
6286
6287 /*
6288 * Update for new !FI->FI transitions, or if continuing to be in !FI:
6289 * fi_before fi update?
6290 * 0 0 1
6291 * 0 1 1
6292 * 1 0 1
6293 * 1 1 0
6294 */
6295 if (!(fi_before && rq->core->core_forceidle_count))
6296 task_vruntime_update(rq_i, rq_i->core_pick, !!rq->core->core_forceidle_count);
6297
6298 rq_i->core_pick->core_occupation = occ;
6299
6300 if (i == cpu) {
6301 rq_i->core_pick = NULL;
6302 continue;
6303 }
6304
6305 /* Did we break L1TF mitigation requirements? */
6306 WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick));
6307
6308 if (rq_i->curr == rq_i->core_pick) {
6309 rq_i->core_pick = NULL;
6310 continue;
6311 }
6312
6313 resched_curr(rq_i);
6314 }
6315
6316out_set_next:
6317 set_next_task(rq, next);
6318out:
6319 if (rq->core->core_forceidle_count && next == rq->idle)
6320 queue_core_balance(rq);
6321
6322 return next;
6323}
6324
6325static bool try_steal_cookie(int this, int that)
6326{
6327 struct rq *dst = cpu_rq(this), *src = cpu_rq(that);
6328 struct task_struct *p;
6329 unsigned long cookie;
6330 bool success = false;
6331
6332 guard(irq)();
6333 guard(double_rq_lock)(dst, src);
6334
6335 cookie = dst->core->core_cookie;
6336 if (!cookie)
6337 return false;
6338
6339 if (dst->curr != dst->idle)
6340 return false;
6341
6342 p = sched_core_find(src, cookie);
6343 if (!p)
6344 return false;
6345
6346 do {
6347 if (p == src->core_pick || p == src->curr)
6348 goto next;
6349
6350 if (!is_cpu_allowed(p, this))
6351 goto next;
6352
6353 if (p->core_occupation > dst->idle->core_occupation)
6354 goto next;
6355 /*
6356 * sched_core_find() and sched_core_next() will ensure
6357 * that task @p is not throttled now, we also need to
6358 * check whether the runqueue of the destination CPU is
6359 * being throttled.
6360 */
6361 if (sched_task_is_throttled(p, this))
6362 goto next;
6363
6364 deactivate_task(src, p, 0);
6365 set_task_cpu(p, this);
6366 activate_task(dst, p, 0);
6367
6368 resched_curr(dst);
6369
6370 success = true;
6371 break;
6372
6373next:
6374 p = sched_core_next(p, cookie);
6375 } while (p);
6376
6377 return success;
6378}
6379
6380static bool steal_cookie_task(int cpu, struct sched_domain *sd)
6381{
6382 int i;
6383
6384 for_each_cpu_wrap(i, sched_domain_span(sd), cpu + 1) {
6385 if (i == cpu)
6386 continue;
6387
6388 if (need_resched())
6389 break;
6390
6391 if (try_steal_cookie(cpu, i))
6392 return true;
6393 }
6394
6395 return false;
6396}
6397
6398static void sched_core_balance(struct rq *rq)
6399{
6400 struct sched_domain *sd;
6401 int cpu = cpu_of(rq);
6402
6403 guard(preempt)();
6404 guard(rcu)();
6405
6406 raw_spin_rq_unlock_irq(rq);
6407 for_each_domain(cpu, sd) {
6408 if (need_resched())
6409 break;
6410
6411 if (steal_cookie_task(cpu, sd))
6412 break;
6413 }
6414 raw_spin_rq_lock_irq(rq);
6415}
6416
6417static DEFINE_PER_CPU(struct balance_callback, core_balance_head);
6418
6419static void queue_core_balance(struct rq *rq)
6420{
6421 if (!sched_core_enabled(rq))
6422 return;
6423
6424 if (!rq->core->core_cookie)
6425 return;
6426
6427 if (!rq->nr_running) /* not forced idle */
6428 return;
6429
6430 queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance);
6431}
6432
6433DEFINE_LOCK_GUARD_1(core_lock, int,
6434 sched_core_lock(*_T->lock, &_T->flags),
6435 sched_core_unlock(*_T->lock, &_T->flags),
6436 unsigned long flags)
6437
6438static void sched_core_cpu_starting(unsigned int cpu)
6439{
6440 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
6441 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
6442 int t;
6443
6444 guard(core_lock)(&cpu);
6445
6446 WARN_ON_ONCE(rq->core != rq);
6447
6448 /* if we're the first, we'll be our own leader */
6449 if (cpumask_weight(smt_mask) == 1)
6450 return;
6451
6452 /* find the leader */
6453 for_each_cpu(t, smt_mask) {
6454 if (t == cpu)
6455 continue;
6456 rq = cpu_rq(t);
6457 if (rq->core == rq) {
6458 core_rq = rq;
6459 break;
6460 }
6461 }
6462
6463 if (WARN_ON_ONCE(!core_rq)) /* whoopsie */
6464 return;
6465
6466 /* install and validate core_rq */
6467 for_each_cpu(t, smt_mask) {
6468 rq = cpu_rq(t);
6469
6470 if (t == cpu)
6471 rq->core = core_rq;
6472
6473 WARN_ON_ONCE(rq->core != core_rq);
6474 }
6475}
6476
6477static void sched_core_cpu_deactivate(unsigned int cpu)
6478{
6479 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
6480 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
6481 int t;
6482
6483 guard(core_lock)(&cpu);
6484
6485 /* if we're the last man standing, nothing to do */
6486 if (cpumask_weight(smt_mask) == 1) {
6487 WARN_ON_ONCE(rq->core != rq);
6488 return;
6489 }
6490
6491 /* if we're not the leader, nothing to do */
6492 if (rq->core != rq)
6493 return;
6494
6495 /* find a new leader */
6496 for_each_cpu(t, smt_mask) {
6497 if (t == cpu)
6498 continue;
6499 core_rq = cpu_rq(t);
6500 break;
6501 }
6502
6503 if (WARN_ON_ONCE(!core_rq)) /* impossible */
6504 return;
6505
6506 /* copy the shared state to the new leader */
6507 core_rq->core_task_seq = rq->core_task_seq;
6508 core_rq->core_pick_seq = rq->core_pick_seq;
6509 core_rq->core_cookie = rq->core_cookie;
6510 core_rq->core_forceidle_count = rq->core_forceidle_count;
6511 core_rq->core_forceidle_seq = rq->core_forceidle_seq;
6512 core_rq->core_forceidle_occupation = rq->core_forceidle_occupation;
6513
6514 /*
6515 * Accounting edge for forced idle is handled in pick_next_task().
6516 * Don't need another one here, since the hotplug thread shouldn't
6517 * have a cookie.
6518 */
6519 core_rq->core_forceidle_start = 0;
6520
6521 /* install new leader */
6522 for_each_cpu(t, smt_mask) {
6523 rq = cpu_rq(t);
6524 rq->core = core_rq;
6525 }
6526}
6527
6528static inline void sched_core_cpu_dying(unsigned int cpu)
6529{
6530 struct rq *rq = cpu_rq(cpu);
6531
6532 if (rq->core != rq)
6533 rq->core = rq;
6534}
6535
6536#else /* !CONFIG_SCHED_CORE */
6537
6538static inline void sched_core_cpu_starting(unsigned int cpu) {}
6539static inline void sched_core_cpu_deactivate(unsigned int cpu) {}
6540static inline void sched_core_cpu_dying(unsigned int cpu) {}
6541
6542static struct task_struct *
6543pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
6544{
6545 return __pick_next_task(rq, prev, rf);
6546}
6547
6548#endif /* CONFIG_SCHED_CORE */
6549
6550/*
6551 * Constants for the sched_mode argument of __schedule().
6552 *
6553 * The mode argument allows RT enabled kernels to differentiate a
6554 * preemption from blocking on an 'sleeping' spin/rwlock. Note that
6555 * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
6556 * optimize the AND operation out and just check for zero.
6557 */
6558#define SM_NONE 0x0
6559#define SM_PREEMPT 0x1
6560#define SM_RTLOCK_WAIT 0x2
6561
6562#ifndef CONFIG_PREEMPT_RT
6563# define SM_MASK_PREEMPT (~0U)
6564#else
6565# define SM_MASK_PREEMPT SM_PREEMPT
6566#endif
6567
6568/*
6569 * __schedule() is the main scheduler function.
6570 *
6571 * The main means of driving the scheduler and thus entering this function are:
6572 *
6573 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
6574 *
6575 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
6576 * paths. For example, see arch/x86/entry_64.S.
6577 *
6578 * To drive preemption between tasks, the scheduler sets the flag in timer
6579 * interrupt handler scheduler_tick().
6580 *
6581 * 3. Wakeups don't really cause entry into schedule(). They add a
6582 * task to the run-queue and that's it.
6583 *
6584 * Now, if the new task added to the run-queue preempts the current
6585 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
6586 * called on the nearest possible occasion:
6587 *
6588 * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
6589 *
6590 * - in syscall or exception context, at the next outmost
6591 * preempt_enable(). (this might be as soon as the wake_up()'s
6592 * spin_unlock()!)
6593 *
6594 * - in IRQ context, return from interrupt-handler to
6595 * preemptible context
6596 *
6597 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
6598 * then at the next:
6599 *
6600 * - cond_resched() call
6601 * - explicit schedule() call
6602 * - return from syscall or exception to user-space
6603 * - return from interrupt-handler to user-space
6604 *
6605 * WARNING: must be called with preemption disabled!
6606 */
6607static void __sched notrace __schedule(unsigned int sched_mode)
6608{
6609 struct task_struct *prev, *next;
6610 unsigned long *switch_count;
6611 unsigned long prev_state;
6612 struct rq_flags rf;
6613 struct rq *rq;
6614 int cpu;
6615
6616 cpu = smp_processor_id();
6617 rq = cpu_rq(cpu);
6618 prev = rq->curr;
6619
6620 schedule_debug(prev, !!sched_mode);
6621
6622 if (sched_feat(HRTICK) || sched_feat(HRTICK_DL))
6623 hrtick_clear(rq);
6624
6625 local_irq_disable();
6626 rcu_note_context_switch(!!sched_mode);
6627
6628 /*
6629 * Make sure that signal_pending_state()->signal_pending() below
6630 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
6631 * done by the caller to avoid the race with signal_wake_up():
6632 *
6633 * __set_current_state(@state) signal_wake_up()
6634 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
6635 * wake_up_state(p, state)
6636 * LOCK rq->lock LOCK p->pi_state
6637 * smp_mb__after_spinlock() smp_mb__after_spinlock()
6638 * if (signal_pending_state()) if (p->state & @state)
6639 *
6640 * Also, the membarrier system call requires a full memory barrier
6641 * after coming from user-space, before storing to rq->curr.
6642 */
6643 rq_lock(rq, &rf);
6644 smp_mb__after_spinlock();
6645
6646 /* Promote REQ to ACT */
6647 rq->clock_update_flags <<= 1;
6648 update_rq_clock(rq);
6649 rq->clock_update_flags = RQCF_UPDATED;
6650
6651 switch_count = &prev->nivcsw;
6652
6653 /*
6654 * We must load prev->state once (task_struct::state is volatile), such
6655 * that we form a control dependency vs deactivate_task() below.
6656 */
6657 prev_state = READ_ONCE(prev->__state);
6658 if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) {
6659 if (signal_pending_state(prev_state, prev)) {
6660 WRITE_ONCE(prev->__state, TASK_RUNNING);
6661 } else {
6662 prev->sched_contributes_to_load =
6663 (prev_state & TASK_UNINTERRUPTIBLE) &&
6664 !(prev_state & TASK_NOLOAD) &&
6665 !(prev_state & TASK_FROZEN);
6666
6667 if (prev->sched_contributes_to_load)
6668 rq->nr_uninterruptible++;
6669
6670 /*
6671 * __schedule() ttwu()
6672 * prev_state = prev->state; if (p->on_rq && ...)
6673 * if (prev_state) goto out;
6674 * p->on_rq = 0; smp_acquire__after_ctrl_dep();
6675 * p->state = TASK_WAKING
6676 *
6677 * Where __schedule() and ttwu() have matching control dependencies.
6678 *
6679 * After this, schedule() must not care about p->state any more.
6680 */
6681 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
6682
6683 if (prev->in_iowait) {
6684 atomic_inc(&rq->nr_iowait);
6685 delayacct_blkio_start();
6686 }
6687 }
6688 switch_count = &prev->nvcsw;
6689 }
6690
6691 next = pick_next_task(rq, prev, &rf);
6692 clear_tsk_need_resched(prev);
6693 clear_preempt_need_resched();
6694#ifdef CONFIG_SCHED_DEBUG
6695 rq->last_seen_need_resched_ns = 0;
6696#endif
6697
6698 if (likely(prev != next)) {
6699 rq->nr_switches++;
6700 /*
6701 * RCU users of rcu_dereference(rq->curr) may not see
6702 * changes to task_struct made by pick_next_task().
6703 */
6704 RCU_INIT_POINTER(rq->curr, next);
6705 /*
6706 * The membarrier system call requires each architecture
6707 * to have a full memory barrier after updating
6708 * rq->curr, before returning to user-space.
6709 *
6710 * Here are the schemes providing that barrier on the
6711 * various architectures:
6712 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
6713 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
6714 * - finish_lock_switch() for weakly-ordered
6715 * architectures where spin_unlock is a full barrier,
6716 * - switch_to() for arm64 (weakly-ordered, spin_unlock
6717 * is a RELEASE barrier),
6718 */
6719 ++*switch_count;
6720
6721 migrate_disable_switch(rq, prev);
6722 psi_sched_switch(prev, next, !task_on_rq_queued(prev));
6723
6724 trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state);
6725
6726 /* Also unlocks the rq: */
6727 rq = context_switch(rq, prev, next, &rf);
6728 } else {
6729 rq_unpin_lock(rq, &rf);
6730 __balance_callbacks(rq);
6731 raw_spin_rq_unlock_irq(rq);
6732 }
6733}
6734
6735void __noreturn do_task_dead(void)
6736{
6737 /* Causes final put_task_struct in finish_task_switch(): */
6738 set_special_state(TASK_DEAD);
6739
6740 /* Tell freezer to ignore us: */
6741 current->flags |= PF_NOFREEZE;
6742
6743 __schedule(SM_NONE);
6744 BUG();
6745
6746 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
6747 for (;;)
6748 cpu_relax();
6749}
6750
6751static inline void sched_submit_work(struct task_struct *tsk)
6752{
6753 static DEFINE_WAIT_OVERRIDE_MAP(sched_map, LD_WAIT_CONFIG);
6754 unsigned int task_flags;
6755
6756 /*
6757 * Establish LD_WAIT_CONFIG context to ensure none of the code called
6758 * will use a blocking primitive -- which would lead to recursion.
6759 */
6760 lock_map_acquire_try(&sched_map);
6761
6762 task_flags = tsk->flags;
6763 /*
6764 * If a worker goes to sleep, notify and ask workqueue whether it
6765 * wants to wake up a task to maintain concurrency.
6766 */
6767 if (task_flags & PF_WQ_WORKER)
6768 wq_worker_sleeping(tsk);
6769 else if (task_flags & PF_IO_WORKER)
6770 io_wq_worker_sleeping(tsk);
6771
6772 /*
6773 * spinlock and rwlock must not flush block requests. This will
6774 * deadlock if the callback attempts to acquire a lock which is
6775 * already acquired.
6776 */
6777 SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT);
6778
6779 /*
6780 * If we are going to sleep and we have plugged IO queued,
6781 * make sure to submit it to avoid deadlocks.
6782 */
6783 blk_flush_plug(tsk->plug, true);
6784
6785 lock_map_release(&sched_map);
6786}
6787
6788static void sched_update_worker(struct task_struct *tsk)
6789{
6790 if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6791 if (tsk->flags & PF_WQ_WORKER)
6792 wq_worker_running(tsk);
6793 else
6794 io_wq_worker_running(tsk);
6795 }
6796}
6797
6798static __always_inline void __schedule_loop(unsigned int sched_mode)
6799{
6800 do {
6801 preempt_disable();
6802 __schedule(sched_mode);
6803 sched_preempt_enable_no_resched();
6804 } while (need_resched());
6805}
6806
6807asmlinkage __visible void __sched schedule(void)
6808{
6809 struct task_struct *tsk = current;
6810
6811#ifdef CONFIG_RT_MUTEXES
6812 lockdep_assert(!tsk->sched_rt_mutex);
6813#endif
6814
6815 if (!task_is_running(tsk))
6816 sched_submit_work(tsk);
6817 __schedule_loop(SM_NONE);
6818 sched_update_worker(tsk);
6819}
6820EXPORT_SYMBOL(schedule);
6821
6822/*
6823 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
6824 * state (have scheduled out non-voluntarily) by making sure that all
6825 * tasks have either left the run queue or have gone into user space.
6826 * As idle tasks do not do either, they must not ever be preempted
6827 * (schedule out non-voluntarily).
6828 *
6829 * schedule_idle() is similar to schedule_preempt_disable() except that it
6830 * never enables preemption because it does not call sched_submit_work().
6831 */
6832void __sched schedule_idle(void)
6833{
6834 /*
6835 * As this skips calling sched_submit_work(), which the idle task does
6836 * regardless because that function is a nop when the task is in a
6837 * TASK_RUNNING state, make sure this isn't used someplace that the
6838 * current task can be in any other state. Note, idle is always in the
6839 * TASK_RUNNING state.
6840 */
6841 WARN_ON_ONCE(current->__state);
6842 do {
6843 __schedule(SM_NONE);
6844 } while (need_resched());
6845}
6846
6847#if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK)
6848asmlinkage __visible void __sched schedule_user(void)
6849{
6850 /*
6851 * If we come here after a random call to set_need_resched(),
6852 * or we have been woken up remotely but the IPI has not yet arrived,
6853 * we haven't yet exited the RCU idle mode. Do it here manually until
6854 * we find a better solution.
6855 *
6856 * NB: There are buggy callers of this function. Ideally we
6857 * should warn if prev_state != CONTEXT_USER, but that will trigger
6858 * too frequently to make sense yet.
6859 */
6860 enum ctx_state prev_state = exception_enter();
6861 schedule();
6862 exception_exit(prev_state);
6863}
6864#endif
6865
6866/**
6867 * schedule_preempt_disabled - called with preemption disabled
6868 *
6869 * Returns with preemption disabled. Note: preempt_count must be 1
6870 */
6871void __sched schedule_preempt_disabled(void)
6872{
6873 sched_preempt_enable_no_resched();
6874 schedule();
6875 preempt_disable();
6876}
6877
6878#ifdef CONFIG_PREEMPT_RT
6879void __sched notrace schedule_rtlock(void)
6880{
6881 __schedule_loop(SM_RTLOCK_WAIT);
6882}
6883NOKPROBE_SYMBOL(schedule_rtlock);
6884#endif
6885
6886static void __sched notrace preempt_schedule_common(void)
6887{
6888 do {
6889 /*
6890 * Because the function tracer can trace preempt_count_sub()
6891 * and it also uses preempt_enable/disable_notrace(), if
6892 * NEED_RESCHED is set, the preempt_enable_notrace() called
6893 * by the function tracer will call this function again and
6894 * cause infinite recursion.
6895 *
6896 * Preemption must be disabled here before the function
6897 * tracer can trace. Break up preempt_disable() into two
6898 * calls. One to disable preemption without fear of being
6899 * traced. The other to still record the preemption latency,
6900 * which can also be traced by the function tracer.
6901 */
6902 preempt_disable_notrace();
6903 preempt_latency_start(1);
6904 __schedule(SM_PREEMPT);
6905 preempt_latency_stop(1);
6906 preempt_enable_no_resched_notrace();
6907
6908 /*
6909 * Check again in case we missed a preemption opportunity
6910 * between schedule and now.
6911 */
6912 } while (need_resched());
6913}
6914
6915#ifdef CONFIG_PREEMPTION
6916/*
6917 * This is the entry point to schedule() from in-kernel preemption
6918 * off of preempt_enable.
6919 */
6920asmlinkage __visible void __sched notrace preempt_schedule(void)
6921{
6922 /*
6923 * If there is a non-zero preempt_count or interrupts are disabled,
6924 * we do not want to preempt the current task. Just return..
6925 */
6926 if (likely(!preemptible()))
6927 return;
6928 preempt_schedule_common();
6929}
6930NOKPROBE_SYMBOL(preempt_schedule);
6931EXPORT_SYMBOL(preempt_schedule);
6932
6933#ifdef CONFIG_PREEMPT_DYNAMIC
6934#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
6935#ifndef preempt_schedule_dynamic_enabled
6936#define preempt_schedule_dynamic_enabled preempt_schedule
6937#define preempt_schedule_dynamic_disabled NULL
6938#endif
6939DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);
6940EXPORT_STATIC_CALL_TRAMP(preempt_schedule);
6941#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
6942static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule);
6943void __sched notrace dynamic_preempt_schedule(void)
6944{
6945 if (!static_branch_unlikely(&sk_dynamic_preempt_schedule))
6946 return;
6947 preempt_schedule();
6948}
6949NOKPROBE_SYMBOL(dynamic_preempt_schedule);
6950EXPORT_SYMBOL(dynamic_preempt_schedule);
6951#endif
6952#endif
6953
6954/**
6955 * preempt_schedule_notrace - preempt_schedule called by tracing
6956 *
6957 * The tracing infrastructure uses preempt_enable_notrace to prevent
6958 * recursion and tracing preempt enabling caused by the tracing
6959 * infrastructure itself. But as tracing can happen in areas coming
6960 * from userspace or just about to enter userspace, a preempt enable
6961 * can occur before user_exit() is called. This will cause the scheduler
6962 * to be called when the system is still in usermode.
6963 *
6964 * To prevent this, the preempt_enable_notrace will use this function
6965 * instead of preempt_schedule() to exit user context if needed before
6966 * calling the scheduler.
6967 */
6968asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
6969{
6970 enum ctx_state prev_ctx;
6971
6972 if (likely(!preemptible()))
6973 return;
6974
6975 do {
6976 /*
6977 * Because the function tracer can trace preempt_count_sub()
6978 * and it also uses preempt_enable/disable_notrace(), if
6979 * NEED_RESCHED is set, the preempt_enable_notrace() called
6980 * by the function tracer will call this function again and
6981 * cause infinite recursion.
6982 *
6983 * Preemption must be disabled here before the function
6984 * tracer can trace. Break up preempt_disable() into two
6985 * calls. One to disable preemption without fear of being
6986 * traced. The other to still record the preemption latency,
6987 * which can also be traced by the function tracer.
6988 */
6989 preempt_disable_notrace();
6990 preempt_latency_start(1);
6991 /*
6992 * Needs preempt disabled in case user_exit() is traced
6993 * and the tracer calls preempt_enable_notrace() causing
6994 * an infinite recursion.
6995 */
6996 prev_ctx = exception_enter();
6997 __schedule(SM_PREEMPT);
6998 exception_exit(prev_ctx);
6999
7000 preempt_latency_stop(1);
7001 preempt_enable_no_resched_notrace();
7002 } while (need_resched());
7003}
7004EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
7005
7006#ifdef CONFIG_PREEMPT_DYNAMIC
7007#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
7008#ifndef preempt_schedule_notrace_dynamic_enabled
7009#define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace
7010#define preempt_schedule_notrace_dynamic_disabled NULL
7011#endif
7012DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);
7013EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
7014#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
7015static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace);
7016void __sched notrace dynamic_preempt_schedule_notrace(void)
7017{
7018 if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace))
7019 return;
7020 preempt_schedule_notrace();
7021}
7022NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace);
7023EXPORT_SYMBOL(dynamic_preempt_schedule_notrace);
7024#endif
7025#endif
7026
7027#endif /* CONFIG_PREEMPTION */
7028
7029/*
7030 * This is the entry point to schedule() from kernel preemption
7031 * off of irq context.
7032 * Note, that this is called and return with irqs disabled. This will
7033 * protect us against recursive calling from irq.
7034 */
7035asmlinkage __visible void __sched preempt_schedule_irq(void)
7036{
7037 enum ctx_state prev_state;
7038
7039 /* Catch callers which need to be fixed */
7040 BUG_ON(preempt_count() || !irqs_disabled());
7041
7042 prev_state = exception_enter();
7043
7044 do {
7045 preempt_disable();
7046 local_irq_enable();
7047 __schedule(SM_PREEMPT);
7048 local_irq_disable();
7049 sched_preempt_enable_no_resched();
7050 } while (need_resched());
7051
7052 exception_exit(prev_state);
7053}
7054
7055int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
7056 void *key)
7057{
7058 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~(WF_SYNC|WF_CURRENT_CPU));
7059 return try_to_wake_up(curr->private, mode, wake_flags);
7060}
7061EXPORT_SYMBOL(default_wake_function);
7062
7063static void __setscheduler_prio(struct task_struct *p, int prio)
7064{
7065 if (dl_prio(prio))
7066 p->sched_class = &dl_sched_class;
7067 else if (rt_prio(prio))
7068 p->sched_class = &rt_sched_class;
7069 else
7070 p->sched_class = &fair_sched_class;
7071
7072 p->prio = prio;
7073}
7074
7075#ifdef CONFIG_RT_MUTEXES
7076
7077/*
7078 * Would be more useful with typeof()/auto_type but they don't mix with
7079 * bit-fields. Since it's a local thing, use int. Keep the generic sounding
7080 * name such that if someone were to implement this function we get to compare
7081 * notes.
7082 */
7083#define fetch_and_set(x, v) ({ int _x = (x); (x) = (v); _x; })
7084
7085void rt_mutex_pre_schedule(void)
7086{
7087 lockdep_assert(!fetch_and_set(current->sched_rt_mutex, 1));
7088 sched_submit_work(current);
7089}
7090
7091void rt_mutex_schedule(void)
7092{
7093 lockdep_assert(current->sched_rt_mutex);
7094 __schedule_loop(SM_NONE);
7095}
7096
7097void rt_mutex_post_schedule(void)
7098{
7099 sched_update_worker(current);
7100 lockdep_assert(fetch_and_set(current->sched_rt_mutex, 0));
7101}
7102
7103static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
7104{
7105 if (pi_task)
7106 prio = min(prio, pi_task->prio);
7107
7108 return prio;
7109}
7110
7111static inline int rt_effective_prio(struct task_struct *p, int prio)
7112{
7113 struct task_struct *pi_task = rt_mutex_get_top_task(p);
7114
7115 return __rt_effective_prio(pi_task, prio);
7116}
7117
7118/*
7119 * rt_mutex_setprio - set the current priority of a task
7120 * @p: task to boost
7121 * @pi_task: donor task
7122 *
7123 * This function changes the 'effective' priority of a task. It does
7124 * not touch ->normal_prio like __setscheduler().
7125 *
7126 * Used by the rt_mutex code to implement priority inheritance
7127 * logic. Call site only calls if the priority of the task changed.
7128 */
7129void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
7130{
7131 int prio, oldprio, queued, running, queue_flag =
7132 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
7133 const struct sched_class *prev_class;
7134 struct rq_flags rf;
7135 struct rq *rq;
7136
7137 /* XXX used to be waiter->prio, not waiter->task->prio */
7138 prio = __rt_effective_prio(pi_task, p->normal_prio);
7139
7140 /*
7141 * If nothing changed; bail early.
7142 */
7143 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
7144 return;
7145
7146 rq = __task_rq_lock(p, &rf);
7147 update_rq_clock(rq);
7148 /*
7149 * Set under pi_lock && rq->lock, such that the value can be used under
7150 * either lock.
7151 *
7152 * Note that there is loads of tricky to make this pointer cache work
7153 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
7154 * ensure a task is de-boosted (pi_task is set to NULL) before the
7155 * task is allowed to run again (and can exit). This ensures the pointer
7156 * points to a blocked task -- which guarantees the task is present.
7157 */
7158 p->pi_top_task = pi_task;
7159
7160 /*
7161 * For FIFO/RR we only need to set prio, if that matches we're done.
7162 */
7163 if (prio == p->prio && !dl_prio(prio))
7164 goto out_unlock;
7165
7166 /*
7167 * Idle task boosting is a nono in general. There is one
7168 * exception, when PREEMPT_RT and NOHZ is active:
7169 *
7170 * The idle task calls get_next_timer_interrupt() and holds
7171 * the timer wheel base->lock on the CPU and another CPU wants
7172 * to access the timer (probably to cancel it). We can safely
7173 * ignore the boosting request, as the idle CPU runs this code
7174 * with interrupts disabled and will complete the lock
7175 * protected section without being interrupted. So there is no
7176 * real need to boost.
7177 */
7178 if (unlikely(p == rq->idle)) {
7179 WARN_ON(p != rq->curr);
7180 WARN_ON(p->pi_blocked_on);
7181 goto out_unlock;
7182 }
7183
7184 trace_sched_pi_setprio(p, pi_task);
7185 oldprio = p->prio;
7186
7187 if (oldprio == prio)
7188 queue_flag &= ~DEQUEUE_MOVE;
7189
7190 prev_class = p->sched_class;
7191 queued = task_on_rq_queued(p);
7192 running = task_current(rq, p);
7193 if (queued)
7194 dequeue_task(rq, p, queue_flag);
7195 if (running)
7196 put_prev_task(rq, p);
7197
7198 /*
7199 * Boosting condition are:
7200 * 1. -rt task is running and holds mutex A
7201 * --> -dl task blocks on mutex A
7202 *
7203 * 2. -dl task is running and holds mutex A
7204 * --> -dl task blocks on mutex A and could preempt the
7205 * running task
7206 */
7207 if (dl_prio(prio)) {
7208 if (!dl_prio(p->normal_prio) ||
7209 (pi_task && dl_prio(pi_task->prio) &&
7210 dl_entity_preempt(&pi_task->dl, &p->dl))) {
7211 p->dl.pi_se = pi_task->dl.pi_se;
7212 queue_flag |= ENQUEUE_REPLENISH;
7213 } else {
7214 p->dl.pi_se = &p->dl;
7215 }
7216 } else if (rt_prio(prio)) {
7217 if (dl_prio(oldprio))
7218 p->dl.pi_se = &p->dl;
7219 if (oldprio < prio)
7220 queue_flag |= ENQUEUE_HEAD;
7221 } else {
7222 if (dl_prio(oldprio))
7223 p->dl.pi_se = &p->dl;
7224 if (rt_prio(oldprio))
7225 p->rt.timeout = 0;
7226 }
7227
7228 __setscheduler_prio(p, prio);
7229
7230 if (queued)
7231 enqueue_task(rq, p, queue_flag);
7232 if (running)
7233 set_next_task(rq, p);
7234
7235 check_class_changed(rq, p, prev_class, oldprio);
7236out_unlock:
7237 /* Avoid rq from going away on us: */
7238 preempt_disable();
7239
7240 rq_unpin_lock(rq, &rf);
7241 __balance_callbacks(rq);
7242 raw_spin_rq_unlock(rq);
7243
7244 preempt_enable();
7245}
7246#else
7247static inline int rt_effective_prio(struct task_struct *p, int prio)
7248{
7249 return prio;
7250}
7251#endif
7252
7253void set_user_nice(struct task_struct *p, long nice)
7254{
7255 bool queued, running;
7256 struct rq *rq;
7257 int old_prio;
7258
7259 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
7260 return;
7261 /*
7262 * We have to be careful, if called from sys_setpriority(),
7263 * the task might be in the middle of scheduling on another CPU.
7264 */
7265 CLASS(task_rq_lock, rq_guard)(p);
7266 rq = rq_guard.rq;
7267
7268 update_rq_clock(rq);
7269
7270 /*
7271 * The RT priorities are set via sched_setscheduler(), but we still
7272 * allow the 'normal' nice value to be set - but as expected
7273 * it won't have any effect on scheduling until the task is
7274 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
7275 */
7276 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
7277 p->static_prio = NICE_TO_PRIO(nice);
7278 return;
7279 }
7280
7281 queued = task_on_rq_queued(p);
7282 running = task_current(rq, p);
7283 if (queued)
7284 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
7285 if (running)
7286 put_prev_task(rq, p);
7287
7288 p->static_prio = NICE_TO_PRIO(nice);
7289 set_load_weight(p, true);
7290 old_prio = p->prio;
7291 p->prio = effective_prio(p);
7292
7293 if (queued)
7294 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
7295 if (running)
7296 set_next_task(rq, p);
7297
7298 /*
7299 * If the task increased its priority or is running and
7300 * lowered its priority, then reschedule its CPU:
7301 */
7302 p->sched_class->prio_changed(rq, p, old_prio);
7303}
7304EXPORT_SYMBOL(set_user_nice);
7305
7306/*
7307 * is_nice_reduction - check if nice value is an actual reduction
7308 *
7309 * Similar to can_nice() but does not perform a capability check.
7310 *
7311 * @p: task
7312 * @nice: nice value
7313 */
7314static bool is_nice_reduction(const struct task_struct *p, const int nice)
7315{
7316 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
7317 int nice_rlim = nice_to_rlimit(nice);
7318
7319 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE));
7320}
7321
7322/*
7323 * can_nice - check if a task can reduce its nice value
7324 * @p: task
7325 * @nice: nice value
7326 */
7327int can_nice(const struct task_struct *p, const int nice)
7328{
7329 return is_nice_reduction(p, nice) || capable(CAP_SYS_NICE);
7330}
7331
7332#ifdef __ARCH_WANT_SYS_NICE
7333
7334/*
7335 * sys_nice - change the priority of the current process.
7336 * @increment: priority increment
7337 *
7338 * sys_setpriority is a more generic, but much slower function that
7339 * does similar things.
7340 */
7341SYSCALL_DEFINE1(nice, int, increment)
7342{
7343 long nice, retval;
7344
7345 /*
7346 * Setpriority might change our priority at the same moment.
7347 * We don't have to worry. Conceptually one call occurs first
7348 * and we have a single winner.
7349 */
7350 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
7351 nice = task_nice(current) + increment;
7352
7353 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
7354 if (increment < 0 && !can_nice(current, nice))
7355 return -EPERM;
7356
7357 retval = security_task_setnice(current, nice);
7358 if (retval)
7359 return retval;
7360
7361 set_user_nice(current, nice);
7362 return 0;
7363}
7364
7365#endif
7366
7367/**
7368 * task_prio - return the priority value of a given task.
7369 * @p: the task in question.
7370 *
7371 * Return: The priority value as seen by users in /proc.
7372 *
7373 * sched policy return value kernel prio user prio/nice
7374 *
7375 * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19]
7376 * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99]
7377 * deadline -101 -1 0
7378 */
7379int task_prio(const struct task_struct *p)
7380{
7381 return p->prio - MAX_RT_PRIO;
7382}
7383
7384/**
7385 * idle_cpu - is a given CPU idle currently?
7386 * @cpu: the processor in question.
7387 *
7388 * Return: 1 if the CPU is currently idle. 0 otherwise.
7389 */
7390int idle_cpu(int cpu)
7391{
7392 struct rq *rq = cpu_rq(cpu);
7393
7394 if (rq->curr != rq->idle)
7395 return 0;
7396
7397 if (rq->nr_running)
7398 return 0;
7399
7400#ifdef CONFIG_SMP
7401 if (rq->ttwu_pending)
7402 return 0;
7403#endif
7404
7405 return 1;
7406}
7407
7408/**
7409 * available_idle_cpu - is a given CPU idle for enqueuing work.
7410 * @cpu: the CPU in question.
7411 *
7412 * Return: 1 if the CPU is currently idle. 0 otherwise.
7413 */
7414int available_idle_cpu(int cpu)
7415{
7416 if (!idle_cpu(cpu))
7417 return 0;
7418
7419 if (vcpu_is_preempted(cpu))
7420 return 0;
7421
7422 return 1;
7423}
7424
7425/**
7426 * idle_task - return the idle task for a given CPU.
7427 * @cpu: the processor in question.
7428 *
7429 * Return: The idle task for the CPU @cpu.
7430 */
7431struct task_struct *idle_task(int cpu)
7432{
7433 return cpu_rq(cpu)->idle;
7434}
7435
7436#ifdef CONFIG_SCHED_CORE
7437int sched_core_idle_cpu(int cpu)
7438{
7439 struct rq *rq = cpu_rq(cpu);
7440
7441 if (sched_core_enabled(rq) && rq->curr == rq->idle)
7442 return 1;
7443
7444 return idle_cpu(cpu);
7445}
7446
7447#endif
7448
7449#ifdef CONFIG_SMP
7450/*
7451 * This function computes an effective utilization for the given CPU, to be
7452 * used for frequency selection given the linear relation: f = u * f_max.
7453 *
7454 * The scheduler tracks the following metrics:
7455 *
7456 * cpu_util_{cfs,rt,dl,irq}()
7457 * cpu_bw_dl()
7458 *
7459 * Where the cfs,rt and dl util numbers are tracked with the same metric and
7460 * synchronized windows and are thus directly comparable.
7461 *
7462 * The cfs,rt,dl utilization are the running times measured with rq->clock_task
7463 * which excludes things like IRQ and steal-time. These latter are then accrued
7464 * in the irq utilization.
7465 *
7466 * The DL bandwidth number otoh is not a measured metric but a value computed
7467 * based on the task model parameters and gives the minimal utilization
7468 * required to meet deadlines.
7469 */
7470unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
7471 unsigned long *min,
7472 unsigned long *max)
7473{
7474 unsigned long util, irq, scale;
7475 struct rq *rq = cpu_rq(cpu);
7476
7477 scale = arch_scale_cpu_capacity(cpu);
7478
7479 /*
7480 * Early check to see if IRQ/steal time saturates the CPU, can be
7481 * because of inaccuracies in how we track these -- see
7482 * update_irq_load_avg().
7483 */
7484 irq = cpu_util_irq(rq);
7485 if (unlikely(irq >= scale)) {
7486 if (min)
7487 *min = scale;
7488 if (max)
7489 *max = scale;
7490 return scale;
7491 }
7492
7493 if (min) {
7494 /*
7495 * The minimum utilization returns the highest level between:
7496 * - the computed DL bandwidth needed with the IRQ pressure which
7497 * steals time to the deadline task.
7498 * - The minimum performance requirement for CFS and/or RT.
7499 */
7500 *min = max(irq + cpu_bw_dl(rq), uclamp_rq_get(rq, UCLAMP_MIN));
7501
7502 /*
7503 * When an RT task is runnable and uclamp is not used, we must
7504 * ensure that the task will run at maximum compute capacity.
7505 */
7506 if (!uclamp_is_used() && rt_rq_is_runnable(&rq->rt))
7507 *min = max(*min, scale);
7508 }
7509
7510 /*
7511 * Because the time spend on RT/DL tasks is visible as 'lost' time to
7512 * CFS tasks and we use the same metric to track the effective
7513 * utilization (PELT windows are synchronized) we can directly add them
7514 * to obtain the CPU's actual utilization.
7515 */
7516 util = util_cfs + cpu_util_rt(rq);
7517 util += cpu_util_dl(rq);
7518
7519 /*
7520 * The maximum hint is a soft bandwidth requirement, which can be lower
7521 * than the actual utilization because of uclamp_max requirements.
7522 */
7523 if (max)
7524 *max = min(scale, uclamp_rq_get(rq, UCLAMP_MAX));
7525
7526 if (util >= scale)
7527 return scale;
7528
7529 /*
7530 * There is still idle time; further improve the number by using the
7531 * irq metric. Because IRQ/steal time is hidden from the task clock we
7532 * need to scale the task numbers:
7533 *
7534 * max - irq
7535 * U' = irq + --------- * U
7536 * max
7537 */
7538 util = scale_irq_capacity(util, irq, scale);
7539 util += irq;
7540
7541 return min(scale, util);
7542}
7543
7544unsigned long sched_cpu_util(int cpu)
7545{
7546 return effective_cpu_util(cpu, cpu_util_cfs(cpu), NULL, NULL);
7547}
7548#endif /* CONFIG_SMP */
7549
7550/**
7551 * find_process_by_pid - find a process with a matching PID value.
7552 * @pid: the pid in question.
7553 *
7554 * The task of @pid, if found. %NULL otherwise.
7555 */
7556static struct task_struct *find_process_by_pid(pid_t pid)
7557{
7558 return pid ? find_task_by_vpid(pid) : current;
7559}
7560
7561static struct task_struct *find_get_task(pid_t pid)
7562{
7563 struct task_struct *p;
7564 guard(rcu)();
7565
7566 p = find_process_by_pid(pid);
7567 if (likely(p))
7568 get_task_struct(p);
7569
7570 return p;
7571}
7572
7573DEFINE_CLASS(find_get_task, struct task_struct *, if (_T) put_task_struct(_T),
7574 find_get_task(pid), pid_t pid)
7575
7576/*
7577 * sched_setparam() passes in -1 for its policy, to let the functions
7578 * it calls know not to change it.
7579 */
7580#define SETPARAM_POLICY -1
7581
7582static void __setscheduler_params(struct task_struct *p,
7583 const struct sched_attr *attr)
7584{
7585 int policy = attr->sched_policy;
7586
7587 if (policy == SETPARAM_POLICY)
7588 policy = p->policy;
7589
7590 p->policy = policy;
7591
7592 if (dl_policy(policy))
7593 __setparam_dl(p, attr);
7594 else if (fair_policy(policy))
7595 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
7596
7597 /*
7598 * __sched_setscheduler() ensures attr->sched_priority == 0 when
7599 * !rt_policy. Always setting this ensures that things like
7600 * getparam()/getattr() don't report silly values for !rt tasks.
7601 */
7602 p->rt_priority = attr->sched_priority;
7603 p->normal_prio = normal_prio(p);
7604 set_load_weight(p, true);
7605}
7606
7607/*
7608 * Check the target process has a UID that matches the current process's:
7609 */
7610static bool check_same_owner(struct task_struct *p)
7611{
7612 const struct cred *cred = current_cred(), *pcred;
7613 guard(rcu)();
7614
7615 pcred = __task_cred(p);
7616 return (uid_eq(cred->euid, pcred->euid) ||
7617 uid_eq(cred->euid, pcred->uid));
7618}
7619
7620/*
7621 * Allow unprivileged RT tasks to decrease priority.
7622 * Only issue a capable test if needed and only once to avoid an audit
7623 * event on permitted non-privileged operations:
7624 */
7625static int user_check_sched_setscheduler(struct task_struct *p,
7626 const struct sched_attr *attr,
7627 int policy, int reset_on_fork)
7628{
7629 if (fair_policy(policy)) {
7630 if (attr->sched_nice < task_nice(p) &&
7631 !is_nice_reduction(p, attr->sched_nice))
7632 goto req_priv;
7633 }
7634
7635 if (rt_policy(policy)) {
7636 unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO);
7637
7638 /* Can't set/change the rt policy: */
7639 if (policy != p->policy && !rlim_rtprio)
7640 goto req_priv;
7641
7642 /* Can't increase priority: */
7643 if (attr->sched_priority > p->rt_priority &&
7644 attr->sched_priority > rlim_rtprio)
7645 goto req_priv;
7646 }
7647
7648 /*
7649 * Can't set/change SCHED_DEADLINE policy at all for now
7650 * (safest behavior); in the future we would like to allow
7651 * unprivileged DL tasks to increase their relative deadline
7652 * or reduce their runtime (both ways reducing utilization)
7653 */
7654 if (dl_policy(policy))
7655 goto req_priv;
7656
7657 /*
7658 * Treat SCHED_IDLE as nice 20. Only allow a switch to
7659 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
7660 */
7661 if (task_has_idle_policy(p) && !idle_policy(policy)) {
7662 if (!is_nice_reduction(p, task_nice(p)))
7663 goto req_priv;
7664 }
7665
7666 /* Can't change other user's priorities: */
7667 if (!check_same_owner(p))
7668 goto req_priv;
7669
7670 /* Normal users shall not reset the sched_reset_on_fork flag: */
7671 if (p->sched_reset_on_fork && !reset_on_fork)
7672 goto req_priv;
7673
7674 return 0;
7675
7676req_priv:
7677 if (!capable(CAP_SYS_NICE))
7678 return -EPERM;
7679
7680 return 0;
7681}
7682
7683static int __sched_setscheduler(struct task_struct *p,
7684 const struct sched_attr *attr,
7685 bool user, bool pi)
7686{
7687 int oldpolicy = -1, policy = attr->sched_policy;
7688 int retval, oldprio, newprio, queued, running;
7689 const struct sched_class *prev_class;
7690 struct balance_callback *head;
7691 struct rq_flags rf;
7692 int reset_on_fork;
7693 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
7694 struct rq *rq;
7695 bool cpuset_locked = false;
7696
7697 /* The pi code expects interrupts enabled */
7698 BUG_ON(pi && in_interrupt());
7699recheck:
7700 /* Double check policy once rq lock held: */
7701 if (policy < 0) {
7702 reset_on_fork = p->sched_reset_on_fork;
7703 policy = oldpolicy = p->policy;
7704 } else {
7705 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
7706
7707 if (!valid_policy(policy))
7708 return -EINVAL;
7709 }
7710
7711 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
7712 return -EINVAL;
7713
7714 /*
7715 * Valid priorities for SCHED_FIFO and SCHED_RR are
7716 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
7717 * SCHED_BATCH and SCHED_IDLE is 0.
7718 */
7719 if (attr->sched_priority > MAX_RT_PRIO-1)
7720 return -EINVAL;
7721 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
7722 (rt_policy(policy) != (attr->sched_priority != 0)))
7723 return -EINVAL;
7724
7725 if (user) {
7726 retval = user_check_sched_setscheduler(p, attr, policy, reset_on_fork);
7727 if (retval)
7728 return retval;
7729
7730 if (attr->sched_flags & SCHED_FLAG_SUGOV)
7731 return -EINVAL;
7732
7733 retval = security_task_setscheduler(p);
7734 if (retval)
7735 return retval;
7736 }
7737
7738 /* Update task specific "requested" clamps */
7739 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
7740 retval = uclamp_validate(p, attr);
7741 if (retval)
7742 return retval;
7743 }
7744
7745 /*
7746 * SCHED_DEADLINE bandwidth accounting relies on stable cpusets
7747 * information.
7748 */
7749 if (dl_policy(policy) || dl_policy(p->policy)) {
7750 cpuset_locked = true;
7751 cpuset_lock();
7752 }
7753
7754 /*
7755 * Make sure no PI-waiters arrive (or leave) while we are
7756 * changing the priority of the task:
7757 *
7758 * To be able to change p->policy safely, the appropriate
7759 * runqueue lock must be held.
7760 */
7761 rq = task_rq_lock(p, &rf);
7762 update_rq_clock(rq);
7763
7764 /*
7765 * Changing the policy of the stop threads its a very bad idea:
7766 */
7767 if (p == rq->stop) {
7768 retval = -EINVAL;
7769 goto unlock;
7770 }
7771
7772 /*
7773 * If not changing anything there's no need to proceed further,
7774 * but store a possible modification of reset_on_fork.
7775 */
7776 if (unlikely(policy == p->policy)) {
7777 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
7778 goto change;
7779 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
7780 goto change;
7781 if (dl_policy(policy) && dl_param_changed(p, attr))
7782 goto change;
7783 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
7784 goto change;
7785
7786 p->sched_reset_on_fork = reset_on_fork;
7787 retval = 0;
7788 goto unlock;
7789 }
7790change:
7791
7792 if (user) {
7793#ifdef CONFIG_RT_GROUP_SCHED
7794 /*
7795 * Do not allow realtime tasks into groups that have no runtime
7796 * assigned.
7797 */
7798 if (rt_bandwidth_enabled() && rt_policy(policy) &&
7799 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
7800 !task_group_is_autogroup(task_group(p))) {
7801 retval = -EPERM;
7802 goto unlock;
7803 }
7804#endif
7805#ifdef CONFIG_SMP
7806 if (dl_bandwidth_enabled() && dl_policy(policy) &&
7807 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
7808 cpumask_t *span = rq->rd->span;
7809
7810 /*
7811 * Don't allow tasks with an affinity mask smaller than
7812 * the entire root_domain to become SCHED_DEADLINE. We
7813 * will also fail if there's no bandwidth available.
7814 */
7815 if (!cpumask_subset(span, p->cpus_ptr) ||
7816 rq->rd->dl_bw.bw == 0) {
7817 retval = -EPERM;
7818 goto unlock;
7819 }
7820 }
7821#endif
7822 }
7823
7824 /* Re-check policy now with rq lock held: */
7825 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
7826 policy = oldpolicy = -1;
7827 task_rq_unlock(rq, p, &rf);
7828 if (cpuset_locked)
7829 cpuset_unlock();
7830 goto recheck;
7831 }
7832
7833 /*
7834 * If setscheduling to SCHED_DEADLINE (or changing the parameters
7835 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
7836 * is available.
7837 */
7838 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
7839 retval = -EBUSY;
7840 goto unlock;
7841 }
7842
7843 p->sched_reset_on_fork = reset_on_fork;
7844 oldprio = p->prio;
7845
7846 newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice);
7847 if (pi) {
7848 /*
7849 * Take priority boosted tasks into account. If the new
7850 * effective priority is unchanged, we just store the new
7851 * normal parameters and do not touch the scheduler class and
7852 * the runqueue. This will be done when the task deboost
7853 * itself.
7854 */
7855 newprio = rt_effective_prio(p, newprio);
7856 if (newprio == oldprio)
7857 queue_flags &= ~DEQUEUE_MOVE;
7858 }
7859
7860 queued = task_on_rq_queued(p);
7861 running = task_current(rq, p);
7862 if (queued)
7863 dequeue_task(rq, p, queue_flags);
7864 if (running)
7865 put_prev_task(rq, p);
7866
7867 prev_class = p->sched_class;
7868
7869 if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
7870 __setscheduler_params(p, attr);
7871 __setscheduler_prio(p, newprio);
7872 }
7873 __setscheduler_uclamp(p, attr);
7874
7875 if (queued) {
7876 /*
7877 * We enqueue to tail when the priority of a task is
7878 * increased (user space view).
7879 */
7880 if (oldprio < p->prio)
7881 queue_flags |= ENQUEUE_HEAD;
7882
7883 enqueue_task(rq, p, queue_flags);
7884 }
7885 if (running)
7886 set_next_task(rq, p);
7887
7888 check_class_changed(rq, p, prev_class, oldprio);
7889
7890 /* Avoid rq from going away on us: */
7891 preempt_disable();
7892 head = splice_balance_callbacks(rq);
7893 task_rq_unlock(rq, p, &rf);
7894
7895 if (pi) {
7896 if (cpuset_locked)
7897 cpuset_unlock();
7898 rt_mutex_adjust_pi(p);
7899 }
7900
7901 /* Run balance callbacks after we've adjusted the PI chain: */
7902 balance_callbacks(rq, head);
7903 preempt_enable();
7904
7905 return 0;
7906
7907unlock:
7908 task_rq_unlock(rq, p, &rf);
7909 if (cpuset_locked)
7910 cpuset_unlock();
7911 return retval;
7912}
7913
7914static int _sched_setscheduler(struct task_struct *p, int policy,
7915 const struct sched_param *param, bool check)
7916{
7917 struct sched_attr attr = {
7918 .sched_policy = policy,
7919 .sched_priority = param->sched_priority,
7920 .sched_nice = PRIO_TO_NICE(p->static_prio),
7921 };
7922
7923 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
7924 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
7925 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
7926 policy &= ~SCHED_RESET_ON_FORK;
7927 attr.sched_policy = policy;
7928 }
7929
7930 return __sched_setscheduler(p, &attr, check, true);
7931}
7932/**
7933 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
7934 * @p: the task in question.
7935 * @policy: new policy.
7936 * @param: structure containing the new RT priority.
7937 *
7938 * Use sched_set_fifo(), read its comment.
7939 *
7940 * Return: 0 on success. An error code otherwise.
7941 *
7942 * NOTE that the task may be already dead.
7943 */
7944int sched_setscheduler(struct task_struct *p, int policy,
7945 const struct sched_param *param)
7946{
7947 return _sched_setscheduler(p, policy, param, true);
7948}
7949
7950int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
7951{
7952 return __sched_setscheduler(p, attr, true, true);
7953}
7954
7955int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
7956{
7957 return __sched_setscheduler(p, attr, false, true);
7958}
7959EXPORT_SYMBOL_GPL(sched_setattr_nocheck);
7960
7961/**
7962 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
7963 * @p: the task in question.
7964 * @policy: new policy.
7965 * @param: structure containing the new RT priority.
7966 *
7967 * Just like sched_setscheduler, only don't bother checking if the
7968 * current context has permission. For example, this is needed in
7969 * stop_machine(): we create temporary high priority worker threads,
7970 * but our caller might not have that capability.
7971 *
7972 * Return: 0 on success. An error code otherwise.
7973 */
7974int sched_setscheduler_nocheck(struct task_struct *p, int policy,
7975 const struct sched_param *param)
7976{
7977 return _sched_setscheduler(p, policy, param, false);
7978}
7979
7980/*
7981 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
7982 * incapable of resource management, which is the one thing an OS really should
7983 * be doing.
7984 *
7985 * This is of course the reason it is limited to privileged users only.
7986 *
7987 * Worse still; it is fundamentally impossible to compose static priority
7988 * workloads. You cannot take two correctly working static prio workloads
7989 * and smash them together and still expect them to work.
7990 *
7991 * For this reason 'all' FIFO tasks the kernel creates are basically at:
7992 *
7993 * MAX_RT_PRIO / 2
7994 *
7995 * The administrator _MUST_ configure the system, the kernel simply doesn't
7996 * know enough information to make a sensible choice.
7997 */
7998void sched_set_fifo(struct task_struct *p)
7999{
8000 struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
8001 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
8002}
8003EXPORT_SYMBOL_GPL(sched_set_fifo);
8004
8005/*
8006 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
8007 */
8008void sched_set_fifo_low(struct task_struct *p)
8009{
8010 struct sched_param sp = { .sched_priority = 1 };
8011 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
8012}
8013EXPORT_SYMBOL_GPL(sched_set_fifo_low);
8014
8015void sched_set_normal(struct task_struct *p, int nice)
8016{
8017 struct sched_attr attr = {
8018 .sched_policy = SCHED_NORMAL,
8019 .sched_nice = nice,
8020 };
8021 WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
8022}
8023EXPORT_SYMBOL_GPL(sched_set_normal);
8024
8025static int
8026do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
8027{
8028 struct sched_param lparam;
8029
8030 if (!param || pid < 0)
8031 return -EINVAL;
8032 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
8033 return -EFAULT;
8034
8035 CLASS(find_get_task, p)(pid);
8036 if (!p)
8037 return -ESRCH;
8038
8039 return sched_setscheduler(p, policy, &lparam);
8040}
8041
8042/*
8043 * Mimics kernel/events/core.c perf_copy_attr().
8044 */
8045static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
8046{
8047 u32 size;
8048 int ret;
8049
8050 /* Zero the full structure, so that a short copy will be nice: */
8051 memset(attr, 0, sizeof(*attr));
8052
8053 ret = get_user(size, &uattr->size);
8054 if (ret)
8055 return ret;
8056
8057 /* ABI compatibility quirk: */
8058 if (!size)
8059 size = SCHED_ATTR_SIZE_VER0;
8060 if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
8061 goto err_size;
8062
8063 ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
8064 if (ret) {
8065 if (ret == -E2BIG)
8066 goto err_size;
8067 return ret;
8068 }
8069
8070 if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
8071 size < SCHED_ATTR_SIZE_VER1)
8072 return -EINVAL;
8073
8074 /*
8075 * XXX: Do we want to be lenient like existing syscalls; or do we want
8076 * to be strict and return an error on out-of-bounds values?
8077 */
8078 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
8079
8080 return 0;
8081
8082err_size:
8083 put_user(sizeof(*attr), &uattr->size);
8084 return -E2BIG;
8085}
8086
8087static void get_params(struct task_struct *p, struct sched_attr *attr)
8088{
8089 if (task_has_dl_policy(p))
8090 __getparam_dl(p, attr);
8091 else if (task_has_rt_policy(p))
8092 attr->sched_priority = p->rt_priority;
8093 else
8094 attr->sched_nice = task_nice(p);
8095}
8096
8097/**
8098 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
8099 * @pid: the pid in question.
8100 * @policy: new policy.
8101 * @param: structure containing the new RT priority.
8102 *
8103 * Return: 0 on success. An error code otherwise.
8104 */
8105SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
8106{
8107 if (policy < 0)
8108 return -EINVAL;
8109
8110 return do_sched_setscheduler(pid, policy, param);
8111}
8112
8113/**
8114 * sys_sched_setparam - set/change the RT priority of a thread
8115 * @pid: the pid in question.
8116 * @param: structure containing the new RT priority.
8117 *
8118 * Return: 0 on success. An error code otherwise.
8119 */
8120SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
8121{
8122 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
8123}
8124
8125/**
8126 * sys_sched_setattr - same as above, but with extended sched_attr
8127 * @pid: the pid in question.
8128 * @uattr: structure containing the extended parameters.
8129 * @flags: for future extension.
8130 */
8131SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
8132 unsigned int, flags)
8133{
8134 struct sched_attr attr;
8135 int retval;
8136
8137 if (!uattr || pid < 0 || flags)
8138 return -EINVAL;
8139
8140 retval = sched_copy_attr(uattr, &attr);
8141 if (retval)
8142 return retval;
8143
8144 if ((int)attr.sched_policy < 0)
8145 return -EINVAL;
8146 if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
8147 attr.sched_policy = SETPARAM_POLICY;
8148
8149 CLASS(find_get_task, p)(pid);
8150 if (!p)
8151 return -ESRCH;
8152
8153 if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
8154 get_params(p, &attr);
8155
8156 return sched_setattr(p, &attr);
8157}
8158
8159/**
8160 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
8161 * @pid: the pid in question.
8162 *
8163 * Return: On success, the policy of the thread. Otherwise, a negative error
8164 * code.
8165 */
8166SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
8167{
8168 struct task_struct *p;
8169 int retval;
8170
8171 if (pid < 0)
8172 return -EINVAL;
8173
8174 guard(rcu)();
8175 p = find_process_by_pid(pid);
8176 if (!p)
8177 return -ESRCH;
8178
8179 retval = security_task_getscheduler(p);
8180 if (!retval) {
8181 retval = p->policy;
8182 if (p->sched_reset_on_fork)
8183 retval |= SCHED_RESET_ON_FORK;
8184 }
8185 return retval;
8186}
8187
8188/**
8189 * sys_sched_getparam - get the RT priority of a thread
8190 * @pid: the pid in question.
8191 * @param: structure containing the RT priority.
8192 *
8193 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
8194 * code.
8195 */
8196SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
8197{
8198 struct sched_param lp = { .sched_priority = 0 };
8199 struct task_struct *p;
8200 int retval;
8201
8202 if (!param || pid < 0)
8203 return -EINVAL;
8204
8205 scoped_guard (rcu) {
8206 p = find_process_by_pid(pid);
8207 if (!p)
8208 return -ESRCH;
8209
8210 retval = security_task_getscheduler(p);
8211 if (retval)
8212 return retval;
8213
8214 if (task_has_rt_policy(p))
8215 lp.sched_priority = p->rt_priority;
8216 }
8217
8218 /*
8219 * This one might sleep, we cannot do it with a spinlock held ...
8220 */
8221 return copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
8222}
8223
8224/*
8225 * Copy the kernel size attribute structure (which might be larger
8226 * than what user-space knows about) to user-space.
8227 *
8228 * Note that all cases are valid: user-space buffer can be larger or
8229 * smaller than the kernel-space buffer. The usual case is that both
8230 * have the same size.
8231 */
8232static int
8233sched_attr_copy_to_user(struct sched_attr __user *uattr,
8234 struct sched_attr *kattr,
8235 unsigned int usize)
8236{
8237 unsigned int ksize = sizeof(*kattr);
8238
8239 if (!access_ok(uattr, usize))
8240 return -EFAULT;
8241
8242 /*
8243 * sched_getattr() ABI forwards and backwards compatibility:
8244 *
8245 * If usize == ksize then we just copy everything to user-space and all is good.
8246 *
8247 * If usize < ksize then we only copy as much as user-space has space for,
8248 * this keeps ABI compatibility as well. We skip the rest.
8249 *
8250 * If usize > ksize then user-space is using a newer version of the ABI,
8251 * which part the kernel doesn't know about. Just ignore it - tooling can
8252 * detect the kernel's knowledge of attributes from the attr->size value
8253 * which is set to ksize in this case.
8254 */
8255 kattr->size = min(usize, ksize);
8256
8257 if (copy_to_user(uattr, kattr, kattr->size))
8258 return -EFAULT;
8259
8260 return 0;
8261}
8262
8263/**
8264 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
8265 * @pid: the pid in question.
8266 * @uattr: structure containing the extended parameters.
8267 * @usize: sizeof(attr) for fwd/bwd comp.
8268 * @flags: for future extension.
8269 */
8270SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
8271 unsigned int, usize, unsigned int, flags)
8272{
8273 struct sched_attr kattr = { };
8274 struct task_struct *p;
8275 int retval;
8276
8277 if (!uattr || pid < 0 || usize > PAGE_SIZE ||
8278 usize < SCHED_ATTR_SIZE_VER0 || flags)
8279 return -EINVAL;
8280
8281 scoped_guard (rcu) {
8282 p = find_process_by_pid(pid);
8283 if (!p)
8284 return -ESRCH;
8285
8286 retval = security_task_getscheduler(p);
8287 if (retval)
8288 return retval;
8289
8290 kattr.sched_policy = p->policy;
8291 if (p->sched_reset_on_fork)
8292 kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
8293 get_params(p, &kattr);
8294 kattr.sched_flags &= SCHED_FLAG_ALL;
8295
8296#ifdef CONFIG_UCLAMP_TASK
8297 /*
8298 * This could race with another potential updater, but this is fine
8299 * because it'll correctly read the old or the new value. We don't need
8300 * to guarantee who wins the race as long as it doesn't return garbage.
8301 */
8302 kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
8303 kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
8304#endif
8305 }
8306
8307 return sched_attr_copy_to_user(uattr, &kattr, usize);
8308}
8309
8310#ifdef CONFIG_SMP
8311int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
8312{
8313 /*
8314 * If the task isn't a deadline task or admission control is
8315 * disabled then we don't care about affinity changes.
8316 */
8317 if (!task_has_dl_policy(p) || !dl_bandwidth_enabled())
8318 return 0;
8319
8320 /*
8321 * Since bandwidth control happens on root_domain basis,
8322 * if admission test is enabled, we only admit -deadline
8323 * tasks allowed to run on all the CPUs in the task's
8324 * root_domain.
8325 */
8326 guard(rcu)();
8327 if (!cpumask_subset(task_rq(p)->rd->span, mask))
8328 return -EBUSY;
8329
8330 return 0;
8331}
8332#endif
8333
8334static int
8335__sched_setaffinity(struct task_struct *p, struct affinity_context *ctx)
8336{
8337 int retval;
8338 cpumask_var_t cpus_allowed, new_mask;
8339
8340 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL))
8341 return -ENOMEM;
8342
8343 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
8344 retval = -ENOMEM;
8345 goto out_free_cpus_allowed;
8346 }
8347
8348 cpuset_cpus_allowed(p, cpus_allowed);
8349 cpumask_and(new_mask, ctx->new_mask, cpus_allowed);
8350
8351 ctx->new_mask = new_mask;
8352 ctx->flags |= SCA_CHECK;
8353
8354 retval = dl_task_check_affinity(p, new_mask);
8355 if (retval)
8356 goto out_free_new_mask;
8357
8358 retval = __set_cpus_allowed_ptr(p, ctx);
8359 if (retval)
8360 goto out_free_new_mask;
8361
8362 cpuset_cpus_allowed(p, cpus_allowed);
8363 if (!cpumask_subset(new_mask, cpus_allowed)) {
8364 /*
8365 * We must have raced with a concurrent cpuset update.
8366 * Just reset the cpumask to the cpuset's cpus_allowed.
8367 */
8368 cpumask_copy(new_mask, cpus_allowed);
8369
8370 /*
8371 * If SCA_USER is set, a 2nd call to __set_cpus_allowed_ptr()
8372 * will restore the previous user_cpus_ptr value.
8373 *
8374 * In the unlikely event a previous user_cpus_ptr exists,
8375 * we need to further restrict the mask to what is allowed
8376 * by that old user_cpus_ptr.
8377 */
8378 if (unlikely((ctx->flags & SCA_USER) && ctx->user_mask)) {
8379 bool empty = !cpumask_and(new_mask, new_mask,
8380 ctx->user_mask);
8381
8382 if (WARN_ON_ONCE(empty))
8383 cpumask_copy(new_mask, cpus_allowed);
8384 }
8385 __set_cpus_allowed_ptr(p, ctx);
8386 retval = -EINVAL;
8387 }
8388
8389out_free_new_mask:
8390 free_cpumask_var(new_mask);
8391out_free_cpus_allowed:
8392 free_cpumask_var(cpus_allowed);
8393 return retval;
8394}
8395
8396long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
8397{
8398 struct affinity_context ac;
8399 struct cpumask *user_mask;
8400 int retval;
8401
8402 CLASS(find_get_task, p)(pid);
8403 if (!p)
8404 return -ESRCH;
8405
8406 if (p->flags & PF_NO_SETAFFINITY)
8407 return -EINVAL;
8408
8409 if (!check_same_owner(p)) {
8410 guard(rcu)();
8411 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
8412 return -EPERM;
8413 }
8414
8415 retval = security_task_setscheduler(p);
8416 if (retval)
8417 return retval;
8418
8419 /*
8420 * With non-SMP configs, user_cpus_ptr/user_mask isn't used and
8421 * alloc_user_cpus_ptr() returns NULL.
8422 */
8423 user_mask = alloc_user_cpus_ptr(NUMA_NO_NODE);
8424 if (user_mask) {
8425 cpumask_copy(user_mask, in_mask);
8426 } else if (IS_ENABLED(CONFIG_SMP)) {
8427 return -ENOMEM;
8428 }
8429
8430 ac = (struct affinity_context){
8431 .new_mask = in_mask,
8432 .user_mask = user_mask,
8433 .flags = SCA_USER,
8434 };
8435
8436 retval = __sched_setaffinity(p, &ac);
8437 kfree(ac.user_mask);
8438
8439 return retval;
8440}
8441
8442static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
8443 struct cpumask *new_mask)
8444{
8445 if (len < cpumask_size())
8446 cpumask_clear(new_mask);
8447 else if (len > cpumask_size())
8448 len = cpumask_size();
8449
8450 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
8451}
8452
8453/**
8454 * sys_sched_setaffinity - set the CPU affinity of a process
8455 * @pid: pid of the process
8456 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8457 * @user_mask_ptr: user-space pointer to the new CPU mask
8458 *
8459 * Return: 0 on success. An error code otherwise.
8460 */
8461SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
8462 unsigned long __user *, user_mask_ptr)
8463{
8464 cpumask_var_t new_mask;
8465 int retval;
8466
8467 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
8468 return -ENOMEM;
8469
8470 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
8471 if (retval == 0)
8472 retval = sched_setaffinity(pid, new_mask);
8473 free_cpumask_var(new_mask);
8474 return retval;
8475}
8476
8477long sched_getaffinity(pid_t pid, struct cpumask *mask)
8478{
8479 struct task_struct *p;
8480 int retval;
8481
8482 guard(rcu)();
8483 p = find_process_by_pid(pid);
8484 if (!p)
8485 return -ESRCH;
8486
8487 retval = security_task_getscheduler(p);
8488 if (retval)
8489 return retval;
8490
8491 guard(raw_spinlock_irqsave)(&p->pi_lock);
8492 cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
8493
8494 return 0;
8495}
8496
8497/**
8498 * sys_sched_getaffinity - get the CPU affinity of a process
8499 * @pid: pid of the process
8500 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
8501 * @user_mask_ptr: user-space pointer to hold the current CPU mask
8502 *
8503 * Return: size of CPU mask copied to user_mask_ptr on success. An
8504 * error code otherwise.
8505 */
8506SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
8507 unsigned long __user *, user_mask_ptr)
8508{
8509 int ret;
8510 cpumask_var_t mask;
8511
8512 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
8513 return -EINVAL;
8514 if (len & (sizeof(unsigned long)-1))
8515 return -EINVAL;
8516
8517 if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
8518 return -ENOMEM;
8519
8520 ret = sched_getaffinity(pid, mask);
8521 if (ret == 0) {
8522 unsigned int retlen = min(len, cpumask_size());
8523
8524 if (copy_to_user(user_mask_ptr, cpumask_bits(mask), retlen))
8525 ret = -EFAULT;
8526 else
8527 ret = retlen;
8528 }
8529 free_cpumask_var(mask);
8530
8531 return ret;
8532}
8533
8534static void do_sched_yield(void)
8535{
8536 struct rq_flags rf;
8537 struct rq *rq;
8538
8539 rq = this_rq_lock_irq(&rf);
8540
8541 schedstat_inc(rq->yld_count);
8542 current->sched_class->yield_task(rq);
8543
8544 preempt_disable();
8545 rq_unlock_irq(rq, &rf);
8546 sched_preempt_enable_no_resched();
8547
8548 schedule();
8549}
8550
8551/**
8552 * sys_sched_yield - yield the current processor to other threads.
8553 *
8554 * This function yields the current CPU to other tasks. If there are no
8555 * other threads running on this CPU then this function will return.
8556 *
8557 * Return: 0.
8558 */
8559SYSCALL_DEFINE0(sched_yield)
8560{
8561 do_sched_yield();
8562 return 0;
8563}
8564
8565#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
8566int __sched __cond_resched(void)
8567{
8568 if (should_resched(0)) {
8569 preempt_schedule_common();
8570 return 1;
8571 }
8572 /*
8573 * In preemptible kernels, ->rcu_read_lock_nesting tells the tick
8574 * whether the current CPU is in an RCU read-side critical section,
8575 * so the tick can report quiescent states even for CPUs looping
8576 * in kernel context. In contrast, in non-preemptible kernels,
8577 * RCU readers leave no in-memory hints, which means that CPU-bound
8578 * processes executing in kernel context might never report an
8579 * RCU quiescent state. Therefore, the following code causes
8580 * cond_resched() to report a quiescent state, but only when RCU
8581 * is in urgent need of one.
8582 */
8583#ifndef CONFIG_PREEMPT_RCU
8584 rcu_all_qs();
8585#endif
8586 return 0;
8587}
8588EXPORT_SYMBOL(__cond_resched);
8589#endif
8590
8591#ifdef CONFIG_PREEMPT_DYNAMIC
8592#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
8593#define cond_resched_dynamic_enabled __cond_resched
8594#define cond_resched_dynamic_disabled ((void *)&__static_call_return0)
8595DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
8596EXPORT_STATIC_CALL_TRAMP(cond_resched);
8597
8598#define might_resched_dynamic_enabled __cond_resched
8599#define might_resched_dynamic_disabled ((void *)&__static_call_return0)
8600DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
8601EXPORT_STATIC_CALL_TRAMP(might_resched);
8602#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
8603static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched);
8604int __sched dynamic_cond_resched(void)
8605{
8606 klp_sched_try_switch();
8607 if (!static_branch_unlikely(&sk_dynamic_cond_resched))
8608 return 0;
8609 return __cond_resched();
8610}
8611EXPORT_SYMBOL(dynamic_cond_resched);
8612
8613static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched);
8614int __sched dynamic_might_resched(void)
8615{
8616 if (!static_branch_unlikely(&sk_dynamic_might_resched))
8617 return 0;
8618 return __cond_resched();
8619}
8620EXPORT_SYMBOL(dynamic_might_resched);
8621#endif
8622#endif
8623
8624/*
8625 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
8626 * call schedule, and on return reacquire the lock.
8627 *
8628 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
8629 * operations here to prevent schedule() from being called twice (once via
8630 * spin_unlock(), once by hand).
8631 */
8632int __cond_resched_lock(spinlock_t *lock)
8633{
8634 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8635 int ret = 0;
8636
8637 lockdep_assert_held(lock);
8638
8639 if (spin_needbreak(lock) || resched) {
8640 spin_unlock(lock);
8641 if (!_cond_resched())
8642 cpu_relax();
8643 ret = 1;
8644 spin_lock(lock);
8645 }
8646 return ret;
8647}
8648EXPORT_SYMBOL(__cond_resched_lock);
8649
8650int __cond_resched_rwlock_read(rwlock_t *lock)
8651{
8652 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8653 int ret = 0;
8654
8655 lockdep_assert_held_read(lock);
8656
8657 if (rwlock_needbreak(lock) || resched) {
8658 read_unlock(lock);
8659 if (!_cond_resched())
8660 cpu_relax();
8661 ret = 1;
8662 read_lock(lock);
8663 }
8664 return ret;
8665}
8666EXPORT_SYMBOL(__cond_resched_rwlock_read);
8667
8668int __cond_resched_rwlock_write(rwlock_t *lock)
8669{
8670 int resched = should_resched(PREEMPT_LOCK_OFFSET);
8671 int ret = 0;
8672
8673 lockdep_assert_held_write(lock);
8674
8675 if (rwlock_needbreak(lock) || resched) {
8676 write_unlock(lock);
8677 if (!_cond_resched())
8678 cpu_relax();
8679 ret = 1;
8680 write_lock(lock);
8681 }
8682 return ret;
8683}
8684EXPORT_SYMBOL(__cond_resched_rwlock_write);
8685
8686#ifdef CONFIG_PREEMPT_DYNAMIC
8687
8688#ifdef CONFIG_GENERIC_ENTRY
8689#include <linux/entry-common.h>
8690#endif
8691
8692/*
8693 * SC:cond_resched
8694 * SC:might_resched
8695 * SC:preempt_schedule
8696 * SC:preempt_schedule_notrace
8697 * SC:irqentry_exit_cond_resched
8698 *
8699 *
8700 * NONE:
8701 * cond_resched <- __cond_resched
8702 * might_resched <- RET0
8703 * preempt_schedule <- NOP
8704 * preempt_schedule_notrace <- NOP
8705 * irqentry_exit_cond_resched <- NOP
8706 *
8707 * VOLUNTARY:
8708 * cond_resched <- __cond_resched
8709 * might_resched <- __cond_resched
8710 * preempt_schedule <- NOP
8711 * preempt_schedule_notrace <- NOP
8712 * irqentry_exit_cond_resched <- NOP
8713 *
8714 * FULL:
8715 * cond_resched <- RET0
8716 * might_resched <- RET0
8717 * preempt_schedule <- preempt_schedule
8718 * preempt_schedule_notrace <- preempt_schedule_notrace
8719 * irqentry_exit_cond_resched <- irqentry_exit_cond_resched
8720 */
8721
8722enum {
8723 preempt_dynamic_undefined = -1,
8724 preempt_dynamic_none,
8725 preempt_dynamic_voluntary,
8726 preempt_dynamic_full,
8727};
8728
8729int preempt_dynamic_mode = preempt_dynamic_undefined;
8730
8731int sched_dynamic_mode(const char *str)
8732{
8733 if (!strcmp(str, "none"))
8734 return preempt_dynamic_none;
8735
8736 if (!strcmp(str, "voluntary"))
8737 return preempt_dynamic_voluntary;
8738
8739 if (!strcmp(str, "full"))
8740 return preempt_dynamic_full;
8741
8742 return -EINVAL;
8743}
8744
8745#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
8746#define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled)
8747#define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled)
8748#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
8749#define preempt_dynamic_enable(f) static_key_enable(&sk_dynamic_##f.key)
8750#define preempt_dynamic_disable(f) static_key_disable(&sk_dynamic_##f.key)
8751#else
8752#error "Unsupported PREEMPT_DYNAMIC mechanism"
8753#endif
8754
8755static DEFINE_MUTEX(sched_dynamic_mutex);
8756static bool klp_override;
8757
8758static void __sched_dynamic_update(int mode)
8759{
8760 /*
8761 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
8762 * the ZERO state, which is invalid.
8763 */
8764 if (!klp_override)
8765 preempt_dynamic_enable(cond_resched);
8766 preempt_dynamic_enable(might_resched);
8767 preempt_dynamic_enable(preempt_schedule);
8768 preempt_dynamic_enable(preempt_schedule_notrace);
8769 preempt_dynamic_enable(irqentry_exit_cond_resched);
8770
8771 switch (mode) {
8772 case preempt_dynamic_none:
8773 if (!klp_override)
8774 preempt_dynamic_enable(cond_resched);
8775 preempt_dynamic_disable(might_resched);
8776 preempt_dynamic_disable(preempt_schedule);
8777 preempt_dynamic_disable(preempt_schedule_notrace);
8778 preempt_dynamic_disable(irqentry_exit_cond_resched);
8779 if (mode != preempt_dynamic_mode)
8780 pr_info("Dynamic Preempt: none\n");
8781 break;
8782
8783 case preempt_dynamic_voluntary:
8784 if (!klp_override)
8785 preempt_dynamic_enable(cond_resched);
8786 preempt_dynamic_enable(might_resched);
8787 preempt_dynamic_disable(preempt_schedule);
8788 preempt_dynamic_disable(preempt_schedule_notrace);
8789 preempt_dynamic_disable(irqentry_exit_cond_resched);
8790 if (mode != preempt_dynamic_mode)
8791 pr_info("Dynamic Preempt: voluntary\n");
8792 break;
8793
8794 case preempt_dynamic_full:
8795 if (!klp_override)
8796 preempt_dynamic_disable(cond_resched);
8797 preempt_dynamic_disable(might_resched);
8798 preempt_dynamic_enable(preempt_schedule);
8799 preempt_dynamic_enable(preempt_schedule_notrace);
8800 preempt_dynamic_enable(irqentry_exit_cond_resched);
8801 if (mode != preempt_dynamic_mode)
8802 pr_info("Dynamic Preempt: full\n");
8803 break;
8804 }
8805
8806 preempt_dynamic_mode = mode;
8807}
8808
8809void sched_dynamic_update(int mode)
8810{
8811 mutex_lock(&sched_dynamic_mutex);
8812 __sched_dynamic_update(mode);
8813 mutex_unlock(&sched_dynamic_mutex);
8814}
8815
8816#ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL
8817
8818static int klp_cond_resched(void)
8819{
8820 __klp_sched_try_switch();
8821 return __cond_resched();
8822}
8823
8824void sched_dynamic_klp_enable(void)
8825{
8826 mutex_lock(&sched_dynamic_mutex);
8827
8828 klp_override = true;
8829 static_call_update(cond_resched, klp_cond_resched);
8830
8831 mutex_unlock(&sched_dynamic_mutex);
8832}
8833
8834void sched_dynamic_klp_disable(void)
8835{
8836 mutex_lock(&sched_dynamic_mutex);
8837
8838 klp_override = false;
8839 __sched_dynamic_update(preempt_dynamic_mode);
8840
8841 mutex_unlock(&sched_dynamic_mutex);
8842}
8843
8844#endif /* CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */
8845
8846static int __init setup_preempt_mode(char *str)
8847{
8848 int mode = sched_dynamic_mode(str);
8849 if (mode < 0) {
8850 pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
8851 return 0;
8852 }
8853
8854 sched_dynamic_update(mode);
8855 return 1;
8856}
8857__setup("preempt=", setup_preempt_mode);
8858
8859static void __init preempt_dynamic_init(void)
8860{
8861 if (preempt_dynamic_mode == preempt_dynamic_undefined) {
8862 if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
8863 sched_dynamic_update(preempt_dynamic_none);
8864 } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
8865 sched_dynamic_update(preempt_dynamic_voluntary);
8866 } else {
8867 /* Default static call setting, nothing to do */
8868 WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
8869 preempt_dynamic_mode = preempt_dynamic_full;
8870 pr_info("Dynamic Preempt: full\n");
8871 }
8872 }
8873}
8874
8875#define PREEMPT_MODEL_ACCESSOR(mode) \
8876 bool preempt_model_##mode(void) \
8877 { \
8878 WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \
8879 return preempt_dynamic_mode == preempt_dynamic_##mode; \
8880 } \
8881 EXPORT_SYMBOL_GPL(preempt_model_##mode)
8882
8883PREEMPT_MODEL_ACCESSOR(none);
8884PREEMPT_MODEL_ACCESSOR(voluntary);
8885PREEMPT_MODEL_ACCESSOR(full);
8886
8887#else /* !CONFIG_PREEMPT_DYNAMIC */
8888
8889static inline void preempt_dynamic_init(void) { }
8890
8891#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
8892
8893/**
8894 * yield - yield the current processor to other threads.
8895 *
8896 * Do not ever use this function, there's a 99% chance you're doing it wrong.
8897 *
8898 * The scheduler is at all times free to pick the calling task as the most
8899 * eligible task to run, if removing the yield() call from your code breaks
8900 * it, it's already broken.
8901 *
8902 * Typical broken usage is:
8903 *
8904 * while (!event)
8905 * yield();
8906 *
8907 * where one assumes that yield() will let 'the other' process run that will
8908 * make event true. If the current task is a SCHED_FIFO task that will never
8909 * happen. Never use yield() as a progress guarantee!!
8910 *
8911 * If you want to use yield() to wait for something, use wait_event().
8912 * If you want to use yield() to be 'nice' for others, use cond_resched().
8913 * If you still want to use yield(), do not!
8914 */
8915void __sched yield(void)
8916{
8917 set_current_state(TASK_RUNNING);
8918 do_sched_yield();
8919}
8920EXPORT_SYMBOL(yield);
8921
8922/**
8923 * yield_to - yield the current processor to another thread in
8924 * your thread group, or accelerate that thread toward the
8925 * processor it's on.
8926 * @p: target task
8927 * @preempt: whether task preemption is allowed or not
8928 *
8929 * It's the caller's job to ensure that the target task struct
8930 * can't go away on us before we can do any checks.
8931 *
8932 * Return:
8933 * true (>0) if we indeed boosted the target task.
8934 * false (0) if we failed to boost the target.
8935 * -ESRCH if there's no task to yield to.
8936 */
8937int __sched yield_to(struct task_struct *p, bool preempt)
8938{
8939 struct task_struct *curr = current;
8940 struct rq *rq, *p_rq;
8941 int yielded = 0;
8942
8943 scoped_guard (irqsave) {
8944 rq = this_rq();
8945
8946again:
8947 p_rq = task_rq(p);
8948 /*
8949 * If we're the only runnable task on the rq and target rq also
8950 * has only one task, there's absolutely no point in yielding.
8951 */
8952 if (rq->nr_running == 1 && p_rq->nr_running == 1)
8953 return -ESRCH;
8954
8955 guard(double_rq_lock)(rq, p_rq);
8956 if (task_rq(p) != p_rq)
8957 goto again;
8958
8959 if (!curr->sched_class->yield_to_task)
8960 return 0;
8961
8962 if (curr->sched_class != p->sched_class)
8963 return 0;
8964
8965 if (task_on_cpu(p_rq, p) || !task_is_running(p))
8966 return 0;
8967
8968 yielded = curr->sched_class->yield_to_task(rq, p);
8969 if (yielded) {
8970 schedstat_inc(rq->yld_count);
8971 /*
8972 * Make p's CPU reschedule; pick_next_entity
8973 * takes care of fairness.
8974 */
8975 if (preempt && rq != p_rq)
8976 resched_curr(p_rq);
8977 }
8978 }
8979
8980 if (yielded)
8981 schedule();
8982
8983 return yielded;
8984}
8985EXPORT_SYMBOL_GPL(yield_to);
8986
8987int io_schedule_prepare(void)
8988{
8989 int old_iowait = current->in_iowait;
8990
8991 current->in_iowait = 1;
8992 blk_flush_plug(current->plug, true);
8993 return old_iowait;
8994}
8995
8996void io_schedule_finish(int token)
8997{
8998 current->in_iowait = token;
8999}
9000
9001/*
9002 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
9003 * that process accounting knows that this is a task in IO wait state.
9004 */
9005long __sched io_schedule_timeout(long timeout)
9006{
9007 int token;
9008 long ret;
9009
9010 token = io_schedule_prepare();
9011 ret = schedule_timeout(timeout);
9012 io_schedule_finish(token);
9013
9014 return ret;
9015}
9016EXPORT_SYMBOL(io_schedule_timeout);
9017
9018void __sched io_schedule(void)
9019{
9020 int token;
9021
9022 token = io_schedule_prepare();
9023 schedule();
9024 io_schedule_finish(token);
9025}
9026EXPORT_SYMBOL(io_schedule);
9027
9028/**
9029 * sys_sched_get_priority_max - return maximum RT priority.
9030 * @policy: scheduling class.
9031 *
9032 * Return: On success, this syscall returns the maximum
9033 * rt_priority that can be used by a given scheduling class.
9034 * On failure, a negative error code is returned.
9035 */
9036SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
9037{
9038 int ret = -EINVAL;
9039
9040 switch (policy) {
9041 case SCHED_FIFO:
9042 case SCHED_RR:
9043 ret = MAX_RT_PRIO-1;
9044 break;
9045 case SCHED_DEADLINE:
9046 case SCHED_NORMAL:
9047 case SCHED_BATCH:
9048 case SCHED_IDLE:
9049 ret = 0;
9050 break;
9051 }
9052 return ret;
9053}
9054
9055/**
9056 * sys_sched_get_priority_min - return minimum RT priority.
9057 * @policy: scheduling class.
9058 *
9059 * Return: On success, this syscall returns the minimum
9060 * rt_priority that can be used by a given scheduling class.
9061 * On failure, a negative error code is returned.
9062 */
9063SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
9064{
9065 int ret = -EINVAL;
9066
9067 switch (policy) {
9068 case SCHED_FIFO:
9069 case SCHED_RR:
9070 ret = 1;
9071 break;
9072 case SCHED_DEADLINE:
9073 case SCHED_NORMAL:
9074 case SCHED_BATCH:
9075 case SCHED_IDLE:
9076 ret = 0;
9077 }
9078 return ret;
9079}
9080
9081static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
9082{
9083 unsigned int time_slice = 0;
9084 int retval;
9085
9086 if (pid < 0)
9087 return -EINVAL;
9088
9089 scoped_guard (rcu) {
9090 struct task_struct *p = find_process_by_pid(pid);
9091 if (!p)
9092 return -ESRCH;
9093
9094 retval = security_task_getscheduler(p);
9095 if (retval)
9096 return retval;
9097
9098 scoped_guard (task_rq_lock, p) {
9099 struct rq *rq = scope.rq;
9100 if (p->sched_class->get_rr_interval)
9101 time_slice = p->sched_class->get_rr_interval(rq, p);
9102 }
9103 }
9104
9105 jiffies_to_timespec64(time_slice, t);
9106 return 0;
9107}
9108
9109/**
9110 * sys_sched_rr_get_interval - return the default timeslice of a process.
9111 * @pid: pid of the process.
9112 * @interval: userspace pointer to the timeslice value.
9113 *
9114 * this syscall writes the default timeslice value of a given process
9115 * into the user-space timespec buffer. A value of '0' means infinity.
9116 *
9117 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
9118 * an error code.
9119 */
9120SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
9121 struct __kernel_timespec __user *, interval)
9122{
9123 struct timespec64 t;
9124 int retval = sched_rr_get_interval(pid, &t);
9125
9126 if (retval == 0)
9127 retval = put_timespec64(&t, interval);
9128
9129 return retval;
9130}
9131
9132#ifdef CONFIG_COMPAT_32BIT_TIME
9133SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
9134 struct old_timespec32 __user *, interval)
9135{
9136 struct timespec64 t;
9137 int retval = sched_rr_get_interval(pid, &t);
9138
9139 if (retval == 0)
9140 retval = put_old_timespec32(&t, interval);
9141 return retval;
9142}
9143#endif
9144
9145void sched_show_task(struct task_struct *p)
9146{
9147 unsigned long free = 0;
9148 int ppid;
9149
9150 if (!try_get_task_stack(p))
9151 return;
9152
9153 pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
9154
9155 if (task_is_running(p))
9156 pr_cont(" running task ");
9157#ifdef CONFIG_DEBUG_STACK_USAGE
9158 free = stack_not_used(p);
9159#endif
9160 ppid = 0;
9161 rcu_read_lock();
9162 if (pid_alive(p))
9163 ppid = task_pid_nr(rcu_dereference(p->real_parent));
9164 rcu_read_unlock();
9165 pr_cont(" stack:%-5lu pid:%-5d tgid:%-5d ppid:%-6d flags:0x%08lx\n",
9166 free, task_pid_nr(p), task_tgid_nr(p),
9167 ppid, read_task_thread_flags(p));
9168
9169 print_worker_info(KERN_INFO, p);
9170 print_stop_info(KERN_INFO, p);
9171 show_stack(p, NULL, KERN_INFO);
9172 put_task_stack(p);
9173}
9174EXPORT_SYMBOL_GPL(sched_show_task);
9175
9176static inline bool
9177state_filter_match(unsigned long state_filter, struct task_struct *p)
9178{
9179 unsigned int state = READ_ONCE(p->__state);
9180
9181 /* no filter, everything matches */
9182 if (!state_filter)
9183 return true;
9184
9185 /* filter, but doesn't match */
9186 if (!(state & state_filter))
9187 return false;
9188
9189 /*
9190 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
9191 * TASK_KILLABLE).
9192 */
9193 if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD))
9194 return false;
9195
9196 return true;
9197}
9198
9199
9200void show_state_filter(unsigned int state_filter)
9201{
9202 struct task_struct *g, *p;
9203
9204 rcu_read_lock();
9205 for_each_process_thread(g, p) {
9206 /*
9207 * reset the NMI-timeout, listing all files on a slow
9208 * console might take a lot of time:
9209 * Also, reset softlockup watchdogs on all CPUs, because
9210 * another CPU might be blocked waiting for us to process
9211 * an IPI.
9212 */
9213 touch_nmi_watchdog();
9214 touch_all_softlockup_watchdogs();
9215 if (state_filter_match(state_filter, p))
9216 sched_show_task(p);
9217 }
9218
9219#ifdef CONFIG_SCHED_DEBUG
9220 if (!state_filter)
9221 sysrq_sched_debug_show();
9222#endif
9223 rcu_read_unlock();
9224 /*
9225 * Only show locks if all tasks are dumped:
9226 */
9227 if (!state_filter)
9228 debug_show_all_locks();
9229}
9230
9231/**
9232 * init_idle - set up an idle thread for a given CPU
9233 * @idle: task in question
9234 * @cpu: CPU the idle task belongs to
9235 *
9236 * NOTE: this function does not set the idle thread's NEED_RESCHED
9237 * flag, to make booting more robust.
9238 */
9239void __init init_idle(struct task_struct *idle, int cpu)
9240{
9241#ifdef CONFIG_SMP
9242 struct affinity_context ac = (struct affinity_context) {
9243 .new_mask = cpumask_of(cpu),
9244 .flags = 0,
9245 };
9246#endif
9247 struct rq *rq = cpu_rq(cpu);
9248 unsigned long flags;
9249
9250 __sched_fork(0, idle);
9251
9252 raw_spin_lock_irqsave(&idle->pi_lock, flags);
9253 raw_spin_rq_lock(rq);
9254
9255 idle->__state = TASK_RUNNING;
9256 idle->se.exec_start = sched_clock();
9257 /*
9258 * PF_KTHREAD should already be set at this point; regardless, make it
9259 * look like a proper per-CPU kthread.
9260 */
9261 idle->flags |= PF_KTHREAD | PF_NO_SETAFFINITY;
9262 kthread_set_per_cpu(idle, cpu);
9263
9264#ifdef CONFIG_SMP
9265 /*
9266 * It's possible that init_idle() gets called multiple times on a task,
9267 * in that case do_set_cpus_allowed() will not do the right thing.
9268 *
9269 * And since this is boot we can forgo the serialization.
9270 */
9271 set_cpus_allowed_common(idle, &ac);
9272#endif
9273 /*
9274 * We're having a chicken and egg problem, even though we are
9275 * holding rq->lock, the CPU isn't yet set to this CPU so the
9276 * lockdep check in task_group() will fail.
9277 *
9278 * Similar case to sched_fork(). / Alternatively we could
9279 * use task_rq_lock() here and obtain the other rq->lock.
9280 *
9281 * Silence PROVE_RCU
9282 */
9283 rcu_read_lock();
9284 __set_task_cpu(idle, cpu);
9285 rcu_read_unlock();
9286
9287 rq->idle = idle;
9288 rcu_assign_pointer(rq->curr, idle);
9289 idle->on_rq = TASK_ON_RQ_QUEUED;
9290#ifdef CONFIG_SMP
9291 idle->on_cpu = 1;
9292#endif
9293 raw_spin_rq_unlock(rq);
9294 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
9295
9296 /* Set the preempt count _outside_ the spinlocks! */
9297 init_idle_preempt_count(idle, cpu);
9298
9299 /*
9300 * The idle tasks have their own, simple scheduling class:
9301 */
9302 idle->sched_class = &idle_sched_class;
9303 ftrace_graph_init_idle_task(idle, cpu);
9304 vtime_init_idle(idle, cpu);
9305#ifdef CONFIG_SMP
9306 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
9307#endif
9308}
9309
9310#ifdef CONFIG_SMP
9311
9312int cpuset_cpumask_can_shrink(const struct cpumask *cur,
9313 const struct cpumask *trial)
9314{
9315 int ret = 1;
9316
9317 if (cpumask_empty(cur))
9318 return ret;
9319
9320 ret = dl_cpuset_cpumask_can_shrink(cur, trial);
9321
9322 return ret;
9323}
9324
9325int task_can_attach(struct task_struct *p)
9326{
9327 int ret = 0;
9328
9329 /*
9330 * Kthreads which disallow setaffinity shouldn't be moved
9331 * to a new cpuset; we don't want to change their CPU
9332 * affinity and isolating such threads by their set of
9333 * allowed nodes is unnecessary. Thus, cpusets are not
9334 * applicable for such threads. This prevents checking for
9335 * success of set_cpus_allowed_ptr() on all attached tasks
9336 * before cpus_mask may be changed.
9337 */
9338 if (p->flags & PF_NO_SETAFFINITY)
9339 ret = -EINVAL;
9340
9341 return ret;
9342}
9343
9344bool sched_smp_initialized __read_mostly;
9345
9346#ifdef CONFIG_NUMA_BALANCING
9347/* Migrate current task p to target_cpu */
9348int migrate_task_to(struct task_struct *p, int target_cpu)
9349{
9350 struct migration_arg arg = { p, target_cpu };
9351 int curr_cpu = task_cpu(p);
9352
9353 if (curr_cpu == target_cpu)
9354 return 0;
9355
9356 if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
9357 return -EINVAL;
9358
9359 /* TODO: This is not properly updating schedstats */
9360
9361 trace_sched_move_numa(p, curr_cpu, target_cpu);
9362 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
9363}
9364
9365/*
9366 * Requeue a task on a given node and accurately track the number of NUMA
9367 * tasks on the runqueues
9368 */
9369void sched_setnuma(struct task_struct *p, int nid)
9370{
9371 bool queued, running;
9372 struct rq_flags rf;
9373 struct rq *rq;
9374
9375 rq = task_rq_lock(p, &rf);
9376 queued = task_on_rq_queued(p);
9377 running = task_current(rq, p);
9378
9379 if (queued)
9380 dequeue_task(rq, p, DEQUEUE_SAVE);
9381 if (running)
9382 put_prev_task(rq, p);
9383
9384 p->numa_preferred_nid = nid;
9385
9386 if (queued)
9387 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
9388 if (running)
9389 set_next_task(rq, p);
9390 task_rq_unlock(rq, p, &rf);
9391}
9392#endif /* CONFIG_NUMA_BALANCING */
9393
9394#ifdef CONFIG_HOTPLUG_CPU
9395/*
9396 * Ensure that the idle task is using init_mm right before its CPU goes
9397 * offline.
9398 */
9399void idle_task_exit(void)
9400{
9401 struct mm_struct *mm = current->active_mm;
9402
9403 BUG_ON(cpu_online(smp_processor_id()));
9404 BUG_ON(current != this_rq()->idle);
9405
9406 if (mm != &init_mm) {
9407 switch_mm(mm, &init_mm, current);
9408 finish_arch_post_lock_switch();
9409 }
9410
9411 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
9412}
9413
9414static int __balance_push_cpu_stop(void *arg)
9415{
9416 struct task_struct *p = arg;
9417 struct rq *rq = this_rq();
9418 struct rq_flags rf;
9419 int cpu;
9420
9421 raw_spin_lock_irq(&p->pi_lock);
9422 rq_lock(rq, &rf);
9423
9424 update_rq_clock(rq);
9425
9426 if (task_rq(p) == rq && task_on_rq_queued(p)) {
9427 cpu = select_fallback_rq(rq->cpu, p);
9428 rq = __migrate_task(rq, &rf, p, cpu);
9429 }
9430
9431 rq_unlock(rq, &rf);
9432 raw_spin_unlock_irq(&p->pi_lock);
9433
9434 put_task_struct(p);
9435
9436 return 0;
9437}
9438
9439static DEFINE_PER_CPU(struct cpu_stop_work, push_work);
9440
9441/*
9442 * Ensure we only run per-cpu kthreads once the CPU goes !active.
9443 *
9444 * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only
9445 * effective when the hotplug motion is down.
9446 */
9447static void balance_push(struct rq *rq)
9448{
9449 struct task_struct *push_task = rq->curr;
9450
9451 lockdep_assert_rq_held(rq);
9452
9453 /*
9454 * Ensure the thing is persistent until balance_push_set(.on = false);
9455 */
9456 rq->balance_callback = &balance_push_callback;
9457
9458 /*
9459 * Only active while going offline and when invoked on the outgoing
9460 * CPU.
9461 */
9462 if (!cpu_dying(rq->cpu) || rq != this_rq())
9463 return;
9464
9465 /*
9466 * Both the cpu-hotplug and stop task are in this case and are
9467 * required to complete the hotplug process.
9468 */
9469 if (kthread_is_per_cpu(push_task) ||
9470 is_migration_disabled(push_task)) {
9471
9472 /*
9473 * If this is the idle task on the outgoing CPU try to wake
9474 * up the hotplug control thread which might wait for the
9475 * last task to vanish. The rcuwait_active() check is
9476 * accurate here because the waiter is pinned on this CPU
9477 * and can't obviously be running in parallel.
9478 *
9479 * On RT kernels this also has to check whether there are
9480 * pinned and scheduled out tasks on the runqueue. They
9481 * need to leave the migrate disabled section first.
9482 */
9483 if (!rq->nr_running && !rq_has_pinned_tasks(rq) &&
9484 rcuwait_active(&rq->hotplug_wait)) {
9485 raw_spin_rq_unlock(rq);
9486 rcuwait_wake_up(&rq->hotplug_wait);
9487 raw_spin_rq_lock(rq);
9488 }
9489 return;
9490 }
9491
9492 get_task_struct(push_task);
9493 /*
9494 * Temporarily drop rq->lock such that we can wake-up the stop task.
9495 * Both preemption and IRQs are still disabled.
9496 */
9497 preempt_disable();
9498 raw_spin_rq_unlock(rq);
9499 stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task,
9500 this_cpu_ptr(&push_work));
9501 preempt_enable();
9502 /*
9503 * At this point need_resched() is true and we'll take the loop in
9504 * schedule(). The next pick is obviously going to be the stop task
9505 * which kthread_is_per_cpu() and will push this task away.
9506 */
9507 raw_spin_rq_lock(rq);
9508}
9509
9510static void balance_push_set(int cpu, bool on)
9511{
9512 struct rq *rq = cpu_rq(cpu);
9513 struct rq_flags rf;
9514
9515 rq_lock_irqsave(rq, &rf);
9516 if (on) {
9517 WARN_ON_ONCE(rq->balance_callback);
9518 rq->balance_callback = &balance_push_callback;
9519 } else if (rq->balance_callback == &balance_push_callback) {
9520 rq->balance_callback = NULL;
9521 }
9522 rq_unlock_irqrestore(rq, &rf);
9523}
9524
9525/*
9526 * Invoked from a CPUs hotplug control thread after the CPU has been marked
9527 * inactive. All tasks which are not per CPU kernel threads are either
9528 * pushed off this CPU now via balance_push() or placed on a different CPU
9529 * during wakeup. Wait until the CPU is quiescent.
9530 */
9531static void balance_hotplug_wait(void)
9532{
9533 struct rq *rq = this_rq();
9534
9535 rcuwait_wait_event(&rq->hotplug_wait,
9536 rq->nr_running == 1 && !rq_has_pinned_tasks(rq),
9537 TASK_UNINTERRUPTIBLE);
9538}
9539
9540#else
9541
9542static inline void balance_push(struct rq *rq)
9543{
9544}
9545
9546static inline void balance_push_set(int cpu, bool on)
9547{
9548}
9549
9550static inline void balance_hotplug_wait(void)
9551{
9552}
9553
9554#endif /* CONFIG_HOTPLUG_CPU */
9555
9556void set_rq_online(struct rq *rq)
9557{
9558 if (!rq->online) {
9559 const struct sched_class *class;
9560
9561 cpumask_set_cpu(rq->cpu, rq->rd->online);
9562 rq->online = 1;
9563
9564 for_each_class(class) {
9565 if (class->rq_online)
9566 class->rq_online(rq);
9567 }
9568 }
9569}
9570
9571void set_rq_offline(struct rq *rq)
9572{
9573 if (rq->online) {
9574 const struct sched_class *class;
9575
9576 update_rq_clock(rq);
9577 for_each_class(class) {
9578 if (class->rq_offline)
9579 class->rq_offline(rq);
9580 }
9581
9582 cpumask_clear_cpu(rq->cpu, rq->rd->online);
9583 rq->online = 0;
9584 }
9585}
9586
9587/*
9588 * used to mark begin/end of suspend/resume:
9589 */
9590static int num_cpus_frozen;
9591
9592/*
9593 * Update cpusets according to cpu_active mask. If cpusets are
9594 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
9595 * around partition_sched_domains().
9596 *
9597 * If we come here as part of a suspend/resume, don't touch cpusets because we
9598 * want to restore it back to its original state upon resume anyway.
9599 */
9600static void cpuset_cpu_active(void)
9601{
9602 if (cpuhp_tasks_frozen) {
9603 /*
9604 * num_cpus_frozen tracks how many CPUs are involved in suspend
9605 * resume sequence. As long as this is not the last online
9606 * operation in the resume sequence, just build a single sched
9607 * domain, ignoring cpusets.
9608 */
9609 partition_sched_domains(1, NULL, NULL);
9610 if (--num_cpus_frozen)
9611 return;
9612 /*
9613 * This is the last CPU online operation. So fall through and
9614 * restore the original sched domains by considering the
9615 * cpuset configurations.
9616 */
9617 cpuset_force_rebuild();
9618 }
9619 cpuset_update_active_cpus();
9620}
9621
9622static int cpuset_cpu_inactive(unsigned int cpu)
9623{
9624 if (!cpuhp_tasks_frozen) {
9625 int ret = dl_bw_check_overflow(cpu);
9626
9627 if (ret)
9628 return ret;
9629 cpuset_update_active_cpus();
9630 } else {
9631 num_cpus_frozen++;
9632 partition_sched_domains(1, NULL, NULL);
9633 }
9634 return 0;
9635}
9636
9637int sched_cpu_activate(unsigned int cpu)
9638{
9639 struct rq *rq = cpu_rq(cpu);
9640 struct rq_flags rf;
9641
9642 /*
9643 * Clear the balance_push callback and prepare to schedule
9644 * regular tasks.
9645 */
9646 balance_push_set(cpu, false);
9647
9648#ifdef CONFIG_SCHED_SMT
9649 /*
9650 * When going up, increment the number of cores with SMT present.
9651 */
9652 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
9653 static_branch_inc_cpuslocked(&sched_smt_present);
9654#endif
9655 set_cpu_active(cpu, true);
9656
9657 if (sched_smp_initialized) {
9658 sched_update_numa(cpu, true);
9659 sched_domains_numa_masks_set(cpu);
9660 cpuset_cpu_active();
9661 }
9662
9663 /*
9664 * Put the rq online, if not already. This happens:
9665 *
9666 * 1) In the early boot process, because we build the real domains
9667 * after all CPUs have been brought up.
9668 *
9669 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
9670 * domains.
9671 */
9672 rq_lock_irqsave(rq, &rf);
9673 if (rq->rd) {
9674 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
9675 set_rq_online(rq);
9676 }
9677 rq_unlock_irqrestore(rq, &rf);
9678
9679 return 0;
9680}
9681
9682int sched_cpu_deactivate(unsigned int cpu)
9683{
9684 struct rq *rq = cpu_rq(cpu);
9685 struct rq_flags rf;
9686 int ret;
9687
9688 /*
9689 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
9690 * load balancing when not active
9691 */
9692 nohz_balance_exit_idle(rq);
9693
9694 set_cpu_active(cpu, false);
9695
9696 /*
9697 * From this point forward, this CPU will refuse to run any task that
9698 * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively
9699 * push those tasks away until this gets cleared, see
9700 * sched_cpu_dying().
9701 */
9702 balance_push_set(cpu, true);
9703
9704 /*
9705 * We've cleared cpu_active_mask / set balance_push, wait for all
9706 * preempt-disabled and RCU users of this state to go away such that
9707 * all new such users will observe it.
9708 *
9709 * Specifically, we rely on ttwu to no longer target this CPU, see
9710 * ttwu_queue_cond() and is_cpu_allowed().
9711 *
9712 * Do sync before park smpboot threads to take care the rcu boost case.
9713 */
9714 synchronize_rcu();
9715
9716 rq_lock_irqsave(rq, &rf);
9717 if (rq->rd) {
9718 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
9719 set_rq_offline(rq);
9720 }
9721 rq_unlock_irqrestore(rq, &rf);
9722
9723#ifdef CONFIG_SCHED_SMT
9724 /*
9725 * When going down, decrement the number of cores with SMT present.
9726 */
9727 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
9728 static_branch_dec_cpuslocked(&sched_smt_present);
9729
9730 sched_core_cpu_deactivate(cpu);
9731#endif
9732
9733 if (!sched_smp_initialized)
9734 return 0;
9735
9736 sched_update_numa(cpu, false);
9737 ret = cpuset_cpu_inactive(cpu);
9738 if (ret) {
9739 balance_push_set(cpu, false);
9740 set_cpu_active(cpu, true);
9741 sched_update_numa(cpu, true);
9742 return ret;
9743 }
9744 sched_domains_numa_masks_clear(cpu);
9745 return 0;
9746}
9747
9748static void sched_rq_cpu_starting(unsigned int cpu)
9749{
9750 struct rq *rq = cpu_rq(cpu);
9751
9752 rq->calc_load_update = calc_load_update;
9753 update_max_interval();
9754}
9755
9756int sched_cpu_starting(unsigned int cpu)
9757{
9758 sched_core_cpu_starting(cpu);
9759 sched_rq_cpu_starting(cpu);
9760 sched_tick_start(cpu);
9761 return 0;
9762}
9763
9764#ifdef CONFIG_HOTPLUG_CPU
9765
9766/*
9767 * Invoked immediately before the stopper thread is invoked to bring the
9768 * CPU down completely. At this point all per CPU kthreads except the
9769 * hotplug thread (current) and the stopper thread (inactive) have been
9770 * either parked or have been unbound from the outgoing CPU. Ensure that
9771 * any of those which might be on the way out are gone.
9772 *
9773 * If after this point a bound task is being woken on this CPU then the
9774 * responsible hotplug callback has failed to do it's job.
9775 * sched_cpu_dying() will catch it with the appropriate fireworks.
9776 */
9777int sched_cpu_wait_empty(unsigned int cpu)
9778{
9779 balance_hotplug_wait();
9780 return 0;
9781}
9782
9783/*
9784 * Since this CPU is going 'away' for a while, fold any nr_active delta we
9785 * might have. Called from the CPU stopper task after ensuring that the
9786 * stopper is the last running task on the CPU, so nr_active count is
9787 * stable. We need to take the teardown thread which is calling this into
9788 * account, so we hand in adjust = 1 to the load calculation.
9789 *
9790 * Also see the comment "Global load-average calculations".
9791 */
9792static void calc_load_migrate(struct rq *rq)
9793{
9794 long delta = calc_load_fold_active(rq, 1);
9795
9796 if (delta)
9797 atomic_long_add(delta, &calc_load_tasks);
9798}
9799
9800static void dump_rq_tasks(struct rq *rq, const char *loglvl)
9801{
9802 struct task_struct *g, *p;
9803 int cpu = cpu_of(rq);
9804
9805 lockdep_assert_rq_held(rq);
9806
9807 printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running);
9808 for_each_process_thread(g, p) {
9809 if (task_cpu(p) != cpu)
9810 continue;
9811
9812 if (!task_on_rq_queued(p))
9813 continue;
9814
9815 printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
9816 }
9817}
9818
9819int sched_cpu_dying(unsigned int cpu)
9820{
9821 struct rq *rq = cpu_rq(cpu);
9822 struct rq_flags rf;
9823
9824 /* Handle pending wakeups and then migrate everything off */
9825 sched_tick_stop(cpu);
9826
9827 rq_lock_irqsave(rq, &rf);
9828 if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
9829 WARN(true, "Dying CPU not properly vacated!");
9830 dump_rq_tasks(rq, KERN_WARNING);
9831 }
9832 rq_unlock_irqrestore(rq, &rf);
9833
9834 calc_load_migrate(rq);
9835 update_max_interval();
9836 hrtick_clear(rq);
9837 sched_core_cpu_dying(cpu);
9838 return 0;
9839}
9840#endif
9841
9842void __init sched_init_smp(void)
9843{
9844 sched_init_numa(NUMA_NO_NODE);
9845
9846 /*
9847 * There's no userspace yet to cause hotplug operations; hence all the
9848 * CPU masks are stable and all blatant races in the below code cannot
9849 * happen.
9850 */
9851 mutex_lock(&sched_domains_mutex);
9852 sched_init_domains(cpu_active_mask);
9853 mutex_unlock(&sched_domains_mutex);
9854
9855 /* Move init over to a non-isolated CPU */
9856 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_DOMAIN)) < 0)
9857 BUG();
9858 current->flags &= ~PF_NO_SETAFFINITY;
9859 sched_init_granularity();
9860
9861 init_sched_rt_class();
9862 init_sched_dl_class();
9863
9864 sched_smp_initialized = true;
9865}
9866
9867static int __init migration_init(void)
9868{
9869 sched_cpu_starting(smp_processor_id());
9870 return 0;
9871}
9872early_initcall(migration_init);
9873
9874#else
9875void __init sched_init_smp(void)
9876{
9877 sched_init_granularity();
9878}
9879#endif /* CONFIG_SMP */
9880
9881int in_sched_functions(unsigned long addr)
9882{
9883 return in_lock_functions(addr) ||
9884 (addr >= (unsigned long)__sched_text_start
9885 && addr < (unsigned long)__sched_text_end);
9886}
9887
9888#ifdef CONFIG_CGROUP_SCHED
9889/*
9890 * Default task group.
9891 * Every task in system belongs to this group at bootup.
9892 */
9893struct task_group root_task_group;
9894LIST_HEAD(task_groups);
9895
9896/* Cacheline aligned slab cache for task_group */
9897static struct kmem_cache *task_group_cache __ro_after_init;
9898#endif
9899
9900void __init sched_init(void)
9901{
9902 unsigned long ptr = 0;
9903 int i;
9904
9905 /* Make sure the linker didn't screw up */
9906 BUG_ON(&idle_sched_class != &fair_sched_class + 1 ||
9907 &fair_sched_class != &rt_sched_class + 1 ||
9908 &rt_sched_class != &dl_sched_class + 1);
9909#ifdef CONFIG_SMP
9910 BUG_ON(&dl_sched_class != &stop_sched_class + 1);
9911#endif
9912
9913 wait_bit_init();
9914
9915#ifdef CONFIG_FAIR_GROUP_SCHED
9916 ptr += 2 * nr_cpu_ids * sizeof(void **);
9917#endif
9918#ifdef CONFIG_RT_GROUP_SCHED
9919 ptr += 2 * nr_cpu_ids * sizeof(void **);
9920#endif
9921 if (ptr) {
9922 ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
9923
9924#ifdef CONFIG_FAIR_GROUP_SCHED
9925 root_task_group.se = (struct sched_entity **)ptr;
9926 ptr += nr_cpu_ids * sizeof(void **);
9927
9928 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
9929 ptr += nr_cpu_ids * sizeof(void **);
9930
9931 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
9932 init_cfs_bandwidth(&root_task_group.cfs_bandwidth, NULL);
9933#endif /* CONFIG_FAIR_GROUP_SCHED */
9934#ifdef CONFIG_RT_GROUP_SCHED
9935 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
9936 ptr += nr_cpu_ids * sizeof(void **);
9937
9938 root_task_group.rt_rq = (struct rt_rq **)ptr;
9939 ptr += nr_cpu_ids * sizeof(void **);
9940
9941#endif /* CONFIG_RT_GROUP_SCHED */
9942 }
9943
9944 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
9945
9946#ifdef CONFIG_SMP
9947 init_defrootdomain();
9948#endif
9949
9950#ifdef CONFIG_RT_GROUP_SCHED
9951 init_rt_bandwidth(&root_task_group.rt_bandwidth,
9952 global_rt_period(), global_rt_runtime());
9953#endif /* CONFIG_RT_GROUP_SCHED */
9954
9955#ifdef CONFIG_CGROUP_SCHED
9956 task_group_cache = KMEM_CACHE(task_group, 0);
9957
9958 list_add(&root_task_group.list, &task_groups);
9959 INIT_LIST_HEAD(&root_task_group.children);
9960 INIT_LIST_HEAD(&root_task_group.siblings);
9961 autogroup_init(&init_task);
9962#endif /* CONFIG_CGROUP_SCHED */
9963
9964 for_each_possible_cpu(i) {
9965 struct rq *rq;
9966
9967 rq = cpu_rq(i);
9968 raw_spin_lock_init(&rq->__lock);
9969 rq->nr_running = 0;
9970 rq->calc_load_active = 0;
9971 rq->calc_load_update = jiffies + LOAD_FREQ;
9972 init_cfs_rq(&rq->cfs);
9973 init_rt_rq(&rq->rt);
9974 init_dl_rq(&rq->dl);
9975#ifdef CONFIG_FAIR_GROUP_SCHED
9976 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
9977 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
9978 /*
9979 * How much CPU bandwidth does root_task_group get?
9980 *
9981 * In case of task-groups formed thr' the cgroup filesystem, it
9982 * gets 100% of the CPU resources in the system. This overall
9983 * system CPU resource is divided among the tasks of
9984 * root_task_group and its child task-groups in a fair manner,
9985 * based on each entity's (task or task-group's) weight
9986 * (se->load.weight).
9987 *
9988 * In other words, if root_task_group has 10 tasks of weight
9989 * 1024) and two child groups A0 and A1 (of weight 1024 each),
9990 * then A0's share of the CPU resource is:
9991 *
9992 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
9993 *
9994 * We achieve this by letting root_task_group's tasks sit
9995 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
9996 */
9997 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
9998#endif /* CONFIG_FAIR_GROUP_SCHED */
9999
10000 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
10001#ifdef CONFIG_RT_GROUP_SCHED
10002 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
10003#endif
10004#ifdef CONFIG_SMP
10005 rq->sd = NULL;
10006 rq->rd = NULL;
10007 rq->cpu_capacity = SCHED_CAPACITY_SCALE;
10008 rq->balance_callback = &balance_push_callback;
10009 rq->active_balance = 0;
10010 rq->next_balance = jiffies;
10011 rq->push_cpu = 0;
10012 rq->cpu = i;
10013 rq->online = 0;
10014 rq->idle_stamp = 0;
10015 rq->avg_idle = 2*sysctl_sched_migration_cost;
10016 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
10017
10018 INIT_LIST_HEAD(&rq->cfs_tasks);
10019
10020 rq_attach_root(rq, &def_root_domain);
10021#ifdef CONFIG_NO_HZ_COMMON
10022 rq->last_blocked_load_update_tick = jiffies;
10023 atomic_set(&rq->nohz_flags, 0);
10024
10025 INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq);
10026#endif
10027#ifdef CONFIG_HOTPLUG_CPU
10028 rcuwait_init(&rq->hotplug_wait);
10029#endif
10030#endif /* CONFIG_SMP */
10031 hrtick_rq_init(rq);
10032 atomic_set(&rq->nr_iowait, 0);
10033
10034#ifdef CONFIG_SCHED_CORE
10035 rq->core = rq;
10036 rq->core_pick = NULL;
10037 rq->core_enabled = 0;
10038 rq->core_tree = RB_ROOT;
10039 rq->core_forceidle_count = 0;
10040 rq->core_forceidle_occupation = 0;
10041 rq->core_forceidle_start = 0;
10042
10043 rq->core_cookie = 0UL;
10044#endif
10045 zalloc_cpumask_var_node(&rq->scratch_mask, GFP_KERNEL, cpu_to_node(i));
10046 }
10047
10048 set_load_weight(&init_task, false);
10049
10050 /*
10051 * The boot idle thread does lazy MMU switching as well:
10052 */
10053 mmgrab_lazy_tlb(&init_mm);
10054 enter_lazy_tlb(&init_mm, current);
10055
10056 /*
10057 * The idle task doesn't need the kthread struct to function, but it
10058 * is dressed up as a per-CPU kthread and thus needs to play the part
10059 * if we want to avoid special-casing it in code that deals with per-CPU
10060 * kthreads.
10061 */
10062 WARN_ON(!set_kthread_struct(current));
10063
10064 /*
10065 * Make us the idle thread. Technically, schedule() should not be
10066 * called from this thread, however somewhere below it might be,
10067 * but because we are the idle thread, we just pick up running again
10068 * when this runqueue becomes "idle".
10069 */
10070 init_idle(current, smp_processor_id());
10071
10072 calc_load_update = jiffies + LOAD_FREQ;
10073
10074#ifdef CONFIG_SMP
10075 idle_thread_set_boot_cpu();
10076 balance_push_set(smp_processor_id(), false);
10077#endif
10078 init_sched_fair_class();
10079
10080 psi_init();
10081
10082 init_uclamp();
10083
10084 preempt_dynamic_init();
10085
10086 scheduler_running = 1;
10087}
10088
10089#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
10090
10091void __might_sleep(const char *file, int line)
10092{
10093 unsigned int state = get_current_state();
10094 /*
10095 * Blocking primitives will set (and therefore destroy) current->state,
10096 * since we will exit with TASK_RUNNING make sure we enter with it,
10097 * otherwise we will destroy state.
10098 */
10099 WARN_ONCE(state != TASK_RUNNING && current->task_state_change,
10100 "do not call blocking ops when !TASK_RUNNING; "
10101 "state=%x set at [<%p>] %pS\n", state,
10102 (void *)current->task_state_change,
10103 (void *)current->task_state_change);
10104
10105 __might_resched(file, line, 0);
10106}
10107EXPORT_SYMBOL(__might_sleep);
10108
10109static void print_preempt_disable_ip(int preempt_offset, unsigned long ip)
10110{
10111 if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT))
10112 return;
10113
10114 if (preempt_count() == preempt_offset)
10115 return;
10116
10117 pr_err("Preemption disabled at:");
10118 print_ip_sym(KERN_ERR, ip);
10119}
10120
10121static inline bool resched_offsets_ok(unsigned int offsets)
10122{
10123 unsigned int nested = preempt_count();
10124
10125 nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT;
10126
10127 return nested == offsets;
10128}
10129
10130void __might_resched(const char *file, int line, unsigned int offsets)
10131{
10132 /* Ratelimiting timestamp: */
10133 static unsigned long prev_jiffy;
10134
10135 unsigned long preempt_disable_ip;
10136
10137 /* WARN_ON_ONCE() by default, no rate limit required: */
10138 rcu_sleep_check();
10139
10140 if ((resched_offsets_ok(offsets) && !irqs_disabled() &&
10141 !is_idle_task(current) && !current->non_block_count) ||
10142 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
10143 oops_in_progress)
10144 return;
10145
10146 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
10147 return;
10148 prev_jiffy = jiffies;
10149
10150 /* Save this before calling printk(), since that will clobber it: */
10151 preempt_disable_ip = get_preempt_disable_ip(current);
10152
10153 pr_err("BUG: sleeping function called from invalid context at %s:%d\n",
10154 file, line);
10155 pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
10156 in_atomic(), irqs_disabled(), current->non_block_count,
10157 current->pid, current->comm);
10158 pr_err("preempt_count: %x, expected: %x\n", preempt_count(),
10159 offsets & MIGHT_RESCHED_PREEMPT_MASK);
10160
10161 if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
10162 pr_err("RCU nest depth: %d, expected: %u\n",
10163 rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT);
10164 }
10165
10166 if (task_stack_end_corrupted(current))
10167 pr_emerg("Thread overran stack, or stack corrupted\n");
10168
10169 debug_show_held_locks(current);
10170 if (irqs_disabled())
10171 print_irqtrace_events(current);
10172
10173 print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK,
10174 preempt_disable_ip);
10175
10176 dump_stack();
10177 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10178}
10179EXPORT_SYMBOL(__might_resched);
10180
10181void __cant_sleep(const char *file, int line, int preempt_offset)
10182{
10183 static unsigned long prev_jiffy;
10184
10185 if (irqs_disabled())
10186 return;
10187
10188 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
10189 return;
10190
10191 if (preempt_count() > preempt_offset)
10192 return;
10193
10194 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
10195 return;
10196 prev_jiffy = jiffies;
10197
10198 printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
10199 printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
10200 in_atomic(), irqs_disabled(),
10201 current->pid, current->comm);
10202
10203 debug_show_held_locks(current);
10204 dump_stack();
10205 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10206}
10207EXPORT_SYMBOL_GPL(__cant_sleep);
10208
10209#ifdef CONFIG_SMP
10210void __cant_migrate(const char *file, int line)
10211{
10212 static unsigned long prev_jiffy;
10213
10214 if (irqs_disabled())
10215 return;
10216
10217 if (is_migration_disabled(current))
10218 return;
10219
10220 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
10221 return;
10222
10223 if (preempt_count() > 0)
10224 return;
10225
10226 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
10227 return;
10228 prev_jiffy = jiffies;
10229
10230 pr_err("BUG: assuming non migratable context at %s:%d\n", file, line);
10231 pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n",
10232 in_atomic(), irqs_disabled(), is_migration_disabled(current),
10233 current->pid, current->comm);
10234
10235 debug_show_held_locks(current);
10236 dump_stack();
10237 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
10238}
10239EXPORT_SYMBOL_GPL(__cant_migrate);
10240#endif
10241#endif
10242
10243#ifdef CONFIG_MAGIC_SYSRQ
10244void normalize_rt_tasks(void)
10245{
10246 struct task_struct *g, *p;
10247 struct sched_attr attr = {
10248 .sched_policy = SCHED_NORMAL,
10249 };
10250
10251 read_lock(&tasklist_lock);
10252 for_each_process_thread(g, p) {
10253 /*
10254 * Only normalize user tasks:
10255 */
10256 if (p->flags & PF_KTHREAD)
10257 continue;
10258
10259 p->se.exec_start = 0;
10260 schedstat_set(p->stats.wait_start, 0);
10261 schedstat_set(p->stats.sleep_start, 0);
10262 schedstat_set(p->stats.block_start, 0);
10263
10264 if (!dl_task(p) && !rt_task(p)) {
10265 /*
10266 * Renice negative nice level userspace
10267 * tasks back to 0:
10268 */
10269 if (task_nice(p) < 0)
10270 set_user_nice(p, 0);
10271 continue;
10272 }
10273
10274 __sched_setscheduler(p, &attr, false, false);
10275 }
10276 read_unlock(&tasklist_lock);
10277}
10278
10279#endif /* CONFIG_MAGIC_SYSRQ */
10280
10281#if defined(CONFIG_KGDB_KDB)
10282/*
10283 * These functions are only useful for kdb.
10284 *
10285 * They can only be called when the whole system has been
10286 * stopped - every CPU needs to be quiescent, and no scheduling
10287 * activity can take place. Using them for anything else would
10288 * be a serious bug, and as a result, they aren't even visible
10289 * under any other configuration.
10290 */
10291
10292/**
10293 * curr_task - return the current task for a given CPU.
10294 * @cpu: the processor in question.
10295 *
10296 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
10297 *
10298 * Return: The current task for @cpu.
10299 */
10300struct task_struct *curr_task(int cpu)
10301{
10302 return cpu_curr(cpu);
10303}
10304
10305#endif /* defined(CONFIG_KGDB_KDB) */
10306
10307#ifdef CONFIG_CGROUP_SCHED
10308/* task_group_lock serializes the addition/removal of task groups */
10309static DEFINE_SPINLOCK(task_group_lock);
10310
10311static inline void alloc_uclamp_sched_group(struct task_group *tg,
10312 struct task_group *parent)
10313{
10314#ifdef CONFIG_UCLAMP_TASK_GROUP
10315 enum uclamp_id clamp_id;
10316
10317 for_each_clamp_id(clamp_id) {
10318 uclamp_se_set(&tg->uclamp_req[clamp_id],
10319 uclamp_none(clamp_id), false);
10320 tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
10321 }
10322#endif
10323}
10324
10325static void sched_free_group(struct task_group *tg)
10326{
10327 free_fair_sched_group(tg);
10328 free_rt_sched_group(tg);
10329 autogroup_free(tg);
10330 kmem_cache_free(task_group_cache, tg);
10331}
10332
10333static void sched_free_group_rcu(struct rcu_head *rcu)
10334{
10335 sched_free_group(container_of(rcu, struct task_group, rcu));
10336}
10337
10338static void sched_unregister_group(struct task_group *tg)
10339{
10340 unregister_fair_sched_group(tg);
10341 unregister_rt_sched_group(tg);
10342 /*
10343 * We have to wait for yet another RCU grace period to expire, as
10344 * print_cfs_stats() might run concurrently.
10345 */
10346 call_rcu(&tg->rcu, sched_free_group_rcu);
10347}
10348
10349/* allocate runqueue etc for a new task group */
10350struct task_group *sched_create_group(struct task_group *parent)
10351{
10352 struct task_group *tg;
10353
10354 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
10355 if (!tg)
10356 return ERR_PTR(-ENOMEM);
10357
10358 if (!alloc_fair_sched_group(tg, parent))
10359 goto err;
10360
10361 if (!alloc_rt_sched_group(tg, parent))
10362 goto err;
10363
10364 alloc_uclamp_sched_group(tg, parent);
10365
10366 return tg;
10367
10368err:
10369 sched_free_group(tg);
10370 return ERR_PTR(-ENOMEM);
10371}
10372
10373void sched_online_group(struct task_group *tg, struct task_group *parent)
10374{
10375 unsigned long flags;
10376
10377 spin_lock_irqsave(&task_group_lock, flags);
10378 list_add_rcu(&tg->list, &task_groups);
10379
10380 /* Root should already exist: */
10381 WARN_ON(!parent);
10382
10383 tg->parent = parent;
10384 INIT_LIST_HEAD(&tg->children);
10385 list_add_rcu(&tg->siblings, &parent->children);
10386 spin_unlock_irqrestore(&task_group_lock, flags);
10387
10388 online_fair_sched_group(tg);
10389}
10390
10391/* rcu callback to free various structures associated with a task group */
10392static void sched_unregister_group_rcu(struct rcu_head *rhp)
10393{
10394 /* Now it should be safe to free those cfs_rqs: */
10395 sched_unregister_group(container_of(rhp, struct task_group, rcu));
10396}
10397
10398void sched_destroy_group(struct task_group *tg)
10399{
10400 /* Wait for possible concurrent references to cfs_rqs complete: */
10401 call_rcu(&tg->rcu, sched_unregister_group_rcu);
10402}
10403
10404void sched_release_group(struct task_group *tg)
10405{
10406 unsigned long flags;
10407
10408 /*
10409 * Unlink first, to avoid walk_tg_tree_from() from finding us (via
10410 * sched_cfs_period_timer()).
10411 *
10412 * For this to be effective, we have to wait for all pending users of
10413 * this task group to leave their RCU critical section to ensure no new
10414 * user will see our dying task group any more. Specifically ensure
10415 * that tg_unthrottle_up() won't add decayed cfs_rq's to it.
10416 *
10417 * We therefore defer calling unregister_fair_sched_group() to
10418 * sched_unregister_group() which is guarantied to get called only after the
10419 * current RCU grace period has expired.
10420 */
10421 spin_lock_irqsave(&task_group_lock, flags);
10422 list_del_rcu(&tg->list);
10423 list_del_rcu(&tg->siblings);
10424 spin_unlock_irqrestore(&task_group_lock, flags);
10425}
10426
10427static struct task_group *sched_get_task_group(struct task_struct *tsk)
10428{
10429 struct task_group *tg;
10430
10431 /*
10432 * All callers are synchronized by task_rq_lock(); we do not use RCU
10433 * which is pointless here. Thus, we pass "true" to task_css_check()
10434 * to prevent lockdep warnings.
10435 */
10436 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
10437 struct task_group, css);
10438 tg = autogroup_task_group(tsk, tg);
10439
10440 return tg;
10441}
10442
10443static void sched_change_group(struct task_struct *tsk, struct task_group *group)
10444{
10445 tsk->sched_task_group = group;
10446
10447#ifdef CONFIG_FAIR_GROUP_SCHED
10448 if (tsk->sched_class->task_change_group)
10449 tsk->sched_class->task_change_group(tsk);
10450 else
10451#endif
10452 set_task_rq(tsk, task_cpu(tsk));
10453}
10454
10455/*
10456 * Change task's runqueue when it moves between groups.
10457 *
10458 * The caller of this function should have put the task in its new group by
10459 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
10460 * its new group.
10461 */
10462void sched_move_task(struct task_struct *tsk)
10463{
10464 int queued, running, queue_flags =
10465 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
10466 struct task_group *group;
10467 struct rq *rq;
10468
10469 CLASS(task_rq_lock, rq_guard)(tsk);
10470 rq = rq_guard.rq;
10471
10472 /*
10473 * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous
10474 * group changes.
10475 */
10476 group = sched_get_task_group(tsk);
10477 if (group == tsk->sched_task_group)
10478 return;
10479
10480 update_rq_clock(rq);
10481
10482 running = task_current(rq, tsk);
10483 queued = task_on_rq_queued(tsk);
10484
10485 if (queued)
10486 dequeue_task(rq, tsk, queue_flags);
10487 if (running)
10488 put_prev_task(rq, tsk);
10489
10490 sched_change_group(tsk, group);
10491
10492 if (queued)
10493 enqueue_task(rq, tsk, queue_flags);
10494 if (running) {
10495 set_next_task(rq, tsk);
10496 /*
10497 * After changing group, the running task may have joined a
10498 * throttled one but it's still the running task. Trigger a
10499 * resched to make sure that task can still run.
10500 */
10501 resched_curr(rq);
10502 }
10503}
10504
10505static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
10506{
10507 return css ? container_of(css, struct task_group, css) : NULL;
10508}
10509
10510static struct cgroup_subsys_state *
10511cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
10512{
10513 struct task_group *parent = css_tg(parent_css);
10514 struct task_group *tg;
10515
10516 if (!parent) {
10517 /* This is early initialization for the top cgroup */
10518 return &root_task_group.css;
10519 }
10520
10521 tg = sched_create_group(parent);
10522 if (IS_ERR(tg))
10523 return ERR_PTR(-ENOMEM);
10524
10525 return &tg->css;
10526}
10527
10528/* Expose task group only after completing cgroup initialization */
10529static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
10530{
10531 struct task_group *tg = css_tg(css);
10532 struct task_group *parent = css_tg(css->parent);
10533
10534 if (parent)
10535 sched_online_group(tg, parent);
10536
10537#ifdef CONFIG_UCLAMP_TASK_GROUP
10538 /* Propagate the effective uclamp value for the new group */
10539 guard(mutex)(&uclamp_mutex);
10540 guard(rcu)();
10541 cpu_util_update_eff(css);
10542#endif
10543
10544 return 0;
10545}
10546
10547static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
10548{
10549 struct task_group *tg = css_tg(css);
10550
10551 sched_release_group(tg);
10552}
10553
10554static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
10555{
10556 struct task_group *tg = css_tg(css);
10557
10558 /*
10559 * Relies on the RCU grace period between css_released() and this.
10560 */
10561 sched_unregister_group(tg);
10562}
10563
10564#ifdef CONFIG_RT_GROUP_SCHED
10565static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
10566{
10567 struct task_struct *task;
10568 struct cgroup_subsys_state *css;
10569
10570 cgroup_taskset_for_each(task, css, tset) {
10571 if (!sched_rt_can_attach(css_tg(css), task))
10572 return -EINVAL;
10573 }
10574 return 0;
10575}
10576#endif
10577
10578static void cpu_cgroup_attach(struct cgroup_taskset *tset)
10579{
10580 struct task_struct *task;
10581 struct cgroup_subsys_state *css;
10582
10583 cgroup_taskset_for_each(task, css, tset)
10584 sched_move_task(task);
10585}
10586
10587#ifdef CONFIG_UCLAMP_TASK_GROUP
10588static void cpu_util_update_eff(struct cgroup_subsys_state *css)
10589{
10590 struct cgroup_subsys_state *top_css = css;
10591 struct uclamp_se *uc_parent = NULL;
10592 struct uclamp_se *uc_se = NULL;
10593 unsigned int eff[UCLAMP_CNT];
10594 enum uclamp_id clamp_id;
10595 unsigned int clamps;
10596
10597 lockdep_assert_held(&uclamp_mutex);
10598 SCHED_WARN_ON(!rcu_read_lock_held());
10599
10600 css_for_each_descendant_pre(css, top_css) {
10601 uc_parent = css_tg(css)->parent
10602 ? css_tg(css)->parent->uclamp : NULL;
10603
10604 for_each_clamp_id(clamp_id) {
10605 /* Assume effective clamps matches requested clamps */
10606 eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
10607 /* Cap effective clamps with parent's effective clamps */
10608 if (uc_parent &&
10609 eff[clamp_id] > uc_parent[clamp_id].value) {
10610 eff[clamp_id] = uc_parent[clamp_id].value;
10611 }
10612 }
10613 /* Ensure protection is always capped by limit */
10614 eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
10615
10616 /* Propagate most restrictive effective clamps */
10617 clamps = 0x0;
10618 uc_se = css_tg(css)->uclamp;
10619 for_each_clamp_id(clamp_id) {
10620 if (eff[clamp_id] == uc_se[clamp_id].value)
10621 continue;
10622 uc_se[clamp_id].value = eff[clamp_id];
10623 uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
10624 clamps |= (0x1 << clamp_id);
10625 }
10626 if (!clamps) {
10627 css = css_rightmost_descendant(css);
10628 continue;
10629 }
10630
10631 /* Immediately update descendants RUNNABLE tasks */
10632 uclamp_update_active_tasks(css);
10633 }
10634}
10635
10636/*
10637 * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
10638 * C expression. Since there is no way to convert a macro argument (N) into a
10639 * character constant, use two levels of macros.
10640 */
10641#define _POW10(exp) ((unsigned int)1e##exp)
10642#define POW10(exp) _POW10(exp)
10643
10644struct uclamp_request {
10645#define UCLAMP_PERCENT_SHIFT 2
10646#define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
10647 s64 percent;
10648 u64 util;
10649 int ret;
10650};
10651
10652static inline struct uclamp_request
10653capacity_from_percent(char *buf)
10654{
10655 struct uclamp_request req = {
10656 .percent = UCLAMP_PERCENT_SCALE,
10657 .util = SCHED_CAPACITY_SCALE,
10658 .ret = 0,
10659 };
10660
10661 buf = strim(buf);
10662 if (strcmp(buf, "max")) {
10663 req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
10664 &req.percent);
10665 if (req.ret)
10666 return req;
10667 if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
10668 req.ret = -ERANGE;
10669 return req;
10670 }
10671
10672 req.util = req.percent << SCHED_CAPACITY_SHIFT;
10673 req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
10674 }
10675
10676 return req;
10677}
10678
10679static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
10680 size_t nbytes, loff_t off,
10681 enum uclamp_id clamp_id)
10682{
10683 struct uclamp_request req;
10684 struct task_group *tg;
10685
10686 req = capacity_from_percent(buf);
10687 if (req.ret)
10688 return req.ret;
10689
10690 static_branch_enable(&sched_uclamp_used);
10691
10692 guard(mutex)(&uclamp_mutex);
10693 guard(rcu)();
10694
10695 tg = css_tg(of_css(of));
10696 if (tg->uclamp_req[clamp_id].value != req.util)
10697 uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
10698
10699 /*
10700 * Because of not recoverable conversion rounding we keep track of the
10701 * exact requested value
10702 */
10703 tg->uclamp_pct[clamp_id] = req.percent;
10704
10705 /* Update effective clamps to track the most restrictive value */
10706 cpu_util_update_eff(of_css(of));
10707
10708 return nbytes;
10709}
10710
10711static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
10712 char *buf, size_t nbytes,
10713 loff_t off)
10714{
10715 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
10716}
10717
10718static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
10719 char *buf, size_t nbytes,
10720 loff_t off)
10721{
10722 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
10723}
10724
10725static inline void cpu_uclamp_print(struct seq_file *sf,
10726 enum uclamp_id clamp_id)
10727{
10728 struct task_group *tg;
10729 u64 util_clamp;
10730 u64 percent;
10731 u32 rem;
10732
10733 scoped_guard (rcu) {
10734 tg = css_tg(seq_css(sf));
10735 util_clamp = tg->uclamp_req[clamp_id].value;
10736 }
10737
10738 if (util_clamp == SCHED_CAPACITY_SCALE) {
10739 seq_puts(sf, "max\n");
10740 return;
10741 }
10742
10743 percent = tg->uclamp_pct[clamp_id];
10744 percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
10745 seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
10746}
10747
10748static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
10749{
10750 cpu_uclamp_print(sf, UCLAMP_MIN);
10751 return 0;
10752}
10753
10754static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
10755{
10756 cpu_uclamp_print(sf, UCLAMP_MAX);
10757 return 0;
10758}
10759#endif /* CONFIG_UCLAMP_TASK_GROUP */
10760
10761#ifdef CONFIG_FAIR_GROUP_SCHED
10762static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
10763 struct cftype *cftype, u64 shareval)
10764{
10765 if (shareval > scale_load_down(ULONG_MAX))
10766 shareval = MAX_SHARES;
10767 return sched_group_set_shares(css_tg(css), scale_load(shareval));
10768}
10769
10770static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
10771 struct cftype *cft)
10772{
10773 struct task_group *tg = css_tg(css);
10774
10775 return (u64) scale_load_down(tg->shares);
10776}
10777
10778#ifdef CONFIG_CFS_BANDWIDTH
10779static DEFINE_MUTEX(cfs_constraints_mutex);
10780
10781const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
10782static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
10783/* More than 203 days if BW_SHIFT equals 20. */
10784static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
10785
10786static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
10787
10788static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
10789 u64 burst)
10790{
10791 int i, ret = 0, runtime_enabled, runtime_was_enabled;
10792 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10793
10794 if (tg == &root_task_group)
10795 return -EINVAL;
10796
10797 /*
10798 * Ensure we have at some amount of bandwidth every period. This is
10799 * to prevent reaching a state of large arrears when throttled via
10800 * entity_tick() resulting in prolonged exit starvation.
10801 */
10802 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
10803 return -EINVAL;
10804
10805 /*
10806 * Likewise, bound things on the other side by preventing insane quota
10807 * periods. This also allows us to normalize in computing quota
10808 * feasibility.
10809 */
10810 if (period > max_cfs_quota_period)
10811 return -EINVAL;
10812
10813 /*
10814 * Bound quota to defend quota against overflow during bandwidth shift.
10815 */
10816 if (quota != RUNTIME_INF && quota > max_cfs_runtime)
10817 return -EINVAL;
10818
10819 if (quota != RUNTIME_INF && (burst > quota ||
10820 burst + quota > max_cfs_runtime))
10821 return -EINVAL;
10822
10823 /*
10824 * Prevent race between setting of cfs_rq->runtime_enabled and
10825 * unthrottle_offline_cfs_rqs().
10826 */
10827 guard(cpus_read_lock)();
10828 guard(mutex)(&cfs_constraints_mutex);
10829
10830 ret = __cfs_schedulable(tg, period, quota);
10831 if (ret)
10832 return ret;
10833
10834 runtime_enabled = quota != RUNTIME_INF;
10835 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
10836 /*
10837 * If we need to toggle cfs_bandwidth_used, off->on must occur
10838 * before making related changes, and on->off must occur afterwards
10839 */
10840 if (runtime_enabled && !runtime_was_enabled)
10841 cfs_bandwidth_usage_inc();
10842
10843 scoped_guard (raw_spinlock_irq, &cfs_b->lock) {
10844 cfs_b->period = ns_to_ktime(period);
10845 cfs_b->quota = quota;
10846 cfs_b->burst = burst;
10847
10848 __refill_cfs_bandwidth_runtime(cfs_b);
10849
10850 /*
10851 * Restart the period timer (if active) to handle new
10852 * period expiry:
10853 */
10854 if (runtime_enabled)
10855 start_cfs_bandwidth(cfs_b);
10856 }
10857
10858 for_each_online_cpu(i) {
10859 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
10860 struct rq *rq = cfs_rq->rq;
10861
10862 guard(rq_lock_irq)(rq);
10863 cfs_rq->runtime_enabled = runtime_enabled;
10864 cfs_rq->runtime_remaining = 0;
10865
10866 if (cfs_rq->throttled)
10867 unthrottle_cfs_rq(cfs_rq);
10868 }
10869
10870 if (runtime_was_enabled && !runtime_enabled)
10871 cfs_bandwidth_usage_dec();
10872
10873 return 0;
10874}
10875
10876static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
10877{
10878 u64 quota, period, burst;
10879
10880 period = ktime_to_ns(tg->cfs_bandwidth.period);
10881 burst = tg->cfs_bandwidth.burst;
10882 if (cfs_quota_us < 0)
10883 quota = RUNTIME_INF;
10884 else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
10885 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
10886 else
10887 return -EINVAL;
10888
10889 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10890}
10891
10892static long tg_get_cfs_quota(struct task_group *tg)
10893{
10894 u64 quota_us;
10895
10896 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
10897 return -1;
10898
10899 quota_us = tg->cfs_bandwidth.quota;
10900 do_div(quota_us, NSEC_PER_USEC);
10901
10902 return quota_us;
10903}
10904
10905static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
10906{
10907 u64 quota, period, burst;
10908
10909 if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
10910 return -EINVAL;
10911
10912 period = (u64)cfs_period_us * NSEC_PER_USEC;
10913 quota = tg->cfs_bandwidth.quota;
10914 burst = tg->cfs_bandwidth.burst;
10915
10916 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10917}
10918
10919static long tg_get_cfs_period(struct task_group *tg)
10920{
10921 u64 cfs_period_us;
10922
10923 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
10924 do_div(cfs_period_us, NSEC_PER_USEC);
10925
10926 return cfs_period_us;
10927}
10928
10929static int tg_set_cfs_burst(struct task_group *tg, long cfs_burst_us)
10930{
10931 u64 quota, period, burst;
10932
10933 if ((u64)cfs_burst_us > U64_MAX / NSEC_PER_USEC)
10934 return -EINVAL;
10935
10936 burst = (u64)cfs_burst_us * NSEC_PER_USEC;
10937 period = ktime_to_ns(tg->cfs_bandwidth.period);
10938 quota = tg->cfs_bandwidth.quota;
10939
10940 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10941}
10942
10943static long tg_get_cfs_burst(struct task_group *tg)
10944{
10945 u64 burst_us;
10946
10947 burst_us = tg->cfs_bandwidth.burst;
10948 do_div(burst_us, NSEC_PER_USEC);
10949
10950 return burst_us;
10951}
10952
10953static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
10954 struct cftype *cft)
10955{
10956 return tg_get_cfs_quota(css_tg(css));
10957}
10958
10959static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
10960 struct cftype *cftype, s64 cfs_quota_us)
10961{
10962 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
10963}
10964
10965static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
10966 struct cftype *cft)
10967{
10968 return tg_get_cfs_period(css_tg(css));
10969}
10970
10971static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
10972 struct cftype *cftype, u64 cfs_period_us)
10973{
10974 return tg_set_cfs_period(css_tg(css), cfs_period_us);
10975}
10976
10977static u64 cpu_cfs_burst_read_u64(struct cgroup_subsys_state *css,
10978 struct cftype *cft)
10979{
10980 return tg_get_cfs_burst(css_tg(css));
10981}
10982
10983static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state *css,
10984 struct cftype *cftype, u64 cfs_burst_us)
10985{
10986 return tg_set_cfs_burst(css_tg(css), cfs_burst_us);
10987}
10988
10989struct cfs_schedulable_data {
10990 struct task_group *tg;
10991 u64 period, quota;
10992};
10993
10994/*
10995 * normalize group quota/period to be quota/max_period
10996 * note: units are usecs
10997 */
10998static u64 normalize_cfs_quota(struct task_group *tg,
10999 struct cfs_schedulable_data *d)
11000{
11001 u64 quota, period;
11002
11003 if (tg == d->tg) {
11004 period = d->period;
11005 quota = d->quota;
11006 } else {
11007 period = tg_get_cfs_period(tg);
11008 quota = tg_get_cfs_quota(tg);
11009 }
11010
11011 /* note: these should typically be equivalent */
11012 if (quota == RUNTIME_INF || quota == -1)
11013 return RUNTIME_INF;
11014
11015 return to_ratio(period, quota);
11016}
11017
11018static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
11019{
11020 struct cfs_schedulable_data *d = data;
11021 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
11022 s64 quota = 0, parent_quota = -1;
11023
11024 if (!tg->parent) {
11025 quota = RUNTIME_INF;
11026 } else {
11027 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
11028
11029 quota = normalize_cfs_quota(tg, d);
11030 parent_quota = parent_b->hierarchical_quota;
11031
11032 /*
11033 * Ensure max(child_quota) <= parent_quota. On cgroup2,
11034 * always take the non-RUNTIME_INF min. On cgroup1, only
11035 * inherit when no limit is set. In both cases this is used
11036 * by the scheduler to determine if a given CFS task has a
11037 * bandwidth constraint at some higher level.
11038 */
11039 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
11040 if (quota == RUNTIME_INF)
11041 quota = parent_quota;
11042 else if (parent_quota != RUNTIME_INF)
11043 quota = min(quota, parent_quota);
11044 } else {
11045 if (quota == RUNTIME_INF)
11046 quota = parent_quota;
11047 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
11048 return -EINVAL;
11049 }
11050 }
11051 cfs_b->hierarchical_quota = quota;
11052
11053 return 0;
11054}
11055
11056static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
11057{
11058 struct cfs_schedulable_data data = {
11059 .tg = tg,
11060 .period = period,
11061 .quota = quota,
11062 };
11063
11064 if (quota != RUNTIME_INF) {
11065 do_div(data.period, NSEC_PER_USEC);
11066 do_div(data.quota, NSEC_PER_USEC);
11067 }
11068
11069 guard(rcu)();
11070 return walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
11071}
11072
11073static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
11074{
11075 struct task_group *tg = css_tg(seq_css(sf));
11076 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
11077
11078 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
11079 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
11080 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
11081
11082 if (schedstat_enabled() && tg != &root_task_group) {
11083 struct sched_statistics *stats;
11084 u64 ws = 0;
11085 int i;
11086
11087 for_each_possible_cpu(i) {
11088 stats = __schedstats_from_se(tg->se[i]);
11089 ws += schedstat_val(stats->wait_sum);
11090 }
11091
11092 seq_printf(sf, "wait_sum %llu\n", ws);
11093 }
11094
11095 seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst);
11096 seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time);
11097
11098 return 0;
11099}
11100
11101static u64 throttled_time_self(struct task_group *tg)
11102{
11103 int i;
11104 u64 total = 0;
11105
11106 for_each_possible_cpu(i) {
11107 total += READ_ONCE(tg->cfs_rq[i]->throttled_clock_self_time);
11108 }
11109
11110 return total;
11111}
11112
11113static int cpu_cfs_local_stat_show(struct seq_file *sf, void *v)
11114{
11115 struct task_group *tg = css_tg(seq_css(sf));
11116
11117 seq_printf(sf, "throttled_time %llu\n", throttled_time_self(tg));
11118
11119 return 0;
11120}
11121#endif /* CONFIG_CFS_BANDWIDTH */
11122#endif /* CONFIG_FAIR_GROUP_SCHED */
11123
11124#ifdef CONFIG_RT_GROUP_SCHED
11125static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
11126 struct cftype *cft, s64 val)
11127{
11128 return sched_group_set_rt_runtime(css_tg(css), val);
11129}
11130
11131static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
11132 struct cftype *cft)
11133{
11134 return sched_group_rt_runtime(css_tg(css));
11135}
11136
11137static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
11138 struct cftype *cftype, u64 rt_period_us)
11139{
11140 return sched_group_set_rt_period(css_tg(css), rt_period_us);
11141}
11142
11143static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
11144 struct cftype *cft)
11145{
11146 return sched_group_rt_period(css_tg(css));
11147}
11148#endif /* CONFIG_RT_GROUP_SCHED */
11149
11150#ifdef CONFIG_FAIR_GROUP_SCHED
11151static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css,
11152 struct cftype *cft)
11153{
11154 return css_tg(css)->idle;
11155}
11156
11157static int cpu_idle_write_s64(struct cgroup_subsys_state *css,
11158 struct cftype *cft, s64 idle)
11159{
11160 return sched_group_set_idle(css_tg(css), idle);
11161}
11162#endif
11163
11164static struct cftype cpu_legacy_files[] = {
11165#ifdef CONFIG_FAIR_GROUP_SCHED
11166 {
11167 .name = "shares",
11168 .read_u64 = cpu_shares_read_u64,
11169 .write_u64 = cpu_shares_write_u64,
11170 },
11171 {
11172 .name = "idle",
11173 .read_s64 = cpu_idle_read_s64,
11174 .write_s64 = cpu_idle_write_s64,
11175 },
11176#endif
11177#ifdef CONFIG_CFS_BANDWIDTH
11178 {
11179 .name = "cfs_quota_us",
11180 .read_s64 = cpu_cfs_quota_read_s64,
11181 .write_s64 = cpu_cfs_quota_write_s64,
11182 },
11183 {
11184 .name = "cfs_period_us",
11185 .read_u64 = cpu_cfs_period_read_u64,
11186 .write_u64 = cpu_cfs_period_write_u64,
11187 },
11188 {
11189 .name = "cfs_burst_us",
11190 .read_u64 = cpu_cfs_burst_read_u64,
11191 .write_u64 = cpu_cfs_burst_write_u64,
11192 },
11193 {
11194 .name = "stat",
11195 .seq_show = cpu_cfs_stat_show,
11196 },
11197 {
11198 .name = "stat.local",
11199 .seq_show = cpu_cfs_local_stat_show,
11200 },
11201#endif
11202#ifdef CONFIG_RT_GROUP_SCHED
11203 {
11204 .name = "rt_runtime_us",
11205 .read_s64 = cpu_rt_runtime_read,
11206 .write_s64 = cpu_rt_runtime_write,
11207 },
11208 {
11209 .name = "rt_period_us",
11210 .read_u64 = cpu_rt_period_read_uint,
11211 .write_u64 = cpu_rt_period_write_uint,
11212 },
11213#endif
11214#ifdef CONFIG_UCLAMP_TASK_GROUP
11215 {
11216 .name = "uclamp.min",
11217 .flags = CFTYPE_NOT_ON_ROOT,
11218 .seq_show = cpu_uclamp_min_show,
11219 .write = cpu_uclamp_min_write,
11220 },
11221 {
11222 .name = "uclamp.max",
11223 .flags = CFTYPE_NOT_ON_ROOT,
11224 .seq_show = cpu_uclamp_max_show,
11225 .write = cpu_uclamp_max_write,
11226 },
11227#endif
11228 { } /* Terminate */
11229};
11230
11231static int cpu_extra_stat_show(struct seq_file *sf,
11232 struct cgroup_subsys_state *css)
11233{
11234#ifdef CONFIG_CFS_BANDWIDTH
11235 {
11236 struct task_group *tg = css_tg(css);
11237 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
11238 u64 throttled_usec, burst_usec;
11239
11240 throttled_usec = cfs_b->throttled_time;
11241 do_div(throttled_usec, NSEC_PER_USEC);
11242 burst_usec = cfs_b->burst_time;
11243 do_div(burst_usec, NSEC_PER_USEC);
11244
11245 seq_printf(sf, "nr_periods %d\n"
11246 "nr_throttled %d\n"
11247 "throttled_usec %llu\n"
11248 "nr_bursts %d\n"
11249 "burst_usec %llu\n",
11250 cfs_b->nr_periods, cfs_b->nr_throttled,
11251 throttled_usec, cfs_b->nr_burst, burst_usec);
11252 }
11253#endif
11254 return 0;
11255}
11256
11257static int cpu_local_stat_show(struct seq_file *sf,
11258 struct cgroup_subsys_state *css)
11259{
11260#ifdef CONFIG_CFS_BANDWIDTH
11261 {
11262 struct task_group *tg = css_tg(css);
11263 u64 throttled_self_usec;
11264
11265 throttled_self_usec = throttled_time_self(tg);
11266 do_div(throttled_self_usec, NSEC_PER_USEC);
11267
11268 seq_printf(sf, "throttled_usec %llu\n",
11269 throttled_self_usec);
11270 }
11271#endif
11272 return 0;
11273}
11274
11275#ifdef CONFIG_FAIR_GROUP_SCHED
11276static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
11277 struct cftype *cft)
11278{
11279 struct task_group *tg = css_tg(css);
11280 u64 weight = scale_load_down(tg->shares);
11281
11282 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
11283}
11284
11285static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
11286 struct cftype *cft, u64 weight)
11287{
11288 /*
11289 * cgroup weight knobs should use the common MIN, DFL and MAX
11290 * values which are 1, 100 and 10000 respectively. While it loses
11291 * a bit of range on both ends, it maps pretty well onto the shares
11292 * value used by scheduler and the round-trip conversions preserve
11293 * the original value over the entire range.
11294 */
11295 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
11296 return -ERANGE;
11297
11298 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
11299
11300 return sched_group_set_shares(css_tg(css), scale_load(weight));
11301}
11302
11303static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
11304 struct cftype *cft)
11305{
11306 unsigned long weight = scale_load_down(css_tg(css)->shares);
11307 int last_delta = INT_MAX;
11308 int prio, delta;
11309
11310 /* find the closest nice value to the current weight */
11311 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
11312 delta = abs(sched_prio_to_weight[prio] - weight);
11313 if (delta >= last_delta)
11314 break;
11315 last_delta = delta;
11316 }
11317
11318 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
11319}
11320
11321static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
11322 struct cftype *cft, s64 nice)
11323{
11324 unsigned long weight;
11325 int idx;
11326
11327 if (nice < MIN_NICE || nice > MAX_NICE)
11328 return -ERANGE;
11329
11330 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
11331 idx = array_index_nospec(idx, 40);
11332 weight = sched_prio_to_weight[idx];
11333
11334 return sched_group_set_shares(css_tg(css), scale_load(weight));
11335}
11336#endif
11337
11338static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
11339 long period, long quota)
11340{
11341 if (quota < 0)
11342 seq_puts(sf, "max");
11343 else
11344 seq_printf(sf, "%ld", quota);
11345
11346 seq_printf(sf, " %ld\n", period);
11347}
11348
11349/* caller should put the current value in *@periodp before calling */
11350static int __maybe_unused cpu_period_quota_parse(char *buf,
11351 u64 *periodp, u64 *quotap)
11352{
11353 char tok[21]; /* U64_MAX */
11354
11355 if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
11356 return -EINVAL;
11357
11358 *periodp *= NSEC_PER_USEC;
11359
11360 if (sscanf(tok, "%llu", quotap))
11361 *quotap *= NSEC_PER_USEC;
11362 else if (!strcmp(tok, "max"))
11363 *quotap = RUNTIME_INF;
11364 else
11365 return -EINVAL;
11366
11367 return 0;
11368}
11369
11370#ifdef CONFIG_CFS_BANDWIDTH
11371static int cpu_max_show(struct seq_file *sf, void *v)
11372{
11373 struct task_group *tg = css_tg(seq_css(sf));
11374
11375 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
11376 return 0;
11377}
11378
11379static ssize_t cpu_max_write(struct kernfs_open_file *of,
11380 char *buf, size_t nbytes, loff_t off)
11381{
11382 struct task_group *tg = css_tg(of_css(of));
11383 u64 period = tg_get_cfs_period(tg);
11384 u64 burst = tg_get_cfs_burst(tg);
11385 u64 quota;
11386 int ret;
11387
11388 ret = cpu_period_quota_parse(buf, &period, "a);
11389 if (!ret)
11390 ret = tg_set_cfs_bandwidth(tg, period, quota, burst);
11391 return ret ?: nbytes;
11392}
11393#endif
11394
11395static struct cftype cpu_files[] = {
11396#ifdef CONFIG_FAIR_GROUP_SCHED
11397 {
11398 .name = "weight",
11399 .flags = CFTYPE_NOT_ON_ROOT,
11400 .read_u64 = cpu_weight_read_u64,
11401 .write_u64 = cpu_weight_write_u64,
11402 },
11403 {
11404 .name = "weight.nice",
11405 .flags = CFTYPE_NOT_ON_ROOT,
11406 .read_s64 = cpu_weight_nice_read_s64,
11407 .write_s64 = cpu_weight_nice_write_s64,
11408 },
11409 {
11410 .name = "idle",
11411 .flags = CFTYPE_NOT_ON_ROOT,
11412 .read_s64 = cpu_idle_read_s64,
11413 .write_s64 = cpu_idle_write_s64,
11414 },
11415#endif
11416#ifdef CONFIG_CFS_BANDWIDTH
11417 {
11418 .name = "max",
11419 .flags = CFTYPE_NOT_ON_ROOT,
11420 .seq_show = cpu_max_show,
11421 .write = cpu_max_write,
11422 },
11423 {
11424 .name = "max.burst",
11425 .flags = CFTYPE_NOT_ON_ROOT,
11426 .read_u64 = cpu_cfs_burst_read_u64,
11427 .write_u64 = cpu_cfs_burst_write_u64,
11428 },
11429#endif
11430#ifdef CONFIG_UCLAMP_TASK_GROUP
11431 {
11432 .name = "uclamp.min",
11433 .flags = CFTYPE_NOT_ON_ROOT,
11434 .seq_show = cpu_uclamp_min_show,
11435 .write = cpu_uclamp_min_write,
11436 },
11437 {
11438 .name = "uclamp.max",
11439 .flags = CFTYPE_NOT_ON_ROOT,
11440 .seq_show = cpu_uclamp_max_show,
11441 .write = cpu_uclamp_max_write,
11442 },
11443#endif
11444 { } /* terminate */
11445};
11446
11447struct cgroup_subsys cpu_cgrp_subsys = {
11448 .css_alloc = cpu_cgroup_css_alloc,
11449 .css_online = cpu_cgroup_css_online,
11450 .css_released = cpu_cgroup_css_released,
11451 .css_free = cpu_cgroup_css_free,
11452 .css_extra_stat_show = cpu_extra_stat_show,
11453 .css_local_stat_show = cpu_local_stat_show,
11454#ifdef CONFIG_RT_GROUP_SCHED
11455 .can_attach = cpu_cgroup_can_attach,
11456#endif
11457 .attach = cpu_cgroup_attach,
11458 .legacy_cftypes = cpu_legacy_files,
11459 .dfl_cftypes = cpu_files,
11460 .early_init = true,
11461 .threaded = true,
11462};
11463
11464#endif /* CONFIG_CGROUP_SCHED */
11465
11466void dump_cpu_task(int cpu)
11467{
11468 if (cpu == smp_processor_id() && in_hardirq()) {
11469 struct pt_regs *regs;
11470
11471 regs = get_irq_regs();
11472 if (regs) {
11473 show_regs(regs);
11474 return;
11475 }
11476 }
11477
11478 if (trigger_single_cpu_backtrace(cpu))
11479 return;
11480
11481 pr_info("Task dump for CPU %d:\n", cpu);
11482 sched_show_task(cpu_curr(cpu));
11483}
11484
11485/*
11486 * Nice levels are multiplicative, with a gentle 10% change for every
11487 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
11488 * nice 1, it will get ~10% less CPU time than another CPU-bound task
11489 * that remained on nice 0.
11490 *
11491 * The "10% effect" is relative and cumulative: from _any_ nice level,
11492 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
11493 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
11494 * If a task goes up by ~10% and another task goes down by ~10% then
11495 * the relative distance between them is ~25%.)
11496 */
11497const int sched_prio_to_weight[40] = {
11498 /* -20 */ 88761, 71755, 56483, 46273, 36291,
11499 /* -15 */ 29154, 23254, 18705, 14949, 11916,
11500 /* -10 */ 9548, 7620, 6100, 4904, 3906,
11501 /* -5 */ 3121, 2501, 1991, 1586, 1277,
11502 /* 0 */ 1024, 820, 655, 526, 423,
11503 /* 5 */ 335, 272, 215, 172, 137,
11504 /* 10 */ 110, 87, 70, 56, 45,
11505 /* 15 */ 36, 29, 23, 18, 15,
11506};
11507
11508/*
11509 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
11510 *
11511 * In cases where the weight does not change often, we can use the
11512 * precalculated inverse to speed up arithmetics by turning divisions
11513 * into multiplications:
11514 */
11515const u32 sched_prio_to_wmult[40] = {
11516 /* -20 */ 48388, 59856, 76040, 92818, 118348,
11517 /* -15 */ 147320, 184698, 229616, 287308, 360437,
11518 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
11519 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
11520 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
11521 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
11522 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
11523 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
11524};
11525
11526void call_trace_sched_update_nr_running(struct rq *rq, int count)
11527{
11528 trace_sched_update_nr_running_tp(rq, count);
11529}
11530
11531#ifdef CONFIG_SCHED_MM_CID
11532
11533/*
11534 * @cid_lock: Guarantee forward-progress of cid allocation.
11535 *
11536 * Concurrency ID allocation within a bitmap is mostly lock-free. The cid_lock
11537 * is only used when contention is detected by the lock-free allocation so
11538 * forward progress can be guaranteed.
11539 */
11540DEFINE_RAW_SPINLOCK(cid_lock);
11541
11542/*
11543 * @use_cid_lock: Select cid allocation behavior: lock-free vs spinlock.
11544 *
11545 * When @use_cid_lock is 0, the cid allocation is lock-free. When contention is
11546 * detected, it is set to 1 to ensure that all newly coming allocations are
11547 * serialized by @cid_lock until the allocation which detected contention
11548 * completes and sets @use_cid_lock back to 0. This guarantees forward progress
11549 * of a cid allocation.
11550 */
11551int use_cid_lock;
11552
11553/*
11554 * mm_cid remote-clear implements a lock-free algorithm to clear per-mm/cpu cid
11555 * concurrently with respect to the execution of the source runqueue context
11556 * switch.
11557 *
11558 * There is one basic properties we want to guarantee here:
11559 *
11560 * (1) Remote-clear should _never_ mark a per-cpu cid UNSET when it is actively
11561 * used by a task. That would lead to concurrent allocation of the cid and
11562 * userspace corruption.
11563 *
11564 * Provide this guarantee by introducing a Dekker memory ordering to guarantee
11565 * that a pair of loads observe at least one of a pair of stores, which can be
11566 * shown as:
11567 *
11568 * X = Y = 0
11569 *
11570 * w[X]=1 w[Y]=1
11571 * MB MB
11572 * r[Y]=y r[X]=x
11573 *
11574 * Which guarantees that x==0 && y==0 is impossible. But rather than using
11575 * values 0 and 1, this algorithm cares about specific state transitions of the
11576 * runqueue current task (as updated by the scheduler context switch), and the
11577 * per-mm/cpu cid value.
11578 *
11579 * Let's introduce task (Y) which has task->mm == mm and task (N) which has
11580 * task->mm != mm for the rest of the discussion. There are two scheduler state
11581 * transitions on context switch we care about:
11582 *
11583 * (TSA) Store to rq->curr with transition from (N) to (Y)
11584 *
11585 * (TSB) Store to rq->curr with transition from (Y) to (N)
11586 *
11587 * On the remote-clear side, there is one transition we care about:
11588 *
11589 * (TMA) cmpxchg to *pcpu_cid to set the LAZY flag
11590 *
11591 * There is also a transition to UNSET state which can be performed from all
11592 * sides (scheduler, remote-clear). It is always performed with a cmpxchg which
11593 * guarantees that only a single thread will succeed:
11594 *
11595 * (TMB) cmpxchg to *pcpu_cid to mark UNSET
11596 *
11597 * Just to be clear, what we do _not_ want to happen is a transition to UNSET
11598 * when a thread is actively using the cid (property (1)).
11599 *
11600 * Let's looks at the relevant combinations of TSA/TSB, and TMA transitions.
11601 *
11602 * Scenario A) (TSA)+(TMA) (from next task perspective)
11603 *
11604 * CPU0 CPU1
11605 *
11606 * Context switch CS-1 Remote-clear
11607 * - store to rq->curr: (N)->(Y) (TSA) - cmpxchg to *pcpu_id to LAZY (TMA)
11608 * (implied barrier after cmpxchg)
11609 * - switch_mm_cid()
11610 * - memory barrier (see switch_mm_cid()
11611 * comment explaining how this barrier
11612 * is combined with other scheduler
11613 * barriers)
11614 * - mm_cid_get (next)
11615 * - READ_ONCE(*pcpu_cid) - rcu_dereference(src_rq->curr)
11616 *
11617 * This Dekker ensures that either task (Y) is observed by the
11618 * rcu_dereference() or the LAZY flag is observed by READ_ONCE(), or both are
11619 * observed.
11620 *
11621 * If task (Y) store is observed by rcu_dereference(), it means that there is
11622 * still an active task on the cpu. Remote-clear will therefore not transition
11623 * to UNSET, which fulfills property (1).
11624 *
11625 * If task (Y) is not observed, but the lazy flag is observed by READ_ONCE(),
11626 * it will move its state to UNSET, which clears the percpu cid perhaps
11627 * uselessly (which is not an issue for correctness). Because task (Y) is not
11628 * observed, CPU1 can move ahead to set the state to UNSET. Because moving
11629 * state to UNSET is done with a cmpxchg expecting that the old state has the
11630 * LAZY flag set, only one thread will successfully UNSET.
11631 *
11632 * If both states (LAZY flag and task (Y)) are observed, the thread on CPU0
11633 * will observe the LAZY flag and transition to UNSET (perhaps uselessly), and
11634 * CPU1 will observe task (Y) and do nothing more, which is fine.
11635 *
11636 * What we are effectively preventing with this Dekker is a scenario where
11637 * neither LAZY flag nor store (Y) are observed, which would fail property (1)
11638 * because this would UNSET a cid which is actively used.
11639 */
11640
11641void sched_mm_cid_migrate_from(struct task_struct *t)
11642{
11643 t->migrate_from_cpu = task_cpu(t);
11644}
11645
11646static
11647int __sched_mm_cid_migrate_from_fetch_cid(struct rq *src_rq,
11648 struct task_struct *t,
11649 struct mm_cid *src_pcpu_cid)
11650{
11651 struct mm_struct *mm = t->mm;
11652 struct task_struct *src_task;
11653 int src_cid, last_mm_cid;
11654
11655 if (!mm)
11656 return -1;
11657
11658 last_mm_cid = t->last_mm_cid;
11659 /*
11660 * If the migrated task has no last cid, or if the current
11661 * task on src rq uses the cid, it means the source cid does not need
11662 * to be moved to the destination cpu.
11663 */
11664 if (last_mm_cid == -1)
11665 return -1;
11666 src_cid = READ_ONCE(src_pcpu_cid->cid);
11667 if (!mm_cid_is_valid(src_cid) || last_mm_cid != src_cid)
11668 return -1;
11669
11670 /*
11671 * If we observe an active task using the mm on this rq, it means we
11672 * are not the last task to be migrated from this cpu for this mm, so
11673 * there is no need to move src_cid to the destination cpu.
11674 */
11675 guard(rcu)();
11676 src_task = rcu_dereference(src_rq->curr);
11677 if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
11678 t->last_mm_cid = -1;
11679 return -1;
11680 }
11681
11682 return src_cid;
11683}
11684
11685static
11686int __sched_mm_cid_migrate_from_try_steal_cid(struct rq *src_rq,
11687 struct task_struct *t,
11688 struct mm_cid *src_pcpu_cid,
11689 int src_cid)
11690{
11691 struct task_struct *src_task;
11692 struct mm_struct *mm = t->mm;
11693 int lazy_cid;
11694
11695 if (src_cid == -1)
11696 return -1;
11697
11698 /*
11699 * Attempt to clear the source cpu cid to move it to the destination
11700 * cpu.
11701 */
11702 lazy_cid = mm_cid_set_lazy_put(src_cid);
11703 if (!try_cmpxchg(&src_pcpu_cid->cid, &src_cid, lazy_cid))
11704 return -1;
11705
11706 /*
11707 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11708 * rq->curr->mm matches the scheduler barrier in context_switch()
11709 * between store to rq->curr and load of prev and next task's
11710 * per-mm/cpu cid.
11711 *
11712 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11713 * rq->curr->mm_cid_active matches the barrier in
11714 * sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and
11715 * sched_mm_cid_after_execve() between store to t->mm_cid_active and
11716 * load of per-mm/cpu cid.
11717 */
11718
11719 /*
11720 * If we observe an active task using the mm on this rq after setting
11721 * the lazy-put flag, this task will be responsible for transitioning
11722 * from lazy-put flag set to MM_CID_UNSET.
11723 */
11724 scoped_guard (rcu) {
11725 src_task = rcu_dereference(src_rq->curr);
11726 if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
11727 /*
11728 * We observed an active task for this mm, there is therefore
11729 * no point in moving this cid to the destination cpu.
11730 */
11731 t->last_mm_cid = -1;
11732 return -1;
11733 }
11734 }
11735
11736 /*
11737 * The src_cid is unused, so it can be unset.
11738 */
11739 if (!try_cmpxchg(&src_pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
11740 return -1;
11741 return src_cid;
11742}
11743
11744/*
11745 * Migration to dst cpu. Called with dst_rq lock held.
11746 * Interrupts are disabled, which keeps the window of cid ownership without the
11747 * source rq lock held small.
11748 */
11749void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t)
11750{
11751 struct mm_cid *src_pcpu_cid, *dst_pcpu_cid;
11752 struct mm_struct *mm = t->mm;
11753 int src_cid, dst_cid, src_cpu;
11754 struct rq *src_rq;
11755
11756 lockdep_assert_rq_held(dst_rq);
11757
11758 if (!mm)
11759 return;
11760 src_cpu = t->migrate_from_cpu;
11761 if (src_cpu == -1) {
11762 t->last_mm_cid = -1;
11763 return;
11764 }
11765 /*
11766 * Move the src cid if the dst cid is unset. This keeps id
11767 * allocation closest to 0 in cases where few threads migrate around
11768 * many cpus.
11769 *
11770 * If destination cid is already set, we may have to just clear
11771 * the src cid to ensure compactness in frequent migrations
11772 * scenarios.
11773 *
11774 * It is not useful to clear the src cid when the number of threads is
11775 * greater or equal to the number of allowed cpus, because user-space
11776 * can expect that the number of allowed cids can reach the number of
11777 * allowed cpus.
11778 */
11779 dst_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu_of(dst_rq));
11780 dst_cid = READ_ONCE(dst_pcpu_cid->cid);
11781 if (!mm_cid_is_unset(dst_cid) &&
11782 atomic_read(&mm->mm_users) >= t->nr_cpus_allowed)
11783 return;
11784 src_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, src_cpu);
11785 src_rq = cpu_rq(src_cpu);
11786 src_cid = __sched_mm_cid_migrate_from_fetch_cid(src_rq, t, src_pcpu_cid);
11787 if (src_cid == -1)
11788 return;
11789 src_cid = __sched_mm_cid_migrate_from_try_steal_cid(src_rq, t, src_pcpu_cid,
11790 src_cid);
11791 if (src_cid == -1)
11792 return;
11793 if (!mm_cid_is_unset(dst_cid)) {
11794 __mm_cid_put(mm, src_cid);
11795 return;
11796 }
11797 /* Move src_cid to dst cpu. */
11798 mm_cid_snapshot_time(dst_rq, mm);
11799 WRITE_ONCE(dst_pcpu_cid->cid, src_cid);
11800}
11801
11802static void sched_mm_cid_remote_clear(struct mm_struct *mm, struct mm_cid *pcpu_cid,
11803 int cpu)
11804{
11805 struct rq *rq = cpu_rq(cpu);
11806 struct task_struct *t;
11807 int cid, lazy_cid;
11808
11809 cid = READ_ONCE(pcpu_cid->cid);
11810 if (!mm_cid_is_valid(cid))
11811 return;
11812
11813 /*
11814 * Clear the cpu cid if it is set to keep cid allocation compact. If
11815 * there happens to be other tasks left on the source cpu using this
11816 * mm, the next task using this mm will reallocate its cid on context
11817 * switch.
11818 */
11819 lazy_cid = mm_cid_set_lazy_put(cid);
11820 if (!try_cmpxchg(&pcpu_cid->cid, &cid, lazy_cid))
11821 return;
11822
11823 /*
11824 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11825 * rq->curr->mm matches the scheduler barrier in context_switch()
11826 * between store to rq->curr and load of prev and next task's
11827 * per-mm/cpu cid.
11828 *
11829 * The implicit barrier after cmpxchg per-mm/cpu cid before loading
11830 * rq->curr->mm_cid_active matches the barrier in
11831 * sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and
11832 * sched_mm_cid_after_execve() between store to t->mm_cid_active and
11833 * load of per-mm/cpu cid.
11834 */
11835
11836 /*
11837 * If we observe an active task using the mm on this rq after setting
11838 * the lazy-put flag, that task will be responsible for transitioning
11839 * from lazy-put flag set to MM_CID_UNSET.
11840 */
11841 scoped_guard (rcu) {
11842 t = rcu_dereference(rq->curr);
11843 if (READ_ONCE(t->mm_cid_active) && t->mm == mm)
11844 return;
11845 }
11846
11847 /*
11848 * The cid is unused, so it can be unset.
11849 * Disable interrupts to keep the window of cid ownership without rq
11850 * lock small.
11851 */
11852 scoped_guard (irqsave) {
11853 if (try_cmpxchg(&pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
11854 __mm_cid_put(mm, cid);
11855 }
11856}
11857
11858static void sched_mm_cid_remote_clear_old(struct mm_struct *mm, int cpu)
11859{
11860 struct rq *rq = cpu_rq(cpu);
11861 struct mm_cid *pcpu_cid;
11862 struct task_struct *curr;
11863 u64 rq_clock;
11864
11865 /*
11866 * rq->clock load is racy on 32-bit but one spurious clear once in a
11867 * while is irrelevant.
11868 */
11869 rq_clock = READ_ONCE(rq->clock);
11870 pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu);
11871
11872 /*
11873 * In order to take care of infrequently scheduled tasks, bump the time
11874 * snapshot associated with this cid if an active task using the mm is
11875 * observed on this rq.
11876 */
11877 scoped_guard (rcu) {
11878 curr = rcu_dereference(rq->curr);
11879 if (READ_ONCE(curr->mm_cid_active) && curr->mm == mm) {
11880 WRITE_ONCE(pcpu_cid->time, rq_clock);
11881 return;
11882 }
11883 }
11884
11885 if (rq_clock < pcpu_cid->time + SCHED_MM_CID_PERIOD_NS)
11886 return;
11887 sched_mm_cid_remote_clear(mm, pcpu_cid, cpu);
11888}
11889
11890static void sched_mm_cid_remote_clear_weight(struct mm_struct *mm, int cpu,
11891 int weight)
11892{
11893 struct mm_cid *pcpu_cid;
11894 int cid;
11895
11896 pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu);
11897 cid = READ_ONCE(pcpu_cid->cid);
11898 if (!mm_cid_is_valid(cid) || cid < weight)
11899 return;
11900 sched_mm_cid_remote_clear(mm, pcpu_cid, cpu);
11901}
11902
11903static void task_mm_cid_work(struct callback_head *work)
11904{
11905 unsigned long now = jiffies, old_scan, next_scan;
11906 struct task_struct *t = current;
11907 struct cpumask *cidmask;
11908 struct mm_struct *mm;
11909 int weight, cpu;
11910
11911 SCHED_WARN_ON(t != container_of(work, struct task_struct, cid_work));
11912
11913 work->next = work; /* Prevent double-add */
11914 if (t->flags & PF_EXITING)
11915 return;
11916 mm = t->mm;
11917 if (!mm)
11918 return;
11919 old_scan = READ_ONCE(mm->mm_cid_next_scan);
11920 next_scan = now + msecs_to_jiffies(MM_CID_SCAN_DELAY);
11921 if (!old_scan) {
11922 unsigned long res;
11923
11924 res = cmpxchg(&mm->mm_cid_next_scan, old_scan, next_scan);
11925 if (res != old_scan)
11926 old_scan = res;
11927 else
11928 old_scan = next_scan;
11929 }
11930 if (time_before(now, old_scan))
11931 return;
11932 if (!try_cmpxchg(&mm->mm_cid_next_scan, &old_scan, next_scan))
11933 return;
11934 cidmask = mm_cidmask(mm);
11935 /* Clear cids that were not recently used. */
11936 for_each_possible_cpu(cpu)
11937 sched_mm_cid_remote_clear_old(mm, cpu);
11938 weight = cpumask_weight(cidmask);
11939 /*
11940 * Clear cids that are greater or equal to the cidmask weight to
11941 * recompact it.
11942 */
11943 for_each_possible_cpu(cpu)
11944 sched_mm_cid_remote_clear_weight(mm, cpu, weight);
11945}
11946
11947void init_sched_mm_cid(struct task_struct *t)
11948{
11949 struct mm_struct *mm = t->mm;
11950 int mm_users = 0;
11951
11952 if (mm) {
11953 mm_users = atomic_read(&mm->mm_users);
11954 if (mm_users == 1)
11955 mm->mm_cid_next_scan = jiffies + msecs_to_jiffies(MM_CID_SCAN_DELAY);
11956 }
11957 t->cid_work.next = &t->cid_work; /* Protect against double add */
11958 init_task_work(&t->cid_work, task_mm_cid_work);
11959}
11960
11961void task_tick_mm_cid(struct rq *rq, struct task_struct *curr)
11962{
11963 struct callback_head *work = &curr->cid_work;
11964 unsigned long now = jiffies;
11965
11966 if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) ||
11967 work->next != work)
11968 return;
11969 if (time_before(now, READ_ONCE(curr->mm->mm_cid_next_scan)))
11970 return;
11971 task_work_add(curr, work, TWA_RESUME);
11972}
11973
11974void sched_mm_cid_exit_signals(struct task_struct *t)
11975{
11976 struct mm_struct *mm = t->mm;
11977 struct rq *rq;
11978
11979 if (!mm)
11980 return;
11981
11982 preempt_disable();
11983 rq = this_rq();
11984 guard(rq_lock_irqsave)(rq);
11985 preempt_enable_no_resched(); /* holding spinlock */
11986 WRITE_ONCE(t->mm_cid_active, 0);
11987 /*
11988 * Store t->mm_cid_active before loading per-mm/cpu cid.
11989 * Matches barrier in sched_mm_cid_remote_clear_old().
11990 */
11991 smp_mb();
11992 mm_cid_put(mm);
11993 t->last_mm_cid = t->mm_cid = -1;
11994}
11995
11996void sched_mm_cid_before_execve(struct task_struct *t)
11997{
11998 struct mm_struct *mm = t->mm;
11999 struct rq *rq;
12000
12001 if (!mm)
12002 return;
12003
12004 preempt_disable();
12005 rq = this_rq();
12006 guard(rq_lock_irqsave)(rq);
12007 preempt_enable_no_resched(); /* holding spinlock */
12008 WRITE_ONCE(t->mm_cid_active, 0);
12009 /*
12010 * Store t->mm_cid_active before loading per-mm/cpu cid.
12011 * Matches barrier in sched_mm_cid_remote_clear_old().
12012 */
12013 smp_mb();
12014 mm_cid_put(mm);
12015 t->last_mm_cid = t->mm_cid = -1;
12016}
12017
12018void sched_mm_cid_after_execve(struct task_struct *t)
12019{
12020 struct mm_struct *mm = t->mm;
12021 struct rq *rq;
12022
12023 if (!mm)
12024 return;
12025
12026 preempt_disable();
12027 rq = this_rq();
12028 scoped_guard (rq_lock_irqsave, rq) {
12029 preempt_enable_no_resched(); /* holding spinlock */
12030 WRITE_ONCE(t->mm_cid_active, 1);
12031 /*
12032 * Store t->mm_cid_active before loading per-mm/cpu cid.
12033 * Matches barrier in sched_mm_cid_remote_clear_old().
12034 */
12035 smp_mb();
12036 t->last_mm_cid = t->mm_cid = mm_cid_get(rq, mm);
12037 }
12038 rseq_set_notify_resume(t);
12039}
12040
12041void sched_mm_cid_fork(struct task_struct *t)
12042{
12043 WARN_ON_ONCE(!t->mm || t->mm_cid != -1);
12044 t->mm_cid_active = 1;
12045}
12046#endif
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/sched/core.c
4 *
5 * Core kernel scheduler code and related syscalls
6 *
7 * Copyright (C) 1991-2002 Linus Torvalds
8 */
9#define CREATE_TRACE_POINTS
10#include <trace/events/sched.h>
11#undef CREATE_TRACE_POINTS
12
13#include "sched.h"
14
15#include <linux/nospec.h>
16
17#include <linux/kcov.h>
18#include <linux/scs.h>
19
20#include <asm/switch_to.h>
21#include <asm/tlb.h>
22
23#include "../workqueue_internal.h"
24#include "../../fs/io-wq.h"
25#include "../smpboot.h"
26
27#include "pelt.h"
28#include "smp.h"
29
30/*
31 * Export tracepoints that act as a bare tracehook (ie: have no trace event
32 * associated with them) to allow external modules to probe them.
33 */
34EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp);
35EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp);
36EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp);
37EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
38EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp);
39EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp);
40EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp);
41EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp);
42EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp);
43EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp);
44
45DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
46
47#ifdef CONFIG_SCHED_DEBUG
48/*
49 * Debugging: various feature bits
50 *
51 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
52 * sysctl_sched_features, defined in sched.h, to allow constants propagation
53 * at compile time and compiler optimization based on features default.
54 */
55#define SCHED_FEAT(name, enabled) \
56 (1UL << __SCHED_FEAT_##name) * enabled |
57const_debug unsigned int sysctl_sched_features =
58#include "features.h"
59 0;
60#undef SCHED_FEAT
61
62/*
63 * Print a warning if need_resched is set for the given duration (if
64 * LATENCY_WARN is enabled).
65 *
66 * If sysctl_resched_latency_warn_once is set, only one warning will be shown
67 * per boot.
68 */
69__read_mostly int sysctl_resched_latency_warn_ms = 100;
70__read_mostly int sysctl_resched_latency_warn_once = 1;
71#endif /* CONFIG_SCHED_DEBUG */
72
73/*
74 * Number of tasks to iterate in a single balance run.
75 * Limited because this is done with IRQs disabled.
76 */
77const_debug unsigned int sysctl_sched_nr_migrate = 32;
78
79/*
80 * period over which we measure -rt task CPU usage in us.
81 * default: 1s
82 */
83unsigned int sysctl_sched_rt_period = 1000000;
84
85__read_mostly int scheduler_running;
86
87#ifdef CONFIG_SCHED_CORE
88
89DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);
90
91/* kernel prio, less is more */
92static inline int __task_prio(struct task_struct *p)
93{
94 if (p->sched_class == &stop_sched_class) /* trumps deadline */
95 return -2;
96
97 if (rt_prio(p->prio)) /* includes deadline */
98 return p->prio; /* [-1, 99] */
99
100 if (p->sched_class == &idle_sched_class)
101 return MAX_RT_PRIO + NICE_WIDTH; /* 140 */
102
103 return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */
104}
105
106/*
107 * l(a,b)
108 * le(a,b) := !l(b,a)
109 * g(a,b) := l(b,a)
110 * ge(a,b) := !l(a,b)
111 */
112
113/* real prio, less is less */
114static inline bool prio_less(struct task_struct *a, struct task_struct *b, bool in_fi)
115{
116
117 int pa = __task_prio(a), pb = __task_prio(b);
118
119 if (-pa < -pb)
120 return true;
121
122 if (-pb < -pa)
123 return false;
124
125 if (pa == -1) /* dl_prio() doesn't work because of stop_class above */
126 return !dl_time_before(a->dl.deadline, b->dl.deadline);
127
128 if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */
129 return cfs_prio_less(a, b, in_fi);
130
131 return false;
132}
133
134static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b)
135{
136 if (a->core_cookie < b->core_cookie)
137 return true;
138
139 if (a->core_cookie > b->core_cookie)
140 return false;
141
142 /* flip prio, so high prio is leftmost */
143 if (prio_less(b, a, task_rq(a)->core->core_forceidle))
144 return true;
145
146 return false;
147}
148
149#define __node_2_sc(node) rb_entry((node), struct task_struct, core_node)
150
151static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b)
152{
153 return __sched_core_less(__node_2_sc(a), __node_2_sc(b));
154}
155
156static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node)
157{
158 const struct task_struct *p = __node_2_sc(node);
159 unsigned long cookie = (unsigned long)key;
160
161 if (cookie < p->core_cookie)
162 return -1;
163
164 if (cookie > p->core_cookie)
165 return 1;
166
167 return 0;
168}
169
170void sched_core_enqueue(struct rq *rq, struct task_struct *p)
171{
172 rq->core->core_task_seq++;
173
174 if (!p->core_cookie)
175 return;
176
177 rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less);
178}
179
180void sched_core_dequeue(struct rq *rq, struct task_struct *p)
181{
182 rq->core->core_task_seq++;
183
184 if (!sched_core_enqueued(p))
185 return;
186
187 rb_erase(&p->core_node, &rq->core_tree);
188 RB_CLEAR_NODE(&p->core_node);
189}
190
191/*
192 * Find left-most (aka, highest priority) task matching @cookie.
193 */
194static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie)
195{
196 struct rb_node *node;
197
198 node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp);
199 /*
200 * The idle task always matches any cookie!
201 */
202 if (!node)
203 return idle_sched_class.pick_task(rq);
204
205 return __node_2_sc(node);
206}
207
208static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie)
209{
210 struct rb_node *node = &p->core_node;
211
212 node = rb_next(node);
213 if (!node)
214 return NULL;
215
216 p = container_of(node, struct task_struct, core_node);
217 if (p->core_cookie != cookie)
218 return NULL;
219
220 return p;
221}
222
223/*
224 * Magic required such that:
225 *
226 * raw_spin_rq_lock(rq);
227 * ...
228 * raw_spin_rq_unlock(rq);
229 *
230 * ends up locking and unlocking the _same_ lock, and all CPUs
231 * always agree on what rq has what lock.
232 *
233 * XXX entirely possible to selectively enable cores, don't bother for now.
234 */
235
236static DEFINE_MUTEX(sched_core_mutex);
237static atomic_t sched_core_count;
238static struct cpumask sched_core_mask;
239
240static void sched_core_lock(int cpu, unsigned long *flags)
241{
242 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
243 int t, i = 0;
244
245 local_irq_save(*flags);
246 for_each_cpu(t, smt_mask)
247 raw_spin_lock_nested(&cpu_rq(t)->__lock, i++);
248}
249
250static void sched_core_unlock(int cpu, unsigned long *flags)
251{
252 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
253 int t;
254
255 for_each_cpu(t, smt_mask)
256 raw_spin_unlock(&cpu_rq(t)->__lock);
257 local_irq_restore(*flags);
258}
259
260static void __sched_core_flip(bool enabled)
261{
262 unsigned long flags;
263 int cpu, t;
264
265 cpus_read_lock();
266
267 /*
268 * Toggle the online cores, one by one.
269 */
270 cpumask_copy(&sched_core_mask, cpu_online_mask);
271 for_each_cpu(cpu, &sched_core_mask) {
272 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
273
274 sched_core_lock(cpu, &flags);
275
276 for_each_cpu(t, smt_mask)
277 cpu_rq(t)->core_enabled = enabled;
278
279 sched_core_unlock(cpu, &flags);
280
281 cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask);
282 }
283
284 /*
285 * Toggle the offline CPUs.
286 */
287 cpumask_copy(&sched_core_mask, cpu_possible_mask);
288 cpumask_andnot(&sched_core_mask, &sched_core_mask, cpu_online_mask);
289
290 for_each_cpu(cpu, &sched_core_mask)
291 cpu_rq(cpu)->core_enabled = enabled;
292
293 cpus_read_unlock();
294}
295
296static void sched_core_assert_empty(void)
297{
298 int cpu;
299
300 for_each_possible_cpu(cpu)
301 WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree));
302}
303
304static void __sched_core_enable(void)
305{
306 static_branch_enable(&__sched_core_enabled);
307 /*
308 * Ensure all previous instances of raw_spin_rq_*lock() have finished
309 * and future ones will observe !sched_core_disabled().
310 */
311 synchronize_rcu();
312 __sched_core_flip(true);
313 sched_core_assert_empty();
314}
315
316static void __sched_core_disable(void)
317{
318 sched_core_assert_empty();
319 __sched_core_flip(false);
320 static_branch_disable(&__sched_core_enabled);
321}
322
323void sched_core_get(void)
324{
325 if (atomic_inc_not_zero(&sched_core_count))
326 return;
327
328 mutex_lock(&sched_core_mutex);
329 if (!atomic_read(&sched_core_count))
330 __sched_core_enable();
331
332 smp_mb__before_atomic();
333 atomic_inc(&sched_core_count);
334 mutex_unlock(&sched_core_mutex);
335}
336
337static void __sched_core_put(struct work_struct *work)
338{
339 if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) {
340 __sched_core_disable();
341 mutex_unlock(&sched_core_mutex);
342 }
343}
344
345void sched_core_put(void)
346{
347 static DECLARE_WORK(_work, __sched_core_put);
348
349 /*
350 * "There can be only one"
351 *
352 * Either this is the last one, or we don't actually need to do any
353 * 'work'. If it is the last *again*, we rely on
354 * WORK_STRUCT_PENDING_BIT.
355 */
356 if (!atomic_add_unless(&sched_core_count, -1, 1))
357 schedule_work(&_work);
358}
359
360#else /* !CONFIG_SCHED_CORE */
361
362static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
363static inline void sched_core_dequeue(struct rq *rq, struct task_struct *p) { }
364
365#endif /* CONFIG_SCHED_CORE */
366
367/*
368 * part of the period that we allow rt tasks to run in us.
369 * default: 0.95s
370 */
371int sysctl_sched_rt_runtime = 950000;
372
373
374/*
375 * Serialization rules:
376 *
377 * Lock order:
378 *
379 * p->pi_lock
380 * rq->lock
381 * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
382 *
383 * rq1->lock
384 * rq2->lock where: rq1 < rq2
385 *
386 * Regular state:
387 *
388 * Normal scheduling state is serialized by rq->lock. __schedule() takes the
389 * local CPU's rq->lock, it optionally removes the task from the runqueue and
390 * always looks at the local rq data structures to find the most eligible task
391 * to run next.
392 *
393 * Task enqueue is also under rq->lock, possibly taken from another CPU.
394 * Wakeups from another LLC domain might use an IPI to transfer the enqueue to
395 * the local CPU to avoid bouncing the runqueue state around [ see
396 * ttwu_queue_wakelist() ]
397 *
398 * Task wakeup, specifically wakeups that involve migration, are horribly
399 * complicated to avoid having to take two rq->locks.
400 *
401 * Special state:
402 *
403 * System-calls and anything external will use task_rq_lock() which acquires
404 * both p->pi_lock and rq->lock. As a consequence the state they change is
405 * stable while holding either lock:
406 *
407 * - sched_setaffinity()/
408 * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
409 * - set_user_nice(): p->se.load, p->*prio
410 * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
411 * p->se.load, p->rt_priority,
412 * p->dl.dl_{runtime, deadline, period, flags, bw, density}
413 * - sched_setnuma(): p->numa_preferred_nid
414 * - sched_move_task()/
415 * cpu_cgroup_fork(): p->sched_task_group
416 * - uclamp_update_active() p->uclamp*
417 *
418 * p->state <- TASK_*:
419 *
420 * is changed locklessly using set_current_state(), __set_current_state() or
421 * set_special_state(), see their respective comments, or by
422 * try_to_wake_up(). This latter uses p->pi_lock to serialize against
423 * concurrent self.
424 *
425 * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
426 *
427 * is set by activate_task() and cleared by deactivate_task(), under
428 * rq->lock. Non-zero indicates the task is runnable, the special
429 * ON_RQ_MIGRATING state is used for migration without holding both
430 * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
431 *
432 * p->on_cpu <- { 0, 1 }:
433 *
434 * is set by prepare_task() and cleared by finish_task() such that it will be
435 * set before p is scheduled-in and cleared after p is scheduled-out, both
436 * under rq->lock. Non-zero indicates the task is running on its CPU.
437 *
438 * [ The astute reader will observe that it is possible for two tasks on one
439 * CPU to have ->on_cpu = 1 at the same time. ]
440 *
441 * task_cpu(p): is changed by set_task_cpu(), the rules are:
442 *
443 * - Don't call set_task_cpu() on a blocked task:
444 *
445 * We don't care what CPU we're not running on, this simplifies hotplug,
446 * the CPU assignment of blocked tasks isn't required to be valid.
447 *
448 * - for try_to_wake_up(), called under p->pi_lock:
449 *
450 * This allows try_to_wake_up() to only take one rq->lock, see its comment.
451 *
452 * - for migration called under rq->lock:
453 * [ see task_on_rq_migrating() in task_rq_lock() ]
454 *
455 * o move_queued_task()
456 * o detach_task()
457 *
458 * - for migration called under double_rq_lock():
459 *
460 * o __migrate_swap_task()
461 * o push_rt_task() / pull_rt_task()
462 * o push_dl_task() / pull_dl_task()
463 * o dl_task_offline_migration()
464 *
465 */
466
467void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
468{
469 raw_spinlock_t *lock;
470
471 /* Matches synchronize_rcu() in __sched_core_enable() */
472 preempt_disable();
473 if (sched_core_disabled()) {
474 raw_spin_lock_nested(&rq->__lock, subclass);
475 /* preempt_count *MUST* be > 1 */
476 preempt_enable_no_resched();
477 return;
478 }
479
480 for (;;) {
481 lock = __rq_lockp(rq);
482 raw_spin_lock_nested(lock, subclass);
483 if (likely(lock == __rq_lockp(rq))) {
484 /* preempt_count *MUST* be > 1 */
485 preempt_enable_no_resched();
486 return;
487 }
488 raw_spin_unlock(lock);
489 }
490}
491
492bool raw_spin_rq_trylock(struct rq *rq)
493{
494 raw_spinlock_t *lock;
495 bool ret;
496
497 /* Matches synchronize_rcu() in __sched_core_enable() */
498 preempt_disable();
499 if (sched_core_disabled()) {
500 ret = raw_spin_trylock(&rq->__lock);
501 preempt_enable();
502 return ret;
503 }
504
505 for (;;) {
506 lock = __rq_lockp(rq);
507 ret = raw_spin_trylock(lock);
508 if (!ret || (likely(lock == __rq_lockp(rq)))) {
509 preempt_enable();
510 return ret;
511 }
512 raw_spin_unlock(lock);
513 }
514}
515
516void raw_spin_rq_unlock(struct rq *rq)
517{
518 raw_spin_unlock(rq_lockp(rq));
519}
520
521#ifdef CONFIG_SMP
522/*
523 * double_rq_lock - safely lock two runqueues
524 */
525void double_rq_lock(struct rq *rq1, struct rq *rq2)
526{
527 lockdep_assert_irqs_disabled();
528
529 if (rq_order_less(rq2, rq1))
530 swap(rq1, rq2);
531
532 raw_spin_rq_lock(rq1);
533 if (__rq_lockp(rq1) == __rq_lockp(rq2))
534 return;
535
536 raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING);
537}
538#endif
539
540/*
541 * __task_rq_lock - lock the rq @p resides on.
542 */
543struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
544 __acquires(rq->lock)
545{
546 struct rq *rq;
547
548 lockdep_assert_held(&p->pi_lock);
549
550 for (;;) {
551 rq = task_rq(p);
552 raw_spin_rq_lock(rq);
553 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
554 rq_pin_lock(rq, rf);
555 return rq;
556 }
557 raw_spin_rq_unlock(rq);
558
559 while (unlikely(task_on_rq_migrating(p)))
560 cpu_relax();
561 }
562}
563
564/*
565 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
566 */
567struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
568 __acquires(p->pi_lock)
569 __acquires(rq->lock)
570{
571 struct rq *rq;
572
573 for (;;) {
574 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
575 rq = task_rq(p);
576 raw_spin_rq_lock(rq);
577 /*
578 * move_queued_task() task_rq_lock()
579 *
580 * ACQUIRE (rq->lock)
581 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
582 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
583 * [S] ->cpu = new_cpu [L] task_rq()
584 * [L] ->on_rq
585 * RELEASE (rq->lock)
586 *
587 * If we observe the old CPU in task_rq_lock(), the acquire of
588 * the old rq->lock will fully serialize against the stores.
589 *
590 * If we observe the new CPU in task_rq_lock(), the address
591 * dependency headed by '[L] rq = task_rq()' and the acquire
592 * will pair with the WMB to ensure we then also see migrating.
593 */
594 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
595 rq_pin_lock(rq, rf);
596 return rq;
597 }
598 raw_spin_rq_unlock(rq);
599 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
600
601 while (unlikely(task_on_rq_migrating(p)))
602 cpu_relax();
603 }
604}
605
606/*
607 * RQ-clock updating methods:
608 */
609
610static void update_rq_clock_task(struct rq *rq, s64 delta)
611{
612/*
613 * In theory, the compile should just see 0 here, and optimize out the call
614 * to sched_rt_avg_update. But I don't trust it...
615 */
616 s64 __maybe_unused steal = 0, irq_delta = 0;
617
618#ifdef CONFIG_IRQ_TIME_ACCOUNTING
619 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
620
621 /*
622 * Since irq_time is only updated on {soft,}irq_exit, we might run into
623 * this case when a previous update_rq_clock() happened inside a
624 * {soft,}irq region.
625 *
626 * When this happens, we stop ->clock_task and only update the
627 * prev_irq_time stamp to account for the part that fit, so that a next
628 * update will consume the rest. This ensures ->clock_task is
629 * monotonic.
630 *
631 * It does however cause some slight miss-attribution of {soft,}irq
632 * time, a more accurate solution would be to update the irq_time using
633 * the current rq->clock timestamp, except that would require using
634 * atomic ops.
635 */
636 if (irq_delta > delta)
637 irq_delta = delta;
638
639 rq->prev_irq_time += irq_delta;
640 delta -= irq_delta;
641#endif
642#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
643 if (static_key_false((¶virt_steal_rq_enabled))) {
644 steal = paravirt_steal_clock(cpu_of(rq));
645 steal -= rq->prev_steal_time_rq;
646
647 if (unlikely(steal > delta))
648 steal = delta;
649
650 rq->prev_steal_time_rq += steal;
651 delta -= steal;
652 }
653#endif
654
655 rq->clock_task += delta;
656
657#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
658 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
659 update_irq_load_avg(rq, irq_delta + steal);
660#endif
661 update_rq_clock_pelt(rq, delta);
662}
663
664void update_rq_clock(struct rq *rq)
665{
666 s64 delta;
667
668 lockdep_assert_rq_held(rq);
669
670 if (rq->clock_update_flags & RQCF_ACT_SKIP)
671 return;
672
673#ifdef CONFIG_SCHED_DEBUG
674 if (sched_feat(WARN_DOUBLE_CLOCK))
675 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
676 rq->clock_update_flags |= RQCF_UPDATED;
677#endif
678
679 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
680 if (delta < 0)
681 return;
682 rq->clock += delta;
683 update_rq_clock_task(rq, delta);
684}
685
686#ifdef CONFIG_SCHED_HRTICK
687/*
688 * Use HR-timers to deliver accurate preemption points.
689 */
690
691static void hrtick_clear(struct rq *rq)
692{
693 if (hrtimer_active(&rq->hrtick_timer))
694 hrtimer_cancel(&rq->hrtick_timer);
695}
696
697/*
698 * High-resolution timer tick.
699 * Runs from hardirq context with interrupts disabled.
700 */
701static enum hrtimer_restart hrtick(struct hrtimer *timer)
702{
703 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
704 struct rq_flags rf;
705
706 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
707
708 rq_lock(rq, &rf);
709 update_rq_clock(rq);
710 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
711 rq_unlock(rq, &rf);
712
713 return HRTIMER_NORESTART;
714}
715
716#ifdef CONFIG_SMP
717
718static void __hrtick_restart(struct rq *rq)
719{
720 struct hrtimer *timer = &rq->hrtick_timer;
721 ktime_t time = rq->hrtick_time;
722
723 hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
724}
725
726/*
727 * called from hardirq (IPI) context
728 */
729static void __hrtick_start(void *arg)
730{
731 struct rq *rq = arg;
732 struct rq_flags rf;
733
734 rq_lock(rq, &rf);
735 __hrtick_restart(rq);
736 rq_unlock(rq, &rf);
737}
738
739/*
740 * Called to set the hrtick timer state.
741 *
742 * called with rq->lock held and irqs disabled
743 */
744void hrtick_start(struct rq *rq, u64 delay)
745{
746 struct hrtimer *timer = &rq->hrtick_timer;
747 s64 delta;
748
749 /*
750 * Don't schedule slices shorter than 10000ns, that just
751 * doesn't make sense and can cause timer DoS.
752 */
753 delta = max_t(s64, delay, 10000LL);
754 rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);
755
756 if (rq == this_rq())
757 __hrtick_restart(rq);
758 else
759 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
760}
761
762#else
763/*
764 * Called to set the hrtick timer state.
765 *
766 * called with rq->lock held and irqs disabled
767 */
768void hrtick_start(struct rq *rq, u64 delay)
769{
770 /*
771 * Don't schedule slices shorter than 10000ns, that just
772 * doesn't make sense. Rely on vruntime for fairness.
773 */
774 delay = max_t(u64, delay, 10000LL);
775 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
776 HRTIMER_MODE_REL_PINNED_HARD);
777}
778
779#endif /* CONFIG_SMP */
780
781static void hrtick_rq_init(struct rq *rq)
782{
783#ifdef CONFIG_SMP
784 INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq);
785#endif
786 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
787 rq->hrtick_timer.function = hrtick;
788}
789#else /* CONFIG_SCHED_HRTICK */
790static inline void hrtick_clear(struct rq *rq)
791{
792}
793
794static inline void hrtick_rq_init(struct rq *rq)
795{
796}
797#endif /* CONFIG_SCHED_HRTICK */
798
799/*
800 * cmpxchg based fetch_or, macro so it works for different integer types
801 */
802#define fetch_or(ptr, mask) \
803 ({ \
804 typeof(ptr) _ptr = (ptr); \
805 typeof(mask) _mask = (mask); \
806 typeof(*_ptr) _old, _val = *_ptr; \
807 \
808 for (;;) { \
809 _old = cmpxchg(_ptr, _val, _val | _mask); \
810 if (_old == _val) \
811 break; \
812 _val = _old; \
813 } \
814 _old; \
815})
816
817#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
818/*
819 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
820 * this avoids any races wrt polling state changes and thereby avoids
821 * spurious IPIs.
822 */
823static bool set_nr_and_not_polling(struct task_struct *p)
824{
825 struct thread_info *ti = task_thread_info(p);
826 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
827}
828
829/*
830 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
831 *
832 * If this returns true, then the idle task promises to call
833 * sched_ttwu_pending() and reschedule soon.
834 */
835static bool set_nr_if_polling(struct task_struct *p)
836{
837 struct thread_info *ti = task_thread_info(p);
838 typeof(ti->flags) old, val = READ_ONCE(ti->flags);
839
840 for (;;) {
841 if (!(val & _TIF_POLLING_NRFLAG))
842 return false;
843 if (val & _TIF_NEED_RESCHED)
844 return true;
845 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
846 if (old == val)
847 break;
848 val = old;
849 }
850 return true;
851}
852
853#else
854static bool set_nr_and_not_polling(struct task_struct *p)
855{
856 set_tsk_need_resched(p);
857 return true;
858}
859
860#ifdef CONFIG_SMP
861static bool set_nr_if_polling(struct task_struct *p)
862{
863 return false;
864}
865#endif
866#endif
867
868static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
869{
870 struct wake_q_node *node = &task->wake_q;
871
872 /*
873 * Atomically grab the task, if ->wake_q is !nil already it means
874 * it's already queued (either by us or someone else) and will get the
875 * wakeup due to that.
876 *
877 * In order to ensure that a pending wakeup will observe our pending
878 * state, even in the failed case, an explicit smp_mb() must be used.
879 */
880 smp_mb__before_atomic();
881 if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
882 return false;
883
884 /*
885 * The head is context local, there can be no concurrency.
886 */
887 *head->lastp = node;
888 head->lastp = &node->next;
889 return true;
890}
891
892/**
893 * wake_q_add() - queue a wakeup for 'later' waking.
894 * @head: the wake_q_head to add @task to
895 * @task: the task to queue for 'later' wakeup
896 *
897 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
898 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
899 * instantly.
900 *
901 * This function must be used as-if it were wake_up_process(); IOW the task
902 * must be ready to be woken at this location.
903 */
904void wake_q_add(struct wake_q_head *head, struct task_struct *task)
905{
906 if (__wake_q_add(head, task))
907 get_task_struct(task);
908}
909
910/**
911 * wake_q_add_safe() - safely queue a wakeup for 'later' waking.
912 * @head: the wake_q_head to add @task to
913 * @task: the task to queue for 'later' wakeup
914 *
915 * Queue a task for later wakeup, most likely by the wake_up_q() call in the
916 * same context, _HOWEVER_ this is not guaranteed, the wakeup can come
917 * instantly.
918 *
919 * This function must be used as-if it were wake_up_process(); IOW the task
920 * must be ready to be woken at this location.
921 *
922 * This function is essentially a task-safe equivalent to wake_q_add(). Callers
923 * that already hold reference to @task can call the 'safe' version and trust
924 * wake_q to do the right thing depending whether or not the @task is already
925 * queued for wakeup.
926 */
927void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
928{
929 if (!__wake_q_add(head, task))
930 put_task_struct(task);
931}
932
933void wake_up_q(struct wake_q_head *head)
934{
935 struct wake_q_node *node = head->first;
936
937 while (node != WAKE_Q_TAIL) {
938 struct task_struct *task;
939
940 task = container_of(node, struct task_struct, wake_q);
941 /* Task can safely be re-inserted now: */
942 node = node->next;
943 task->wake_q.next = NULL;
944
945 /*
946 * wake_up_process() executes a full barrier, which pairs with
947 * the queueing in wake_q_add() so as not to miss wakeups.
948 */
949 wake_up_process(task);
950 put_task_struct(task);
951 }
952}
953
954/*
955 * resched_curr - mark rq's current task 'to be rescheduled now'.
956 *
957 * On UP this means the setting of the need_resched flag, on SMP it
958 * might also involve a cross-CPU call to trigger the scheduler on
959 * the target CPU.
960 */
961void resched_curr(struct rq *rq)
962{
963 struct task_struct *curr = rq->curr;
964 int cpu;
965
966 lockdep_assert_rq_held(rq);
967
968 if (test_tsk_need_resched(curr))
969 return;
970
971 cpu = cpu_of(rq);
972
973 if (cpu == smp_processor_id()) {
974 set_tsk_need_resched(curr);
975 set_preempt_need_resched();
976 return;
977 }
978
979 if (set_nr_and_not_polling(curr))
980 smp_send_reschedule(cpu);
981 else
982 trace_sched_wake_idle_without_ipi(cpu);
983}
984
985void resched_cpu(int cpu)
986{
987 struct rq *rq = cpu_rq(cpu);
988 unsigned long flags;
989
990 raw_spin_rq_lock_irqsave(rq, flags);
991 if (cpu_online(cpu) || cpu == smp_processor_id())
992 resched_curr(rq);
993 raw_spin_rq_unlock_irqrestore(rq, flags);
994}
995
996#ifdef CONFIG_SMP
997#ifdef CONFIG_NO_HZ_COMMON
998/*
999 * In the semi idle case, use the nearest busy CPU for migrating timers
1000 * from an idle CPU. This is good for power-savings.
1001 *
1002 * We don't do similar optimization for completely idle system, as
1003 * selecting an idle CPU will add more delays to the timers than intended
1004 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
1005 */
1006int get_nohz_timer_target(void)
1007{
1008 int i, cpu = smp_processor_id(), default_cpu = -1;
1009 struct sched_domain *sd;
1010
1011 if (housekeeping_cpu(cpu, HK_FLAG_TIMER)) {
1012 if (!idle_cpu(cpu))
1013 return cpu;
1014 default_cpu = cpu;
1015 }
1016
1017 rcu_read_lock();
1018 for_each_domain(cpu, sd) {
1019 for_each_cpu_and(i, sched_domain_span(sd),
1020 housekeeping_cpumask(HK_FLAG_TIMER)) {
1021 if (cpu == i)
1022 continue;
1023
1024 if (!idle_cpu(i)) {
1025 cpu = i;
1026 goto unlock;
1027 }
1028 }
1029 }
1030
1031 if (default_cpu == -1)
1032 default_cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
1033 cpu = default_cpu;
1034unlock:
1035 rcu_read_unlock();
1036 return cpu;
1037}
1038
1039/*
1040 * When add_timer_on() enqueues a timer into the timer wheel of an
1041 * idle CPU then this timer might expire before the next timer event
1042 * which is scheduled to wake up that CPU. In case of a completely
1043 * idle system the next event might even be infinite time into the
1044 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
1045 * leaves the inner idle loop so the newly added timer is taken into
1046 * account when the CPU goes back to idle and evaluates the timer
1047 * wheel for the next timer event.
1048 */
1049static void wake_up_idle_cpu(int cpu)
1050{
1051 struct rq *rq = cpu_rq(cpu);
1052
1053 if (cpu == smp_processor_id())
1054 return;
1055
1056 if (set_nr_and_not_polling(rq->idle))
1057 smp_send_reschedule(cpu);
1058 else
1059 trace_sched_wake_idle_without_ipi(cpu);
1060}
1061
1062static bool wake_up_full_nohz_cpu(int cpu)
1063{
1064 /*
1065 * We just need the target to call irq_exit() and re-evaluate
1066 * the next tick. The nohz full kick at least implies that.
1067 * If needed we can still optimize that later with an
1068 * empty IRQ.
1069 */
1070 if (cpu_is_offline(cpu))
1071 return true; /* Don't try to wake offline CPUs. */
1072 if (tick_nohz_full_cpu(cpu)) {
1073 if (cpu != smp_processor_id() ||
1074 tick_nohz_tick_stopped())
1075 tick_nohz_full_kick_cpu(cpu);
1076 return true;
1077 }
1078
1079 return false;
1080}
1081
1082/*
1083 * Wake up the specified CPU. If the CPU is going offline, it is the
1084 * caller's responsibility to deal with the lost wakeup, for example,
1085 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
1086 */
1087void wake_up_nohz_cpu(int cpu)
1088{
1089 if (!wake_up_full_nohz_cpu(cpu))
1090 wake_up_idle_cpu(cpu);
1091}
1092
1093static void nohz_csd_func(void *info)
1094{
1095 struct rq *rq = info;
1096 int cpu = cpu_of(rq);
1097 unsigned int flags;
1098
1099 /*
1100 * Release the rq::nohz_csd.
1101 */
1102 flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu));
1103 WARN_ON(!(flags & NOHZ_KICK_MASK));
1104
1105 rq->idle_balance = idle_cpu(cpu);
1106 if (rq->idle_balance && !need_resched()) {
1107 rq->nohz_idle_balance = flags;
1108 raise_softirq_irqoff(SCHED_SOFTIRQ);
1109 }
1110}
1111
1112#endif /* CONFIG_NO_HZ_COMMON */
1113
1114#ifdef CONFIG_NO_HZ_FULL
1115bool sched_can_stop_tick(struct rq *rq)
1116{
1117 int fifo_nr_running;
1118
1119 /* Deadline tasks, even if single, need the tick */
1120 if (rq->dl.dl_nr_running)
1121 return false;
1122
1123 /*
1124 * If there are more than one RR tasks, we need the tick to affect the
1125 * actual RR behaviour.
1126 */
1127 if (rq->rt.rr_nr_running) {
1128 if (rq->rt.rr_nr_running == 1)
1129 return true;
1130 else
1131 return false;
1132 }
1133
1134 /*
1135 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
1136 * forced preemption between FIFO tasks.
1137 */
1138 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
1139 if (fifo_nr_running)
1140 return true;
1141
1142 /*
1143 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
1144 * if there's more than one we need the tick for involuntary
1145 * preemption.
1146 */
1147 if (rq->nr_running > 1)
1148 return false;
1149
1150 return true;
1151}
1152#endif /* CONFIG_NO_HZ_FULL */
1153#endif /* CONFIG_SMP */
1154
1155#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
1156 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
1157/*
1158 * Iterate task_group tree rooted at *from, calling @down when first entering a
1159 * node and @up when leaving it for the final time.
1160 *
1161 * Caller must hold rcu_lock or sufficient equivalent.
1162 */
1163int walk_tg_tree_from(struct task_group *from,
1164 tg_visitor down, tg_visitor up, void *data)
1165{
1166 struct task_group *parent, *child;
1167 int ret;
1168
1169 parent = from;
1170
1171down:
1172 ret = (*down)(parent, data);
1173 if (ret)
1174 goto out;
1175 list_for_each_entry_rcu(child, &parent->children, siblings) {
1176 parent = child;
1177 goto down;
1178
1179up:
1180 continue;
1181 }
1182 ret = (*up)(parent, data);
1183 if (ret || parent == from)
1184 goto out;
1185
1186 child = parent;
1187 parent = parent->parent;
1188 if (parent)
1189 goto up;
1190out:
1191 return ret;
1192}
1193
1194int tg_nop(struct task_group *tg, void *data)
1195{
1196 return 0;
1197}
1198#endif
1199
1200static void set_load_weight(struct task_struct *p, bool update_load)
1201{
1202 int prio = p->static_prio - MAX_RT_PRIO;
1203 struct load_weight *load = &p->se.load;
1204
1205 /*
1206 * SCHED_IDLE tasks get minimal weight:
1207 */
1208 if (task_has_idle_policy(p)) {
1209 load->weight = scale_load(WEIGHT_IDLEPRIO);
1210 load->inv_weight = WMULT_IDLEPRIO;
1211 return;
1212 }
1213
1214 /*
1215 * SCHED_OTHER tasks have to update their load when changing their
1216 * weight
1217 */
1218 if (update_load && p->sched_class == &fair_sched_class) {
1219 reweight_task(p, prio);
1220 } else {
1221 load->weight = scale_load(sched_prio_to_weight[prio]);
1222 load->inv_weight = sched_prio_to_wmult[prio];
1223 }
1224}
1225
1226#ifdef CONFIG_UCLAMP_TASK
1227/*
1228 * Serializes updates of utilization clamp values
1229 *
1230 * The (slow-path) user-space triggers utilization clamp value updates which
1231 * can require updates on (fast-path) scheduler's data structures used to
1232 * support enqueue/dequeue operations.
1233 * While the per-CPU rq lock protects fast-path update operations, user-space
1234 * requests are serialized using a mutex to reduce the risk of conflicting
1235 * updates or API abuses.
1236 */
1237static DEFINE_MUTEX(uclamp_mutex);
1238
1239/* Max allowed minimum utilization */
1240unsigned int sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE;
1241
1242/* Max allowed maximum utilization */
1243unsigned int sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE;
1244
1245/*
1246 * By default RT tasks run at the maximum performance point/capacity of the
1247 * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to
1248 * SCHED_CAPACITY_SCALE.
1249 *
1250 * This knob allows admins to change the default behavior when uclamp is being
1251 * used. In battery powered devices, particularly, running at the maximum
1252 * capacity and frequency will increase energy consumption and shorten the
1253 * battery life.
1254 *
1255 * This knob only affects RT tasks that their uclamp_se->user_defined == false.
1256 *
1257 * This knob will not override the system default sched_util_clamp_min defined
1258 * above.
1259 */
1260unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE;
1261
1262/* All clamps are required to be less or equal than these values */
1263static struct uclamp_se uclamp_default[UCLAMP_CNT];
1264
1265/*
1266 * This static key is used to reduce the uclamp overhead in the fast path. It
1267 * primarily disables the call to uclamp_rq_{inc, dec}() in
1268 * enqueue/dequeue_task().
1269 *
1270 * This allows users to continue to enable uclamp in their kernel config with
1271 * minimum uclamp overhead in the fast path.
1272 *
1273 * As soon as userspace modifies any of the uclamp knobs, the static key is
1274 * enabled, since we have an actual users that make use of uclamp
1275 * functionality.
1276 *
1277 * The knobs that would enable this static key are:
1278 *
1279 * * A task modifying its uclamp value with sched_setattr().
1280 * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs.
1281 * * An admin modifying the cgroup cpu.uclamp.{min, max}
1282 */
1283DEFINE_STATIC_KEY_FALSE(sched_uclamp_used);
1284
1285/* Integer rounded range for each bucket */
1286#define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS)
1287
1288#define for_each_clamp_id(clamp_id) \
1289 for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++)
1290
1291static inline unsigned int uclamp_bucket_id(unsigned int clamp_value)
1292{
1293 return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1);
1294}
1295
1296static inline unsigned int uclamp_none(enum uclamp_id clamp_id)
1297{
1298 if (clamp_id == UCLAMP_MIN)
1299 return 0;
1300 return SCHED_CAPACITY_SCALE;
1301}
1302
1303static inline void uclamp_se_set(struct uclamp_se *uc_se,
1304 unsigned int value, bool user_defined)
1305{
1306 uc_se->value = value;
1307 uc_se->bucket_id = uclamp_bucket_id(value);
1308 uc_se->user_defined = user_defined;
1309}
1310
1311static inline unsigned int
1312uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id,
1313 unsigned int clamp_value)
1314{
1315 /*
1316 * Avoid blocked utilization pushing up the frequency when we go
1317 * idle (which drops the max-clamp) by retaining the last known
1318 * max-clamp.
1319 */
1320 if (clamp_id == UCLAMP_MAX) {
1321 rq->uclamp_flags |= UCLAMP_FLAG_IDLE;
1322 return clamp_value;
1323 }
1324
1325 return uclamp_none(UCLAMP_MIN);
1326}
1327
1328static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id,
1329 unsigned int clamp_value)
1330{
1331 /* Reset max-clamp retention only on idle exit */
1332 if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1333 return;
1334
1335 WRITE_ONCE(rq->uclamp[clamp_id].value, clamp_value);
1336}
1337
1338static inline
1339unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id,
1340 unsigned int clamp_value)
1341{
1342 struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket;
1343 int bucket_id = UCLAMP_BUCKETS - 1;
1344
1345 /*
1346 * Since both min and max clamps are max aggregated, find the
1347 * top most bucket with tasks in.
1348 */
1349 for ( ; bucket_id >= 0; bucket_id--) {
1350 if (!bucket[bucket_id].tasks)
1351 continue;
1352 return bucket[bucket_id].value;
1353 }
1354
1355 /* No tasks -- default clamp values */
1356 return uclamp_idle_value(rq, clamp_id, clamp_value);
1357}
1358
1359static void __uclamp_update_util_min_rt_default(struct task_struct *p)
1360{
1361 unsigned int default_util_min;
1362 struct uclamp_se *uc_se;
1363
1364 lockdep_assert_held(&p->pi_lock);
1365
1366 uc_se = &p->uclamp_req[UCLAMP_MIN];
1367
1368 /* Only sync if user didn't override the default */
1369 if (uc_se->user_defined)
1370 return;
1371
1372 default_util_min = sysctl_sched_uclamp_util_min_rt_default;
1373 uclamp_se_set(uc_se, default_util_min, false);
1374}
1375
1376static void uclamp_update_util_min_rt_default(struct task_struct *p)
1377{
1378 struct rq_flags rf;
1379 struct rq *rq;
1380
1381 if (!rt_task(p))
1382 return;
1383
1384 /* Protect updates to p->uclamp_* */
1385 rq = task_rq_lock(p, &rf);
1386 __uclamp_update_util_min_rt_default(p);
1387 task_rq_unlock(rq, p, &rf);
1388}
1389
1390static void uclamp_sync_util_min_rt_default(void)
1391{
1392 struct task_struct *g, *p;
1393
1394 /*
1395 * copy_process() sysctl_uclamp
1396 * uclamp_min_rt = X;
1397 * write_lock(&tasklist_lock) read_lock(&tasklist_lock)
1398 * // link thread smp_mb__after_spinlock()
1399 * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock);
1400 * sched_post_fork() for_each_process_thread()
1401 * __uclamp_sync_rt() __uclamp_sync_rt()
1402 *
1403 * Ensures that either sched_post_fork() will observe the new
1404 * uclamp_min_rt or for_each_process_thread() will observe the new
1405 * task.
1406 */
1407 read_lock(&tasklist_lock);
1408 smp_mb__after_spinlock();
1409 read_unlock(&tasklist_lock);
1410
1411 rcu_read_lock();
1412 for_each_process_thread(g, p)
1413 uclamp_update_util_min_rt_default(p);
1414 rcu_read_unlock();
1415}
1416
1417static inline struct uclamp_se
1418uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
1419{
1420 /* Copy by value as we could modify it */
1421 struct uclamp_se uc_req = p->uclamp_req[clamp_id];
1422#ifdef CONFIG_UCLAMP_TASK_GROUP
1423 unsigned int tg_min, tg_max, value;
1424
1425 /*
1426 * Tasks in autogroups or root task group will be
1427 * restricted by system defaults.
1428 */
1429 if (task_group_is_autogroup(task_group(p)))
1430 return uc_req;
1431 if (task_group(p) == &root_task_group)
1432 return uc_req;
1433
1434 tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
1435 tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
1436 value = uc_req.value;
1437 value = clamp(value, tg_min, tg_max);
1438 uclamp_se_set(&uc_req, value, false);
1439#endif
1440
1441 return uc_req;
1442}
1443
1444/*
1445 * The effective clamp bucket index of a task depends on, by increasing
1446 * priority:
1447 * - the task specific clamp value, when explicitly requested from userspace
1448 * - the task group effective clamp value, for tasks not either in the root
1449 * group or in an autogroup
1450 * - the system default clamp value, defined by the sysadmin
1451 */
1452static inline struct uclamp_se
1453uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
1454{
1455 struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id);
1456 struct uclamp_se uc_max = uclamp_default[clamp_id];
1457
1458 /* System default restrictions always apply */
1459 if (unlikely(uc_req.value > uc_max.value))
1460 return uc_max;
1461
1462 return uc_req;
1463}
1464
1465unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
1466{
1467 struct uclamp_se uc_eff;
1468
1469 /* Task currently refcounted: use back-annotated (effective) value */
1470 if (p->uclamp[clamp_id].active)
1471 return (unsigned long)p->uclamp[clamp_id].value;
1472
1473 uc_eff = uclamp_eff_get(p, clamp_id);
1474
1475 return (unsigned long)uc_eff.value;
1476}
1477
1478/*
1479 * When a task is enqueued on a rq, the clamp bucket currently defined by the
1480 * task's uclamp::bucket_id is refcounted on that rq. This also immediately
1481 * updates the rq's clamp value if required.
1482 *
1483 * Tasks can have a task-specific value requested from user-space, track
1484 * within each bucket the maximum value for tasks refcounted in it.
1485 * This "local max aggregation" allows to track the exact "requested" value
1486 * for each bucket when all its RUNNABLE tasks require the same clamp.
1487 */
1488static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p,
1489 enum uclamp_id clamp_id)
1490{
1491 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1492 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1493 struct uclamp_bucket *bucket;
1494
1495 lockdep_assert_rq_held(rq);
1496
1497 /* Update task effective clamp */
1498 p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id);
1499
1500 bucket = &uc_rq->bucket[uc_se->bucket_id];
1501 bucket->tasks++;
1502 uc_se->active = true;
1503
1504 uclamp_idle_reset(rq, clamp_id, uc_se->value);
1505
1506 /*
1507 * Local max aggregation: rq buckets always track the max
1508 * "requested" clamp value of its RUNNABLE tasks.
1509 */
1510 if (bucket->tasks == 1 || uc_se->value > bucket->value)
1511 bucket->value = uc_se->value;
1512
1513 if (uc_se->value > READ_ONCE(uc_rq->value))
1514 WRITE_ONCE(uc_rq->value, uc_se->value);
1515}
1516
1517/*
1518 * When a task is dequeued from a rq, the clamp bucket refcounted by the task
1519 * is released. If this is the last task reference counting the rq's max
1520 * active clamp value, then the rq's clamp value is updated.
1521 *
1522 * Both refcounted tasks and rq's cached clamp values are expected to be
1523 * always valid. If it's detected they are not, as defensive programming,
1524 * enforce the expected state and warn.
1525 */
1526static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p,
1527 enum uclamp_id clamp_id)
1528{
1529 struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id];
1530 struct uclamp_se *uc_se = &p->uclamp[clamp_id];
1531 struct uclamp_bucket *bucket;
1532 unsigned int bkt_clamp;
1533 unsigned int rq_clamp;
1534
1535 lockdep_assert_rq_held(rq);
1536
1537 /*
1538 * If sched_uclamp_used was enabled after task @p was enqueued,
1539 * we could end up with unbalanced call to uclamp_rq_dec_id().
1540 *
1541 * In this case the uc_se->active flag should be false since no uclamp
1542 * accounting was performed at enqueue time and we can just return
1543 * here.
1544 *
1545 * Need to be careful of the following enqueue/dequeue ordering
1546 * problem too
1547 *
1548 * enqueue(taskA)
1549 * // sched_uclamp_used gets enabled
1550 * enqueue(taskB)
1551 * dequeue(taskA)
1552 * // Must not decrement bucket->tasks here
1553 * dequeue(taskB)
1554 *
1555 * where we could end up with stale data in uc_se and
1556 * bucket[uc_se->bucket_id].
1557 *
1558 * The following check here eliminates the possibility of such race.
1559 */
1560 if (unlikely(!uc_se->active))
1561 return;
1562
1563 bucket = &uc_rq->bucket[uc_se->bucket_id];
1564
1565 SCHED_WARN_ON(!bucket->tasks);
1566 if (likely(bucket->tasks))
1567 bucket->tasks--;
1568
1569 uc_se->active = false;
1570
1571 /*
1572 * Keep "local max aggregation" simple and accept to (possibly)
1573 * overboost some RUNNABLE tasks in the same bucket.
1574 * The rq clamp bucket value is reset to its base value whenever
1575 * there are no more RUNNABLE tasks refcounting it.
1576 */
1577 if (likely(bucket->tasks))
1578 return;
1579
1580 rq_clamp = READ_ONCE(uc_rq->value);
1581 /*
1582 * Defensive programming: this should never happen. If it happens,
1583 * e.g. due to future modification, warn and fixup the expected value.
1584 */
1585 SCHED_WARN_ON(bucket->value > rq_clamp);
1586 if (bucket->value >= rq_clamp) {
1587 bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value);
1588 WRITE_ONCE(uc_rq->value, bkt_clamp);
1589 }
1590}
1591
1592static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
1593{
1594 enum uclamp_id clamp_id;
1595
1596 /*
1597 * Avoid any overhead until uclamp is actually used by the userspace.
1598 *
1599 * The condition is constructed such that a NOP is generated when
1600 * sched_uclamp_used is disabled.
1601 */
1602 if (!static_branch_unlikely(&sched_uclamp_used))
1603 return;
1604
1605 if (unlikely(!p->sched_class->uclamp_enabled))
1606 return;
1607
1608 for_each_clamp_id(clamp_id)
1609 uclamp_rq_inc_id(rq, p, clamp_id);
1610
1611 /* Reset clamp idle holding when there is one RUNNABLE task */
1612 if (rq->uclamp_flags & UCLAMP_FLAG_IDLE)
1613 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1614}
1615
1616static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p)
1617{
1618 enum uclamp_id clamp_id;
1619
1620 /*
1621 * Avoid any overhead until uclamp is actually used by the userspace.
1622 *
1623 * The condition is constructed such that a NOP is generated when
1624 * sched_uclamp_used is disabled.
1625 */
1626 if (!static_branch_unlikely(&sched_uclamp_used))
1627 return;
1628
1629 if (unlikely(!p->sched_class->uclamp_enabled))
1630 return;
1631
1632 for_each_clamp_id(clamp_id)
1633 uclamp_rq_dec_id(rq, p, clamp_id);
1634}
1635
1636static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p,
1637 enum uclamp_id clamp_id)
1638{
1639 if (!p->uclamp[clamp_id].active)
1640 return;
1641
1642 uclamp_rq_dec_id(rq, p, clamp_id);
1643 uclamp_rq_inc_id(rq, p, clamp_id);
1644
1645 /*
1646 * Make sure to clear the idle flag if we've transiently reached 0
1647 * active tasks on rq.
1648 */
1649 if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE))
1650 rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE;
1651}
1652
1653static inline void
1654uclamp_update_active(struct task_struct *p)
1655{
1656 enum uclamp_id clamp_id;
1657 struct rq_flags rf;
1658 struct rq *rq;
1659
1660 /*
1661 * Lock the task and the rq where the task is (or was) queued.
1662 *
1663 * We might lock the (previous) rq of a !RUNNABLE task, but that's the
1664 * price to pay to safely serialize util_{min,max} updates with
1665 * enqueues, dequeues and migration operations.
1666 * This is the same locking schema used by __set_cpus_allowed_ptr().
1667 */
1668 rq = task_rq_lock(p, &rf);
1669
1670 /*
1671 * Setting the clamp bucket is serialized by task_rq_lock().
1672 * If the task is not yet RUNNABLE and its task_struct is not
1673 * affecting a valid clamp bucket, the next time it's enqueued,
1674 * it will already see the updated clamp bucket value.
1675 */
1676 for_each_clamp_id(clamp_id)
1677 uclamp_rq_reinc_id(rq, p, clamp_id);
1678
1679 task_rq_unlock(rq, p, &rf);
1680}
1681
1682#ifdef CONFIG_UCLAMP_TASK_GROUP
1683static inline void
1684uclamp_update_active_tasks(struct cgroup_subsys_state *css)
1685{
1686 struct css_task_iter it;
1687 struct task_struct *p;
1688
1689 css_task_iter_start(css, 0, &it);
1690 while ((p = css_task_iter_next(&it)))
1691 uclamp_update_active(p);
1692 css_task_iter_end(&it);
1693}
1694
1695static void cpu_util_update_eff(struct cgroup_subsys_state *css);
1696static void uclamp_update_root_tg(void)
1697{
1698 struct task_group *tg = &root_task_group;
1699
1700 uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN],
1701 sysctl_sched_uclamp_util_min, false);
1702 uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX],
1703 sysctl_sched_uclamp_util_max, false);
1704
1705 rcu_read_lock();
1706 cpu_util_update_eff(&root_task_group.css);
1707 rcu_read_unlock();
1708}
1709#else
1710static void uclamp_update_root_tg(void) { }
1711#endif
1712
1713int sysctl_sched_uclamp_handler(struct ctl_table *table, int write,
1714 void *buffer, size_t *lenp, loff_t *ppos)
1715{
1716 bool update_root_tg = false;
1717 int old_min, old_max, old_min_rt;
1718 int result;
1719
1720 mutex_lock(&uclamp_mutex);
1721 old_min = sysctl_sched_uclamp_util_min;
1722 old_max = sysctl_sched_uclamp_util_max;
1723 old_min_rt = sysctl_sched_uclamp_util_min_rt_default;
1724
1725 result = proc_dointvec(table, write, buffer, lenp, ppos);
1726 if (result)
1727 goto undo;
1728 if (!write)
1729 goto done;
1730
1731 if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max ||
1732 sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE ||
1733 sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) {
1734
1735 result = -EINVAL;
1736 goto undo;
1737 }
1738
1739 if (old_min != sysctl_sched_uclamp_util_min) {
1740 uclamp_se_set(&uclamp_default[UCLAMP_MIN],
1741 sysctl_sched_uclamp_util_min, false);
1742 update_root_tg = true;
1743 }
1744 if (old_max != sysctl_sched_uclamp_util_max) {
1745 uclamp_se_set(&uclamp_default[UCLAMP_MAX],
1746 sysctl_sched_uclamp_util_max, false);
1747 update_root_tg = true;
1748 }
1749
1750 if (update_root_tg) {
1751 static_branch_enable(&sched_uclamp_used);
1752 uclamp_update_root_tg();
1753 }
1754
1755 if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) {
1756 static_branch_enable(&sched_uclamp_used);
1757 uclamp_sync_util_min_rt_default();
1758 }
1759
1760 /*
1761 * We update all RUNNABLE tasks only when task groups are in use.
1762 * Otherwise, keep it simple and do just a lazy update at each next
1763 * task enqueue time.
1764 */
1765
1766 goto done;
1767
1768undo:
1769 sysctl_sched_uclamp_util_min = old_min;
1770 sysctl_sched_uclamp_util_max = old_max;
1771 sysctl_sched_uclamp_util_min_rt_default = old_min_rt;
1772done:
1773 mutex_unlock(&uclamp_mutex);
1774
1775 return result;
1776}
1777
1778static int uclamp_validate(struct task_struct *p,
1779 const struct sched_attr *attr)
1780{
1781 int util_min = p->uclamp_req[UCLAMP_MIN].value;
1782 int util_max = p->uclamp_req[UCLAMP_MAX].value;
1783
1784 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
1785 util_min = attr->sched_util_min;
1786
1787 if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
1788 return -EINVAL;
1789 }
1790
1791 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
1792 util_max = attr->sched_util_max;
1793
1794 if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
1795 return -EINVAL;
1796 }
1797
1798 if (util_min != -1 && util_max != -1 && util_min > util_max)
1799 return -EINVAL;
1800
1801 /*
1802 * We have valid uclamp attributes; make sure uclamp is enabled.
1803 *
1804 * We need to do that here, because enabling static branches is a
1805 * blocking operation which obviously cannot be done while holding
1806 * scheduler locks.
1807 */
1808 static_branch_enable(&sched_uclamp_used);
1809
1810 return 0;
1811}
1812
1813static bool uclamp_reset(const struct sched_attr *attr,
1814 enum uclamp_id clamp_id,
1815 struct uclamp_se *uc_se)
1816{
1817 /* Reset on sched class change for a non user-defined clamp value. */
1818 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) &&
1819 !uc_se->user_defined)
1820 return true;
1821
1822 /* Reset on sched_util_{min,max} == -1. */
1823 if (clamp_id == UCLAMP_MIN &&
1824 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1825 attr->sched_util_min == -1) {
1826 return true;
1827 }
1828
1829 if (clamp_id == UCLAMP_MAX &&
1830 attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1831 attr->sched_util_max == -1) {
1832 return true;
1833 }
1834
1835 return false;
1836}
1837
1838static void __setscheduler_uclamp(struct task_struct *p,
1839 const struct sched_attr *attr)
1840{
1841 enum uclamp_id clamp_id;
1842
1843 for_each_clamp_id(clamp_id) {
1844 struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
1845 unsigned int value;
1846
1847 if (!uclamp_reset(attr, clamp_id, uc_se))
1848 continue;
1849
1850 /*
1851 * RT by default have a 100% boost value that could be modified
1852 * at runtime.
1853 */
1854 if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
1855 value = sysctl_sched_uclamp_util_min_rt_default;
1856 else
1857 value = uclamp_none(clamp_id);
1858
1859 uclamp_se_set(uc_se, value, false);
1860
1861 }
1862
1863 if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
1864 return;
1865
1866 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
1867 attr->sched_util_min != -1) {
1868 uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
1869 attr->sched_util_min, true);
1870 }
1871
1872 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
1873 attr->sched_util_max != -1) {
1874 uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
1875 attr->sched_util_max, true);
1876 }
1877}
1878
1879static void uclamp_fork(struct task_struct *p)
1880{
1881 enum uclamp_id clamp_id;
1882
1883 /*
1884 * We don't need to hold task_rq_lock() when updating p->uclamp_* here
1885 * as the task is still at its early fork stages.
1886 */
1887 for_each_clamp_id(clamp_id)
1888 p->uclamp[clamp_id].active = false;
1889
1890 if (likely(!p->sched_reset_on_fork))
1891 return;
1892
1893 for_each_clamp_id(clamp_id) {
1894 uclamp_se_set(&p->uclamp_req[clamp_id],
1895 uclamp_none(clamp_id), false);
1896 }
1897}
1898
1899static void uclamp_post_fork(struct task_struct *p)
1900{
1901 uclamp_update_util_min_rt_default(p);
1902}
1903
1904static void __init init_uclamp_rq(struct rq *rq)
1905{
1906 enum uclamp_id clamp_id;
1907 struct uclamp_rq *uc_rq = rq->uclamp;
1908
1909 for_each_clamp_id(clamp_id) {
1910 uc_rq[clamp_id] = (struct uclamp_rq) {
1911 .value = uclamp_none(clamp_id)
1912 };
1913 }
1914
1915 rq->uclamp_flags = 0;
1916}
1917
1918static void __init init_uclamp(void)
1919{
1920 struct uclamp_se uc_max = {};
1921 enum uclamp_id clamp_id;
1922 int cpu;
1923
1924 for_each_possible_cpu(cpu)
1925 init_uclamp_rq(cpu_rq(cpu));
1926
1927 for_each_clamp_id(clamp_id) {
1928 uclamp_se_set(&init_task.uclamp_req[clamp_id],
1929 uclamp_none(clamp_id), false);
1930 }
1931
1932 /* System defaults allow max clamp values for both indexes */
1933 uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false);
1934 for_each_clamp_id(clamp_id) {
1935 uclamp_default[clamp_id] = uc_max;
1936#ifdef CONFIG_UCLAMP_TASK_GROUP
1937 root_task_group.uclamp_req[clamp_id] = uc_max;
1938 root_task_group.uclamp[clamp_id] = uc_max;
1939#endif
1940 }
1941}
1942
1943#else /* CONFIG_UCLAMP_TASK */
1944static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { }
1945static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { }
1946static inline int uclamp_validate(struct task_struct *p,
1947 const struct sched_attr *attr)
1948{
1949 return -EOPNOTSUPP;
1950}
1951static void __setscheduler_uclamp(struct task_struct *p,
1952 const struct sched_attr *attr) { }
1953static inline void uclamp_fork(struct task_struct *p) { }
1954static inline void uclamp_post_fork(struct task_struct *p) { }
1955static inline void init_uclamp(void) { }
1956#endif /* CONFIG_UCLAMP_TASK */
1957
1958bool sched_task_on_rq(struct task_struct *p)
1959{
1960 return task_on_rq_queued(p);
1961}
1962
1963static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
1964{
1965 if (!(flags & ENQUEUE_NOCLOCK))
1966 update_rq_clock(rq);
1967
1968 if (!(flags & ENQUEUE_RESTORE)) {
1969 sched_info_enqueue(rq, p);
1970 psi_enqueue(p, flags & ENQUEUE_WAKEUP);
1971 }
1972
1973 uclamp_rq_inc(rq, p);
1974 p->sched_class->enqueue_task(rq, p, flags);
1975
1976 if (sched_core_enabled(rq))
1977 sched_core_enqueue(rq, p);
1978}
1979
1980static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
1981{
1982 if (sched_core_enabled(rq))
1983 sched_core_dequeue(rq, p);
1984
1985 if (!(flags & DEQUEUE_NOCLOCK))
1986 update_rq_clock(rq);
1987
1988 if (!(flags & DEQUEUE_SAVE)) {
1989 sched_info_dequeue(rq, p);
1990 psi_dequeue(p, flags & DEQUEUE_SLEEP);
1991 }
1992
1993 uclamp_rq_dec(rq, p);
1994 p->sched_class->dequeue_task(rq, p, flags);
1995}
1996
1997void activate_task(struct rq *rq, struct task_struct *p, int flags)
1998{
1999 enqueue_task(rq, p, flags);
2000
2001 p->on_rq = TASK_ON_RQ_QUEUED;
2002}
2003
2004void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
2005{
2006 p->on_rq = (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING;
2007
2008 dequeue_task(rq, p, flags);
2009}
2010
2011static inline int __normal_prio(int policy, int rt_prio, int nice)
2012{
2013 int prio;
2014
2015 if (dl_policy(policy))
2016 prio = MAX_DL_PRIO - 1;
2017 else if (rt_policy(policy))
2018 prio = MAX_RT_PRIO - 1 - rt_prio;
2019 else
2020 prio = NICE_TO_PRIO(nice);
2021
2022 return prio;
2023}
2024
2025/*
2026 * Calculate the expected normal priority: i.e. priority
2027 * without taking RT-inheritance into account. Might be
2028 * boosted by interactivity modifiers. Changes upon fork,
2029 * setprio syscalls, and whenever the interactivity
2030 * estimator recalculates.
2031 */
2032static inline int normal_prio(struct task_struct *p)
2033{
2034 return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
2035}
2036
2037/*
2038 * Calculate the current priority, i.e. the priority
2039 * taken into account by the scheduler. This value might
2040 * be boosted by RT tasks, or might be boosted by
2041 * interactivity modifiers. Will be RT if the task got
2042 * RT-boosted. If not then it returns p->normal_prio.
2043 */
2044static int effective_prio(struct task_struct *p)
2045{
2046 p->normal_prio = normal_prio(p);
2047 /*
2048 * If we are RT tasks or we were boosted to RT priority,
2049 * keep the priority unchanged. Otherwise, update priority
2050 * to the normal priority:
2051 */
2052 if (!rt_prio(p->prio))
2053 return p->normal_prio;
2054 return p->prio;
2055}
2056
2057/**
2058 * task_curr - is this task currently executing on a CPU?
2059 * @p: the task in question.
2060 *
2061 * Return: 1 if the task is currently executing. 0 otherwise.
2062 */
2063inline int task_curr(const struct task_struct *p)
2064{
2065 return cpu_curr(task_cpu(p)) == p;
2066}
2067
2068/*
2069 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
2070 * use the balance_callback list if you want balancing.
2071 *
2072 * this means any call to check_class_changed() must be followed by a call to
2073 * balance_callback().
2074 */
2075static inline void check_class_changed(struct rq *rq, struct task_struct *p,
2076 const struct sched_class *prev_class,
2077 int oldprio)
2078{
2079 if (prev_class != p->sched_class) {
2080 if (prev_class->switched_from)
2081 prev_class->switched_from(rq, p);
2082
2083 p->sched_class->switched_to(rq, p);
2084 } else if (oldprio != p->prio || dl_task(p))
2085 p->sched_class->prio_changed(rq, p, oldprio);
2086}
2087
2088void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
2089{
2090 if (p->sched_class == rq->curr->sched_class)
2091 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
2092 else if (p->sched_class > rq->curr->sched_class)
2093 resched_curr(rq);
2094
2095 /*
2096 * A queue event has occurred, and we're going to schedule. In
2097 * this case, we can save a useless back to back clock update.
2098 */
2099 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
2100 rq_clock_skip_update(rq);
2101}
2102
2103#ifdef CONFIG_SMP
2104
2105static void
2106__do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags);
2107
2108static int __set_cpus_allowed_ptr(struct task_struct *p,
2109 const struct cpumask *new_mask,
2110 u32 flags);
2111
2112static void migrate_disable_switch(struct rq *rq, struct task_struct *p)
2113{
2114 if (likely(!p->migration_disabled))
2115 return;
2116
2117 if (p->cpus_ptr != &p->cpus_mask)
2118 return;
2119
2120 /*
2121 * Violates locking rules! see comment in __do_set_cpus_allowed().
2122 */
2123 __do_set_cpus_allowed(p, cpumask_of(rq->cpu), SCA_MIGRATE_DISABLE);
2124}
2125
2126void migrate_disable(void)
2127{
2128 struct task_struct *p = current;
2129
2130 if (p->migration_disabled) {
2131 p->migration_disabled++;
2132 return;
2133 }
2134
2135 preempt_disable();
2136 this_rq()->nr_pinned++;
2137 p->migration_disabled = 1;
2138 preempt_enable();
2139}
2140EXPORT_SYMBOL_GPL(migrate_disable);
2141
2142void migrate_enable(void)
2143{
2144 struct task_struct *p = current;
2145
2146 if (p->migration_disabled > 1) {
2147 p->migration_disabled--;
2148 return;
2149 }
2150
2151 /*
2152 * Ensure stop_task runs either before or after this, and that
2153 * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
2154 */
2155 preempt_disable();
2156 if (p->cpus_ptr != &p->cpus_mask)
2157 __set_cpus_allowed_ptr(p, &p->cpus_mask, SCA_MIGRATE_ENABLE);
2158 /*
2159 * Mustn't clear migration_disabled() until cpus_ptr points back at the
2160 * regular cpus_mask, otherwise things that race (eg.
2161 * select_fallback_rq) get confused.
2162 */
2163 barrier();
2164 p->migration_disabled = 0;
2165 this_rq()->nr_pinned--;
2166 preempt_enable();
2167}
2168EXPORT_SYMBOL_GPL(migrate_enable);
2169
2170static inline bool rq_has_pinned_tasks(struct rq *rq)
2171{
2172 return rq->nr_pinned;
2173}
2174
2175/*
2176 * Per-CPU kthreads are allowed to run on !active && online CPUs, see
2177 * __set_cpus_allowed_ptr() and select_fallback_rq().
2178 */
2179static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
2180{
2181 /* When not in the task's cpumask, no point in looking further. */
2182 if (!cpumask_test_cpu(cpu, p->cpus_ptr))
2183 return false;
2184
2185 /* migrate_disabled() must be allowed to finish. */
2186 if (is_migration_disabled(p))
2187 return cpu_online(cpu);
2188
2189 /* Non kernel threads are not allowed during either online or offline. */
2190 if (!(p->flags & PF_KTHREAD))
2191 return cpu_active(cpu);
2192
2193 /* KTHREAD_IS_PER_CPU is always allowed. */
2194 if (kthread_is_per_cpu(p))
2195 return cpu_online(cpu);
2196
2197 /* Regular kernel threads don't get to stay during offline. */
2198 if (cpu_dying(cpu))
2199 return false;
2200
2201 /* But are allowed during online. */
2202 return cpu_online(cpu);
2203}
2204
2205/*
2206 * This is how migration works:
2207 *
2208 * 1) we invoke migration_cpu_stop() on the target CPU using
2209 * stop_one_cpu().
2210 * 2) stopper starts to run (implicitly forcing the migrated thread
2211 * off the CPU)
2212 * 3) it checks whether the migrated task is still in the wrong runqueue.
2213 * 4) if it's in the wrong runqueue then the migration thread removes
2214 * it and puts it into the right queue.
2215 * 5) stopper completes and stop_one_cpu() returns and the migration
2216 * is done.
2217 */
2218
2219/*
2220 * move_queued_task - move a queued task to new rq.
2221 *
2222 * Returns (locked) new rq. Old rq's lock is released.
2223 */
2224static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
2225 struct task_struct *p, int new_cpu)
2226{
2227 lockdep_assert_rq_held(rq);
2228
2229 deactivate_task(rq, p, DEQUEUE_NOCLOCK);
2230 set_task_cpu(p, new_cpu);
2231 rq_unlock(rq, rf);
2232
2233 rq = cpu_rq(new_cpu);
2234
2235 rq_lock(rq, rf);
2236 BUG_ON(task_cpu(p) != new_cpu);
2237 activate_task(rq, p, 0);
2238 check_preempt_curr(rq, p, 0);
2239
2240 return rq;
2241}
2242
2243struct migration_arg {
2244 struct task_struct *task;
2245 int dest_cpu;
2246 struct set_affinity_pending *pending;
2247};
2248
2249/*
2250 * @refs: number of wait_for_completion()
2251 * @stop_pending: is @stop_work in use
2252 */
2253struct set_affinity_pending {
2254 refcount_t refs;
2255 unsigned int stop_pending;
2256 struct completion done;
2257 struct cpu_stop_work stop_work;
2258 struct migration_arg arg;
2259};
2260
2261/*
2262 * Move (not current) task off this CPU, onto the destination CPU. We're doing
2263 * this because either it can't run here any more (set_cpus_allowed()
2264 * away from this CPU, or CPU going down), or because we're
2265 * attempting to rebalance this task on exec (sched_exec).
2266 *
2267 * So we race with normal scheduler movements, but that's OK, as long
2268 * as the task is no longer on this CPU.
2269 */
2270static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
2271 struct task_struct *p, int dest_cpu)
2272{
2273 /* Affinity changed (again). */
2274 if (!is_cpu_allowed(p, dest_cpu))
2275 return rq;
2276
2277 update_rq_clock(rq);
2278 rq = move_queued_task(rq, rf, p, dest_cpu);
2279
2280 return rq;
2281}
2282
2283/*
2284 * migration_cpu_stop - this will be executed by a highprio stopper thread
2285 * and performs thread migration by bumping thread off CPU then
2286 * 'pushing' onto another runqueue.
2287 */
2288static int migration_cpu_stop(void *data)
2289{
2290 struct migration_arg *arg = data;
2291 struct set_affinity_pending *pending = arg->pending;
2292 struct task_struct *p = arg->task;
2293 struct rq *rq = this_rq();
2294 bool complete = false;
2295 struct rq_flags rf;
2296
2297 /*
2298 * The original target CPU might have gone down and we might
2299 * be on another CPU but it doesn't matter.
2300 */
2301 local_irq_save(rf.flags);
2302 /*
2303 * We need to explicitly wake pending tasks before running
2304 * __migrate_task() such that we will not miss enforcing cpus_ptr
2305 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
2306 */
2307 flush_smp_call_function_from_idle();
2308
2309 raw_spin_lock(&p->pi_lock);
2310 rq_lock(rq, &rf);
2311
2312 /*
2313 * If we were passed a pending, then ->stop_pending was set, thus
2314 * p->migration_pending must have remained stable.
2315 */
2316 WARN_ON_ONCE(pending && pending != p->migration_pending);
2317
2318 /*
2319 * If task_rq(p) != rq, it cannot be migrated here, because we're
2320 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
2321 * we're holding p->pi_lock.
2322 */
2323 if (task_rq(p) == rq) {
2324 if (is_migration_disabled(p))
2325 goto out;
2326
2327 if (pending) {
2328 p->migration_pending = NULL;
2329 complete = true;
2330
2331 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask))
2332 goto out;
2333 }
2334
2335 if (task_on_rq_queued(p))
2336 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
2337 else
2338 p->wake_cpu = arg->dest_cpu;
2339
2340 /*
2341 * XXX __migrate_task() can fail, at which point we might end
2342 * up running on a dodgy CPU, AFAICT this can only happen
2343 * during CPU hotplug, at which point we'll get pushed out
2344 * anyway, so it's probably not a big deal.
2345 */
2346
2347 } else if (pending) {
2348 /*
2349 * This happens when we get migrated between migrate_enable()'s
2350 * preempt_enable() and scheduling the stopper task. At that
2351 * point we're a regular task again and not current anymore.
2352 *
2353 * A !PREEMPT kernel has a giant hole here, which makes it far
2354 * more likely.
2355 */
2356
2357 /*
2358 * The task moved before the stopper got to run. We're holding
2359 * ->pi_lock, so the allowed mask is stable - if it got
2360 * somewhere allowed, we're done.
2361 */
2362 if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) {
2363 p->migration_pending = NULL;
2364 complete = true;
2365 goto out;
2366 }
2367
2368 /*
2369 * When migrate_enable() hits a rq mis-match we can't reliably
2370 * determine is_migration_disabled() and so have to chase after
2371 * it.
2372 */
2373 WARN_ON_ONCE(!pending->stop_pending);
2374 task_rq_unlock(rq, p, &rf);
2375 stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
2376 &pending->arg, &pending->stop_work);
2377 return 0;
2378 }
2379out:
2380 if (pending)
2381 pending->stop_pending = false;
2382 task_rq_unlock(rq, p, &rf);
2383
2384 if (complete)
2385 complete_all(&pending->done);
2386
2387 return 0;
2388}
2389
2390int push_cpu_stop(void *arg)
2391{
2392 struct rq *lowest_rq = NULL, *rq = this_rq();
2393 struct task_struct *p = arg;
2394
2395 raw_spin_lock_irq(&p->pi_lock);
2396 raw_spin_rq_lock(rq);
2397
2398 if (task_rq(p) != rq)
2399 goto out_unlock;
2400
2401 if (is_migration_disabled(p)) {
2402 p->migration_flags |= MDF_PUSH;
2403 goto out_unlock;
2404 }
2405
2406 p->migration_flags &= ~MDF_PUSH;
2407
2408 if (p->sched_class->find_lock_rq)
2409 lowest_rq = p->sched_class->find_lock_rq(p, rq);
2410
2411 if (!lowest_rq)
2412 goto out_unlock;
2413
2414 // XXX validate p is still the highest prio task
2415 if (task_rq(p) == rq) {
2416 deactivate_task(rq, p, 0);
2417 set_task_cpu(p, lowest_rq->cpu);
2418 activate_task(lowest_rq, p, 0);
2419 resched_curr(lowest_rq);
2420 }
2421
2422 double_unlock_balance(rq, lowest_rq);
2423
2424out_unlock:
2425 rq->push_busy = false;
2426 raw_spin_rq_unlock(rq);
2427 raw_spin_unlock_irq(&p->pi_lock);
2428
2429 put_task_struct(p);
2430 return 0;
2431}
2432
2433/*
2434 * sched_class::set_cpus_allowed must do the below, but is not required to
2435 * actually call this function.
2436 */
2437void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
2438{
2439 if (flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) {
2440 p->cpus_ptr = new_mask;
2441 return;
2442 }
2443
2444 cpumask_copy(&p->cpus_mask, new_mask);
2445 p->nr_cpus_allowed = cpumask_weight(new_mask);
2446}
2447
2448static void
2449__do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask, u32 flags)
2450{
2451 struct rq *rq = task_rq(p);
2452 bool queued, running;
2453
2454 /*
2455 * This here violates the locking rules for affinity, since we're only
2456 * supposed to change these variables while holding both rq->lock and
2457 * p->pi_lock.
2458 *
2459 * HOWEVER, it magically works, because ttwu() is the only code that
2460 * accesses these variables under p->pi_lock and only does so after
2461 * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
2462 * before finish_task().
2463 *
2464 * XXX do further audits, this smells like something putrid.
2465 */
2466 if (flags & SCA_MIGRATE_DISABLE)
2467 SCHED_WARN_ON(!p->on_cpu);
2468 else
2469 lockdep_assert_held(&p->pi_lock);
2470
2471 queued = task_on_rq_queued(p);
2472 running = task_current(rq, p);
2473
2474 if (queued) {
2475 /*
2476 * Because __kthread_bind() calls this on blocked tasks without
2477 * holding rq->lock.
2478 */
2479 lockdep_assert_rq_held(rq);
2480 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
2481 }
2482 if (running)
2483 put_prev_task(rq, p);
2484
2485 p->sched_class->set_cpus_allowed(p, new_mask, flags);
2486
2487 if (queued)
2488 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
2489 if (running)
2490 set_next_task(rq, p);
2491}
2492
2493void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
2494{
2495 __do_set_cpus_allowed(p, new_mask, 0);
2496}
2497
2498/*
2499 * This function is wildly self concurrent; here be dragons.
2500 *
2501 *
2502 * When given a valid mask, __set_cpus_allowed_ptr() must block until the
2503 * designated task is enqueued on an allowed CPU. If that task is currently
2504 * running, we have to kick it out using the CPU stopper.
2505 *
2506 * Migrate-Disable comes along and tramples all over our nice sandcastle.
2507 * Consider:
2508 *
2509 * Initial conditions: P0->cpus_mask = [0, 1]
2510 *
2511 * P0@CPU0 P1
2512 *
2513 * migrate_disable();
2514 * <preempted>
2515 * set_cpus_allowed_ptr(P0, [1]);
2516 *
2517 * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes
2518 * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region).
2519 * This means we need the following scheme:
2520 *
2521 * P0@CPU0 P1
2522 *
2523 * migrate_disable();
2524 * <preempted>
2525 * set_cpus_allowed_ptr(P0, [1]);
2526 * <blocks>
2527 * <resumes>
2528 * migrate_enable();
2529 * __set_cpus_allowed_ptr();
2530 * <wakes local stopper>
2531 * `--> <woken on migration completion>
2532 *
2533 * Now the fun stuff: there may be several P1-like tasks, i.e. multiple
2534 * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any
2535 * task p are serialized by p->pi_lock, which we can leverage: the one that
2536 * should come into effect at the end of the Migrate-Disable region is the last
2537 * one. This means we only need to track a single cpumask (i.e. p->cpus_mask),
2538 * but we still need to properly signal those waiting tasks at the appropriate
2539 * moment.
2540 *
2541 * This is implemented using struct set_affinity_pending. The first
2542 * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will
2543 * setup an instance of that struct and install it on the targeted task_struct.
2544 * Any and all further callers will reuse that instance. Those then wait for
2545 * a completion signaled at the tail of the CPU stopper callback (1), triggered
2546 * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()).
2547 *
2548 *
2549 * (1) In the cases covered above. There is one more where the completion is
2550 * signaled within affine_move_task() itself: when a subsequent affinity request
2551 * occurs after the stopper bailed out due to the targeted task still being
2552 * Migrate-Disable. Consider:
2553 *
2554 * Initial conditions: P0->cpus_mask = [0, 1]
2555 *
2556 * CPU0 P1 P2
2557 * <P0>
2558 * migrate_disable();
2559 * <preempted>
2560 * set_cpus_allowed_ptr(P0, [1]);
2561 * <blocks>
2562 * <migration/0>
2563 * migration_cpu_stop()
2564 * is_migration_disabled()
2565 * <bails>
2566 * set_cpus_allowed_ptr(P0, [0, 1]);
2567 * <signal completion>
2568 * <awakes>
2569 *
2570 * Note that the above is safe vs a concurrent migrate_enable(), as any
2571 * pending affinity completion is preceded by an uninstallation of
2572 * p->migration_pending done with p->pi_lock held.
2573 */
2574static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf,
2575 int dest_cpu, unsigned int flags)
2576{
2577 struct set_affinity_pending my_pending = { }, *pending = NULL;
2578 bool stop_pending, complete = false;
2579
2580 /* Can the task run on the task's current CPU? If so, we're done */
2581 if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
2582 struct task_struct *push_task = NULL;
2583
2584 if ((flags & SCA_MIGRATE_ENABLE) &&
2585 (p->migration_flags & MDF_PUSH) && !rq->push_busy) {
2586 rq->push_busy = true;
2587 push_task = get_task_struct(p);
2588 }
2589
2590 /*
2591 * If there are pending waiters, but no pending stop_work,
2592 * then complete now.
2593 */
2594 pending = p->migration_pending;
2595 if (pending && !pending->stop_pending) {
2596 p->migration_pending = NULL;
2597 complete = true;
2598 }
2599
2600 task_rq_unlock(rq, p, rf);
2601
2602 if (push_task) {
2603 stop_one_cpu_nowait(rq->cpu, push_cpu_stop,
2604 p, &rq->push_work);
2605 }
2606
2607 if (complete)
2608 complete_all(&pending->done);
2609
2610 return 0;
2611 }
2612
2613 if (!(flags & SCA_MIGRATE_ENABLE)) {
2614 /* serialized by p->pi_lock */
2615 if (!p->migration_pending) {
2616 /* Install the request */
2617 refcount_set(&my_pending.refs, 1);
2618 init_completion(&my_pending.done);
2619 my_pending.arg = (struct migration_arg) {
2620 .task = p,
2621 .dest_cpu = dest_cpu,
2622 .pending = &my_pending,
2623 };
2624
2625 p->migration_pending = &my_pending;
2626 } else {
2627 pending = p->migration_pending;
2628 refcount_inc(&pending->refs);
2629 /*
2630 * Affinity has changed, but we've already installed a
2631 * pending. migration_cpu_stop() *must* see this, else
2632 * we risk a completion of the pending despite having a
2633 * task on a disallowed CPU.
2634 *
2635 * Serialized by p->pi_lock, so this is safe.
2636 */
2637 pending->arg.dest_cpu = dest_cpu;
2638 }
2639 }
2640 pending = p->migration_pending;
2641 /*
2642 * - !MIGRATE_ENABLE:
2643 * we'll have installed a pending if there wasn't one already.
2644 *
2645 * - MIGRATE_ENABLE:
2646 * we're here because the current CPU isn't matching anymore,
2647 * the only way that can happen is because of a concurrent
2648 * set_cpus_allowed_ptr() call, which should then still be
2649 * pending completion.
2650 *
2651 * Either way, we really should have a @pending here.
2652 */
2653 if (WARN_ON_ONCE(!pending)) {
2654 task_rq_unlock(rq, p, rf);
2655 return -EINVAL;
2656 }
2657
2658 if (task_running(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) {
2659 /*
2660 * MIGRATE_ENABLE gets here because 'p == current', but for
2661 * anything else we cannot do is_migration_disabled(), punt
2662 * and have the stopper function handle it all race-free.
2663 */
2664 stop_pending = pending->stop_pending;
2665 if (!stop_pending)
2666 pending->stop_pending = true;
2667
2668 if (flags & SCA_MIGRATE_ENABLE)
2669 p->migration_flags &= ~MDF_PUSH;
2670
2671 task_rq_unlock(rq, p, rf);
2672
2673 if (!stop_pending) {
2674 stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop,
2675 &pending->arg, &pending->stop_work);
2676 }
2677
2678 if (flags & SCA_MIGRATE_ENABLE)
2679 return 0;
2680 } else {
2681
2682 if (!is_migration_disabled(p)) {
2683 if (task_on_rq_queued(p))
2684 rq = move_queued_task(rq, rf, p, dest_cpu);
2685
2686 if (!pending->stop_pending) {
2687 p->migration_pending = NULL;
2688 complete = true;
2689 }
2690 }
2691 task_rq_unlock(rq, p, rf);
2692
2693 if (complete)
2694 complete_all(&pending->done);
2695 }
2696
2697 wait_for_completion(&pending->done);
2698
2699 if (refcount_dec_and_test(&pending->refs))
2700 wake_up_var(&pending->refs); /* No UaF, just an address */
2701
2702 /*
2703 * Block the original owner of &pending until all subsequent callers
2704 * have seen the completion and decremented the refcount
2705 */
2706 wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs));
2707
2708 /* ARGH */
2709 WARN_ON_ONCE(my_pending.stop_pending);
2710
2711 return 0;
2712}
2713
2714/*
2715 * Change a given task's CPU affinity. Migrate the thread to a
2716 * proper CPU and schedule it away if the CPU it's executing on
2717 * is removed from the allowed bitmask.
2718 *
2719 * NOTE: the caller must have a valid reference to the task, the
2720 * task must not exit() & deallocate itself prematurely. The
2721 * call is not atomic; no spinlocks may be held.
2722 */
2723static int __set_cpus_allowed_ptr(struct task_struct *p,
2724 const struct cpumask *new_mask,
2725 u32 flags)
2726{
2727 const struct cpumask *cpu_valid_mask = cpu_active_mask;
2728 unsigned int dest_cpu;
2729 struct rq_flags rf;
2730 struct rq *rq;
2731 int ret = 0;
2732
2733 rq = task_rq_lock(p, &rf);
2734 update_rq_clock(rq);
2735
2736 if (p->flags & PF_KTHREAD || is_migration_disabled(p)) {
2737 /*
2738 * Kernel threads are allowed on online && !active CPUs,
2739 * however, during cpu-hot-unplug, even these might get pushed
2740 * away if not KTHREAD_IS_PER_CPU.
2741 *
2742 * Specifically, migration_disabled() tasks must not fail the
2743 * cpumask_any_and_distribute() pick below, esp. so on
2744 * SCA_MIGRATE_ENABLE, otherwise we'll not call
2745 * set_cpus_allowed_common() and actually reset p->cpus_ptr.
2746 */
2747 cpu_valid_mask = cpu_online_mask;
2748 }
2749
2750 /*
2751 * Must re-check here, to close a race against __kthread_bind(),
2752 * sched_setaffinity() is not guaranteed to observe the flag.
2753 */
2754 if ((flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
2755 ret = -EINVAL;
2756 goto out;
2757 }
2758
2759 if (!(flags & SCA_MIGRATE_ENABLE)) {
2760 if (cpumask_equal(&p->cpus_mask, new_mask))
2761 goto out;
2762
2763 if (WARN_ON_ONCE(p == current &&
2764 is_migration_disabled(p) &&
2765 !cpumask_test_cpu(task_cpu(p), new_mask))) {
2766 ret = -EBUSY;
2767 goto out;
2768 }
2769 }
2770
2771 /*
2772 * Picking a ~random cpu helps in cases where we are changing affinity
2773 * for groups of tasks (ie. cpuset), so that load balancing is not
2774 * immediately required to distribute the tasks within their new mask.
2775 */
2776 dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, new_mask);
2777 if (dest_cpu >= nr_cpu_ids) {
2778 ret = -EINVAL;
2779 goto out;
2780 }
2781
2782 __do_set_cpus_allowed(p, new_mask, flags);
2783
2784 return affine_move_task(rq, p, &rf, dest_cpu, flags);
2785
2786out:
2787 task_rq_unlock(rq, p, &rf);
2788
2789 return ret;
2790}
2791
2792int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
2793{
2794 return __set_cpus_allowed_ptr(p, new_mask, 0);
2795}
2796EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
2797
2798void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
2799{
2800#ifdef CONFIG_SCHED_DEBUG
2801 unsigned int state = READ_ONCE(p->__state);
2802
2803 /*
2804 * We should never call set_task_cpu() on a blocked task,
2805 * ttwu() will sort out the placement.
2806 */
2807 WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq);
2808
2809 /*
2810 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
2811 * because schedstat_wait_{start,end} rebase migrating task's wait_start
2812 * time relying on p->on_rq.
2813 */
2814 WARN_ON_ONCE(state == TASK_RUNNING &&
2815 p->sched_class == &fair_sched_class &&
2816 (p->on_rq && !task_on_rq_migrating(p)));
2817
2818#ifdef CONFIG_LOCKDEP
2819 /*
2820 * The caller should hold either p->pi_lock or rq->lock, when changing
2821 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
2822 *
2823 * sched_move_task() holds both and thus holding either pins the cgroup,
2824 * see task_group().
2825 *
2826 * Furthermore, all task_rq users should acquire both locks, see
2827 * task_rq_lock().
2828 */
2829 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
2830 lockdep_is_held(__rq_lockp(task_rq(p)))));
2831#endif
2832 /*
2833 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
2834 */
2835 WARN_ON_ONCE(!cpu_online(new_cpu));
2836
2837 WARN_ON_ONCE(is_migration_disabled(p));
2838#endif
2839
2840 trace_sched_migrate_task(p, new_cpu);
2841
2842 if (task_cpu(p) != new_cpu) {
2843 if (p->sched_class->migrate_task_rq)
2844 p->sched_class->migrate_task_rq(p, new_cpu);
2845 p->se.nr_migrations++;
2846 rseq_migrate(p);
2847 perf_event_task_migrate(p);
2848 }
2849
2850 __set_task_cpu(p, new_cpu);
2851}
2852
2853#ifdef CONFIG_NUMA_BALANCING
2854static void __migrate_swap_task(struct task_struct *p, int cpu)
2855{
2856 if (task_on_rq_queued(p)) {
2857 struct rq *src_rq, *dst_rq;
2858 struct rq_flags srf, drf;
2859
2860 src_rq = task_rq(p);
2861 dst_rq = cpu_rq(cpu);
2862
2863 rq_pin_lock(src_rq, &srf);
2864 rq_pin_lock(dst_rq, &drf);
2865
2866 deactivate_task(src_rq, p, 0);
2867 set_task_cpu(p, cpu);
2868 activate_task(dst_rq, p, 0);
2869 check_preempt_curr(dst_rq, p, 0);
2870
2871 rq_unpin_lock(dst_rq, &drf);
2872 rq_unpin_lock(src_rq, &srf);
2873
2874 } else {
2875 /*
2876 * Task isn't running anymore; make it appear like we migrated
2877 * it before it went to sleep. This means on wakeup we make the
2878 * previous CPU our target instead of where it really is.
2879 */
2880 p->wake_cpu = cpu;
2881 }
2882}
2883
2884struct migration_swap_arg {
2885 struct task_struct *src_task, *dst_task;
2886 int src_cpu, dst_cpu;
2887};
2888
2889static int migrate_swap_stop(void *data)
2890{
2891 struct migration_swap_arg *arg = data;
2892 struct rq *src_rq, *dst_rq;
2893 int ret = -EAGAIN;
2894
2895 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
2896 return -EAGAIN;
2897
2898 src_rq = cpu_rq(arg->src_cpu);
2899 dst_rq = cpu_rq(arg->dst_cpu);
2900
2901 double_raw_lock(&arg->src_task->pi_lock,
2902 &arg->dst_task->pi_lock);
2903 double_rq_lock(src_rq, dst_rq);
2904
2905 if (task_cpu(arg->dst_task) != arg->dst_cpu)
2906 goto unlock;
2907
2908 if (task_cpu(arg->src_task) != arg->src_cpu)
2909 goto unlock;
2910
2911 if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr))
2912 goto unlock;
2913
2914 if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr))
2915 goto unlock;
2916
2917 __migrate_swap_task(arg->src_task, arg->dst_cpu);
2918 __migrate_swap_task(arg->dst_task, arg->src_cpu);
2919
2920 ret = 0;
2921
2922unlock:
2923 double_rq_unlock(src_rq, dst_rq);
2924 raw_spin_unlock(&arg->dst_task->pi_lock);
2925 raw_spin_unlock(&arg->src_task->pi_lock);
2926
2927 return ret;
2928}
2929
2930/*
2931 * Cross migrate two tasks
2932 */
2933int migrate_swap(struct task_struct *cur, struct task_struct *p,
2934 int target_cpu, int curr_cpu)
2935{
2936 struct migration_swap_arg arg;
2937 int ret = -EINVAL;
2938
2939 arg = (struct migration_swap_arg){
2940 .src_task = cur,
2941 .src_cpu = curr_cpu,
2942 .dst_task = p,
2943 .dst_cpu = target_cpu,
2944 };
2945
2946 if (arg.src_cpu == arg.dst_cpu)
2947 goto out;
2948
2949 /*
2950 * These three tests are all lockless; this is OK since all of them
2951 * will be re-checked with proper locks held further down the line.
2952 */
2953 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
2954 goto out;
2955
2956 if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr))
2957 goto out;
2958
2959 if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr))
2960 goto out;
2961
2962 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
2963 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
2964
2965out:
2966 return ret;
2967}
2968#endif /* CONFIG_NUMA_BALANCING */
2969
2970/*
2971 * wait_task_inactive - wait for a thread to unschedule.
2972 *
2973 * If @match_state is nonzero, it's the @p->state value just checked and
2974 * not expected to change. If it changes, i.e. @p might have woken up,
2975 * then return zero. When we succeed in waiting for @p to be off its CPU,
2976 * we return a positive number (its total switch count). If a second call
2977 * a short while later returns the same number, the caller can be sure that
2978 * @p has remained unscheduled the whole time.
2979 *
2980 * The caller must ensure that the task *will* unschedule sometime soon,
2981 * else this function might spin for a *long* time. This function can't
2982 * be called with interrupts off, or it may introduce deadlock with
2983 * smp_call_function() if an IPI is sent by the same process we are
2984 * waiting to become inactive.
2985 */
2986unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
2987{
2988 int running, queued;
2989 struct rq_flags rf;
2990 unsigned long ncsw;
2991 struct rq *rq;
2992
2993 for (;;) {
2994 /*
2995 * We do the initial early heuristics without holding
2996 * any task-queue locks at all. We'll only try to get
2997 * the runqueue lock when things look like they will
2998 * work out!
2999 */
3000 rq = task_rq(p);
3001
3002 /*
3003 * If the task is actively running on another CPU
3004 * still, just relax and busy-wait without holding
3005 * any locks.
3006 *
3007 * NOTE! Since we don't hold any locks, it's not
3008 * even sure that "rq" stays as the right runqueue!
3009 * But we don't care, since "task_running()" will
3010 * return false if the runqueue has changed and p
3011 * is actually now running somewhere else!
3012 */
3013 while (task_running(rq, p)) {
3014 if (match_state && unlikely(READ_ONCE(p->__state) != match_state))
3015 return 0;
3016 cpu_relax();
3017 }
3018
3019 /*
3020 * Ok, time to look more closely! We need the rq
3021 * lock now, to be *sure*. If we're wrong, we'll
3022 * just go back and repeat.
3023 */
3024 rq = task_rq_lock(p, &rf);
3025 trace_sched_wait_task(p);
3026 running = task_running(rq, p);
3027 queued = task_on_rq_queued(p);
3028 ncsw = 0;
3029 if (!match_state || READ_ONCE(p->__state) == match_state)
3030 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
3031 task_rq_unlock(rq, p, &rf);
3032
3033 /*
3034 * If it changed from the expected state, bail out now.
3035 */
3036 if (unlikely(!ncsw))
3037 break;
3038
3039 /*
3040 * Was it really running after all now that we
3041 * checked with the proper locks actually held?
3042 *
3043 * Oops. Go back and try again..
3044 */
3045 if (unlikely(running)) {
3046 cpu_relax();
3047 continue;
3048 }
3049
3050 /*
3051 * It's not enough that it's not actively running,
3052 * it must be off the runqueue _entirely_, and not
3053 * preempted!
3054 *
3055 * So if it was still runnable (but just not actively
3056 * running right now), it's preempted, and we should
3057 * yield - it could be a while.
3058 */
3059 if (unlikely(queued)) {
3060 ktime_t to = NSEC_PER_SEC / HZ;
3061
3062 set_current_state(TASK_UNINTERRUPTIBLE);
3063 schedule_hrtimeout(&to, HRTIMER_MODE_REL);
3064 continue;
3065 }
3066
3067 /*
3068 * Ahh, all good. It wasn't running, and it wasn't
3069 * runnable, which means that it will never become
3070 * running in the future either. We're all done!
3071 */
3072 break;
3073 }
3074
3075 return ncsw;
3076}
3077
3078/***
3079 * kick_process - kick a running thread to enter/exit the kernel
3080 * @p: the to-be-kicked thread
3081 *
3082 * Cause a process which is running on another CPU to enter
3083 * kernel-mode, without any delay. (to get signals handled.)
3084 *
3085 * NOTE: this function doesn't have to take the runqueue lock,
3086 * because all it wants to ensure is that the remote task enters
3087 * the kernel. If the IPI races and the task has been migrated
3088 * to another CPU then no harm is done and the purpose has been
3089 * achieved as well.
3090 */
3091void kick_process(struct task_struct *p)
3092{
3093 int cpu;
3094
3095 preempt_disable();
3096 cpu = task_cpu(p);
3097 if ((cpu != smp_processor_id()) && task_curr(p))
3098 smp_send_reschedule(cpu);
3099 preempt_enable();
3100}
3101EXPORT_SYMBOL_GPL(kick_process);
3102
3103/*
3104 * ->cpus_ptr is protected by both rq->lock and p->pi_lock
3105 *
3106 * A few notes on cpu_active vs cpu_online:
3107 *
3108 * - cpu_active must be a subset of cpu_online
3109 *
3110 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
3111 * see __set_cpus_allowed_ptr(). At this point the newly online
3112 * CPU isn't yet part of the sched domains, and balancing will not
3113 * see it.
3114 *
3115 * - on CPU-down we clear cpu_active() to mask the sched domains and
3116 * avoid the load balancer to place new tasks on the to be removed
3117 * CPU. Existing tasks will remain running there and will be taken
3118 * off.
3119 *
3120 * This means that fallback selection must not select !active CPUs.
3121 * And can assume that any active CPU must be online. Conversely
3122 * select_task_rq() below may allow selection of !active CPUs in order
3123 * to satisfy the above rules.
3124 */
3125static int select_fallback_rq(int cpu, struct task_struct *p)
3126{
3127 int nid = cpu_to_node(cpu);
3128 const struct cpumask *nodemask = NULL;
3129 enum { cpuset, possible, fail } state = cpuset;
3130 int dest_cpu;
3131
3132 /*
3133 * If the node that the CPU is on has been offlined, cpu_to_node()
3134 * will return -1. There is no CPU on the node, and we should
3135 * select the CPU on the other node.
3136 */
3137 if (nid != -1) {
3138 nodemask = cpumask_of_node(nid);
3139
3140 /* Look for allowed, online CPU in same node. */
3141 for_each_cpu(dest_cpu, nodemask) {
3142 if (!cpu_active(dest_cpu))
3143 continue;
3144 if (cpumask_test_cpu(dest_cpu, p->cpus_ptr))
3145 return dest_cpu;
3146 }
3147 }
3148
3149 for (;;) {
3150 /* Any allowed, online CPU? */
3151 for_each_cpu(dest_cpu, p->cpus_ptr) {
3152 if (!is_cpu_allowed(p, dest_cpu))
3153 continue;
3154
3155 goto out;
3156 }
3157
3158 /* No more Mr. Nice Guy. */
3159 switch (state) {
3160 case cpuset:
3161 if (IS_ENABLED(CONFIG_CPUSETS)) {
3162 cpuset_cpus_allowed_fallback(p);
3163 state = possible;
3164 break;
3165 }
3166 fallthrough;
3167 case possible:
3168 /*
3169 * XXX When called from select_task_rq() we only
3170 * hold p->pi_lock and again violate locking order.
3171 *
3172 * More yuck to audit.
3173 */
3174 do_set_cpus_allowed(p, cpu_possible_mask);
3175 state = fail;
3176 break;
3177
3178 case fail:
3179 BUG();
3180 break;
3181 }
3182 }
3183
3184out:
3185 if (state != cpuset) {
3186 /*
3187 * Don't tell them about moving exiting tasks or
3188 * kernel threads (both mm NULL), since they never
3189 * leave kernel.
3190 */
3191 if (p->mm && printk_ratelimit()) {
3192 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
3193 task_pid_nr(p), p->comm, cpu);
3194 }
3195 }
3196
3197 return dest_cpu;
3198}
3199
3200/*
3201 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable.
3202 */
3203static inline
3204int select_task_rq(struct task_struct *p, int cpu, int wake_flags)
3205{
3206 lockdep_assert_held(&p->pi_lock);
3207
3208 if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p))
3209 cpu = p->sched_class->select_task_rq(p, cpu, wake_flags);
3210 else
3211 cpu = cpumask_any(p->cpus_ptr);
3212
3213 /*
3214 * In order not to call set_task_cpu() on a blocking task we need
3215 * to rely on ttwu() to place the task on a valid ->cpus_ptr
3216 * CPU.
3217 *
3218 * Since this is common to all placement strategies, this lives here.
3219 *
3220 * [ this allows ->select_task() to simply return task_cpu(p) and
3221 * not worry about this generic constraint ]
3222 */
3223 if (unlikely(!is_cpu_allowed(p, cpu)))
3224 cpu = select_fallback_rq(task_cpu(p), p);
3225
3226 return cpu;
3227}
3228
3229void sched_set_stop_task(int cpu, struct task_struct *stop)
3230{
3231 static struct lock_class_key stop_pi_lock;
3232 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
3233 struct task_struct *old_stop = cpu_rq(cpu)->stop;
3234
3235 if (stop) {
3236 /*
3237 * Make it appear like a SCHED_FIFO task, its something
3238 * userspace knows about and won't get confused about.
3239 *
3240 * Also, it will make PI more or less work without too
3241 * much confusion -- but then, stop work should not
3242 * rely on PI working anyway.
3243 */
3244 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
3245
3246 stop->sched_class = &stop_sched_class;
3247
3248 /*
3249 * The PI code calls rt_mutex_setprio() with ->pi_lock held to
3250 * adjust the effective priority of a task. As a result,
3251 * rt_mutex_setprio() can trigger (RT) balancing operations,
3252 * which can then trigger wakeups of the stop thread to push
3253 * around the current task.
3254 *
3255 * The stop task itself will never be part of the PI-chain, it
3256 * never blocks, therefore that ->pi_lock recursion is safe.
3257 * Tell lockdep about this by placing the stop->pi_lock in its
3258 * own class.
3259 */
3260 lockdep_set_class(&stop->pi_lock, &stop_pi_lock);
3261 }
3262
3263 cpu_rq(cpu)->stop = stop;
3264
3265 if (old_stop) {
3266 /*
3267 * Reset it back to a normal scheduling class so that
3268 * it can die in pieces.
3269 */
3270 old_stop->sched_class = &rt_sched_class;
3271 }
3272}
3273
3274#else /* CONFIG_SMP */
3275
3276static inline int __set_cpus_allowed_ptr(struct task_struct *p,
3277 const struct cpumask *new_mask,
3278 u32 flags)
3279{
3280 return set_cpus_allowed_ptr(p, new_mask);
3281}
3282
3283static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { }
3284
3285static inline bool rq_has_pinned_tasks(struct rq *rq)
3286{
3287 return false;
3288}
3289
3290#endif /* !CONFIG_SMP */
3291
3292static void
3293ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
3294{
3295 struct rq *rq;
3296
3297 if (!schedstat_enabled())
3298 return;
3299
3300 rq = this_rq();
3301
3302#ifdef CONFIG_SMP
3303 if (cpu == rq->cpu) {
3304 __schedstat_inc(rq->ttwu_local);
3305 __schedstat_inc(p->se.statistics.nr_wakeups_local);
3306 } else {
3307 struct sched_domain *sd;
3308
3309 __schedstat_inc(p->se.statistics.nr_wakeups_remote);
3310 rcu_read_lock();
3311 for_each_domain(rq->cpu, sd) {
3312 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
3313 __schedstat_inc(sd->ttwu_wake_remote);
3314 break;
3315 }
3316 }
3317 rcu_read_unlock();
3318 }
3319
3320 if (wake_flags & WF_MIGRATED)
3321 __schedstat_inc(p->se.statistics.nr_wakeups_migrate);
3322#endif /* CONFIG_SMP */
3323
3324 __schedstat_inc(rq->ttwu_count);
3325 __schedstat_inc(p->se.statistics.nr_wakeups);
3326
3327 if (wake_flags & WF_SYNC)
3328 __schedstat_inc(p->se.statistics.nr_wakeups_sync);
3329}
3330
3331/*
3332 * Mark the task runnable and perform wakeup-preemption.
3333 */
3334static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
3335 struct rq_flags *rf)
3336{
3337 check_preempt_curr(rq, p, wake_flags);
3338 WRITE_ONCE(p->__state, TASK_RUNNING);
3339 trace_sched_wakeup(p);
3340
3341#ifdef CONFIG_SMP
3342 if (p->sched_class->task_woken) {
3343 /*
3344 * Our task @p is fully woken up and running; so it's safe to
3345 * drop the rq->lock, hereafter rq is only used for statistics.
3346 */
3347 rq_unpin_lock(rq, rf);
3348 p->sched_class->task_woken(rq, p);
3349 rq_repin_lock(rq, rf);
3350 }
3351
3352 if (rq->idle_stamp) {
3353 u64 delta = rq_clock(rq) - rq->idle_stamp;
3354 u64 max = 2*rq->max_idle_balance_cost;
3355
3356 update_avg(&rq->avg_idle, delta);
3357
3358 if (rq->avg_idle > max)
3359 rq->avg_idle = max;
3360
3361 rq->wake_stamp = jiffies;
3362 rq->wake_avg_idle = rq->avg_idle / 2;
3363
3364 rq->idle_stamp = 0;
3365 }
3366#endif
3367}
3368
3369static void
3370ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
3371 struct rq_flags *rf)
3372{
3373 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
3374
3375 lockdep_assert_rq_held(rq);
3376
3377 if (p->sched_contributes_to_load)
3378 rq->nr_uninterruptible--;
3379
3380#ifdef CONFIG_SMP
3381 if (wake_flags & WF_MIGRATED)
3382 en_flags |= ENQUEUE_MIGRATED;
3383 else
3384#endif
3385 if (p->in_iowait) {
3386 delayacct_blkio_end(p);
3387 atomic_dec(&task_rq(p)->nr_iowait);
3388 }
3389
3390 activate_task(rq, p, en_flags);
3391 ttwu_do_wakeup(rq, p, wake_flags, rf);
3392}
3393
3394/*
3395 * Consider @p being inside a wait loop:
3396 *
3397 * for (;;) {
3398 * set_current_state(TASK_UNINTERRUPTIBLE);
3399 *
3400 * if (CONDITION)
3401 * break;
3402 *
3403 * schedule();
3404 * }
3405 * __set_current_state(TASK_RUNNING);
3406 *
3407 * between set_current_state() and schedule(). In this case @p is still
3408 * runnable, so all that needs doing is change p->state back to TASK_RUNNING in
3409 * an atomic manner.
3410 *
3411 * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
3412 * then schedule() must still happen and p->state can be changed to
3413 * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
3414 * need to do a full wakeup with enqueue.
3415 *
3416 * Returns: %true when the wakeup is done,
3417 * %false otherwise.
3418 */
3419static int ttwu_runnable(struct task_struct *p, int wake_flags)
3420{
3421 struct rq_flags rf;
3422 struct rq *rq;
3423 int ret = 0;
3424
3425 rq = __task_rq_lock(p, &rf);
3426 if (task_on_rq_queued(p)) {
3427 /* check_preempt_curr() may use rq clock */
3428 update_rq_clock(rq);
3429 ttwu_do_wakeup(rq, p, wake_flags, &rf);
3430 ret = 1;
3431 }
3432 __task_rq_unlock(rq, &rf);
3433
3434 return ret;
3435}
3436
3437#ifdef CONFIG_SMP
3438void sched_ttwu_pending(void *arg)
3439{
3440 struct llist_node *llist = arg;
3441 struct rq *rq = this_rq();
3442 struct task_struct *p, *t;
3443 struct rq_flags rf;
3444
3445 if (!llist)
3446 return;
3447
3448 /*
3449 * rq::ttwu_pending racy indication of out-standing wakeups.
3450 * Races such that false-negatives are possible, since they
3451 * are shorter lived that false-positives would be.
3452 */
3453 WRITE_ONCE(rq->ttwu_pending, 0);
3454
3455 rq_lock_irqsave(rq, &rf);
3456 update_rq_clock(rq);
3457
3458 llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
3459 if (WARN_ON_ONCE(p->on_cpu))
3460 smp_cond_load_acquire(&p->on_cpu, !VAL);
3461
3462 if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
3463 set_task_cpu(p, cpu_of(rq));
3464
3465 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
3466 }
3467
3468 rq_unlock_irqrestore(rq, &rf);
3469}
3470
3471void send_call_function_single_ipi(int cpu)
3472{
3473 struct rq *rq = cpu_rq(cpu);
3474
3475 if (!set_nr_if_polling(rq->idle))
3476 arch_send_call_function_single_ipi(cpu);
3477 else
3478 trace_sched_wake_idle_without_ipi(cpu);
3479}
3480
3481/*
3482 * Queue a task on the target CPUs wake_list and wake the CPU via IPI if
3483 * necessary. The wakee CPU on receipt of the IPI will queue the task
3484 * via sched_ttwu_wakeup() for activation so the wakee incurs the cost
3485 * of the wakeup instead of the waker.
3486 */
3487static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3488{
3489 struct rq *rq = cpu_rq(cpu);
3490
3491 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
3492
3493 WRITE_ONCE(rq->ttwu_pending, 1);
3494 __smp_call_single_queue(cpu, &p->wake_entry.llist);
3495}
3496
3497void wake_up_if_idle(int cpu)
3498{
3499 struct rq *rq = cpu_rq(cpu);
3500 struct rq_flags rf;
3501
3502 rcu_read_lock();
3503
3504 if (!is_idle_task(rcu_dereference(rq->curr)))
3505 goto out;
3506
3507 if (set_nr_if_polling(rq->idle)) {
3508 trace_sched_wake_idle_without_ipi(cpu);
3509 } else {
3510 rq_lock_irqsave(rq, &rf);
3511 if (is_idle_task(rq->curr))
3512 smp_send_reschedule(cpu);
3513 /* Else CPU is not idle, do nothing here: */
3514 rq_unlock_irqrestore(rq, &rf);
3515 }
3516
3517out:
3518 rcu_read_unlock();
3519}
3520
3521bool cpus_share_cache(int this_cpu, int that_cpu)
3522{
3523 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
3524}
3525
3526static inline bool ttwu_queue_cond(int cpu, int wake_flags)
3527{
3528 /*
3529 * Do not complicate things with the async wake_list while the CPU is
3530 * in hotplug state.
3531 */
3532 if (!cpu_active(cpu))
3533 return false;
3534
3535 /*
3536 * If the CPU does not share cache, then queue the task on the
3537 * remote rqs wakelist to avoid accessing remote data.
3538 */
3539 if (!cpus_share_cache(smp_processor_id(), cpu))
3540 return true;
3541
3542 /*
3543 * If the task is descheduling and the only running task on the
3544 * CPU then use the wakelist to offload the task activation to
3545 * the soon-to-be-idle CPU as the current CPU is likely busy.
3546 * nr_running is checked to avoid unnecessary task stacking.
3547 */
3548 if ((wake_flags & WF_ON_CPU) && cpu_rq(cpu)->nr_running <= 1)
3549 return true;
3550
3551 return false;
3552}
3553
3554static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3555{
3556 if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(cpu, wake_flags)) {
3557 if (WARN_ON_ONCE(cpu == smp_processor_id()))
3558 return false;
3559
3560 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
3561 __ttwu_queue_wakelist(p, cpu, wake_flags);
3562 return true;
3563 }
3564
3565 return false;
3566}
3567
3568#else /* !CONFIG_SMP */
3569
3570static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
3571{
3572 return false;
3573}
3574
3575#endif /* CONFIG_SMP */
3576
3577static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
3578{
3579 struct rq *rq = cpu_rq(cpu);
3580 struct rq_flags rf;
3581
3582 if (ttwu_queue_wakelist(p, cpu, wake_flags))
3583 return;
3584
3585 rq_lock(rq, &rf);
3586 update_rq_clock(rq);
3587 ttwu_do_activate(rq, p, wake_flags, &rf);
3588 rq_unlock(rq, &rf);
3589}
3590
3591/*
3592 * Notes on Program-Order guarantees on SMP systems.
3593 *
3594 * MIGRATION
3595 *
3596 * The basic program-order guarantee on SMP systems is that when a task [t]
3597 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
3598 * execution on its new CPU [c1].
3599 *
3600 * For migration (of runnable tasks) this is provided by the following means:
3601 *
3602 * A) UNLOCK of the rq(c0)->lock scheduling out task t
3603 * B) migration for t is required to synchronize *both* rq(c0)->lock and
3604 * rq(c1)->lock (if not at the same time, then in that order).
3605 * C) LOCK of the rq(c1)->lock scheduling in task
3606 *
3607 * Release/acquire chaining guarantees that B happens after A and C after B.
3608 * Note: the CPU doing B need not be c0 or c1
3609 *
3610 * Example:
3611 *
3612 * CPU0 CPU1 CPU2
3613 *
3614 * LOCK rq(0)->lock
3615 * sched-out X
3616 * sched-in Y
3617 * UNLOCK rq(0)->lock
3618 *
3619 * LOCK rq(0)->lock // orders against CPU0
3620 * dequeue X
3621 * UNLOCK rq(0)->lock
3622 *
3623 * LOCK rq(1)->lock
3624 * enqueue X
3625 * UNLOCK rq(1)->lock
3626 *
3627 * LOCK rq(1)->lock // orders against CPU2
3628 * sched-out Z
3629 * sched-in X
3630 * UNLOCK rq(1)->lock
3631 *
3632 *
3633 * BLOCKING -- aka. SLEEP + WAKEUP
3634 *
3635 * For blocking we (obviously) need to provide the same guarantee as for
3636 * migration. However the means are completely different as there is no lock
3637 * chain to provide order. Instead we do:
3638 *
3639 * 1) smp_store_release(X->on_cpu, 0) -- finish_task()
3640 * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
3641 *
3642 * Example:
3643 *
3644 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
3645 *
3646 * LOCK rq(0)->lock LOCK X->pi_lock
3647 * dequeue X
3648 * sched-out X
3649 * smp_store_release(X->on_cpu, 0);
3650 *
3651 * smp_cond_load_acquire(&X->on_cpu, !VAL);
3652 * X->state = WAKING
3653 * set_task_cpu(X,2)
3654 *
3655 * LOCK rq(2)->lock
3656 * enqueue X
3657 * X->state = RUNNING
3658 * UNLOCK rq(2)->lock
3659 *
3660 * LOCK rq(2)->lock // orders against CPU1
3661 * sched-out Z
3662 * sched-in X
3663 * UNLOCK rq(2)->lock
3664 *
3665 * UNLOCK X->pi_lock
3666 * UNLOCK rq(0)->lock
3667 *
3668 *
3669 * However, for wakeups there is a second guarantee we must provide, namely we
3670 * must ensure that CONDITION=1 done by the caller can not be reordered with
3671 * accesses to the task state; see try_to_wake_up() and set_current_state().
3672 */
3673
3674/**
3675 * try_to_wake_up - wake up a thread
3676 * @p: the thread to be awakened
3677 * @state: the mask of task states that can be woken
3678 * @wake_flags: wake modifier flags (WF_*)
3679 *
3680 * Conceptually does:
3681 *
3682 * If (@state & @p->state) @p->state = TASK_RUNNING.
3683 *
3684 * If the task was not queued/runnable, also place it back on a runqueue.
3685 *
3686 * This function is atomic against schedule() which would dequeue the task.
3687 *
3688 * It issues a full memory barrier before accessing @p->state, see the comment
3689 * with set_current_state().
3690 *
3691 * Uses p->pi_lock to serialize against concurrent wake-ups.
3692 *
3693 * Relies on p->pi_lock stabilizing:
3694 * - p->sched_class
3695 * - p->cpus_ptr
3696 * - p->sched_task_group
3697 * in order to do migration, see its use of select_task_rq()/set_task_cpu().
3698 *
3699 * Tries really hard to only take one task_rq(p)->lock for performance.
3700 * Takes rq->lock in:
3701 * - ttwu_runnable() -- old rq, unavoidable, see comment there;
3702 * - ttwu_queue() -- new rq, for enqueue of the task;
3703 * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
3704 *
3705 * As a consequence we race really badly with just about everything. See the
3706 * many memory barriers and their comments for details.
3707 *
3708 * Return: %true if @p->state changes (an actual wakeup was done),
3709 * %false otherwise.
3710 */
3711static int
3712try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
3713{
3714 unsigned long flags;
3715 int cpu, success = 0;
3716
3717 preempt_disable();
3718 if (p == current) {
3719 /*
3720 * We're waking current, this means 'p->on_rq' and 'task_cpu(p)
3721 * == smp_processor_id()'. Together this means we can special
3722 * case the whole 'p->on_rq && ttwu_runnable()' case below
3723 * without taking any locks.
3724 *
3725 * In particular:
3726 * - we rely on Program-Order guarantees for all the ordering,
3727 * - we're serialized against set_special_state() by virtue of
3728 * it disabling IRQs (this allows not taking ->pi_lock).
3729 */
3730 if (!(READ_ONCE(p->__state) & state))
3731 goto out;
3732
3733 success = 1;
3734 trace_sched_waking(p);
3735 WRITE_ONCE(p->__state, TASK_RUNNING);
3736 trace_sched_wakeup(p);
3737 goto out;
3738 }
3739
3740 /*
3741 * If we are going to wake up a thread waiting for CONDITION we
3742 * need to ensure that CONDITION=1 done by the caller can not be
3743 * reordered with p->state check below. This pairs with smp_store_mb()
3744 * in set_current_state() that the waiting thread does.
3745 */
3746 raw_spin_lock_irqsave(&p->pi_lock, flags);
3747 smp_mb__after_spinlock();
3748 if (!(READ_ONCE(p->__state) & state))
3749 goto unlock;
3750
3751 trace_sched_waking(p);
3752
3753 /* We're going to change ->state: */
3754 success = 1;
3755
3756 /*
3757 * Ensure we load p->on_rq _after_ p->state, otherwise it would
3758 * be possible to, falsely, observe p->on_rq == 0 and get stuck
3759 * in smp_cond_load_acquire() below.
3760 *
3761 * sched_ttwu_pending() try_to_wake_up()
3762 * STORE p->on_rq = 1 LOAD p->state
3763 * UNLOCK rq->lock
3764 *
3765 * __schedule() (switch to task 'p')
3766 * LOCK rq->lock smp_rmb();
3767 * smp_mb__after_spinlock();
3768 * UNLOCK rq->lock
3769 *
3770 * [task p]
3771 * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
3772 *
3773 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
3774 * __schedule(). See the comment for smp_mb__after_spinlock().
3775 *
3776 * A similar smb_rmb() lives in try_invoke_on_locked_down_task().
3777 */
3778 smp_rmb();
3779 if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
3780 goto unlock;
3781
3782#ifdef CONFIG_SMP
3783 /*
3784 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
3785 * possible to, falsely, observe p->on_cpu == 0.
3786 *
3787 * One must be running (->on_cpu == 1) in order to remove oneself
3788 * from the runqueue.
3789 *
3790 * __schedule() (switch to task 'p') try_to_wake_up()
3791 * STORE p->on_cpu = 1 LOAD p->on_rq
3792 * UNLOCK rq->lock
3793 *
3794 * __schedule() (put 'p' to sleep)
3795 * LOCK rq->lock smp_rmb();
3796 * smp_mb__after_spinlock();
3797 * STORE p->on_rq = 0 LOAD p->on_cpu
3798 *
3799 * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
3800 * __schedule(). See the comment for smp_mb__after_spinlock().
3801 *
3802 * Form a control-dep-acquire with p->on_rq == 0 above, to ensure
3803 * schedule()'s deactivate_task() has 'happened' and p will no longer
3804 * care about it's own p->state. See the comment in __schedule().
3805 */
3806 smp_acquire__after_ctrl_dep();
3807
3808 /*
3809 * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
3810 * == 0), which means we need to do an enqueue, change p->state to
3811 * TASK_WAKING such that we can unlock p->pi_lock before doing the
3812 * enqueue, such as ttwu_queue_wakelist().
3813 */
3814 WRITE_ONCE(p->__state, TASK_WAKING);
3815
3816 /*
3817 * If the owning (remote) CPU is still in the middle of schedule() with
3818 * this task as prev, considering queueing p on the remote CPUs wake_list
3819 * which potentially sends an IPI instead of spinning on p->on_cpu to
3820 * let the waker make forward progress. This is safe because IRQs are
3821 * disabled and the IPI will deliver after on_cpu is cleared.
3822 *
3823 * Ensure we load task_cpu(p) after p->on_cpu:
3824 *
3825 * set_task_cpu(p, cpu);
3826 * STORE p->cpu = @cpu
3827 * __schedule() (switch to task 'p')
3828 * LOCK rq->lock
3829 * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
3830 * STORE p->on_cpu = 1 LOAD p->cpu
3831 *
3832 * to ensure we observe the correct CPU on which the task is currently
3833 * scheduling.
3834 */
3835 if (smp_load_acquire(&p->on_cpu) &&
3836 ttwu_queue_wakelist(p, task_cpu(p), wake_flags | WF_ON_CPU))
3837 goto unlock;
3838
3839 /*
3840 * If the owning (remote) CPU is still in the middle of schedule() with
3841 * this task as prev, wait until it's done referencing the task.
3842 *
3843 * Pairs with the smp_store_release() in finish_task().
3844 *
3845 * This ensures that tasks getting woken will be fully ordered against
3846 * their previous state and preserve Program Order.
3847 */
3848 smp_cond_load_acquire(&p->on_cpu, !VAL);
3849
3850 cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU);
3851 if (task_cpu(p) != cpu) {
3852 if (p->in_iowait) {
3853 delayacct_blkio_end(p);
3854 atomic_dec(&task_rq(p)->nr_iowait);
3855 }
3856
3857 wake_flags |= WF_MIGRATED;
3858 psi_ttwu_dequeue(p);
3859 set_task_cpu(p, cpu);
3860 }
3861#else
3862 cpu = task_cpu(p);
3863#endif /* CONFIG_SMP */
3864
3865 ttwu_queue(p, cpu, wake_flags);
3866unlock:
3867 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3868out:
3869 if (success)
3870 ttwu_stat(p, task_cpu(p), wake_flags);
3871 preempt_enable();
3872
3873 return success;
3874}
3875
3876/**
3877 * try_invoke_on_locked_down_task - Invoke a function on task in fixed state
3878 * @p: Process for which the function is to be invoked, can be @current.
3879 * @func: Function to invoke.
3880 * @arg: Argument to function.
3881 *
3882 * If the specified task can be quickly locked into a definite state
3883 * (either sleeping or on a given runqueue), arrange to keep it in that
3884 * state while invoking @func(@arg). This function can use ->on_rq and
3885 * task_curr() to work out what the state is, if required. Given that
3886 * @func can be invoked with a runqueue lock held, it had better be quite
3887 * lightweight.
3888 *
3889 * Returns:
3890 * @false if the task slipped out from under the locks.
3891 * @true if the task was locked onto a runqueue or is sleeping.
3892 * However, @func can override this by returning @false.
3893 */
3894bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
3895{
3896 struct rq_flags rf;
3897 bool ret = false;
3898 struct rq *rq;
3899
3900 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
3901 if (p->on_rq) {
3902 rq = __task_rq_lock(p, &rf);
3903 if (task_rq(p) == rq)
3904 ret = func(p, arg);
3905 rq_unlock(rq, &rf);
3906 } else {
3907 switch (READ_ONCE(p->__state)) {
3908 case TASK_RUNNING:
3909 case TASK_WAKING:
3910 break;
3911 default:
3912 smp_rmb(); // See smp_rmb() comment in try_to_wake_up().
3913 if (!p->on_rq)
3914 ret = func(p, arg);
3915 }
3916 }
3917 raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
3918 return ret;
3919}
3920
3921/**
3922 * wake_up_process - Wake up a specific process
3923 * @p: The process to be woken up.
3924 *
3925 * Attempt to wake up the nominated process and move it to the set of runnable
3926 * processes.
3927 *
3928 * Return: 1 if the process was woken up, 0 if it was already running.
3929 *
3930 * This function executes a full memory barrier before accessing the task state.
3931 */
3932int wake_up_process(struct task_struct *p)
3933{
3934 return try_to_wake_up(p, TASK_NORMAL, 0);
3935}
3936EXPORT_SYMBOL(wake_up_process);
3937
3938int wake_up_state(struct task_struct *p, unsigned int state)
3939{
3940 return try_to_wake_up(p, state, 0);
3941}
3942
3943/*
3944 * Perform scheduler related setup for a newly forked process p.
3945 * p is forked by current.
3946 *
3947 * __sched_fork() is basic setup used by init_idle() too:
3948 */
3949static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
3950{
3951 p->on_rq = 0;
3952
3953 p->se.on_rq = 0;
3954 p->se.exec_start = 0;
3955 p->se.sum_exec_runtime = 0;
3956 p->se.prev_sum_exec_runtime = 0;
3957 p->se.nr_migrations = 0;
3958 p->se.vruntime = 0;
3959 INIT_LIST_HEAD(&p->se.group_node);
3960
3961#ifdef CONFIG_FAIR_GROUP_SCHED
3962 p->se.cfs_rq = NULL;
3963#endif
3964
3965#ifdef CONFIG_SCHEDSTATS
3966 /* Even if schedstat is disabled, there should not be garbage */
3967 memset(&p->se.statistics, 0, sizeof(p->se.statistics));
3968#endif
3969
3970 RB_CLEAR_NODE(&p->dl.rb_node);
3971 init_dl_task_timer(&p->dl);
3972 init_dl_inactive_task_timer(&p->dl);
3973 __dl_clear_params(p);
3974
3975 INIT_LIST_HEAD(&p->rt.run_list);
3976 p->rt.timeout = 0;
3977 p->rt.time_slice = sched_rr_timeslice;
3978 p->rt.on_rq = 0;
3979 p->rt.on_list = 0;
3980
3981#ifdef CONFIG_PREEMPT_NOTIFIERS
3982 INIT_HLIST_HEAD(&p->preempt_notifiers);
3983#endif
3984
3985#ifdef CONFIG_COMPACTION
3986 p->capture_control = NULL;
3987#endif
3988 init_numa_balancing(clone_flags, p);
3989#ifdef CONFIG_SMP
3990 p->wake_entry.u_flags = CSD_TYPE_TTWU;
3991 p->migration_pending = NULL;
3992#endif
3993}
3994
3995DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
3996
3997#ifdef CONFIG_NUMA_BALANCING
3998
3999void set_numabalancing_state(bool enabled)
4000{
4001 if (enabled)
4002 static_branch_enable(&sched_numa_balancing);
4003 else
4004 static_branch_disable(&sched_numa_balancing);
4005}
4006
4007#ifdef CONFIG_PROC_SYSCTL
4008int sysctl_numa_balancing(struct ctl_table *table, int write,
4009 void *buffer, size_t *lenp, loff_t *ppos)
4010{
4011 struct ctl_table t;
4012 int err;
4013 int state = static_branch_likely(&sched_numa_balancing);
4014
4015 if (write && !capable(CAP_SYS_ADMIN))
4016 return -EPERM;
4017
4018 t = *table;
4019 t.data = &state;
4020 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4021 if (err < 0)
4022 return err;
4023 if (write)
4024 set_numabalancing_state(state);
4025 return err;
4026}
4027#endif
4028#endif
4029
4030#ifdef CONFIG_SCHEDSTATS
4031
4032DEFINE_STATIC_KEY_FALSE(sched_schedstats);
4033
4034static void set_schedstats(bool enabled)
4035{
4036 if (enabled)
4037 static_branch_enable(&sched_schedstats);
4038 else
4039 static_branch_disable(&sched_schedstats);
4040}
4041
4042void force_schedstat_enabled(void)
4043{
4044 if (!schedstat_enabled()) {
4045 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
4046 static_branch_enable(&sched_schedstats);
4047 }
4048}
4049
4050static int __init setup_schedstats(char *str)
4051{
4052 int ret = 0;
4053 if (!str)
4054 goto out;
4055
4056 if (!strcmp(str, "enable")) {
4057 set_schedstats(true);
4058 ret = 1;
4059 } else if (!strcmp(str, "disable")) {
4060 set_schedstats(false);
4061 ret = 1;
4062 }
4063out:
4064 if (!ret)
4065 pr_warn("Unable to parse schedstats=\n");
4066
4067 return ret;
4068}
4069__setup("schedstats=", setup_schedstats);
4070
4071#ifdef CONFIG_PROC_SYSCTL
4072int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
4073 size_t *lenp, loff_t *ppos)
4074{
4075 struct ctl_table t;
4076 int err;
4077 int state = static_branch_likely(&sched_schedstats);
4078
4079 if (write && !capable(CAP_SYS_ADMIN))
4080 return -EPERM;
4081
4082 t = *table;
4083 t.data = &state;
4084 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
4085 if (err < 0)
4086 return err;
4087 if (write)
4088 set_schedstats(state);
4089 return err;
4090}
4091#endif /* CONFIG_PROC_SYSCTL */
4092#endif /* CONFIG_SCHEDSTATS */
4093
4094/*
4095 * fork()/clone()-time setup:
4096 */
4097int sched_fork(unsigned long clone_flags, struct task_struct *p)
4098{
4099 unsigned long flags;
4100
4101 __sched_fork(clone_flags, p);
4102 /*
4103 * We mark the process as NEW here. This guarantees that
4104 * nobody will actually run it, and a signal or other external
4105 * event cannot wake it up and insert it on the runqueue either.
4106 */
4107 p->__state = TASK_NEW;
4108
4109 /*
4110 * Make sure we do not leak PI boosting priority to the child.
4111 */
4112 p->prio = current->normal_prio;
4113
4114 uclamp_fork(p);
4115
4116 /*
4117 * Revert to default priority/policy on fork if requested.
4118 */
4119 if (unlikely(p->sched_reset_on_fork)) {
4120 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
4121 p->policy = SCHED_NORMAL;
4122 p->static_prio = NICE_TO_PRIO(0);
4123 p->rt_priority = 0;
4124 } else if (PRIO_TO_NICE(p->static_prio) < 0)
4125 p->static_prio = NICE_TO_PRIO(0);
4126
4127 p->prio = p->normal_prio = p->static_prio;
4128 set_load_weight(p, false);
4129
4130 /*
4131 * We don't need the reset flag anymore after the fork. It has
4132 * fulfilled its duty:
4133 */
4134 p->sched_reset_on_fork = 0;
4135 }
4136
4137 if (dl_prio(p->prio))
4138 return -EAGAIN;
4139 else if (rt_prio(p->prio))
4140 p->sched_class = &rt_sched_class;
4141 else
4142 p->sched_class = &fair_sched_class;
4143
4144 init_entity_runnable_average(&p->se);
4145
4146 /*
4147 * The child is not yet in the pid-hash so no cgroup attach races,
4148 * and the cgroup is pinned to this child due to cgroup_fork()
4149 * is ran before sched_fork().
4150 *
4151 * Silence PROVE_RCU.
4152 */
4153 raw_spin_lock_irqsave(&p->pi_lock, flags);
4154 rseq_migrate(p);
4155 /*
4156 * We're setting the CPU for the first time, we don't migrate,
4157 * so use __set_task_cpu().
4158 */
4159 __set_task_cpu(p, smp_processor_id());
4160 if (p->sched_class->task_fork)
4161 p->sched_class->task_fork(p);
4162 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4163
4164#ifdef CONFIG_SCHED_INFO
4165 if (likely(sched_info_on()))
4166 memset(&p->sched_info, 0, sizeof(p->sched_info));
4167#endif
4168#if defined(CONFIG_SMP)
4169 p->on_cpu = 0;
4170#endif
4171 init_task_preempt_count(p);
4172#ifdef CONFIG_SMP
4173 plist_node_init(&p->pushable_tasks, MAX_PRIO);
4174 RB_CLEAR_NODE(&p->pushable_dl_tasks);
4175#endif
4176 return 0;
4177}
4178
4179void sched_post_fork(struct task_struct *p)
4180{
4181 uclamp_post_fork(p);
4182}
4183
4184unsigned long to_ratio(u64 period, u64 runtime)
4185{
4186 if (runtime == RUNTIME_INF)
4187 return BW_UNIT;
4188
4189 /*
4190 * Doing this here saves a lot of checks in all
4191 * the calling paths, and returning zero seems
4192 * safe for them anyway.
4193 */
4194 if (period == 0)
4195 return 0;
4196
4197 return div64_u64(runtime << BW_SHIFT, period);
4198}
4199
4200/*
4201 * wake_up_new_task - wake up a newly created task for the first time.
4202 *
4203 * This function will do some initial scheduler statistics housekeeping
4204 * that must be done for every newly created context, then puts the task
4205 * on the runqueue and wakes it.
4206 */
4207void wake_up_new_task(struct task_struct *p)
4208{
4209 struct rq_flags rf;
4210 struct rq *rq;
4211
4212 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
4213 WRITE_ONCE(p->__state, TASK_RUNNING);
4214#ifdef CONFIG_SMP
4215 /*
4216 * Fork balancing, do it here and not earlier because:
4217 * - cpus_ptr can change in the fork path
4218 * - any previously selected CPU might disappear through hotplug
4219 *
4220 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
4221 * as we're not fully set-up yet.
4222 */
4223 p->recent_used_cpu = task_cpu(p);
4224 rseq_migrate(p);
4225 __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK));
4226#endif
4227 rq = __task_rq_lock(p, &rf);
4228 update_rq_clock(rq);
4229 post_init_entity_util_avg(p);
4230
4231 activate_task(rq, p, ENQUEUE_NOCLOCK);
4232 trace_sched_wakeup_new(p);
4233 check_preempt_curr(rq, p, WF_FORK);
4234#ifdef CONFIG_SMP
4235 if (p->sched_class->task_woken) {
4236 /*
4237 * Nothing relies on rq->lock after this, so it's fine to
4238 * drop it.
4239 */
4240 rq_unpin_lock(rq, &rf);
4241 p->sched_class->task_woken(rq, p);
4242 rq_repin_lock(rq, &rf);
4243 }
4244#endif
4245 task_rq_unlock(rq, p, &rf);
4246}
4247
4248#ifdef CONFIG_PREEMPT_NOTIFIERS
4249
4250static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
4251
4252void preempt_notifier_inc(void)
4253{
4254 static_branch_inc(&preempt_notifier_key);
4255}
4256EXPORT_SYMBOL_GPL(preempt_notifier_inc);
4257
4258void preempt_notifier_dec(void)
4259{
4260 static_branch_dec(&preempt_notifier_key);
4261}
4262EXPORT_SYMBOL_GPL(preempt_notifier_dec);
4263
4264/**
4265 * preempt_notifier_register - tell me when current is being preempted & rescheduled
4266 * @notifier: notifier struct to register
4267 */
4268void preempt_notifier_register(struct preempt_notifier *notifier)
4269{
4270 if (!static_branch_unlikely(&preempt_notifier_key))
4271 WARN(1, "registering preempt_notifier while notifiers disabled\n");
4272
4273 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
4274}
4275EXPORT_SYMBOL_GPL(preempt_notifier_register);
4276
4277/**
4278 * preempt_notifier_unregister - no longer interested in preemption notifications
4279 * @notifier: notifier struct to unregister
4280 *
4281 * This is *not* safe to call from within a preemption notifier.
4282 */
4283void preempt_notifier_unregister(struct preempt_notifier *notifier)
4284{
4285 hlist_del(¬ifier->link);
4286}
4287EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
4288
4289static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
4290{
4291 struct preempt_notifier *notifier;
4292
4293 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4294 notifier->ops->sched_in(notifier, raw_smp_processor_id());
4295}
4296
4297static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4298{
4299 if (static_branch_unlikely(&preempt_notifier_key))
4300 __fire_sched_in_preempt_notifiers(curr);
4301}
4302
4303static void
4304__fire_sched_out_preempt_notifiers(struct task_struct *curr,
4305 struct task_struct *next)
4306{
4307 struct preempt_notifier *notifier;
4308
4309 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
4310 notifier->ops->sched_out(notifier, next);
4311}
4312
4313static __always_inline void
4314fire_sched_out_preempt_notifiers(struct task_struct *curr,
4315 struct task_struct *next)
4316{
4317 if (static_branch_unlikely(&preempt_notifier_key))
4318 __fire_sched_out_preempt_notifiers(curr, next);
4319}
4320
4321#else /* !CONFIG_PREEMPT_NOTIFIERS */
4322
4323static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
4324{
4325}
4326
4327static inline void
4328fire_sched_out_preempt_notifiers(struct task_struct *curr,
4329 struct task_struct *next)
4330{
4331}
4332
4333#endif /* CONFIG_PREEMPT_NOTIFIERS */
4334
4335static inline void prepare_task(struct task_struct *next)
4336{
4337#ifdef CONFIG_SMP
4338 /*
4339 * Claim the task as running, we do this before switching to it
4340 * such that any running task will have this set.
4341 *
4342 * See the ttwu() WF_ON_CPU case and its ordering comment.
4343 */
4344 WRITE_ONCE(next->on_cpu, 1);
4345#endif
4346}
4347
4348static inline void finish_task(struct task_struct *prev)
4349{
4350#ifdef CONFIG_SMP
4351 /*
4352 * This must be the very last reference to @prev from this CPU. After
4353 * p->on_cpu is cleared, the task can be moved to a different CPU. We
4354 * must ensure this doesn't happen until the switch is completely
4355 * finished.
4356 *
4357 * In particular, the load of prev->state in finish_task_switch() must
4358 * happen before this.
4359 *
4360 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
4361 */
4362 smp_store_release(&prev->on_cpu, 0);
4363#endif
4364}
4365
4366#ifdef CONFIG_SMP
4367
4368static void do_balance_callbacks(struct rq *rq, struct callback_head *head)
4369{
4370 void (*func)(struct rq *rq);
4371 struct callback_head *next;
4372
4373 lockdep_assert_rq_held(rq);
4374
4375 while (head) {
4376 func = (void (*)(struct rq *))head->func;
4377 next = head->next;
4378 head->next = NULL;
4379 head = next;
4380
4381 func(rq);
4382 }
4383}
4384
4385static void balance_push(struct rq *rq);
4386
4387struct callback_head balance_push_callback = {
4388 .next = NULL,
4389 .func = (void (*)(struct callback_head *))balance_push,
4390};
4391
4392static inline struct callback_head *splice_balance_callbacks(struct rq *rq)
4393{
4394 struct callback_head *head = rq->balance_callback;
4395
4396 lockdep_assert_rq_held(rq);
4397 if (head)
4398 rq->balance_callback = NULL;
4399
4400 return head;
4401}
4402
4403static void __balance_callbacks(struct rq *rq)
4404{
4405 do_balance_callbacks(rq, splice_balance_callbacks(rq));
4406}
4407
4408static inline void balance_callbacks(struct rq *rq, struct callback_head *head)
4409{
4410 unsigned long flags;
4411
4412 if (unlikely(head)) {
4413 raw_spin_rq_lock_irqsave(rq, flags);
4414 do_balance_callbacks(rq, head);
4415 raw_spin_rq_unlock_irqrestore(rq, flags);
4416 }
4417}
4418
4419#else
4420
4421static inline void __balance_callbacks(struct rq *rq)
4422{
4423}
4424
4425static inline struct callback_head *splice_balance_callbacks(struct rq *rq)
4426{
4427 return NULL;
4428}
4429
4430static inline void balance_callbacks(struct rq *rq, struct callback_head *head)
4431{
4432}
4433
4434#endif
4435
4436static inline void
4437prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
4438{
4439 /*
4440 * Since the runqueue lock will be released by the next
4441 * task (which is an invalid locking op but in the case
4442 * of the scheduler it's an obvious special-case), so we
4443 * do an early lockdep release here:
4444 */
4445 rq_unpin_lock(rq, rf);
4446 spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_);
4447#ifdef CONFIG_DEBUG_SPINLOCK
4448 /* this is a valid case when another task releases the spinlock */
4449 rq_lockp(rq)->owner = next;
4450#endif
4451}
4452
4453static inline void finish_lock_switch(struct rq *rq)
4454{
4455 /*
4456 * If we are tracking spinlock dependencies then we have to
4457 * fix up the runqueue lock - which gets 'carried over' from
4458 * prev into current:
4459 */
4460 spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_);
4461 __balance_callbacks(rq);
4462 raw_spin_rq_unlock_irq(rq);
4463}
4464
4465/*
4466 * NOP if the arch has not defined these:
4467 */
4468
4469#ifndef prepare_arch_switch
4470# define prepare_arch_switch(next) do { } while (0)
4471#endif
4472
4473#ifndef finish_arch_post_lock_switch
4474# define finish_arch_post_lock_switch() do { } while (0)
4475#endif
4476
4477static inline void kmap_local_sched_out(void)
4478{
4479#ifdef CONFIG_KMAP_LOCAL
4480 if (unlikely(current->kmap_ctrl.idx))
4481 __kmap_local_sched_out();
4482#endif
4483}
4484
4485static inline void kmap_local_sched_in(void)
4486{
4487#ifdef CONFIG_KMAP_LOCAL
4488 if (unlikely(current->kmap_ctrl.idx))
4489 __kmap_local_sched_in();
4490#endif
4491}
4492
4493/**
4494 * prepare_task_switch - prepare to switch tasks
4495 * @rq: the runqueue preparing to switch
4496 * @prev: the current task that is being switched out
4497 * @next: the task we are going to switch to.
4498 *
4499 * This is called with the rq lock held and interrupts off. It must
4500 * be paired with a subsequent finish_task_switch after the context
4501 * switch.
4502 *
4503 * prepare_task_switch sets up locking and calls architecture specific
4504 * hooks.
4505 */
4506static inline void
4507prepare_task_switch(struct rq *rq, struct task_struct *prev,
4508 struct task_struct *next)
4509{
4510 kcov_prepare_switch(prev);
4511 sched_info_switch(rq, prev, next);
4512 perf_event_task_sched_out(prev, next);
4513 rseq_preempt(prev);
4514 fire_sched_out_preempt_notifiers(prev, next);
4515 kmap_local_sched_out();
4516 prepare_task(next);
4517 prepare_arch_switch(next);
4518}
4519
4520/**
4521 * finish_task_switch - clean up after a task-switch
4522 * @prev: the thread we just switched away from.
4523 *
4524 * finish_task_switch must be called after the context switch, paired
4525 * with a prepare_task_switch call before the context switch.
4526 * finish_task_switch will reconcile locking set up by prepare_task_switch,
4527 * and do any other architecture-specific cleanup actions.
4528 *
4529 * Note that we may have delayed dropping an mm in context_switch(). If
4530 * so, we finish that here outside of the runqueue lock. (Doing it
4531 * with the lock held can cause deadlocks; see schedule() for
4532 * details.)
4533 *
4534 * The context switch have flipped the stack from under us and restored the
4535 * local variables which were saved when this task called schedule() in the
4536 * past. prev == current is still correct but we need to recalculate this_rq
4537 * because prev may have moved to another CPU.
4538 */
4539static struct rq *finish_task_switch(struct task_struct *prev)
4540 __releases(rq->lock)
4541{
4542 struct rq *rq = this_rq();
4543 struct mm_struct *mm = rq->prev_mm;
4544 long prev_state;
4545
4546 /*
4547 * The previous task will have left us with a preempt_count of 2
4548 * because it left us after:
4549 *
4550 * schedule()
4551 * preempt_disable(); // 1
4552 * __schedule()
4553 * raw_spin_lock_irq(&rq->lock) // 2
4554 *
4555 * Also, see FORK_PREEMPT_COUNT.
4556 */
4557 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
4558 "corrupted preempt_count: %s/%d/0x%x\n",
4559 current->comm, current->pid, preempt_count()))
4560 preempt_count_set(FORK_PREEMPT_COUNT);
4561
4562 rq->prev_mm = NULL;
4563
4564 /*
4565 * A task struct has one reference for the use as "current".
4566 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
4567 * schedule one last time. The schedule call will never return, and
4568 * the scheduled task must drop that reference.
4569 *
4570 * We must observe prev->state before clearing prev->on_cpu (in
4571 * finish_task), otherwise a concurrent wakeup can get prev
4572 * running on another CPU and we could rave with its RUNNING -> DEAD
4573 * transition, resulting in a double drop.
4574 */
4575 prev_state = READ_ONCE(prev->__state);
4576 vtime_task_switch(prev);
4577 perf_event_task_sched_in(prev, current);
4578 finish_task(prev);
4579 tick_nohz_task_switch();
4580 finish_lock_switch(rq);
4581 finish_arch_post_lock_switch();
4582 kcov_finish_switch(current);
4583 /*
4584 * kmap_local_sched_out() is invoked with rq::lock held and
4585 * interrupts disabled. There is no requirement for that, but the
4586 * sched out code does not have an interrupt enabled section.
4587 * Restoring the maps on sched in does not require interrupts being
4588 * disabled either.
4589 */
4590 kmap_local_sched_in();
4591
4592 fire_sched_in_preempt_notifiers(current);
4593 /*
4594 * When switching through a kernel thread, the loop in
4595 * membarrier_{private,global}_expedited() may have observed that
4596 * kernel thread and not issued an IPI. It is therefore possible to
4597 * schedule between user->kernel->user threads without passing though
4598 * switch_mm(). Membarrier requires a barrier after storing to
4599 * rq->curr, before returning to userspace, so provide them here:
4600 *
4601 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
4602 * provided by mmdrop(),
4603 * - a sync_core for SYNC_CORE.
4604 */
4605 if (mm) {
4606 membarrier_mm_sync_core_before_usermode(mm);
4607 mmdrop(mm);
4608 }
4609 if (unlikely(prev_state == TASK_DEAD)) {
4610 if (prev->sched_class->task_dead)
4611 prev->sched_class->task_dead(prev);
4612
4613 /*
4614 * Remove function-return probe instances associated with this
4615 * task and put them back on the free list.
4616 */
4617 kprobe_flush_task(prev);
4618
4619 /* Task is done with its stack. */
4620 put_task_stack(prev);
4621
4622 put_task_struct_rcu_user(prev);
4623 }
4624
4625 return rq;
4626}
4627
4628/**
4629 * schedule_tail - first thing a freshly forked thread must call.
4630 * @prev: the thread we just switched away from.
4631 */
4632asmlinkage __visible void schedule_tail(struct task_struct *prev)
4633 __releases(rq->lock)
4634{
4635 /*
4636 * New tasks start with FORK_PREEMPT_COUNT, see there and
4637 * finish_task_switch() for details.
4638 *
4639 * finish_task_switch() will drop rq->lock() and lower preempt_count
4640 * and the preempt_enable() will end up enabling preemption (on
4641 * PREEMPT_COUNT kernels).
4642 */
4643
4644 finish_task_switch(prev);
4645 preempt_enable();
4646
4647 if (current->set_child_tid)
4648 put_user(task_pid_vnr(current), current->set_child_tid);
4649
4650 calculate_sigpending();
4651}
4652
4653/*
4654 * context_switch - switch to the new MM and the new thread's register state.
4655 */
4656static __always_inline struct rq *
4657context_switch(struct rq *rq, struct task_struct *prev,
4658 struct task_struct *next, struct rq_flags *rf)
4659{
4660 prepare_task_switch(rq, prev, next);
4661
4662 /*
4663 * For paravirt, this is coupled with an exit in switch_to to
4664 * combine the page table reload and the switch backend into
4665 * one hypercall.
4666 */
4667 arch_start_context_switch(prev);
4668
4669 /*
4670 * kernel -> kernel lazy + transfer active
4671 * user -> kernel lazy + mmgrab() active
4672 *
4673 * kernel -> user switch + mmdrop() active
4674 * user -> user switch
4675 */
4676 if (!next->mm) { // to kernel
4677 enter_lazy_tlb(prev->active_mm, next);
4678
4679 next->active_mm = prev->active_mm;
4680 if (prev->mm) // from user
4681 mmgrab(prev->active_mm);
4682 else
4683 prev->active_mm = NULL;
4684 } else { // to user
4685 membarrier_switch_mm(rq, prev->active_mm, next->mm);
4686 /*
4687 * sys_membarrier() requires an smp_mb() between setting
4688 * rq->curr / membarrier_switch_mm() and returning to userspace.
4689 *
4690 * The below provides this either through switch_mm(), or in
4691 * case 'prev->active_mm == next->mm' through
4692 * finish_task_switch()'s mmdrop().
4693 */
4694 switch_mm_irqs_off(prev->active_mm, next->mm, next);
4695
4696 if (!prev->mm) { // from kernel
4697 /* will mmdrop() in finish_task_switch(). */
4698 rq->prev_mm = prev->active_mm;
4699 prev->active_mm = NULL;
4700 }
4701 }
4702
4703 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
4704
4705 prepare_lock_switch(rq, next, rf);
4706
4707 /* Here we just switch the register state and the stack. */
4708 switch_to(prev, next, prev);
4709 barrier();
4710
4711 return finish_task_switch(prev);
4712}
4713
4714/*
4715 * nr_running and nr_context_switches:
4716 *
4717 * externally visible scheduler statistics: current number of runnable
4718 * threads, total number of context switches performed since bootup.
4719 */
4720unsigned int nr_running(void)
4721{
4722 unsigned int i, sum = 0;
4723
4724 for_each_online_cpu(i)
4725 sum += cpu_rq(i)->nr_running;
4726
4727 return sum;
4728}
4729
4730/*
4731 * Check if only the current task is running on the CPU.
4732 *
4733 * Caution: this function does not check that the caller has disabled
4734 * preemption, thus the result might have a time-of-check-to-time-of-use
4735 * race. The caller is responsible to use it correctly, for example:
4736 *
4737 * - from a non-preemptible section (of course)
4738 *
4739 * - from a thread that is bound to a single CPU
4740 *
4741 * - in a loop with very short iterations (e.g. a polling loop)
4742 */
4743bool single_task_running(void)
4744{
4745 return raw_rq()->nr_running == 1;
4746}
4747EXPORT_SYMBOL(single_task_running);
4748
4749unsigned long long nr_context_switches(void)
4750{
4751 int i;
4752 unsigned long long sum = 0;
4753
4754 for_each_possible_cpu(i)
4755 sum += cpu_rq(i)->nr_switches;
4756
4757 return sum;
4758}
4759
4760/*
4761 * Consumers of these two interfaces, like for example the cpuidle menu
4762 * governor, are using nonsensical data. Preferring shallow idle state selection
4763 * for a CPU that has IO-wait which might not even end up running the task when
4764 * it does become runnable.
4765 */
4766
4767unsigned int nr_iowait_cpu(int cpu)
4768{
4769 return atomic_read(&cpu_rq(cpu)->nr_iowait);
4770}
4771
4772/*
4773 * IO-wait accounting, and how it's mostly bollocks (on SMP).
4774 *
4775 * The idea behind IO-wait account is to account the idle time that we could
4776 * have spend running if it were not for IO. That is, if we were to improve the
4777 * storage performance, we'd have a proportional reduction in IO-wait time.
4778 *
4779 * This all works nicely on UP, where, when a task blocks on IO, we account
4780 * idle time as IO-wait, because if the storage were faster, it could've been
4781 * running and we'd not be idle.
4782 *
4783 * This has been extended to SMP, by doing the same for each CPU. This however
4784 * is broken.
4785 *
4786 * Imagine for instance the case where two tasks block on one CPU, only the one
4787 * CPU will have IO-wait accounted, while the other has regular idle. Even
4788 * though, if the storage were faster, both could've ran at the same time,
4789 * utilising both CPUs.
4790 *
4791 * This means, that when looking globally, the current IO-wait accounting on
4792 * SMP is a lower bound, by reason of under accounting.
4793 *
4794 * Worse, since the numbers are provided per CPU, they are sometimes
4795 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
4796 * associated with any one particular CPU, it can wake to another CPU than it
4797 * blocked on. This means the per CPU IO-wait number is meaningless.
4798 *
4799 * Task CPU affinities can make all that even more 'interesting'.
4800 */
4801
4802unsigned int nr_iowait(void)
4803{
4804 unsigned int i, sum = 0;
4805
4806 for_each_possible_cpu(i)
4807 sum += nr_iowait_cpu(i);
4808
4809 return sum;
4810}
4811
4812#ifdef CONFIG_SMP
4813
4814/*
4815 * sched_exec - execve() is a valuable balancing opportunity, because at
4816 * this point the task has the smallest effective memory and cache footprint.
4817 */
4818void sched_exec(void)
4819{
4820 struct task_struct *p = current;
4821 unsigned long flags;
4822 int dest_cpu;
4823
4824 raw_spin_lock_irqsave(&p->pi_lock, flags);
4825 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC);
4826 if (dest_cpu == smp_processor_id())
4827 goto unlock;
4828
4829 if (likely(cpu_active(dest_cpu))) {
4830 struct migration_arg arg = { p, dest_cpu };
4831
4832 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4833 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
4834 return;
4835 }
4836unlock:
4837 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4838}
4839
4840#endif
4841
4842DEFINE_PER_CPU(struct kernel_stat, kstat);
4843DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
4844
4845EXPORT_PER_CPU_SYMBOL(kstat);
4846EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
4847
4848/*
4849 * The function fair_sched_class.update_curr accesses the struct curr
4850 * and its field curr->exec_start; when called from task_sched_runtime(),
4851 * we observe a high rate of cache misses in practice.
4852 * Prefetching this data results in improved performance.
4853 */
4854static inline void prefetch_curr_exec_start(struct task_struct *p)
4855{
4856#ifdef CONFIG_FAIR_GROUP_SCHED
4857 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
4858#else
4859 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
4860#endif
4861 prefetch(curr);
4862 prefetch(&curr->exec_start);
4863}
4864
4865/*
4866 * Return accounted runtime for the task.
4867 * In case the task is currently running, return the runtime plus current's
4868 * pending runtime that have not been accounted yet.
4869 */
4870unsigned long long task_sched_runtime(struct task_struct *p)
4871{
4872 struct rq_flags rf;
4873 struct rq *rq;
4874 u64 ns;
4875
4876#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
4877 /*
4878 * 64-bit doesn't need locks to atomically read a 64-bit value.
4879 * So we have a optimization chance when the task's delta_exec is 0.
4880 * Reading ->on_cpu is racy, but this is ok.
4881 *
4882 * If we race with it leaving CPU, we'll take a lock. So we're correct.
4883 * If we race with it entering CPU, unaccounted time is 0. This is
4884 * indistinguishable from the read occurring a few cycles earlier.
4885 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
4886 * been accounted, so we're correct here as well.
4887 */
4888 if (!p->on_cpu || !task_on_rq_queued(p))
4889 return p->se.sum_exec_runtime;
4890#endif
4891
4892 rq = task_rq_lock(p, &rf);
4893 /*
4894 * Must be ->curr _and_ ->on_rq. If dequeued, we would
4895 * project cycles that may never be accounted to this
4896 * thread, breaking clock_gettime().
4897 */
4898 if (task_current(rq, p) && task_on_rq_queued(p)) {
4899 prefetch_curr_exec_start(p);
4900 update_rq_clock(rq);
4901 p->sched_class->update_curr(rq);
4902 }
4903 ns = p->se.sum_exec_runtime;
4904 task_rq_unlock(rq, p, &rf);
4905
4906 return ns;
4907}
4908
4909#ifdef CONFIG_SCHED_DEBUG
4910static u64 cpu_resched_latency(struct rq *rq)
4911{
4912 int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
4913 u64 resched_latency, now = rq_clock(rq);
4914 static bool warned_once;
4915
4916 if (sysctl_resched_latency_warn_once && warned_once)
4917 return 0;
4918
4919 if (!need_resched() || !latency_warn_ms)
4920 return 0;
4921
4922 if (system_state == SYSTEM_BOOTING)
4923 return 0;
4924
4925 if (!rq->last_seen_need_resched_ns) {
4926 rq->last_seen_need_resched_ns = now;
4927 rq->ticks_without_resched = 0;
4928 return 0;
4929 }
4930
4931 rq->ticks_without_resched++;
4932 resched_latency = now - rq->last_seen_need_resched_ns;
4933 if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
4934 return 0;
4935
4936 warned_once = true;
4937
4938 return resched_latency;
4939}
4940
4941static int __init setup_resched_latency_warn_ms(char *str)
4942{
4943 long val;
4944
4945 if ((kstrtol(str, 0, &val))) {
4946 pr_warn("Unable to set resched_latency_warn_ms\n");
4947 return 1;
4948 }
4949
4950 sysctl_resched_latency_warn_ms = val;
4951 return 1;
4952}
4953__setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
4954#else
4955static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
4956#endif /* CONFIG_SCHED_DEBUG */
4957
4958/*
4959 * This function gets called by the timer code, with HZ frequency.
4960 * We call it with interrupts disabled.
4961 */
4962void scheduler_tick(void)
4963{
4964 int cpu = smp_processor_id();
4965 struct rq *rq = cpu_rq(cpu);
4966 struct task_struct *curr = rq->curr;
4967 struct rq_flags rf;
4968 unsigned long thermal_pressure;
4969 u64 resched_latency;
4970
4971 arch_scale_freq_tick();
4972 sched_clock_tick();
4973
4974 rq_lock(rq, &rf);
4975
4976 update_rq_clock(rq);
4977 thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
4978 update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
4979 curr->sched_class->task_tick(rq, curr, 0);
4980 if (sched_feat(LATENCY_WARN))
4981 resched_latency = cpu_resched_latency(rq);
4982 calc_global_load_tick(rq);
4983
4984 rq_unlock(rq, &rf);
4985
4986 if (sched_feat(LATENCY_WARN) && resched_latency)
4987 resched_latency_warn(cpu, resched_latency);
4988
4989 perf_event_task_tick();
4990
4991#ifdef CONFIG_SMP
4992 rq->idle_balance = idle_cpu(cpu);
4993 trigger_load_balance(rq);
4994#endif
4995}
4996
4997#ifdef CONFIG_NO_HZ_FULL
4998
4999struct tick_work {
5000 int cpu;
5001 atomic_t state;
5002 struct delayed_work work;
5003};
5004/* Values for ->state, see diagram below. */
5005#define TICK_SCHED_REMOTE_OFFLINE 0
5006#define TICK_SCHED_REMOTE_OFFLINING 1
5007#define TICK_SCHED_REMOTE_RUNNING 2
5008
5009/*
5010 * State diagram for ->state:
5011 *
5012 *
5013 * TICK_SCHED_REMOTE_OFFLINE
5014 * | ^
5015 * | |
5016 * | | sched_tick_remote()
5017 * | |
5018 * | |
5019 * +--TICK_SCHED_REMOTE_OFFLINING
5020 * | ^
5021 * | |
5022 * sched_tick_start() | | sched_tick_stop()
5023 * | |
5024 * V |
5025 * TICK_SCHED_REMOTE_RUNNING
5026 *
5027 *
5028 * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
5029 * and sched_tick_start() are happy to leave the state in RUNNING.
5030 */
5031
5032static struct tick_work __percpu *tick_work_cpu;
5033
5034static void sched_tick_remote(struct work_struct *work)
5035{
5036 struct delayed_work *dwork = to_delayed_work(work);
5037 struct tick_work *twork = container_of(dwork, struct tick_work, work);
5038 int cpu = twork->cpu;
5039 struct rq *rq = cpu_rq(cpu);
5040 struct task_struct *curr;
5041 struct rq_flags rf;
5042 u64 delta;
5043 int os;
5044
5045 /*
5046 * Handle the tick only if it appears the remote CPU is running in full
5047 * dynticks mode. The check is racy by nature, but missing a tick or
5048 * having one too much is no big deal because the scheduler tick updates
5049 * statistics and checks timeslices in a time-independent way, regardless
5050 * of when exactly it is running.
5051 */
5052 if (!tick_nohz_tick_stopped_cpu(cpu))
5053 goto out_requeue;
5054
5055 rq_lock_irq(rq, &rf);
5056 curr = rq->curr;
5057 if (cpu_is_offline(cpu))
5058 goto out_unlock;
5059
5060 update_rq_clock(rq);
5061
5062 if (!is_idle_task(curr)) {
5063 /*
5064 * Make sure the next tick runs within a reasonable
5065 * amount of time.
5066 */
5067 delta = rq_clock_task(rq) - curr->se.exec_start;
5068 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
5069 }
5070 curr->sched_class->task_tick(rq, curr, 0);
5071
5072 calc_load_nohz_remote(rq);
5073out_unlock:
5074 rq_unlock_irq(rq, &rf);
5075out_requeue:
5076
5077 /*
5078 * Run the remote tick once per second (1Hz). This arbitrary
5079 * frequency is large enough to avoid overload but short enough
5080 * to keep scheduler internal stats reasonably up to date. But
5081 * first update state to reflect hotplug activity if required.
5082 */
5083 os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
5084 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
5085 if (os == TICK_SCHED_REMOTE_RUNNING)
5086 queue_delayed_work(system_unbound_wq, dwork, HZ);
5087}
5088
5089static void sched_tick_start(int cpu)
5090{
5091 int os;
5092 struct tick_work *twork;
5093
5094 if (housekeeping_cpu(cpu, HK_FLAG_TICK))
5095 return;
5096
5097 WARN_ON_ONCE(!tick_work_cpu);
5098
5099 twork = per_cpu_ptr(tick_work_cpu, cpu);
5100 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
5101 WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
5102 if (os == TICK_SCHED_REMOTE_OFFLINE) {
5103 twork->cpu = cpu;
5104 INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
5105 queue_delayed_work(system_unbound_wq, &twork->work, HZ);
5106 }
5107}
5108
5109#ifdef CONFIG_HOTPLUG_CPU
5110static void sched_tick_stop(int cpu)
5111{
5112 struct tick_work *twork;
5113 int os;
5114
5115 if (housekeeping_cpu(cpu, HK_FLAG_TICK))
5116 return;
5117
5118 WARN_ON_ONCE(!tick_work_cpu);
5119
5120 twork = per_cpu_ptr(tick_work_cpu, cpu);
5121 /* There cannot be competing actions, but don't rely on stop-machine. */
5122 os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
5123 WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
5124 /* Don't cancel, as this would mess up the state machine. */
5125}
5126#endif /* CONFIG_HOTPLUG_CPU */
5127
5128int __init sched_tick_offload_init(void)
5129{
5130 tick_work_cpu = alloc_percpu(struct tick_work);
5131 BUG_ON(!tick_work_cpu);
5132 return 0;
5133}
5134
5135#else /* !CONFIG_NO_HZ_FULL */
5136static inline void sched_tick_start(int cpu) { }
5137static inline void sched_tick_stop(int cpu) { }
5138#endif
5139
5140#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
5141 defined(CONFIG_TRACE_PREEMPT_TOGGLE))
5142/*
5143 * If the value passed in is equal to the current preempt count
5144 * then we just disabled preemption. Start timing the latency.
5145 */
5146static inline void preempt_latency_start(int val)
5147{
5148 if (preempt_count() == val) {
5149 unsigned long ip = get_lock_parent_ip();
5150#ifdef CONFIG_DEBUG_PREEMPT
5151 current->preempt_disable_ip = ip;
5152#endif
5153 trace_preempt_off(CALLER_ADDR0, ip);
5154 }
5155}
5156
5157void preempt_count_add(int val)
5158{
5159#ifdef CONFIG_DEBUG_PREEMPT
5160 /*
5161 * Underflow?
5162 */
5163 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
5164 return;
5165#endif
5166 __preempt_count_add(val);
5167#ifdef CONFIG_DEBUG_PREEMPT
5168 /*
5169 * Spinlock count overflowing soon?
5170 */
5171 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
5172 PREEMPT_MASK - 10);
5173#endif
5174 preempt_latency_start(val);
5175}
5176EXPORT_SYMBOL(preempt_count_add);
5177NOKPROBE_SYMBOL(preempt_count_add);
5178
5179/*
5180 * If the value passed in equals to the current preempt count
5181 * then we just enabled preemption. Stop timing the latency.
5182 */
5183static inline void preempt_latency_stop(int val)
5184{
5185 if (preempt_count() == val)
5186 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
5187}
5188
5189void preempt_count_sub(int val)
5190{
5191#ifdef CONFIG_DEBUG_PREEMPT
5192 /*
5193 * Underflow?
5194 */
5195 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
5196 return;
5197 /*
5198 * Is the spinlock portion underflowing?
5199 */
5200 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
5201 !(preempt_count() & PREEMPT_MASK)))
5202 return;
5203#endif
5204
5205 preempt_latency_stop(val);
5206 __preempt_count_sub(val);
5207}
5208EXPORT_SYMBOL(preempt_count_sub);
5209NOKPROBE_SYMBOL(preempt_count_sub);
5210
5211#else
5212static inline void preempt_latency_start(int val) { }
5213static inline void preempt_latency_stop(int val) { }
5214#endif
5215
5216static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
5217{
5218#ifdef CONFIG_DEBUG_PREEMPT
5219 return p->preempt_disable_ip;
5220#else
5221 return 0;
5222#endif
5223}
5224
5225/*
5226 * Print scheduling while atomic bug:
5227 */
5228static noinline void __schedule_bug(struct task_struct *prev)
5229{
5230 /* Save this before calling printk(), since that will clobber it */
5231 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
5232
5233 if (oops_in_progress)
5234 return;
5235
5236 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
5237 prev->comm, prev->pid, preempt_count());
5238
5239 debug_show_held_locks(prev);
5240 print_modules();
5241 if (irqs_disabled())
5242 print_irqtrace_events(prev);
5243 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
5244 && in_atomic_preempt_off()) {
5245 pr_err("Preemption disabled at:");
5246 print_ip_sym(KERN_ERR, preempt_disable_ip);
5247 }
5248 if (panic_on_warn)
5249 panic("scheduling while atomic\n");
5250
5251 dump_stack();
5252 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5253}
5254
5255/*
5256 * Various schedule()-time debugging checks and statistics:
5257 */
5258static inline void schedule_debug(struct task_struct *prev, bool preempt)
5259{
5260#ifdef CONFIG_SCHED_STACK_END_CHECK
5261 if (task_stack_end_corrupted(prev))
5262 panic("corrupted stack end detected inside scheduler\n");
5263
5264 if (task_scs_end_corrupted(prev))
5265 panic("corrupted shadow stack detected inside scheduler\n");
5266#endif
5267
5268#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
5269 if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) {
5270 printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
5271 prev->comm, prev->pid, prev->non_block_count);
5272 dump_stack();
5273 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
5274 }
5275#endif
5276
5277 if (unlikely(in_atomic_preempt_off())) {
5278 __schedule_bug(prev);
5279 preempt_count_set(PREEMPT_DISABLED);
5280 }
5281 rcu_sleep_check();
5282 SCHED_WARN_ON(ct_state() == CONTEXT_USER);
5283
5284 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
5285
5286 schedstat_inc(this_rq()->sched_count);
5287}
5288
5289static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
5290 struct rq_flags *rf)
5291{
5292#ifdef CONFIG_SMP
5293 const struct sched_class *class;
5294 /*
5295 * We must do the balancing pass before put_prev_task(), such
5296 * that when we release the rq->lock the task is in the same
5297 * state as before we took rq->lock.
5298 *
5299 * We can terminate the balance pass as soon as we know there is
5300 * a runnable task of @class priority or higher.
5301 */
5302 for_class_range(class, prev->sched_class, &idle_sched_class) {
5303 if (class->balance(rq, prev, rf))
5304 break;
5305 }
5306#endif
5307
5308 put_prev_task(rq, prev);
5309}
5310
5311/*
5312 * Pick up the highest-prio task:
5313 */
5314static inline struct task_struct *
5315__pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
5316{
5317 const struct sched_class *class;
5318 struct task_struct *p;
5319
5320 /*
5321 * Optimization: we know that if all tasks are in the fair class we can
5322 * call that function directly, but only if the @prev task wasn't of a
5323 * higher scheduling class, because otherwise those lose the
5324 * opportunity to pull in more work from other CPUs.
5325 */
5326 if (likely(prev->sched_class <= &fair_sched_class &&
5327 rq->nr_running == rq->cfs.h_nr_running)) {
5328
5329 p = pick_next_task_fair(rq, prev, rf);
5330 if (unlikely(p == RETRY_TASK))
5331 goto restart;
5332
5333 /* Assume the next prioritized class is idle_sched_class */
5334 if (!p) {
5335 put_prev_task(rq, prev);
5336 p = pick_next_task_idle(rq);
5337 }
5338
5339 return p;
5340 }
5341
5342restart:
5343 put_prev_task_balance(rq, prev, rf);
5344
5345 for_each_class(class) {
5346 p = class->pick_next_task(rq);
5347 if (p)
5348 return p;
5349 }
5350
5351 /* The idle class should always have a runnable task: */
5352 BUG();
5353}
5354
5355#ifdef CONFIG_SCHED_CORE
5356static inline bool is_task_rq_idle(struct task_struct *t)
5357{
5358 return (task_rq(t)->idle == t);
5359}
5360
5361static inline bool cookie_equals(struct task_struct *a, unsigned long cookie)
5362{
5363 return is_task_rq_idle(a) || (a->core_cookie == cookie);
5364}
5365
5366static inline bool cookie_match(struct task_struct *a, struct task_struct *b)
5367{
5368 if (is_task_rq_idle(a) || is_task_rq_idle(b))
5369 return true;
5370
5371 return a->core_cookie == b->core_cookie;
5372}
5373
5374// XXX fairness/fwd progress conditions
5375/*
5376 * Returns
5377 * - NULL if there is no runnable task for this class.
5378 * - the highest priority task for this runqueue if it matches
5379 * rq->core->core_cookie or its priority is greater than max.
5380 * - Else returns idle_task.
5381 */
5382static struct task_struct *
5383pick_task(struct rq *rq, const struct sched_class *class, struct task_struct *max, bool in_fi)
5384{
5385 struct task_struct *class_pick, *cookie_pick;
5386 unsigned long cookie = rq->core->core_cookie;
5387
5388 class_pick = class->pick_task(rq);
5389 if (!class_pick)
5390 return NULL;
5391
5392 if (!cookie) {
5393 /*
5394 * If class_pick is tagged, return it only if it has
5395 * higher priority than max.
5396 */
5397 if (max && class_pick->core_cookie &&
5398 prio_less(class_pick, max, in_fi))
5399 return idle_sched_class.pick_task(rq);
5400
5401 return class_pick;
5402 }
5403
5404 /*
5405 * If class_pick is idle or matches cookie, return early.
5406 */
5407 if (cookie_equals(class_pick, cookie))
5408 return class_pick;
5409
5410 cookie_pick = sched_core_find(rq, cookie);
5411
5412 /*
5413 * If class > max && class > cookie, it is the highest priority task on
5414 * the core (so far) and it must be selected, otherwise we must go with
5415 * the cookie pick in order to satisfy the constraint.
5416 */
5417 if (prio_less(cookie_pick, class_pick, in_fi) &&
5418 (!max || prio_less(max, class_pick, in_fi)))
5419 return class_pick;
5420
5421 return cookie_pick;
5422}
5423
5424extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi);
5425
5426static struct task_struct *
5427pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
5428{
5429 struct task_struct *next, *max = NULL;
5430 const struct sched_class *class;
5431 const struct cpumask *smt_mask;
5432 bool fi_before = false;
5433 int i, j, cpu, occ = 0;
5434 bool need_sync;
5435
5436 if (!sched_core_enabled(rq))
5437 return __pick_next_task(rq, prev, rf);
5438
5439 cpu = cpu_of(rq);
5440
5441 /* Stopper task is switching into idle, no need core-wide selection. */
5442 if (cpu_is_offline(cpu)) {
5443 /*
5444 * Reset core_pick so that we don't enter the fastpath when
5445 * coming online. core_pick would already be migrated to
5446 * another cpu during offline.
5447 */
5448 rq->core_pick = NULL;
5449 return __pick_next_task(rq, prev, rf);
5450 }
5451
5452 /*
5453 * If there were no {en,de}queues since we picked (IOW, the task
5454 * pointers are all still valid), and we haven't scheduled the last
5455 * pick yet, do so now.
5456 *
5457 * rq->core_pick can be NULL if no selection was made for a CPU because
5458 * it was either offline or went offline during a sibling's core-wide
5459 * selection. In this case, do a core-wide selection.
5460 */
5461 if (rq->core->core_pick_seq == rq->core->core_task_seq &&
5462 rq->core->core_pick_seq != rq->core_sched_seq &&
5463 rq->core_pick) {
5464 WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq);
5465
5466 next = rq->core_pick;
5467 if (next != prev) {
5468 put_prev_task(rq, prev);
5469 set_next_task(rq, next);
5470 }
5471
5472 rq->core_pick = NULL;
5473 return next;
5474 }
5475
5476 put_prev_task_balance(rq, prev, rf);
5477
5478 smt_mask = cpu_smt_mask(cpu);
5479 need_sync = !!rq->core->core_cookie;
5480
5481 /* reset state */
5482 rq->core->core_cookie = 0UL;
5483 if (rq->core->core_forceidle) {
5484 need_sync = true;
5485 fi_before = true;
5486 rq->core->core_forceidle = false;
5487 }
5488
5489 /*
5490 * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq
5491 *
5492 * @task_seq guards the task state ({en,de}queues)
5493 * @pick_seq is the @task_seq we did a selection on
5494 * @sched_seq is the @pick_seq we scheduled
5495 *
5496 * However, preemptions can cause multiple picks on the same task set.
5497 * 'Fix' this by also increasing @task_seq for every pick.
5498 */
5499 rq->core->core_task_seq++;
5500
5501 /*
5502 * Optimize for common case where this CPU has no cookies
5503 * and there are no cookied tasks running on siblings.
5504 */
5505 if (!need_sync) {
5506 for_each_class(class) {
5507 next = class->pick_task(rq);
5508 if (next)
5509 break;
5510 }
5511
5512 if (!next->core_cookie) {
5513 rq->core_pick = NULL;
5514 /*
5515 * For robustness, update the min_vruntime_fi for
5516 * unconstrained picks as well.
5517 */
5518 WARN_ON_ONCE(fi_before);
5519 task_vruntime_update(rq, next, false);
5520 goto done;
5521 }
5522 }
5523
5524 for_each_cpu(i, smt_mask) {
5525 struct rq *rq_i = cpu_rq(i);
5526
5527 rq_i->core_pick = NULL;
5528
5529 if (i != cpu)
5530 update_rq_clock(rq_i);
5531 }
5532
5533 /*
5534 * Try and select tasks for each sibling in descending sched_class
5535 * order.
5536 */
5537 for_each_class(class) {
5538again:
5539 for_each_cpu_wrap(i, smt_mask, cpu) {
5540 struct rq *rq_i = cpu_rq(i);
5541 struct task_struct *p;
5542
5543 if (rq_i->core_pick)
5544 continue;
5545
5546 /*
5547 * If this sibling doesn't yet have a suitable task to
5548 * run; ask for the most eligible task, given the
5549 * highest priority task already selected for this
5550 * core.
5551 */
5552 p = pick_task(rq_i, class, max, fi_before);
5553 if (!p)
5554 continue;
5555
5556 if (!is_task_rq_idle(p))
5557 occ++;
5558
5559 rq_i->core_pick = p;
5560 if (rq_i->idle == p && rq_i->nr_running) {
5561 rq->core->core_forceidle = true;
5562 if (!fi_before)
5563 rq->core->core_forceidle_seq++;
5564 }
5565
5566 /*
5567 * If this new candidate is of higher priority than the
5568 * previous; and they're incompatible; we need to wipe
5569 * the slate and start over. pick_task makes sure that
5570 * p's priority is more than max if it doesn't match
5571 * max's cookie.
5572 *
5573 * NOTE: this is a linear max-filter and is thus bounded
5574 * in execution time.
5575 */
5576 if (!max || !cookie_match(max, p)) {
5577 struct task_struct *old_max = max;
5578
5579 rq->core->core_cookie = p->core_cookie;
5580 max = p;
5581
5582 if (old_max) {
5583 rq->core->core_forceidle = false;
5584 for_each_cpu(j, smt_mask) {
5585 if (j == i)
5586 continue;
5587
5588 cpu_rq(j)->core_pick = NULL;
5589 }
5590 occ = 1;
5591 goto again;
5592 }
5593 }
5594 }
5595 }
5596
5597 rq->core->core_pick_seq = rq->core->core_task_seq;
5598 next = rq->core_pick;
5599 rq->core_sched_seq = rq->core->core_pick_seq;
5600
5601 /* Something should have been selected for current CPU */
5602 WARN_ON_ONCE(!next);
5603
5604 /*
5605 * Reschedule siblings
5606 *
5607 * NOTE: L1TF -- at this point we're no longer running the old task and
5608 * sending an IPI (below) ensures the sibling will no longer be running
5609 * their task. This ensures there is no inter-sibling overlap between
5610 * non-matching user state.
5611 */
5612 for_each_cpu(i, smt_mask) {
5613 struct rq *rq_i = cpu_rq(i);
5614
5615 /*
5616 * An online sibling might have gone offline before a task
5617 * could be picked for it, or it might be offline but later
5618 * happen to come online, but its too late and nothing was
5619 * picked for it. That's Ok - it will pick tasks for itself,
5620 * so ignore it.
5621 */
5622 if (!rq_i->core_pick)
5623 continue;
5624
5625 /*
5626 * Update for new !FI->FI transitions, or if continuing to be in !FI:
5627 * fi_before fi update?
5628 * 0 0 1
5629 * 0 1 1
5630 * 1 0 1
5631 * 1 1 0
5632 */
5633 if (!(fi_before && rq->core->core_forceidle))
5634 task_vruntime_update(rq_i, rq_i->core_pick, rq->core->core_forceidle);
5635
5636 rq_i->core_pick->core_occupation = occ;
5637
5638 if (i == cpu) {
5639 rq_i->core_pick = NULL;
5640 continue;
5641 }
5642
5643 /* Did we break L1TF mitigation requirements? */
5644 WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick));
5645
5646 if (rq_i->curr == rq_i->core_pick) {
5647 rq_i->core_pick = NULL;
5648 continue;
5649 }
5650
5651 resched_curr(rq_i);
5652 }
5653
5654done:
5655 set_next_task(rq, next);
5656 return next;
5657}
5658
5659static bool try_steal_cookie(int this, int that)
5660{
5661 struct rq *dst = cpu_rq(this), *src = cpu_rq(that);
5662 struct task_struct *p;
5663 unsigned long cookie;
5664 bool success = false;
5665
5666 local_irq_disable();
5667 double_rq_lock(dst, src);
5668
5669 cookie = dst->core->core_cookie;
5670 if (!cookie)
5671 goto unlock;
5672
5673 if (dst->curr != dst->idle)
5674 goto unlock;
5675
5676 p = sched_core_find(src, cookie);
5677 if (p == src->idle)
5678 goto unlock;
5679
5680 do {
5681 if (p == src->core_pick || p == src->curr)
5682 goto next;
5683
5684 if (!cpumask_test_cpu(this, &p->cpus_mask))
5685 goto next;
5686
5687 if (p->core_occupation > dst->idle->core_occupation)
5688 goto next;
5689
5690 p->on_rq = TASK_ON_RQ_MIGRATING;
5691 deactivate_task(src, p, 0);
5692 set_task_cpu(p, this);
5693 activate_task(dst, p, 0);
5694 p->on_rq = TASK_ON_RQ_QUEUED;
5695
5696 resched_curr(dst);
5697
5698 success = true;
5699 break;
5700
5701next:
5702 p = sched_core_next(p, cookie);
5703 } while (p);
5704
5705unlock:
5706 double_rq_unlock(dst, src);
5707 local_irq_enable();
5708
5709 return success;
5710}
5711
5712static bool steal_cookie_task(int cpu, struct sched_domain *sd)
5713{
5714 int i;
5715
5716 for_each_cpu_wrap(i, sched_domain_span(sd), cpu) {
5717 if (i == cpu)
5718 continue;
5719
5720 if (need_resched())
5721 break;
5722
5723 if (try_steal_cookie(cpu, i))
5724 return true;
5725 }
5726
5727 return false;
5728}
5729
5730static void sched_core_balance(struct rq *rq)
5731{
5732 struct sched_domain *sd;
5733 int cpu = cpu_of(rq);
5734
5735 preempt_disable();
5736 rcu_read_lock();
5737 raw_spin_rq_unlock_irq(rq);
5738 for_each_domain(cpu, sd) {
5739 if (need_resched())
5740 break;
5741
5742 if (steal_cookie_task(cpu, sd))
5743 break;
5744 }
5745 raw_spin_rq_lock_irq(rq);
5746 rcu_read_unlock();
5747 preempt_enable();
5748}
5749
5750static DEFINE_PER_CPU(struct callback_head, core_balance_head);
5751
5752void queue_core_balance(struct rq *rq)
5753{
5754 if (!sched_core_enabled(rq))
5755 return;
5756
5757 if (!rq->core->core_cookie)
5758 return;
5759
5760 if (!rq->nr_running) /* not forced idle */
5761 return;
5762
5763 queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance);
5764}
5765
5766static void sched_core_cpu_starting(unsigned int cpu)
5767{
5768 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
5769 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
5770 unsigned long flags;
5771 int t;
5772
5773 sched_core_lock(cpu, &flags);
5774
5775 WARN_ON_ONCE(rq->core != rq);
5776
5777 /* if we're the first, we'll be our own leader */
5778 if (cpumask_weight(smt_mask) == 1)
5779 goto unlock;
5780
5781 /* find the leader */
5782 for_each_cpu(t, smt_mask) {
5783 if (t == cpu)
5784 continue;
5785 rq = cpu_rq(t);
5786 if (rq->core == rq) {
5787 core_rq = rq;
5788 break;
5789 }
5790 }
5791
5792 if (WARN_ON_ONCE(!core_rq)) /* whoopsie */
5793 goto unlock;
5794
5795 /* install and validate core_rq */
5796 for_each_cpu(t, smt_mask) {
5797 rq = cpu_rq(t);
5798
5799 if (t == cpu)
5800 rq->core = core_rq;
5801
5802 WARN_ON_ONCE(rq->core != core_rq);
5803 }
5804
5805unlock:
5806 sched_core_unlock(cpu, &flags);
5807}
5808
5809static void sched_core_cpu_deactivate(unsigned int cpu)
5810{
5811 const struct cpumask *smt_mask = cpu_smt_mask(cpu);
5812 struct rq *rq = cpu_rq(cpu), *core_rq = NULL;
5813 unsigned long flags;
5814 int t;
5815
5816 sched_core_lock(cpu, &flags);
5817
5818 /* if we're the last man standing, nothing to do */
5819 if (cpumask_weight(smt_mask) == 1) {
5820 WARN_ON_ONCE(rq->core != rq);
5821 goto unlock;
5822 }
5823
5824 /* if we're not the leader, nothing to do */
5825 if (rq->core != rq)
5826 goto unlock;
5827
5828 /* find a new leader */
5829 for_each_cpu(t, smt_mask) {
5830 if (t == cpu)
5831 continue;
5832 core_rq = cpu_rq(t);
5833 break;
5834 }
5835
5836 if (WARN_ON_ONCE(!core_rq)) /* impossible */
5837 goto unlock;
5838
5839 /* copy the shared state to the new leader */
5840 core_rq->core_task_seq = rq->core_task_seq;
5841 core_rq->core_pick_seq = rq->core_pick_seq;
5842 core_rq->core_cookie = rq->core_cookie;
5843 core_rq->core_forceidle = rq->core_forceidle;
5844 core_rq->core_forceidle_seq = rq->core_forceidle_seq;
5845
5846 /* install new leader */
5847 for_each_cpu(t, smt_mask) {
5848 rq = cpu_rq(t);
5849 rq->core = core_rq;
5850 }
5851
5852unlock:
5853 sched_core_unlock(cpu, &flags);
5854}
5855
5856static inline void sched_core_cpu_dying(unsigned int cpu)
5857{
5858 struct rq *rq = cpu_rq(cpu);
5859
5860 if (rq->core != rq)
5861 rq->core = rq;
5862}
5863
5864#else /* !CONFIG_SCHED_CORE */
5865
5866static inline void sched_core_cpu_starting(unsigned int cpu) {}
5867static inline void sched_core_cpu_deactivate(unsigned int cpu) {}
5868static inline void sched_core_cpu_dying(unsigned int cpu) {}
5869
5870static struct task_struct *
5871pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
5872{
5873 return __pick_next_task(rq, prev, rf);
5874}
5875
5876#endif /* CONFIG_SCHED_CORE */
5877
5878/*
5879 * __schedule() is the main scheduler function.
5880 *
5881 * The main means of driving the scheduler and thus entering this function are:
5882 *
5883 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
5884 *
5885 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
5886 * paths. For example, see arch/x86/entry_64.S.
5887 *
5888 * To drive preemption between tasks, the scheduler sets the flag in timer
5889 * interrupt handler scheduler_tick().
5890 *
5891 * 3. Wakeups don't really cause entry into schedule(). They add a
5892 * task to the run-queue and that's it.
5893 *
5894 * Now, if the new task added to the run-queue preempts the current
5895 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
5896 * called on the nearest possible occasion:
5897 *
5898 * - If the kernel is preemptible (CONFIG_PREEMPTION=y):
5899 *
5900 * - in syscall or exception context, at the next outmost
5901 * preempt_enable(). (this might be as soon as the wake_up()'s
5902 * spin_unlock()!)
5903 *
5904 * - in IRQ context, return from interrupt-handler to
5905 * preemptible context
5906 *
5907 * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
5908 * then at the next:
5909 *
5910 * - cond_resched() call
5911 * - explicit schedule() call
5912 * - return from syscall or exception to user-space
5913 * - return from interrupt-handler to user-space
5914 *
5915 * WARNING: must be called with preemption disabled!
5916 */
5917static void __sched notrace __schedule(bool preempt)
5918{
5919 struct task_struct *prev, *next;
5920 unsigned long *switch_count;
5921 unsigned long prev_state;
5922 struct rq_flags rf;
5923 struct rq *rq;
5924 int cpu;
5925
5926 cpu = smp_processor_id();
5927 rq = cpu_rq(cpu);
5928 prev = rq->curr;
5929
5930 schedule_debug(prev, preempt);
5931
5932 if (sched_feat(HRTICK) || sched_feat(HRTICK_DL))
5933 hrtick_clear(rq);
5934
5935 local_irq_disable();
5936 rcu_note_context_switch(preempt);
5937
5938 /*
5939 * Make sure that signal_pending_state()->signal_pending() below
5940 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
5941 * done by the caller to avoid the race with signal_wake_up():
5942 *
5943 * __set_current_state(@state) signal_wake_up()
5944 * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
5945 * wake_up_state(p, state)
5946 * LOCK rq->lock LOCK p->pi_state
5947 * smp_mb__after_spinlock() smp_mb__after_spinlock()
5948 * if (signal_pending_state()) if (p->state & @state)
5949 *
5950 * Also, the membarrier system call requires a full memory barrier
5951 * after coming from user-space, before storing to rq->curr.
5952 */
5953 rq_lock(rq, &rf);
5954 smp_mb__after_spinlock();
5955
5956 /* Promote REQ to ACT */
5957 rq->clock_update_flags <<= 1;
5958 update_rq_clock(rq);
5959
5960 switch_count = &prev->nivcsw;
5961
5962 /*
5963 * We must load prev->state once (task_struct::state is volatile), such
5964 * that:
5965 *
5966 * - we form a control dependency vs deactivate_task() below.
5967 * - ptrace_{,un}freeze_traced() can change ->state underneath us.
5968 */
5969 prev_state = READ_ONCE(prev->__state);
5970 if (!preempt && prev_state) {
5971 if (signal_pending_state(prev_state, prev)) {
5972 WRITE_ONCE(prev->__state, TASK_RUNNING);
5973 } else {
5974 prev->sched_contributes_to_load =
5975 (prev_state & TASK_UNINTERRUPTIBLE) &&
5976 !(prev_state & TASK_NOLOAD) &&
5977 !(prev->flags & PF_FROZEN);
5978
5979 if (prev->sched_contributes_to_load)
5980 rq->nr_uninterruptible++;
5981
5982 /*
5983 * __schedule() ttwu()
5984 * prev_state = prev->state; if (p->on_rq && ...)
5985 * if (prev_state) goto out;
5986 * p->on_rq = 0; smp_acquire__after_ctrl_dep();
5987 * p->state = TASK_WAKING
5988 *
5989 * Where __schedule() and ttwu() have matching control dependencies.
5990 *
5991 * After this, schedule() must not care about p->state any more.
5992 */
5993 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
5994
5995 if (prev->in_iowait) {
5996 atomic_inc(&rq->nr_iowait);
5997 delayacct_blkio_start();
5998 }
5999 }
6000 switch_count = &prev->nvcsw;
6001 }
6002
6003 next = pick_next_task(rq, prev, &rf);
6004 clear_tsk_need_resched(prev);
6005 clear_preempt_need_resched();
6006#ifdef CONFIG_SCHED_DEBUG
6007 rq->last_seen_need_resched_ns = 0;
6008#endif
6009
6010 if (likely(prev != next)) {
6011 rq->nr_switches++;
6012 /*
6013 * RCU users of rcu_dereference(rq->curr) may not see
6014 * changes to task_struct made by pick_next_task().
6015 */
6016 RCU_INIT_POINTER(rq->curr, next);
6017 /*
6018 * The membarrier system call requires each architecture
6019 * to have a full memory barrier after updating
6020 * rq->curr, before returning to user-space.
6021 *
6022 * Here are the schemes providing that barrier on the
6023 * various architectures:
6024 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
6025 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
6026 * - finish_lock_switch() for weakly-ordered
6027 * architectures where spin_unlock is a full barrier,
6028 * - switch_to() for arm64 (weakly-ordered, spin_unlock
6029 * is a RELEASE barrier),
6030 */
6031 ++*switch_count;
6032
6033 migrate_disable_switch(rq, prev);
6034 psi_sched_switch(prev, next, !task_on_rq_queued(prev));
6035
6036 trace_sched_switch(preempt, prev, next);
6037
6038 /* Also unlocks the rq: */
6039 rq = context_switch(rq, prev, next, &rf);
6040 } else {
6041 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
6042
6043 rq_unpin_lock(rq, &rf);
6044 __balance_callbacks(rq);
6045 raw_spin_rq_unlock_irq(rq);
6046 }
6047}
6048
6049void __noreturn do_task_dead(void)
6050{
6051 /* Causes final put_task_struct in finish_task_switch(): */
6052 set_special_state(TASK_DEAD);
6053
6054 /* Tell freezer to ignore us: */
6055 current->flags |= PF_NOFREEZE;
6056
6057 __schedule(false);
6058 BUG();
6059
6060 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
6061 for (;;)
6062 cpu_relax();
6063}
6064
6065static inline void sched_submit_work(struct task_struct *tsk)
6066{
6067 unsigned int task_flags;
6068
6069 if (task_is_running(tsk))
6070 return;
6071
6072 task_flags = tsk->flags;
6073 /*
6074 * If a worker went to sleep, notify and ask workqueue whether
6075 * it wants to wake up a task to maintain concurrency.
6076 * As this function is called inside the schedule() context,
6077 * we disable preemption to avoid it calling schedule() again
6078 * in the possible wakeup of a kworker and because wq_worker_sleeping()
6079 * requires it.
6080 */
6081 if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6082 preempt_disable();
6083 if (task_flags & PF_WQ_WORKER)
6084 wq_worker_sleeping(tsk);
6085 else
6086 io_wq_worker_sleeping(tsk);
6087 preempt_enable_no_resched();
6088 }
6089
6090 if (tsk_is_pi_blocked(tsk))
6091 return;
6092
6093 /*
6094 * If we are going to sleep and we have plugged IO queued,
6095 * make sure to submit it to avoid deadlocks.
6096 */
6097 if (blk_needs_flush_plug(tsk))
6098 blk_schedule_flush_plug(tsk);
6099}
6100
6101static void sched_update_worker(struct task_struct *tsk)
6102{
6103 if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
6104 if (tsk->flags & PF_WQ_WORKER)
6105 wq_worker_running(tsk);
6106 else
6107 io_wq_worker_running(tsk);
6108 }
6109}
6110
6111asmlinkage __visible void __sched schedule(void)
6112{
6113 struct task_struct *tsk = current;
6114
6115 sched_submit_work(tsk);
6116 do {
6117 preempt_disable();
6118 __schedule(false);
6119 sched_preempt_enable_no_resched();
6120 } while (need_resched());
6121 sched_update_worker(tsk);
6122}
6123EXPORT_SYMBOL(schedule);
6124
6125/*
6126 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
6127 * state (have scheduled out non-voluntarily) by making sure that all
6128 * tasks have either left the run queue or have gone into user space.
6129 * As idle tasks do not do either, they must not ever be preempted
6130 * (schedule out non-voluntarily).
6131 *
6132 * schedule_idle() is similar to schedule_preempt_disable() except that it
6133 * never enables preemption because it does not call sched_submit_work().
6134 */
6135void __sched schedule_idle(void)
6136{
6137 /*
6138 * As this skips calling sched_submit_work(), which the idle task does
6139 * regardless because that function is a nop when the task is in a
6140 * TASK_RUNNING state, make sure this isn't used someplace that the
6141 * current task can be in any other state. Note, idle is always in the
6142 * TASK_RUNNING state.
6143 */
6144 WARN_ON_ONCE(current->__state);
6145 do {
6146 __schedule(false);
6147 } while (need_resched());
6148}
6149
6150#if defined(CONFIG_CONTEXT_TRACKING) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK)
6151asmlinkage __visible void __sched schedule_user(void)
6152{
6153 /*
6154 * If we come here after a random call to set_need_resched(),
6155 * or we have been woken up remotely but the IPI has not yet arrived,
6156 * we haven't yet exited the RCU idle mode. Do it here manually until
6157 * we find a better solution.
6158 *
6159 * NB: There are buggy callers of this function. Ideally we
6160 * should warn if prev_state != CONTEXT_USER, but that will trigger
6161 * too frequently to make sense yet.
6162 */
6163 enum ctx_state prev_state = exception_enter();
6164 schedule();
6165 exception_exit(prev_state);
6166}
6167#endif
6168
6169/**
6170 * schedule_preempt_disabled - called with preemption disabled
6171 *
6172 * Returns with preemption disabled. Note: preempt_count must be 1
6173 */
6174void __sched schedule_preempt_disabled(void)
6175{
6176 sched_preempt_enable_no_resched();
6177 schedule();
6178 preempt_disable();
6179}
6180
6181static void __sched notrace preempt_schedule_common(void)
6182{
6183 do {
6184 /*
6185 * Because the function tracer can trace preempt_count_sub()
6186 * and it also uses preempt_enable/disable_notrace(), if
6187 * NEED_RESCHED is set, the preempt_enable_notrace() called
6188 * by the function tracer will call this function again and
6189 * cause infinite recursion.
6190 *
6191 * Preemption must be disabled here before the function
6192 * tracer can trace. Break up preempt_disable() into two
6193 * calls. One to disable preemption without fear of being
6194 * traced. The other to still record the preemption latency,
6195 * which can also be traced by the function tracer.
6196 */
6197 preempt_disable_notrace();
6198 preempt_latency_start(1);
6199 __schedule(true);
6200 preempt_latency_stop(1);
6201 preempt_enable_no_resched_notrace();
6202
6203 /*
6204 * Check again in case we missed a preemption opportunity
6205 * between schedule and now.
6206 */
6207 } while (need_resched());
6208}
6209
6210#ifdef CONFIG_PREEMPTION
6211/*
6212 * This is the entry point to schedule() from in-kernel preemption
6213 * off of preempt_enable.
6214 */
6215asmlinkage __visible void __sched notrace preempt_schedule(void)
6216{
6217 /*
6218 * If there is a non-zero preempt_count or interrupts are disabled,
6219 * we do not want to preempt the current task. Just return..
6220 */
6221 if (likely(!preemptible()))
6222 return;
6223
6224 preempt_schedule_common();
6225}
6226NOKPROBE_SYMBOL(preempt_schedule);
6227EXPORT_SYMBOL(preempt_schedule);
6228
6229#ifdef CONFIG_PREEMPT_DYNAMIC
6230DEFINE_STATIC_CALL(preempt_schedule, __preempt_schedule_func);
6231EXPORT_STATIC_CALL_TRAMP(preempt_schedule);
6232#endif
6233
6234
6235/**
6236 * preempt_schedule_notrace - preempt_schedule called by tracing
6237 *
6238 * The tracing infrastructure uses preempt_enable_notrace to prevent
6239 * recursion and tracing preempt enabling caused by the tracing
6240 * infrastructure itself. But as tracing can happen in areas coming
6241 * from userspace or just about to enter userspace, a preempt enable
6242 * can occur before user_exit() is called. This will cause the scheduler
6243 * to be called when the system is still in usermode.
6244 *
6245 * To prevent this, the preempt_enable_notrace will use this function
6246 * instead of preempt_schedule() to exit user context if needed before
6247 * calling the scheduler.
6248 */
6249asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
6250{
6251 enum ctx_state prev_ctx;
6252
6253 if (likely(!preemptible()))
6254 return;
6255
6256 do {
6257 /*
6258 * Because the function tracer can trace preempt_count_sub()
6259 * and it also uses preempt_enable/disable_notrace(), if
6260 * NEED_RESCHED is set, the preempt_enable_notrace() called
6261 * by the function tracer will call this function again and
6262 * cause infinite recursion.
6263 *
6264 * Preemption must be disabled here before the function
6265 * tracer can trace. Break up preempt_disable() into two
6266 * calls. One to disable preemption without fear of being
6267 * traced. The other to still record the preemption latency,
6268 * which can also be traced by the function tracer.
6269 */
6270 preempt_disable_notrace();
6271 preempt_latency_start(1);
6272 /*
6273 * Needs preempt disabled in case user_exit() is traced
6274 * and the tracer calls preempt_enable_notrace() causing
6275 * an infinite recursion.
6276 */
6277 prev_ctx = exception_enter();
6278 __schedule(true);
6279 exception_exit(prev_ctx);
6280
6281 preempt_latency_stop(1);
6282 preempt_enable_no_resched_notrace();
6283 } while (need_resched());
6284}
6285EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
6286
6287#ifdef CONFIG_PREEMPT_DYNAMIC
6288DEFINE_STATIC_CALL(preempt_schedule_notrace, __preempt_schedule_notrace_func);
6289EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
6290#endif
6291
6292#endif /* CONFIG_PREEMPTION */
6293
6294#ifdef CONFIG_PREEMPT_DYNAMIC
6295
6296#include <linux/entry-common.h>
6297
6298/*
6299 * SC:cond_resched
6300 * SC:might_resched
6301 * SC:preempt_schedule
6302 * SC:preempt_schedule_notrace
6303 * SC:irqentry_exit_cond_resched
6304 *
6305 *
6306 * NONE:
6307 * cond_resched <- __cond_resched
6308 * might_resched <- RET0
6309 * preempt_schedule <- NOP
6310 * preempt_schedule_notrace <- NOP
6311 * irqentry_exit_cond_resched <- NOP
6312 *
6313 * VOLUNTARY:
6314 * cond_resched <- __cond_resched
6315 * might_resched <- __cond_resched
6316 * preempt_schedule <- NOP
6317 * preempt_schedule_notrace <- NOP
6318 * irqentry_exit_cond_resched <- NOP
6319 *
6320 * FULL:
6321 * cond_resched <- RET0
6322 * might_resched <- RET0
6323 * preempt_schedule <- preempt_schedule
6324 * preempt_schedule_notrace <- preempt_schedule_notrace
6325 * irqentry_exit_cond_resched <- irqentry_exit_cond_resched
6326 */
6327
6328enum {
6329 preempt_dynamic_none = 0,
6330 preempt_dynamic_voluntary,
6331 preempt_dynamic_full,
6332};
6333
6334int preempt_dynamic_mode = preempt_dynamic_full;
6335
6336int sched_dynamic_mode(const char *str)
6337{
6338 if (!strcmp(str, "none"))
6339 return preempt_dynamic_none;
6340
6341 if (!strcmp(str, "voluntary"))
6342 return preempt_dynamic_voluntary;
6343
6344 if (!strcmp(str, "full"))
6345 return preempt_dynamic_full;
6346
6347 return -EINVAL;
6348}
6349
6350void sched_dynamic_update(int mode)
6351{
6352 /*
6353 * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
6354 * the ZERO state, which is invalid.
6355 */
6356 static_call_update(cond_resched, __cond_resched);
6357 static_call_update(might_resched, __cond_resched);
6358 static_call_update(preempt_schedule, __preempt_schedule_func);
6359 static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
6360 static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
6361
6362 switch (mode) {
6363 case preempt_dynamic_none:
6364 static_call_update(cond_resched, __cond_resched);
6365 static_call_update(might_resched, (void *)&__static_call_return0);
6366 static_call_update(preempt_schedule, NULL);
6367 static_call_update(preempt_schedule_notrace, NULL);
6368 static_call_update(irqentry_exit_cond_resched, NULL);
6369 pr_info("Dynamic Preempt: none\n");
6370 break;
6371
6372 case preempt_dynamic_voluntary:
6373 static_call_update(cond_resched, __cond_resched);
6374 static_call_update(might_resched, __cond_resched);
6375 static_call_update(preempt_schedule, NULL);
6376 static_call_update(preempt_schedule_notrace, NULL);
6377 static_call_update(irqentry_exit_cond_resched, NULL);
6378 pr_info("Dynamic Preempt: voluntary\n");
6379 break;
6380
6381 case preempt_dynamic_full:
6382 static_call_update(cond_resched, (void *)&__static_call_return0);
6383 static_call_update(might_resched, (void *)&__static_call_return0);
6384 static_call_update(preempt_schedule, __preempt_schedule_func);
6385 static_call_update(preempt_schedule_notrace, __preempt_schedule_notrace_func);
6386 static_call_update(irqentry_exit_cond_resched, irqentry_exit_cond_resched);
6387 pr_info("Dynamic Preempt: full\n");
6388 break;
6389 }
6390
6391 preempt_dynamic_mode = mode;
6392}
6393
6394static int __init setup_preempt_mode(char *str)
6395{
6396 int mode = sched_dynamic_mode(str);
6397 if (mode < 0) {
6398 pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
6399 return 1;
6400 }
6401
6402 sched_dynamic_update(mode);
6403 return 0;
6404}
6405__setup("preempt=", setup_preempt_mode);
6406
6407#endif /* CONFIG_PREEMPT_DYNAMIC */
6408
6409/*
6410 * This is the entry point to schedule() from kernel preemption
6411 * off of irq context.
6412 * Note, that this is called and return with irqs disabled. This will
6413 * protect us against recursive calling from irq.
6414 */
6415asmlinkage __visible void __sched preempt_schedule_irq(void)
6416{
6417 enum ctx_state prev_state;
6418
6419 /* Catch callers which need to be fixed */
6420 BUG_ON(preempt_count() || !irqs_disabled());
6421
6422 prev_state = exception_enter();
6423
6424 do {
6425 preempt_disable();
6426 local_irq_enable();
6427 __schedule(true);
6428 local_irq_disable();
6429 sched_preempt_enable_no_resched();
6430 } while (need_resched());
6431
6432 exception_exit(prev_state);
6433}
6434
6435int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
6436 void *key)
6437{
6438 WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC);
6439 return try_to_wake_up(curr->private, mode, wake_flags);
6440}
6441EXPORT_SYMBOL(default_wake_function);
6442
6443static void __setscheduler_prio(struct task_struct *p, int prio)
6444{
6445 if (dl_prio(prio))
6446 p->sched_class = &dl_sched_class;
6447 else if (rt_prio(prio))
6448 p->sched_class = &rt_sched_class;
6449 else
6450 p->sched_class = &fair_sched_class;
6451
6452 p->prio = prio;
6453}
6454
6455#ifdef CONFIG_RT_MUTEXES
6456
6457static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
6458{
6459 if (pi_task)
6460 prio = min(prio, pi_task->prio);
6461
6462 return prio;
6463}
6464
6465static inline int rt_effective_prio(struct task_struct *p, int prio)
6466{
6467 struct task_struct *pi_task = rt_mutex_get_top_task(p);
6468
6469 return __rt_effective_prio(pi_task, prio);
6470}
6471
6472/*
6473 * rt_mutex_setprio - set the current priority of a task
6474 * @p: task to boost
6475 * @pi_task: donor task
6476 *
6477 * This function changes the 'effective' priority of a task. It does
6478 * not touch ->normal_prio like __setscheduler().
6479 *
6480 * Used by the rt_mutex code to implement priority inheritance
6481 * logic. Call site only calls if the priority of the task changed.
6482 */
6483void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
6484{
6485 int prio, oldprio, queued, running, queue_flag =
6486 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
6487 const struct sched_class *prev_class;
6488 struct rq_flags rf;
6489 struct rq *rq;
6490
6491 /* XXX used to be waiter->prio, not waiter->task->prio */
6492 prio = __rt_effective_prio(pi_task, p->normal_prio);
6493
6494 /*
6495 * If nothing changed; bail early.
6496 */
6497 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
6498 return;
6499
6500 rq = __task_rq_lock(p, &rf);
6501 update_rq_clock(rq);
6502 /*
6503 * Set under pi_lock && rq->lock, such that the value can be used under
6504 * either lock.
6505 *
6506 * Note that there is loads of tricky to make this pointer cache work
6507 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
6508 * ensure a task is de-boosted (pi_task is set to NULL) before the
6509 * task is allowed to run again (and can exit). This ensures the pointer
6510 * points to a blocked task -- which guarantees the task is present.
6511 */
6512 p->pi_top_task = pi_task;
6513
6514 /*
6515 * For FIFO/RR we only need to set prio, if that matches we're done.
6516 */
6517 if (prio == p->prio && !dl_prio(prio))
6518 goto out_unlock;
6519
6520 /*
6521 * Idle task boosting is a nono in general. There is one
6522 * exception, when PREEMPT_RT and NOHZ is active:
6523 *
6524 * The idle task calls get_next_timer_interrupt() and holds
6525 * the timer wheel base->lock on the CPU and another CPU wants
6526 * to access the timer (probably to cancel it). We can safely
6527 * ignore the boosting request, as the idle CPU runs this code
6528 * with interrupts disabled and will complete the lock
6529 * protected section without being interrupted. So there is no
6530 * real need to boost.
6531 */
6532 if (unlikely(p == rq->idle)) {
6533 WARN_ON(p != rq->curr);
6534 WARN_ON(p->pi_blocked_on);
6535 goto out_unlock;
6536 }
6537
6538 trace_sched_pi_setprio(p, pi_task);
6539 oldprio = p->prio;
6540
6541 if (oldprio == prio)
6542 queue_flag &= ~DEQUEUE_MOVE;
6543
6544 prev_class = p->sched_class;
6545 queued = task_on_rq_queued(p);
6546 running = task_current(rq, p);
6547 if (queued)
6548 dequeue_task(rq, p, queue_flag);
6549 if (running)
6550 put_prev_task(rq, p);
6551
6552 /*
6553 * Boosting condition are:
6554 * 1. -rt task is running and holds mutex A
6555 * --> -dl task blocks on mutex A
6556 *
6557 * 2. -dl task is running and holds mutex A
6558 * --> -dl task blocks on mutex A and could preempt the
6559 * running task
6560 */
6561 if (dl_prio(prio)) {
6562 if (!dl_prio(p->normal_prio) ||
6563 (pi_task && dl_prio(pi_task->prio) &&
6564 dl_entity_preempt(&pi_task->dl, &p->dl))) {
6565 p->dl.pi_se = pi_task->dl.pi_se;
6566 queue_flag |= ENQUEUE_REPLENISH;
6567 } else {
6568 p->dl.pi_se = &p->dl;
6569 }
6570 } else if (rt_prio(prio)) {
6571 if (dl_prio(oldprio))
6572 p->dl.pi_se = &p->dl;
6573 if (oldprio < prio)
6574 queue_flag |= ENQUEUE_HEAD;
6575 } else {
6576 if (dl_prio(oldprio))
6577 p->dl.pi_se = &p->dl;
6578 if (rt_prio(oldprio))
6579 p->rt.timeout = 0;
6580 }
6581
6582 __setscheduler_prio(p, prio);
6583
6584 if (queued)
6585 enqueue_task(rq, p, queue_flag);
6586 if (running)
6587 set_next_task(rq, p);
6588
6589 check_class_changed(rq, p, prev_class, oldprio);
6590out_unlock:
6591 /* Avoid rq from going away on us: */
6592 preempt_disable();
6593
6594 rq_unpin_lock(rq, &rf);
6595 __balance_callbacks(rq);
6596 raw_spin_rq_unlock(rq);
6597
6598 preempt_enable();
6599}
6600#else
6601static inline int rt_effective_prio(struct task_struct *p, int prio)
6602{
6603 return prio;
6604}
6605#endif
6606
6607void set_user_nice(struct task_struct *p, long nice)
6608{
6609 bool queued, running;
6610 int old_prio;
6611 struct rq_flags rf;
6612 struct rq *rq;
6613
6614 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
6615 return;
6616 /*
6617 * We have to be careful, if called from sys_setpriority(),
6618 * the task might be in the middle of scheduling on another CPU.
6619 */
6620 rq = task_rq_lock(p, &rf);
6621 update_rq_clock(rq);
6622
6623 /*
6624 * The RT priorities are set via sched_setscheduler(), but we still
6625 * allow the 'normal' nice value to be set - but as expected
6626 * it won't have any effect on scheduling until the task is
6627 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
6628 */
6629 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
6630 p->static_prio = NICE_TO_PRIO(nice);
6631 goto out_unlock;
6632 }
6633 queued = task_on_rq_queued(p);
6634 running = task_current(rq, p);
6635 if (queued)
6636 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
6637 if (running)
6638 put_prev_task(rq, p);
6639
6640 p->static_prio = NICE_TO_PRIO(nice);
6641 set_load_weight(p, true);
6642 old_prio = p->prio;
6643 p->prio = effective_prio(p);
6644
6645 if (queued)
6646 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
6647 if (running)
6648 set_next_task(rq, p);
6649
6650 /*
6651 * If the task increased its priority or is running and
6652 * lowered its priority, then reschedule its CPU:
6653 */
6654 p->sched_class->prio_changed(rq, p, old_prio);
6655
6656out_unlock:
6657 task_rq_unlock(rq, p, &rf);
6658}
6659EXPORT_SYMBOL(set_user_nice);
6660
6661/*
6662 * can_nice - check if a task can reduce its nice value
6663 * @p: task
6664 * @nice: nice value
6665 */
6666int can_nice(const struct task_struct *p, const int nice)
6667{
6668 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
6669 int nice_rlim = nice_to_rlimit(nice);
6670
6671 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
6672 capable(CAP_SYS_NICE));
6673}
6674
6675#ifdef __ARCH_WANT_SYS_NICE
6676
6677/*
6678 * sys_nice - change the priority of the current process.
6679 * @increment: priority increment
6680 *
6681 * sys_setpriority is a more generic, but much slower function that
6682 * does similar things.
6683 */
6684SYSCALL_DEFINE1(nice, int, increment)
6685{
6686 long nice, retval;
6687
6688 /*
6689 * Setpriority might change our priority at the same moment.
6690 * We don't have to worry. Conceptually one call occurs first
6691 * and we have a single winner.
6692 */
6693 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
6694 nice = task_nice(current) + increment;
6695
6696 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
6697 if (increment < 0 && !can_nice(current, nice))
6698 return -EPERM;
6699
6700 retval = security_task_setnice(current, nice);
6701 if (retval)
6702 return retval;
6703
6704 set_user_nice(current, nice);
6705 return 0;
6706}
6707
6708#endif
6709
6710/**
6711 * task_prio - return the priority value of a given task.
6712 * @p: the task in question.
6713 *
6714 * Return: The priority value as seen by users in /proc.
6715 *
6716 * sched policy return value kernel prio user prio/nice
6717 *
6718 * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19]
6719 * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99]
6720 * deadline -101 -1 0
6721 */
6722int task_prio(const struct task_struct *p)
6723{
6724 return p->prio - MAX_RT_PRIO;
6725}
6726
6727/**
6728 * idle_cpu - is a given CPU idle currently?
6729 * @cpu: the processor in question.
6730 *
6731 * Return: 1 if the CPU is currently idle. 0 otherwise.
6732 */
6733int idle_cpu(int cpu)
6734{
6735 struct rq *rq = cpu_rq(cpu);
6736
6737 if (rq->curr != rq->idle)
6738 return 0;
6739
6740 if (rq->nr_running)
6741 return 0;
6742
6743#ifdef CONFIG_SMP
6744 if (rq->ttwu_pending)
6745 return 0;
6746#endif
6747
6748 return 1;
6749}
6750
6751/**
6752 * available_idle_cpu - is a given CPU idle for enqueuing work.
6753 * @cpu: the CPU in question.
6754 *
6755 * Return: 1 if the CPU is currently idle. 0 otherwise.
6756 */
6757int available_idle_cpu(int cpu)
6758{
6759 if (!idle_cpu(cpu))
6760 return 0;
6761
6762 if (vcpu_is_preempted(cpu))
6763 return 0;
6764
6765 return 1;
6766}
6767
6768/**
6769 * idle_task - return the idle task for a given CPU.
6770 * @cpu: the processor in question.
6771 *
6772 * Return: The idle task for the CPU @cpu.
6773 */
6774struct task_struct *idle_task(int cpu)
6775{
6776 return cpu_rq(cpu)->idle;
6777}
6778
6779#ifdef CONFIG_SMP
6780/*
6781 * This function computes an effective utilization for the given CPU, to be
6782 * used for frequency selection given the linear relation: f = u * f_max.
6783 *
6784 * The scheduler tracks the following metrics:
6785 *
6786 * cpu_util_{cfs,rt,dl,irq}()
6787 * cpu_bw_dl()
6788 *
6789 * Where the cfs,rt and dl util numbers are tracked with the same metric and
6790 * synchronized windows and are thus directly comparable.
6791 *
6792 * The cfs,rt,dl utilization are the running times measured with rq->clock_task
6793 * which excludes things like IRQ and steal-time. These latter are then accrued
6794 * in the irq utilization.
6795 *
6796 * The DL bandwidth number otoh is not a measured metric but a value computed
6797 * based on the task model parameters and gives the minimal utilization
6798 * required to meet deadlines.
6799 */
6800unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
6801 unsigned long max, enum cpu_util_type type,
6802 struct task_struct *p)
6803{
6804 unsigned long dl_util, util, irq;
6805 struct rq *rq = cpu_rq(cpu);
6806
6807 if (!uclamp_is_used() &&
6808 type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt)) {
6809 return max;
6810 }
6811
6812 /*
6813 * Early check to see if IRQ/steal time saturates the CPU, can be
6814 * because of inaccuracies in how we track these -- see
6815 * update_irq_load_avg().
6816 */
6817 irq = cpu_util_irq(rq);
6818 if (unlikely(irq >= max))
6819 return max;
6820
6821 /*
6822 * Because the time spend on RT/DL tasks is visible as 'lost' time to
6823 * CFS tasks and we use the same metric to track the effective
6824 * utilization (PELT windows are synchronized) we can directly add them
6825 * to obtain the CPU's actual utilization.
6826 *
6827 * CFS and RT utilization can be boosted or capped, depending on
6828 * utilization clamp constraints requested by currently RUNNABLE
6829 * tasks.
6830 * When there are no CFS RUNNABLE tasks, clamps are released and
6831 * frequency will be gracefully reduced with the utilization decay.
6832 */
6833 util = util_cfs + cpu_util_rt(rq);
6834 if (type == FREQUENCY_UTIL)
6835 util = uclamp_rq_util_with(rq, util, p);
6836
6837 dl_util = cpu_util_dl(rq);
6838
6839 /*
6840 * For frequency selection we do not make cpu_util_dl() a permanent part
6841 * of this sum because we want to use cpu_bw_dl() later on, but we need
6842 * to check if the CFS+RT+DL sum is saturated (ie. no idle time) such
6843 * that we select f_max when there is no idle time.
6844 *
6845 * NOTE: numerical errors or stop class might cause us to not quite hit
6846 * saturation when we should -- something for later.
6847 */
6848 if (util + dl_util >= max)
6849 return max;
6850
6851 /*
6852 * OTOH, for energy computation we need the estimated running time, so
6853 * include util_dl and ignore dl_bw.
6854 */
6855 if (type == ENERGY_UTIL)
6856 util += dl_util;
6857
6858 /*
6859 * There is still idle time; further improve the number by using the
6860 * irq metric. Because IRQ/steal time is hidden from the task clock we
6861 * need to scale the task numbers:
6862 *
6863 * max - irq
6864 * U' = irq + --------- * U
6865 * max
6866 */
6867 util = scale_irq_capacity(util, irq, max);
6868 util += irq;
6869
6870 /*
6871 * Bandwidth required by DEADLINE must always be granted while, for
6872 * FAIR and RT, we use blocked utilization of IDLE CPUs as a mechanism
6873 * to gracefully reduce the frequency when no tasks show up for longer
6874 * periods of time.
6875 *
6876 * Ideally we would like to set bw_dl as min/guaranteed freq and util +
6877 * bw_dl as requested freq. However, cpufreq is not yet ready for such
6878 * an interface. So, we only do the latter for now.
6879 */
6880 if (type == FREQUENCY_UTIL)
6881 util += cpu_bw_dl(rq);
6882
6883 return min(max, util);
6884}
6885
6886unsigned long sched_cpu_util(int cpu, unsigned long max)
6887{
6888 return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max,
6889 ENERGY_UTIL, NULL);
6890}
6891#endif /* CONFIG_SMP */
6892
6893/**
6894 * find_process_by_pid - find a process with a matching PID value.
6895 * @pid: the pid in question.
6896 *
6897 * The task of @pid, if found. %NULL otherwise.
6898 */
6899static struct task_struct *find_process_by_pid(pid_t pid)
6900{
6901 return pid ? find_task_by_vpid(pid) : current;
6902}
6903
6904/*
6905 * sched_setparam() passes in -1 for its policy, to let the functions
6906 * it calls know not to change it.
6907 */
6908#define SETPARAM_POLICY -1
6909
6910static void __setscheduler_params(struct task_struct *p,
6911 const struct sched_attr *attr)
6912{
6913 int policy = attr->sched_policy;
6914
6915 if (policy == SETPARAM_POLICY)
6916 policy = p->policy;
6917
6918 p->policy = policy;
6919
6920 if (dl_policy(policy))
6921 __setparam_dl(p, attr);
6922 else if (fair_policy(policy))
6923 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
6924
6925 /*
6926 * __sched_setscheduler() ensures attr->sched_priority == 0 when
6927 * !rt_policy. Always setting this ensures that things like
6928 * getparam()/getattr() don't report silly values for !rt tasks.
6929 */
6930 p->rt_priority = attr->sched_priority;
6931 p->normal_prio = normal_prio(p);
6932 set_load_weight(p, true);
6933}
6934
6935/*
6936 * Check the target process has a UID that matches the current process's:
6937 */
6938static bool check_same_owner(struct task_struct *p)
6939{
6940 const struct cred *cred = current_cred(), *pcred;
6941 bool match;
6942
6943 rcu_read_lock();
6944 pcred = __task_cred(p);
6945 match = (uid_eq(cred->euid, pcred->euid) ||
6946 uid_eq(cred->euid, pcred->uid));
6947 rcu_read_unlock();
6948 return match;
6949}
6950
6951static int __sched_setscheduler(struct task_struct *p,
6952 const struct sched_attr *attr,
6953 bool user, bool pi)
6954{
6955 int oldpolicy = -1, policy = attr->sched_policy;
6956 int retval, oldprio, newprio, queued, running;
6957 const struct sched_class *prev_class;
6958 struct callback_head *head;
6959 struct rq_flags rf;
6960 int reset_on_fork;
6961 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
6962 struct rq *rq;
6963
6964 /* The pi code expects interrupts enabled */
6965 BUG_ON(pi && in_interrupt());
6966recheck:
6967 /* Double check policy once rq lock held: */
6968 if (policy < 0) {
6969 reset_on_fork = p->sched_reset_on_fork;
6970 policy = oldpolicy = p->policy;
6971 } else {
6972 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
6973
6974 if (!valid_policy(policy))
6975 return -EINVAL;
6976 }
6977
6978 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
6979 return -EINVAL;
6980
6981 /*
6982 * Valid priorities for SCHED_FIFO and SCHED_RR are
6983 * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
6984 * SCHED_BATCH and SCHED_IDLE is 0.
6985 */
6986 if (attr->sched_priority > MAX_RT_PRIO-1)
6987 return -EINVAL;
6988 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
6989 (rt_policy(policy) != (attr->sched_priority != 0)))
6990 return -EINVAL;
6991
6992 /*
6993 * Allow unprivileged RT tasks to decrease priority:
6994 */
6995 if (user && !capable(CAP_SYS_NICE)) {
6996 if (fair_policy(policy)) {
6997 if (attr->sched_nice < task_nice(p) &&
6998 !can_nice(p, attr->sched_nice))
6999 return -EPERM;
7000 }
7001
7002 if (rt_policy(policy)) {
7003 unsigned long rlim_rtprio =
7004 task_rlimit(p, RLIMIT_RTPRIO);
7005
7006 /* Can't set/change the rt policy: */
7007 if (policy != p->policy && !rlim_rtprio)
7008 return -EPERM;
7009
7010 /* Can't increase priority: */
7011 if (attr->sched_priority > p->rt_priority &&
7012 attr->sched_priority > rlim_rtprio)
7013 return -EPERM;
7014 }
7015
7016 /*
7017 * Can't set/change SCHED_DEADLINE policy at all for now
7018 * (safest behavior); in the future we would like to allow
7019 * unprivileged DL tasks to increase their relative deadline
7020 * or reduce their runtime (both ways reducing utilization)
7021 */
7022 if (dl_policy(policy))
7023 return -EPERM;
7024
7025 /*
7026 * Treat SCHED_IDLE as nice 20. Only allow a switch to
7027 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
7028 */
7029 if (task_has_idle_policy(p) && !idle_policy(policy)) {
7030 if (!can_nice(p, task_nice(p)))
7031 return -EPERM;
7032 }
7033
7034 /* Can't change other user's priorities: */
7035 if (!check_same_owner(p))
7036 return -EPERM;
7037
7038 /* Normal users shall not reset the sched_reset_on_fork flag: */
7039 if (p->sched_reset_on_fork && !reset_on_fork)
7040 return -EPERM;
7041 }
7042
7043 if (user) {
7044 if (attr->sched_flags & SCHED_FLAG_SUGOV)
7045 return -EINVAL;
7046
7047 retval = security_task_setscheduler(p);
7048 if (retval)
7049 return retval;
7050 }
7051
7052 /* Update task specific "requested" clamps */
7053 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
7054 retval = uclamp_validate(p, attr);
7055 if (retval)
7056 return retval;
7057 }
7058
7059 if (pi)
7060 cpuset_read_lock();
7061
7062 /*
7063 * Make sure no PI-waiters arrive (or leave) while we are
7064 * changing the priority of the task:
7065 *
7066 * To be able to change p->policy safely, the appropriate
7067 * runqueue lock must be held.
7068 */
7069 rq = task_rq_lock(p, &rf);
7070 update_rq_clock(rq);
7071
7072 /*
7073 * Changing the policy of the stop threads its a very bad idea:
7074 */
7075 if (p == rq->stop) {
7076 retval = -EINVAL;
7077 goto unlock;
7078 }
7079
7080 /*
7081 * If not changing anything there's no need to proceed further,
7082 * but store a possible modification of reset_on_fork.
7083 */
7084 if (unlikely(policy == p->policy)) {
7085 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
7086 goto change;
7087 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
7088 goto change;
7089 if (dl_policy(policy) && dl_param_changed(p, attr))
7090 goto change;
7091 if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
7092 goto change;
7093
7094 p->sched_reset_on_fork = reset_on_fork;
7095 retval = 0;
7096 goto unlock;
7097 }
7098change:
7099
7100 if (user) {
7101#ifdef CONFIG_RT_GROUP_SCHED
7102 /*
7103 * Do not allow realtime tasks into groups that have no runtime
7104 * assigned.
7105 */
7106 if (rt_bandwidth_enabled() && rt_policy(policy) &&
7107 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
7108 !task_group_is_autogroup(task_group(p))) {
7109 retval = -EPERM;
7110 goto unlock;
7111 }
7112#endif
7113#ifdef CONFIG_SMP
7114 if (dl_bandwidth_enabled() && dl_policy(policy) &&
7115 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
7116 cpumask_t *span = rq->rd->span;
7117
7118 /*
7119 * Don't allow tasks with an affinity mask smaller than
7120 * the entire root_domain to become SCHED_DEADLINE. We
7121 * will also fail if there's no bandwidth available.
7122 */
7123 if (!cpumask_subset(span, p->cpus_ptr) ||
7124 rq->rd->dl_bw.bw == 0) {
7125 retval = -EPERM;
7126 goto unlock;
7127 }
7128 }
7129#endif
7130 }
7131
7132 /* Re-check policy now with rq lock held: */
7133 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
7134 policy = oldpolicy = -1;
7135 task_rq_unlock(rq, p, &rf);
7136 if (pi)
7137 cpuset_read_unlock();
7138 goto recheck;
7139 }
7140
7141 /*
7142 * If setscheduling to SCHED_DEADLINE (or changing the parameters
7143 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
7144 * is available.
7145 */
7146 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
7147 retval = -EBUSY;
7148 goto unlock;
7149 }
7150
7151 p->sched_reset_on_fork = reset_on_fork;
7152 oldprio = p->prio;
7153
7154 newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice);
7155 if (pi) {
7156 /*
7157 * Take priority boosted tasks into account. If the new
7158 * effective priority is unchanged, we just store the new
7159 * normal parameters and do not touch the scheduler class and
7160 * the runqueue. This will be done when the task deboost
7161 * itself.
7162 */
7163 newprio = rt_effective_prio(p, newprio);
7164 if (newprio == oldprio)
7165 queue_flags &= ~DEQUEUE_MOVE;
7166 }
7167
7168 queued = task_on_rq_queued(p);
7169 running = task_current(rq, p);
7170 if (queued)
7171 dequeue_task(rq, p, queue_flags);
7172 if (running)
7173 put_prev_task(rq, p);
7174
7175 prev_class = p->sched_class;
7176
7177 if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
7178 __setscheduler_params(p, attr);
7179 __setscheduler_prio(p, newprio);
7180 }
7181 __setscheduler_uclamp(p, attr);
7182
7183 if (queued) {
7184 /*
7185 * We enqueue to tail when the priority of a task is
7186 * increased (user space view).
7187 */
7188 if (oldprio < p->prio)
7189 queue_flags |= ENQUEUE_HEAD;
7190
7191 enqueue_task(rq, p, queue_flags);
7192 }
7193 if (running)
7194 set_next_task(rq, p);
7195
7196 check_class_changed(rq, p, prev_class, oldprio);
7197
7198 /* Avoid rq from going away on us: */
7199 preempt_disable();
7200 head = splice_balance_callbacks(rq);
7201 task_rq_unlock(rq, p, &rf);
7202
7203 if (pi) {
7204 cpuset_read_unlock();
7205 rt_mutex_adjust_pi(p);
7206 }
7207
7208 /* Run balance callbacks after we've adjusted the PI chain: */
7209 balance_callbacks(rq, head);
7210 preempt_enable();
7211
7212 return 0;
7213
7214unlock:
7215 task_rq_unlock(rq, p, &rf);
7216 if (pi)
7217 cpuset_read_unlock();
7218 return retval;
7219}
7220
7221static int _sched_setscheduler(struct task_struct *p, int policy,
7222 const struct sched_param *param, bool check)
7223{
7224 struct sched_attr attr = {
7225 .sched_policy = policy,
7226 .sched_priority = param->sched_priority,
7227 .sched_nice = PRIO_TO_NICE(p->static_prio),
7228 };
7229
7230 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
7231 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
7232 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
7233 policy &= ~SCHED_RESET_ON_FORK;
7234 attr.sched_policy = policy;
7235 }
7236
7237 return __sched_setscheduler(p, &attr, check, true);
7238}
7239/**
7240 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
7241 * @p: the task in question.
7242 * @policy: new policy.
7243 * @param: structure containing the new RT priority.
7244 *
7245 * Use sched_set_fifo(), read its comment.
7246 *
7247 * Return: 0 on success. An error code otherwise.
7248 *
7249 * NOTE that the task may be already dead.
7250 */
7251int sched_setscheduler(struct task_struct *p, int policy,
7252 const struct sched_param *param)
7253{
7254 return _sched_setscheduler(p, policy, param, true);
7255}
7256
7257int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
7258{
7259 return __sched_setscheduler(p, attr, true, true);
7260}
7261
7262int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
7263{
7264 return __sched_setscheduler(p, attr, false, true);
7265}
7266EXPORT_SYMBOL_GPL(sched_setattr_nocheck);
7267
7268/**
7269 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
7270 * @p: the task in question.
7271 * @policy: new policy.
7272 * @param: structure containing the new RT priority.
7273 *
7274 * Just like sched_setscheduler, only don't bother checking if the
7275 * current context has permission. For example, this is needed in
7276 * stop_machine(): we create temporary high priority worker threads,
7277 * but our caller might not have that capability.
7278 *
7279 * Return: 0 on success. An error code otherwise.
7280 */
7281int sched_setscheduler_nocheck(struct task_struct *p, int policy,
7282 const struct sched_param *param)
7283{
7284 return _sched_setscheduler(p, policy, param, false);
7285}
7286
7287/*
7288 * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
7289 * incapable of resource management, which is the one thing an OS really should
7290 * be doing.
7291 *
7292 * This is of course the reason it is limited to privileged users only.
7293 *
7294 * Worse still; it is fundamentally impossible to compose static priority
7295 * workloads. You cannot take two correctly working static prio workloads
7296 * and smash them together and still expect them to work.
7297 *
7298 * For this reason 'all' FIFO tasks the kernel creates are basically at:
7299 *
7300 * MAX_RT_PRIO / 2
7301 *
7302 * The administrator _MUST_ configure the system, the kernel simply doesn't
7303 * know enough information to make a sensible choice.
7304 */
7305void sched_set_fifo(struct task_struct *p)
7306{
7307 struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
7308 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
7309}
7310EXPORT_SYMBOL_GPL(sched_set_fifo);
7311
7312/*
7313 * For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
7314 */
7315void sched_set_fifo_low(struct task_struct *p)
7316{
7317 struct sched_param sp = { .sched_priority = 1 };
7318 WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
7319}
7320EXPORT_SYMBOL_GPL(sched_set_fifo_low);
7321
7322void sched_set_normal(struct task_struct *p, int nice)
7323{
7324 struct sched_attr attr = {
7325 .sched_policy = SCHED_NORMAL,
7326 .sched_nice = nice,
7327 };
7328 WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
7329}
7330EXPORT_SYMBOL_GPL(sched_set_normal);
7331
7332static int
7333do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
7334{
7335 struct sched_param lparam;
7336 struct task_struct *p;
7337 int retval;
7338
7339 if (!param || pid < 0)
7340 return -EINVAL;
7341 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
7342 return -EFAULT;
7343
7344 rcu_read_lock();
7345 retval = -ESRCH;
7346 p = find_process_by_pid(pid);
7347 if (likely(p))
7348 get_task_struct(p);
7349 rcu_read_unlock();
7350
7351 if (likely(p)) {
7352 retval = sched_setscheduler(p, policy, &lparam);
7353 put_task_struct(p);
7354 }
7355
7356 return retval;
7357}
7358
7359/*
7360 * Mimics kernel/events/core.c perf_copy_attr().
7361 */
7362static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
7363{
7364 u32 size;
7365 int ret;
7366
7367 /* Zero the full structure, so that a short copy will be nice: */
7368 memset(attr, 0, sizeof(*attr));
7369
7370 ret = get_user(size, &uattr->size);
7371 if (ret)
7372 return ret;
7373
7374 /* ABI compatibility quirk: */
7375 if (!size)
7376 size = SCHED_ATTR_SIZE_VER0;
7377 if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
7378 goto err_size;
7379
7380 ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
7381 if (ret) {
7382 if (ret == -E2BIG)
7383 goto err_size;
7384 return ret;
7385 }
7386
7387 if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
7388 size < SCHED_ATTR_SIZE_VER1)
7389 return -EINVAL;
7390
7391 /*
7392 * XXX: Do we want to be lenient like existing syscalls; or do we want
7393 * to be strict and return an error on out-of-bounds values?
7394 */
7395 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
7396
7397 return 0;
7398
7399err_size:
7400 put_user(sizeof(*attr), &uattr->size);
7401 return -E2BIG;
7402}
7403
7404/**
7405 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
7406 * @pid: the pid in question.
7407 * @policy: new policy.
7408 * @param: structure containing the new RT priority.
7409 *
7410 * Return: 0 on success. An error code otherwise.
7411 */
7412SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
7413{
7414 if (policy < 0)
7415 return -EINVAL;
7416
7417 return do_sched_setscheduler(pid, policy, param);
7418}
7419
7420/**
7421 * sys_sched_setparam - set/change the RT priority of a thread
7422 * @pid: the pid in question.
7423 * @param: structure containing the new RT priority.
7424 *
7425 * Return: 0 on success. An error code otherwise.
7426 */
7427SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
7428{
7429 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
7430}
7431
7432/**
7433 * sys_sched_setattr - same as above, but with extended sched_attr
7434 * @pid: the pid in question.
7435 * @uattr: structure containing the extended parameters.
7436 * @flags: for future extension.
7437 */
7438SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
7439 unsigned int, flags)
7440{
7441 struct sched_attr attr;
7442 struct task_struct *p;
7443 int retval;
7444
7445 if (!uattr || pid < 0 || flags)
7446 return -EINVAL;
7447
7448 retval = sched_copy_attr(uattr, &attr);
7449 if (retval)
7450 return retval;
7451
7452 if ((int)attr.sched_policy < 0)
7453 return -EINVAL;
7454 if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
7455 attr.sched_policy = SETPARAM_POLICY;
7456
7457 rcu_read_lock();
7458 retval = -ESRCH;
7459 p = find_process_by_pid(pid);
7460 if (likely(p))
7461 get_task_struct(p);
7462 rcu_read_unlock();
7463
7464 if (likely(p)) {
7465 retval = sched_setattr(p, &attr);
7466 put_task_struct(p);
7467 }
7468
7469 return retval;
7470}
7471
7472/**
7473 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
7474 * @pid: the pid in question.
7475 *
7476 * Return: On success, the policy of the thread. Otherwise, a negative error
7477 * code.
7478 */
7479SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
7480{
7481 struct task_struct *p;
7482 int retval;
7483
7484 if (pid < 0)
7485 return -EINVAL;
7486
7487 retval = -ESRCH;
7488 rcu_read_lock();
7489 p = find_process_by_pid(pid);
7490 if (p) {
7491 retval = security_task_getscheduler(p);
7492 if (!retval)
7493 retval = p->policy
7494 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
7495 }
7496 rcu_read_unlock();
7497 return retval;
7498}
7499
7500/**
7501 * sys_sched_getparam - get the RT priority of a thread
7502 * @pid: the pid in question.
7503 * @param: structure containing the RT priority.
7504 *
7505 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
7506 * code.
7507 */
7508SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
7509{
7510 struct sched_param lp = { .sched_priority = 0 };
7511 struct task_struct *p;
7512 int retval;
7513
7514 if (!param || pid < 0)
7515 return -EINVAL;
7516
7517 rcu_read_lock();
7518 p = find_process_by_pid(pid);
7519 retval = -ESRCH;
7520 if (!p)
7521 goto out_unlock;
7522
7523 retval = security_task_getscheduler(p);
7524 if (retval)
7525 goto out_unlock;
7526
7527 if (task_has_rt_policy(p))
7528 lp.sched_priority = p->rt_priority;
7529 rcu_read_unlock();
7530
7531 /*
7532 * This one might sleep, we cannot do it with a spinlock held ...
7533 */
7534 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
7535
7536 return retval;
7537
7538out_unlock:
7539 rcu_read_unlock();
7540 return retval;
7541}
7542
7543/*
7544 * Copy the kernel size attribute structure (which might be larger
7545 * than what user-space knows about) to user-space.
7546 *
7547 * Note that all cases are valid: user-space buffer can be larger or
7548 * smaller than the kernel-space buffer. The usual case is that both
7549 * have the same size.
7550 */
7551static int
7552sched_attr_copy_to_user(struct sched_attr __user *uattr,
7553 struct sched_attr *kattr,
7554 unsigned int usize)
7555{
7556 unsigned int ksize = sizeof(*kattr);
7557
7558 if (!access_ok(uattr, usize))
7559 return -EFAULT;
7560
7561 /*
7562 * sched_getattr() ABI forwards and backwards compatibility:
7563 *
7564 * If usize == ksize then we just copy everything to user-space and all is good.
7565 *
7566 * If usize < ksize then we only copy as much as user-space has space for,
7567 * this keeps ABI compatibility as well. We skip the rest.
7568 *
7569 * If usize > ksize then user-space is using a newer version of the ABI,
7570 * which part the kernel doesn't know about. Just ignore it - tooling can
7571 * detect the kernel's knowledge of attributes from the attr->size value
7572 * which is set to ksize in this case.
7573 */
7574 kattr->size = min(usize, ksize);
7575
7576 if (copy_to_user(uattr, kattr, kattr->size))
7577 return -EFAULT;
7578
7579 return 0;
7580}
7581
7582/**
7583 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
7584 * @pid: the pid in question.
7585 * @uattr: structure containing the extended parameters.
7586 * @usize: sizeof(attr) for fwd/bwd comp.
7587 * @flags: for future extension.
7588 */
7589SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
7590 unsigned int, usize, unsigned int, flags)
7591{
7592 struct sched_attr kattr = { };
7593 struct task_struct *p;
7594 int retval;
7595
7596 if (!uattr || pid < 0 || usize > PAGE_SIZE ||
7597 usize < SCHED_ATTR_SIZE_VER0 || flags)
7598 return -EINVAL;
7599
7600 rcu_read_lock();
7601 p = find_process_by_pid(pid);
7602 retval = -ESRCH;
7603 if (!p)
7604 goto out_unlock;
7605
7606 retval = security_task_getscheduler(p);
7607 if (retval)
7608 goto out_unlock;
7609
7610 kattr.sched_policy = p->policy;
7611 if (p->sched_reset_on_fork)
7612 kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
7613 if (task_has_dl_policy(p))
7614 __getparam_dl(p, &kattr);
7615 else if (task_has_rt_policy(p))
7616 kattr.sched_priority = p->rt_priority;
7617 else
7618 kattr.sched_nice = task_nice(p);
7619
7620#ifdef CONFIG_UCLAMP_TASK
7621 /*
7622 * This could race with another potential updater, but this is fine
7623 * because it'll correctly read the old or the new value. We don't need
7624 * to guarantee who wins the race as long as it doesn't return garbage.
7625 */
7626 kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
7627 kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
7628#endif
7629
7630 rcu_read_unlock();
7631
7632 return sched_attr_copy_to_user(uattr, &kattr, usize);
7633
7634out_unlock:
7635 rcu_read_unlock();
7636 return retval;
7637}
7638
7639long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
7640{
7641 cpumask_var_t cpus_allowed, new_mask;
7642 struct task_struct *p;
7643 int retval;
7644
7645 rcu_read_lock();
7646
7647 p = find_process_by_pid(pid);
7648 if (!p) {
7649 rcu_read_unlock();
7650 return -ESRCH;
7651 }
7652
7653 /* Prevent p going away */
7654 get_task_struct(p);
7655 rcu_read_unlock();
7656
7657 if (p->flags & PF_NO_SETAFFINITY) {
7658 retval = -EINVAL;
7659 goto out_put_task;
7660 }
7661 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
7662 retval = -ENOMEM;
7663 goto out_put_task;
7664 }
7665 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
7666 retval = -ENOMEM;
7667 goto out_free_cpus_allowed;
7668 }
7669 retval = -EPERM;
7670 if (!check_same_owner(p)) {
7671 rcu_read_lock();
7672 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
7673 rcu_read_unlock();
7674 goto out_free_new_mask;
7675 }
7676 rcu_read_unlock();
7677 }
7678
7679 retval = security_task_setscheduler(p);
7680 if (retval)
7681 goto out_free_new_mask;
7682
7683
7684 cpuset_cpus_allowed(p, cpus_allowed);
7685 cpumask_and(new_mask, in_mask, cpus_allowed);
7686
7687 /*
7688 * Since bandwidth control happens on root_domain basis,
7689 * if admission test is enabled, we only admit -deadline
7690 * tasks allowed to run on all the CPUs in the task's
7691 * root_domain.
7692 */
7693#ifdef CONFIG_SMP
7694 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
7695 rcu_read_lock();
7696 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
7697 retval = -EBUSY;
7698 rcu_read_unlock();
7699 goto out_free_new_mask;
7700 }
7701 rcu_read_unlock();
7702 }
7703#endif
7704again:
7705 retval = __set_cpus_allowed_ptr(p, new_mask, SCA_CHECK);
7706
7707 if (!retval) {
7708 cpuset_cpus_allowed(p, cpus_allowed);
7709 if (!cpumask_subset(new_mask, cpus_allowed)) {
7710 /*
7711 * We must have raced with a concurrent cpuset
7712 * update. Just reset the cpus_allowed to the
7713 * cpuset's cpus_allowed
7714 */
7715 cpumask_copy(new_mask, cpus_allowed);
7716 goto again;
7717 }
7718 }
7719out_free_new_mask:
7720 free_cpumask_var(new_mask);
7721out_free_cpus_allowed:
7722 free_cpumask_var(cpus_allowed);
7723out_put_task:
7724 put_task_struct(p);
7725 return retval;
7726}
7727
7728static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
7729 struct cpumask *new_mask)
7730{
7731 if (len < cpumask_size())
7732 cpumask_clear(new_mask);
7733 else if (len > cpumask_size())
7734 len = cpumask_size();
7735
7736 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
7737}
7738
7739/**
7740 * sys_sched_setaffinity - set the CPU affinity of a process
7741 * @pid: pid of the process
7742 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
7743 * @user_mask_ptr: user-space pointer to the new CPU mask
7744 *
7745 * Return: 0 on success. An error code otherwise.
7746 */
7747SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
7748 unsigned long __user *, user_mask_ptr)
7749{
7750 cpumask_var_t new_mask;
7751 int retval;
7752
7753 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
7754 return -ENOMEM;
7755
7756 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
7757 if (retval == 0)
7758 retval = sched_setaffinity(pid, new_mask);
7759 free_cpumask_var(new_mask);
7760 return retval;
7761}
7762
7763long sched_getaffinity(pid_t pid, struct cpumask *mask)
7764{
7765 struct task_struct *p;
7766 unsigned long flags;
7767 int retval;
7768
7769 rcu_read_lock();
7770
7771 retval = -ESRCH;
7772 p = find_process_by_pid(pid);
7773 if (!p)
7774 goto out_unlock;
7775
7776 retval = security_task_getscheduler(p);
7777 if (retval)
7778 goto out_unlock;
7779
7780 raw_spin_lock_irqsave(&p->pi_lock, flags);
7781 cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
7782 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
7783
7784out_unlock:
7785 rcu_read_unlock();
7786
7787 return retval;
7788}
7789
7790/**
7791 * sys_sched_getaffinity - get the CPU affinity of a process
7792 * @pid: pid of the process
7793 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
7794 * @user_mask_ptr: user-space pointer to hold the current CPU mask
7795 *
7796 * Return: size of CPU mask copied to user_mask_ptr on success. An
7797 * error code otherwise.
7798 */
7799SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
7800 unsigned long __user *, user_mask_ptr)
7801{
7802 int ret;
7803 cpumask_var_t mask;
7804
7805 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
7806 return -EINVAL;
7807 if (len & (sizeof(unsigned long)-1))
7808 return -EINVAL;
7809
7810 if (!alloc_cpumask_var(&mask, GFP_KERNEL))
7811 return -ENOMEM;
7812
7813 ret = sched_getaffinity(pid, mask);
7814 if (ret == 0) {
7815 unsigned int retlen = min(len, cpumask_size());
7816
7817 if (copy_to_user(user_mask_ptr, mask, retlen))
7818 ret = -EFAULT;
7819 else
7820 ret = retlen;
7821 }
7822 free_cpumask_var(mask);
7823
7824 return ret;
7825}
7826
7827static void do_sched_yield(void)
7828{
7829 struct rq_flags rf;
7830 struct rq *rq;
7831
7832 rq = this_rq_lock_irq(&rf);
7833
7834 schedstat_inc(rq->yld_count);
7835 current->sched_class->yield_task(rq);
7836
7837 preempt_disable();
7838 rq_unlock_irq(rq, &rf);
7839 sched_preempt_enable_no_resched();
7840
7841 schedule();
7842}
7843
7844/**
7845 * sys_sched_yield - yield the current processor to other threads.
7846 *
7847 * This function yields the current CPU to other tasks. If there are no
7848 * other threads running on this CPU then this function will return.
7849 *
7850 * Return: 0.
7851 */
7852SYSCALL_DEFINE0(sched_yield)
7853{
7854 do_sched_yield();
7855 return 0;
7856}
7857
7858#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
7859int __sched __cond_resched(void)
7860{
7861 if (should_resched(0)) {
7862 preempt_schedule_common();
7863 return 1;
7864 }
7865#ifndef CONFIG_PREEMPT_RCU
7866 rcu_all_qs();
7867#endif
7868 return 0;
7869}
7870EXPORT_SYMBOL(__cond_resched);
7871#endif
7872
7873#ifdef CONFIG_PREEMPT_DYNAMIC
7874DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
7875EXPORT_STATIC_CALL_TRAMP(cond_resched);
7876
7877DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
7878EXPORT_STATIC_CALL_TRAMP(might_resched);
7879#endif
7880
7881/*
7882 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
7883 * call schedule, and on return reacquire the lock.
7884 *
7885 * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
7886 * operations here to prevent schedule() from being called twice (once via
7887 * spin_unlock(), once by hand).
7888 */
7889int __cond_resched_lock(spinlock_t *lock)
7890{
7891 int resched = should_resched(PREEMPT_LOCK_OFFSET);
7892 int ret = 0;
7893
7894 lockdep_assert_held(lock);
7895
7896 if (spin_needbreak(lock) || resched) {
7897 spin_unlock(lock);
7898 if (resched)
7899 preempt_schedule_common();
7900 else
7901 cpu_relax();
7902 ret = 1;
7903 spin_lock(lock);
7904 }
7905 return ret;
7906}
7907EXPORT_SYMBOL(__cond_resched_lock);
7908
7909int __cond_resched_rwlock_read(rwlock_t *lock)
7910{
7911 int resched = should_resched(PREEMPT_LOCK_OFFSET);
7912 int ret = 0;
7913
7914 lockdep_assert_held_read(lock);
7915
7916 if (rwlock_needbreak(lock) || resched) {
7917 read_unlock(lock);
7918 if (resched)
7919 preempt_schedule_common();
7920 else
7921 cpu_relax();
7922 ret = 1;
7923 read_lock(lock);
7924 }
7925 return ret;
7926}
7927EXPORT_SYMBOL(__cond_resched_rwlock_read);
7928
7929int __cond_resched_rwlock_write(rwlock_t *lock)
7930{
7931 int resched = should_resched(PREEMPT_LOCK_OFFSET);
7932 int ret = 0;
7933
7934 lockdep_assert_held_write(lock);
7935
7936 if (rwlock_needbreak(lock) || resched) {
7937 write_unlock(lock);
7938 if (resched)
7939 preempt_schedule_common();
7940 else
7941 cpu_relax();
7942 ret = 1;
7943 write_lock(lock);
7944 }
7945 return ret;
7946}
7947EXPORT_SYMBOL(__cond_resched_rwlock_write);
7948
7949/**
7950 * yield - yield the current processor to other threads.
7951 *
7952 * Do not ever use this function, there's a 99% chance you're doing it wrong.
7953 *
7954 * The scheduler is at all times free to pick the calling task as the most
7955 * eligible task to run, if removing the yield() call from your code breaks
7956 * it, it's already broken.
7957 *
7958 * Typical broken usage is:
7959 *
7960 * while (!event)
7961 * yield();
7962 *
7963 * where one assumes that yield() will let 'the other' process run that will
7964 * make event true. If the current task is a SCHED_FIFO task that will never
7965 * happen. Never use yield() as a progress guarantee!!
7966 *
7967 * If you want to use yield() to wait for something, use wait_event().
7968 * If you want to use yield() to be 'nice' for others, use cond_resched().
7969 * If you still want to use yield(), do not!
7970 */
7971void __sched yield(void)
7972{
7973 set_current_state(TASK_RUNNING);
7974 do_sched_yield();
7975}
7976EXPORT_SYMBOL(yield);
7977
7978/**
7979 * yield_to - yield the current processor to another thread in
7980 * your thread group, or accelerate that thread toward the
7981 * processor it's on.
7982 * @p: target task
7983 * @preempt: whether task preemption is allowed or not
7984 *
7985 * It's the caller's job to ensure that the target task struct
7986 * can't go away on us before we can do any checks.
7987 *
7988 * Return:
7989 * true (>0) if we indeed boosted the target task.
7990 * false (0) if we failed to boost the target.
7991 * -ESRCH if there's no task to yield to.
7992 */
7993int __sched yield_to(struct task_struct *p, bool preempt)
7994{
7995 struct task_struct *curr = current;
7996 struct rq *rq, *p_rq;
7997 unsigned long flags;
7998 int yielded = 0;
7999
8000 local_irq_save(flags);
8001 rq = this_rq();
8002
8003again:
8004 p_rq = task_rq(p);
8005 /*
8006 * If we're the only runnable task on the rq and target rq also
8007 * has only one task, there's absolutely no point in yielding.
8008 */
8009 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
8010 yielded = -ESRCH;
8011 goto out_irq;
8012 }
8013
8014 double_rq_lock(rq, p_rq);
8015 if (task_rq(p) != p_rq) {
8016 double_rq_unlock(rq, p_rq);
8017 goto again;
8018 }
8019
8020 if (!curr->sched_class->yield_to_task)
8021 goto out_unlock;
8022
8023 if (curr->sched_class != p->sched_class)
8024 goto out_unlock;
8025
8026 if (task_running(p_rq, p) || !task_is_running(p))
8027 goto out_unlock;
8028
8029 yielded = curr->sched_class->yield_to_task(rq, p);
8030 if (yielded) {
8031 schedstat_inc(rq->yld_count);
8032 /*
8033 * Make p's CPU reschedule; pick_next_entity takes care of
8034 * fairness.
8035 */
8036 if (preempt && rq != p_rq)
8037 resched_curr(p_rq);
8038 }
8039
8040out_unlock:
8041 double_rq_unlock(rq, p_rq);
8042out_irq:
8043 local_irq_restore(flags);
8044
8045 if (yielded > 0)
8046 schedule();
8047
8048 return yielded;
8049}
8050EXPORT_SYMBOL_GPL(yield_to);
8051
8052int io_schedule_prepare(void)
8053{
8054 int old_iowait = current->in_iowait;
8055
8056 current->in_iowait = 1;
8057 blk_schedule_flush_plug(current);
8058
8059 return old_iowait;
8060}
8061
8062void io_schedule_finish(int token)
8063{
8064 current->in_iowait = token;
8065}
8066
8067/*
8068 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
8069 * that process accounting knows that this is a task in IO wait state.
8070 */
8071long __sched io_schedule_timeout(long timeout)
8072{
8073 int token;
8074 long ret;
8075
8076 token = io_schedule_prepare();
8077 ret = schedule_timeout(timeout);
8078 io_schedule_finish(token);
8079
8080 return ret;
8081}
8082EXPORT_SYMBOL(io_schedule_timeout);
8083
8084void __sched io_schedule(void)
8085{
8086 int token;
8087
8088 token = io_schedule_prepare();
8089 schedule();
8090 io_schedule_finish(token);
8091}
8092EXPORT_SYMBOL(io_schedule);
8093
8094/**
8095 * sys_sched_get_priority_max - return maximum RT priority.
8096 * @policy: scheduling class.
8097 *
8098 * Return: On success, this syscall returns the maximum
8099 * rt_priority that can be used by a given scheduling class.
8100 * On failure, a negative error code is returned.
8101 */
8102SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
8103{
8104 int ret = -EINVAL;
8105
8106 switch (policy) {
8107 case SCHED_FIFO:
8108 case SCHED_RR:
8109 ret = MAX_RT_PRIO-1;
8110 break;
8111 case SCHED_DEADLINE:
8112 case SCHED_NORMAL:
8113 case SCHED_BATCH:
8114 case SCHED_IDLE:
8115 ret = 0;
8116 break;
8117 }
8118 return ret;
8119}
8120
8121/**
8122 * sys_sched_get_priority_min - return minimum RT priority.
8123 * @policy: scheduling class.
8124 *
8125 * Return: On success, this syscall returns the minimum
8126 * rt_priority that can be used by a given scheduling class.
8127 * On failure, a negative error code is returned.
8128 */
8129SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
8130{
8131 int ret = -EINVAL;
8132
8133 switch (policy) {
8134 case SCHED_FIFO:
8135 case SCHED_RR:
8136 ret = 1;
8137 break;
8138 case SCHED_DEADLINE:
8139 case SCHED_NORMAL:
8140 case SCHED_BATCH:
8141 case SCHED_IDLE:
8142 ret = 0;
8143 }
8144 return ret;
8145}
8146
8147static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
8148{
8149 struct task_struct *p;
8150 unsigned int time_slice;
8151 struct rq_flags rf;
8152 struct rq *rq;
8153 int retval;
8154
8155 if (pid < 0)
8156 return -EINVAL;
8157
8158 retval = -ESRCH;
8159 rcu_read_lock();
8160 p = find_process_by_pid(pid);
8161 if (!p)
8162 goto out_unlock;
8163
8164 retval = security_task_getscheduler(p);
8165 if (retval)
8166 goto out_unlock;
8167
8168 rq = task_rq_lock(p, &rf);
8169 time_slice = 0;
8170 if (p->sched_class->get_rr_interval)
8171 time_slice = p->sched_class->get_rr_interval(rq, p);
8172 task_rq_unlock(rq, p, &rf);
8173
8174 rcu_read_unlock();
8175 jiffies_to_timespec64(time_slice, t);
8176 return 0;
8177
8178out_unlock:
8179 rcu_read_unlock();
8180 return retval;
8181}
8182
8183/**
8184 * sys_sched_rr_get_interval - return the default timeslice of a process.
8185 * @pid: pid of the process.
8186 * @interval: userspace pointer to the timeslice value.
8187 *
8188 * this syscall writes the default timeslice value of a given process
8189 * into the user-space timespec buffer. A value of '0' means infinity.
8190 *
8191 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
8192 * an error code.
8193 */
8194SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
8195 struct __kernel_timespec __user *, interval)
8196{
8197 struct timespec64 t;
8198 int retval = sched_rr_get_interval(pid, &t);
8199
8200 if (retval == 0)
8201 retval = put_timespec64(&t, interval);
8202
8203 return retval;
8204}
8205
8206#ifdef CONFIG_COMPAT_32BIT_TIME
8207SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
8208 struct old_timespec32 __user *, interval)
8209{
8210 struct timespec64 t;
8211 int retval = sched_rr_get_interval(pid, &t);
8212
8213 if (retval == 0)
8214 retval = put_old_timespec32(&t, interval);
8215 return retval;
8216}
8217#endif
8218
8219void sched_show_task(struct task_struct *p)
8220{
8221 unsigned long free = 0;
8222 int ppid;
8223
8224 if (!try_get_task_stack(p))
8225 return;
8226
8227 pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
8228
8229 if (task_is_running(p))
8230 pr_cont(" running task ");
8231#ifdef CONFIG_DEBUG_STACK_USAGE
8232 free = stack_not_used(p);
8233#endif
8234 ppid = 0;
8235 rcu_read_lock();
8236 if (pid_alive(p))
8237 ppid = task_pid_nr(rcu_dereference(p->real_parent));
8238 rcu_read_unlock();
8239 pr_cont(" stack:%5lu pid:%5d ppid:%6d flags:0x%08lx\n",
8240 free, task_pid_nr(p), ppid,
8241 (unsigned long)task_thread_info(p)->flags);
8242
8243 print_worker_info(KERN_INFO, p);
8244 print_stop_info(KERN_INFO, p);
8245 show_stack(p, NULL, KERN_INFO);
8246 put_task_stack(p);
8247}
8248EXPORT_SYMBOL_GPL(sched_show_task);
8249
8250static inline bool
8251state_filter_match(unsigned long state_filter, struct task_struct *p)
8252{
8253 unsigned int state = READ_ONCE(p->__state);
8254
8255 /* no filter, everything matches */
8256 if (!state_filter)
8257 return true;
8258
8259 /* filter, but doesn't match */
8260 if (!(state & state_filter))
8261 return false;
8262
8263 /*
8264 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
8265 * TASK_KILLABLE).
8266 */
8267 if (state_filter == TASK_UNINTERRUPTIBLE && state == TASK_IDLE)
8268 return false;
8269
8270 return true;
8271}
8272
8273
8274void show_state_filter(unsigned int state_filter)
8275{
8276 struct task_struct *g, *p;
8277
8278 rcu_read_lock();
8279 for_each_process_thread(g, p) {
8280 /*
8281 * reset the NMI-timeout, listing all files on a slow
8282 * console might take a lot of time:
8283 * Also, reset softlockup watchdogs on all CPUs, because
8284 * another CPU might be blocked waiting for us to process
8285 * an IPI.
8286 */
8287 touch_nmi_watchdog();
8288 touch_all_softlockup_watchdogs();
8289 if (state_filter_match(state_filter, p))
8290 sched_show_task(p);
8291 }
8292
8293#ifdef CONFIG_SCHED_DEBUG
8294 if (!state_filter)
8295 sysrq_sched_debug_show();
8296#endif
8297 rcu_read_unlock();
8298 /*
8299 * Only show locks if all tasks are dumped:
8300 */
8301 if (!state_filter)
8302 debug_show_all_locks();
8303}
8304
8305/**
8306 * init_idle - set up an idle thread for a given CPU
8307 * @idle: task in question
8308 * @cpu: CPU the idle task belongs to
8309 *
8310 * NOTE: this function does not set the idle thread's NEED_RESCHED
8311 * flag, to make booting more robust.
8312 */
8313void __init init_idle(struct task_struct *idle, int cpu)
8314{
8315 struct rq *rq = cpu_rq(cpu);
8316 unsigned long flags;
8317
8318 __sched_fork(0, idle);
8319
8320 /*
8321 * The idle task doesn't need the kthread struct to function, but it
8322 * is dressed up as a per-CPU kthread and thus needs to play the part
8323 * if we want to avoid special-casing it in code that deals with per-CPU
8324 * kthreads.
8325 */
8326 set_kthread_struct(idle);
8327
8328 raw_spin_lock_irqsave(&idle->pi_lock, flags);
8329 raw_spin_rq_lock(rq);
8330
8331 idle->__state = TASK_RUNNING;
8332 idle->se.exec_start = sched_clock();
8333 /*
8334 * PF_KTHREAD should already be set at this point; regardless, make it
8335 * look like a proper per-CPU kthread.
8336 */
8337 idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY;
8338 kthread_set_per_cpu(idle, cpu);
8339
8340 scs_task_reset(idle);
8341 kasan_unpoison_task_stack(idle);
8342
8343#ifdef CONFIG_SMP
8344 /*
8345 * It's possible that init_idle() gets called multiple times on a task,
8346 * in that case do_set_cpus_allowed() will not do the right thing.
8347 *
8348 * And since this is boot we can forgo the serialization.
8349 */
8350 set_cpus_allowed_common(idle, cpumask_of(cpu), 0);
8351#endif
8352 /*
8353 * We're having a chicken and egg problem, even though we are
8354 * holding rq->lock, the CPU isn't yet set to this CPU so the
8355 * lockdep check in task_group() will fail.
8356 *
8357 * Similar case to sched_fork(). / Alternatively we could
8358 * use task_rq_lock() here and obtain the other rq->lock.
8359 *
8360 * Silence PROVE_RCU
8361 */
8362 rcu_read_lock();
8363 __set_task_cpu(idle, cpu);
8364 rcu_read_unlock();
8365
8366 rq->idle = idle;
8367 rcu_assign_pointer(rq->curr, idle);
8368 idle->on_rq = TASK_ON_RQ_QUEUED;
8369#ifdef CONFIG_SMP
8370 idle->on_cpu = 1;
8371#endif
8372 raw_spin_rq_unlock(rq);
8373 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
8374
8375 /* Set the preempt count _outside_ the spinlocks! */
8376 init_idle_preempt_count(idle, cpu);
8377
8378 /*
8379 * The idle tasks have their own, simple scheduling class:
8380 */
8381 idle->sched_class = &idle_sched_class;
8382 ftrace_graph_init_idle_task(idle, cpu);
8383 vtime_init_idle(idle, cpu);
8384#ifdef CONFIG_SMP
8385 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
8386#endif
8387}
8388
8389#ifdef CONFIG_SMP
8390
8391int cpuset_cpumask_can_shrink(const struct cpumask *cur,
8392 const struct cpumask *trial)
8393{
8394 int ret = 1;
8395
8396 if (!cpumask_weight(cur))
8397 return ret;
8398
8399 ret = dl_cpuset_cpumask_can_shrink(cur, trial);
8400
8401 return ret;
8402}
8403
8404int task_can_attach(struct task_struct *p,
8405 const struct cpumask *cs_cpus_allowed)
8406{
8407 int ret = 0;
8408
8409 /*
8410 * Kthreads which disallow setaffinity shouldn't be moved
8411 * to a new cpuset; we don't want to change their CPU
8412 * affinity and isolating such threads by their set of
8413 * allowed nodes is unnecessary. Thus, cpusets are not
8414 * applicable for such threads. This prevents checking for
8415 * success of set_cpus_allowed_ptr() on all attached tasks
8416 * before cpus_mask may be changed.
8417 */
8418 if (p->flags & PF_NO_SETAFFINITY) {
8419 ret = -EINVAL;
8420 goto out;
8421 }
8422
8423 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
8424 cs_cpus_allowed))
8425 ret = dl_task_can_attach(p, cs_cpus_allowed);
8426
8427out:
8428 return ret;
8429}
8430
8431bool sched_smp_initialized __read_mostly;
8432
8433#ifdef CONFIG_NUMA_BALANCING
8434/* Migrate current task p to target_cpu */
8435int migrate_task_to(struct task_struct *p, int target_cpu)
8436{
8437 struct migration_arg arg = { p, target_cpu };
8438 int curr_cpu = task_cpu(p);
8439
8440 if (curr_cpu == target_cpu)
8441 return 0;
8442
8443 if (!cpumask_test_cpu(target_cpu, p->cpus_ptr))
8444 return -EINVAL;
8445
8446 /* TODO: This is not properly updating schedstats */
8447
8448 trace_sched_move_numa(p, curr_cpu, target_cpu);
8449 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
8450}
8451
8452/*
8453 * Requeue a task on a given node and accurately track the number of NUMA
8454 * tasks on the runqueues
8455 */
8456void sched_setnuma(struct task_struct *p, int nid)
8457{
8458 bool queued, running;
8459 struct rq_flags rf;
8460 struct rq *rq;
8461
8462 rq = task_rq_lock(p, &rf);
8463 queued = task_on_rq_queued(p);
8464 running = task_current(rq, p);
8465
8466 if (queued)
8467 dequeue_task(rq, p, DEQUEUE_SAVE);
8468 if (running)
8469 put_prev_task(rq, p);
8470
8471 p->numa_preferred_nid = nid;
8472
8473 if (queued)
8474 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
8475 if (running)
8476 set_next_task(rq, p);
8477 task_rq_unlock(rq, p, &rf);
8478}
8479#endif /* CONFIG_NUMA_BALANCING */
8480
8481#ifdef CONFIG_HOTPLUG_CPU
8482/*
8483 * Ensure that the idle task is using init_mm right before its CPU goes
8484 * offline.
8485 */
8486void idle_task_exit(void)
8487{
8488 struct mm_struct *mm = current->active_mm;
8489
8490 BUG_ON(cpu_online(smp_processor_id()));
8491 BUG_ON(current != this_rq()->idle);
8492
8493 if (mm != &init_mm) {
8494 switch_mm(mm, &init_mm, current);
8495 finish_arch_post_lock_switch();
8496 }
8497
8498 scs_task_reset(current);
8499 /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
8500}
8501
8502static int __balance_push_cpu_stop(void *arg)
8503{
8504 struct task_struct *p = arg;
8505 struct rq *rq = this_rq();
8506 struct rq_flags rf;
8507 int cpu;
8508
8509 raw_spin_lock_irq(&p->pi_lock);
8510 rq_lock(rq, &rf);
8511
8512 update_rq_clock(rq);
8513
8514 if (task_rq(p) == rq && task_on_rq_queued(p)) {
8515 cpu = select_fallback_rq(rq->cpu, p);
8516 rq = __migrate_task(rq, &rf, p, cpu);
8517 }
8518
8519 rq_unlock(rq, &rf);
8520 raw_spin_unlock_irq(&p->pi_lock);
8521
8522 put_task_struct(p);
8523
8524 return 0;
8525}
8526
8527static DEFINE_PER_CPU(struct cpu_stop_work, push_work);
8528
8529/*
8530 * Ensure we only run per-cpu kthreads once the CPU goes !active.
8531 *
8532 * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only
8533 * effective when the hotplug motion is down.
8534 */
8535static void balance_push(struct rq *rq)
8536{
8537 struct task_struct *push_task = rq->curr;
8538
8539 lockdep_assert_rq_held(rq);
8540
8541 /*
8542 * Ensure the thing is persistent until balance_push_set(.on = false);
8543 */
8544 rq->balance_callback = &balance_push_callback;
8545
8546 /*
8547 * Only active while going offline and when invoked on the outgoing
8548 * CPU.
8549 */
8550 if (!cpu_dying(rq->cpu) || rq != this_rq())
8551 return;
8552
8553 /*
8554 * Both the cpu-hotplug and stop task are in this case and are
8555 * required to complete the hotplug process.
8556 */
8557 if (kthread_is_per_cpu(push_task) ||
8558 is_migration_disabled(push_task)) {
8559
8560 /*
8561 * If this is the idle task on the outgoing CPU try to wake
8562 * up the hotplug control thread which might wait for the
8563 * last task to vanish. The rcuwait_active() check is
8564 * accurate here because the waiter is pinned on this CPU
8565 * and can't obviously be running in parallel.
8566 *
8567 * On RT kernels this also has to check whether there are
8568 * pinned and scheduled out tasks on the runqueue. They
8569 * need to leave the migrate disabled section first.
8570 */
8571 if (!rq->nr_running && !rq_has_pinned_tasks(rq) &&
8572 rcuwait_active(&rq->hotplug_wait)) {
8573 raw_spin_rq_unlock(rq);
8574 rcuwait_wake_up(&rq->hotplug_wait);
8575 raw_spin_rq_lock(rq);
8576 }
8577 return;
8578 }
8579
8580 get_task_struct(push_task);
8581 /*
8582 * Temporarily drop rq->lock such that we can wake-up the stop task.
8583 * Both preemption and IRQs are still disabled.
8584 */
8585 raw_spin_rq_unlock(rq);
8586 stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task,
8587 this_cpu_ptr(&push_work));
8588 /*
8589 * At this point need_resched() is true and we'll take the loop in
8590 * schedule(). The next pick is obviously going to be the stop task
8591 * which kthread_is_per_cpu() and will push this task away.
8592 */
8593 raw_spin_rq_lock(rq);
8594}
8595
8596static void balance_push_set(int cpu, bool on)
8597{
8598 struct rq *rq = cpu_rq(cpu);
8599 struct rq_flags rf;
8600
8601 rq_lock_irqsave(rq, &rf);
8602 if (on) {
8603 WARN_ON_ONCE(rq->balance_callback);
8604 rq->balance_callback = &balance_push_callback;
8605 } else if (rq->balance_callback == &balance_push_callback) {
8606 rq->balance_callback = NULL;
8607 }
8608 rq_unlock_irqrestore(rq, &rf);
8609}
8610
8611/*
8612 * Invoked from a CPUs hotplug control thread after the CPU has been marked
8613 * inactive. All tasks which are not per CPU kernel threads are either
8614 * pushed off this CPU now via balance_push() or placed on a different CPU
8615 * during wakeup. Wait until the CPU is quiescent.
8616 */
8617static void balance_hotplug_wait(void)
8618{
8619 struct rq *rq = this_rq();
8620
8621 rcuwait_wait_event(&rq->hotplug_wait,
8622 rq->nr_running == 1 && !rq_has_pinned_tasks(rq),
8623 TASK_UNINTERRUPTIBLE);
8624}
8625
8626#else
8627
8628static inline void balance_push(struct rq *rq)
8629{
8630}
8631
8632static inline void balance_push_set(int cpu, bool on)
8633{
8634}
8635
8636static inline void balance_hotplug_wait(void)
8637{
8638}
8639
8640#endif /* CONFIG_HOTPLUG_CPU */
8641
8642void set_rq_online(struct rq *rq)
8643{
8644 if (!rq->online) {
8645 const struct sched_class *class;
8646
8647 cpumask_set_cpu(rq->cpu, rq->rd->online);
8648 rq->online = 1;
8649
8650 for_each_class(class) {
8651 if (class->rq_online)
8652 class->rq_online(rq);
8653 }
8654 }
8655}
8656
8657void set_rq_offline(struct rq *rq)
8658{
8659 if (rq->online) {
8660 const struct sched_class *class;
8661
8662 for_each_class(class) {
8663 if (class->rq_offline)
8664 class->rq_offline(rq);
8665 }
8666
8667 cpumask_clear_cpu(rq->cpu, rq->rd->online);
8668 rq->online = 0;
8669 }
8670}
8671
8672/*
8673 * used to mark begin/end of suspend/resume:
8674 */
8675static int num_cpus_frozen;
8676
8677/*
8678 * Update cpusets according to cpu_active mask. If cpusets are
8679 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
8680 * around partition_sched_domains().
8681 *
8682 * If we come here as part of a suspend/resume, don't touch cpusets because we
8683 * want to restore it back to its original state upon resume anyway.
8684 */
8685static void cpuset_cpu_active(void)
8686{
8687 if (cpuhp_tasks_frozen) {
8688 /*
8689 * num_cpus_frozen tracks how many CPUs are involved in suspend
8690 * resume sequence. As long as this is not the last online
8691 * operation in the resume sequence, just build a single sched
8692 * domain, ignoring cpusets.
8693 */
8694 partition_sched_domains(1, NULL, NULL);
8695 if (--num_cpus_frozen)
8696 return;
8697 /*
8698 * This is the last CPU online operation. So fall through and
8699 * restore the original sched domains by considering the
8700 * cpuset configurations.
8701 */
8702 cpuset_force_rebuild();
8703 }
8704 cpuset_update_active_cpus();
8705}
8706
8707static int cpuset_cpu_inactive(unsigned int cpu)
8708{
8709 if (!cpuhp_tasks_frozen) {
8710 if (dl_cpu_busy(cpu))
8711 return -EBUSY;
8712 cpuset_update_active_cpus();
8713 } else {
8714 num_cpus_frozen++;
8715 partition_sched_domains(1, NULL, NULL);
8716 }
8717 return 0;
8718}
8719
8720int sched_cpu_activate(unsigned int cpu)
8721{
8722 struct rq *rq = cpu_rq(cpu);
8723 struct rq_flags rf;
8724
8725 /*
8726 * Clear the balance_push callback and prepare to schedule
8727 * regular tasks.
8728 */
8729 balance_push_set(cpu, false);
8730
8731#ifdef CONFIG_SCHED_SMT
8732 /*
8733 * When going up, increment the number of cores with SMT present.
8734 */
8735 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
8736 static_branch_inc_cpuslocked(&sched_smt_present);
8737#endif
8738 set_cpu_active(cpu, true);
8739
8740 if (sched_smp_initialized) {
8741 sched_domains_numa_masks_set(cpu);
8742 cpuset_cpu_active();
8743 }
8744
8745 /*
8746 * Put the rq online, if not already. This happens:
8747 *
8748 * 1) In the early boot process, because we build the real domains
8749 * after all CPUs have been brought up.
8750 *
8751 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
8752 * domains.
8753 */
8754 rq_lock_irqsave(rq, &rf);
8755 if (rq->rd) {
8756 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
8757 set_rq_online(rq);
8758 }
8759 rq_unlock_irqrestore(rq, &rf);
8760
8761 return 0;
8762}
8763
8764int sched_cpu_deactivate(unsigned int cpu)
8765{
8766 struct rq *rq = cpu_rq(cpu);
8767 struct rq_flags rf;
8768 int ret;
8769
8770 /*
8771 * Remove CPU from nohz.idle_cpus_mask to prevent participating in
8772 * load balancing when not active
8773 */
8774 nohz_balance_exit_idle(rq);
8775
8776 set_cpu_active(cpu, false);
8777
8778 /*
8779 * From this point forward, this CPU will refuse to run any task that
8780 * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively
8781 * push those tasks away until this gets cleared, see
8782 * sched_cpu_dying().
8783 */
8784 balance_push_set(cpu, true);
8785
8786 /*
8787 * We've cleared cpu_active_mask / set balance_push, wait for all
8788 * preempt-disabled and RCU users of this state to go away such that
8789 * all new such users will observe it.
8790 *
8791 * Specifically, we rely on ttwu to no longer target this CPU, see
8792 * ttwu_queue_cond() and is_cpu_allowed().
8793 *
8794 * Do sync before park smpboot threads to take care the rcu boost case.
8795 */
8796 synchronize_rcu();
8797
8798 rq_lock_irqsave(rq, &rf);
8799 if (rq->rd) {
8800 update_rq_clock(rq);
8801 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
8802 set_rq_offline(rq);
8803 }
8804 rq_unlock_irqrestore(rq, &rf);
8805
8806#ifdef CONFIG_SCHED_SMT
8807 /*
8808 * When going down, decrement the number of cores with SMT present.
8809 */
8810 if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
8811 static_branch_dec_cpuslocked(&sched_smt_present);
8812
8813 sched_core_cpu_deactivate(cpu);
8814#endif
8815
8816 if (!sched_smp_initialized)
8817 return 0;
8818
8819 ret = cpuset_cpu_inactive(cpu);
8820 if (ret) {
8821 balance_push_set(cpu, false);
8822 set_cpu_active(cpu, true);
8823 return ret;
8824 }
8825 sched_domains_numa_masks_clear(cpu);
8826 return 0;
8827}
8828
8829static void sched_rq_cpu_starting(unsigned int cpu)
8830{
8831 struct rq *rq = cpu_rq(cpu);
8832
8833 rq->calc_load_update = calc_load_update;
8834 update_max_interval();
8835}
8836
8837int sched_cpu_starting(unsigned int cpu)
8838{
8839 sched_core_cpu_starting(cpu);
8840 sched_rq_cpu_starting(cpu);
8841 sched_tick_start(cpu);
8842 return 0;
8843}
8844
8845#ifdef CONFIG_HOTPLUG_CPU
8846
8847/*
8848 * Invoked immediately before the stopper thread is invoked to bring the
8849 * CPU down completely. At this point all per CPU kthreads except the
8850 * hotplug thread (current) and the stopper thread (inactive) have been
8851 * either parked or have been unbound from the outgoing CPU. Ensure that
8852 * any of those which might be on the way out are gone.
8853 *
8854 * If after this point a bound task is being woken on this CPU then the
8855 * responsible hotplug callback has failed to do it's job.
8856 * sched_cpu_dying() will catch it with the appropriate fireworks.
8857 */
8858int sched_cpu_wait_empty(unsigned int cpu)
8859{
8860 balance_hotplug_wait();
8861 return 0;
8862}
8863
8864/*
8865 * Since this CPU is going 'away' for a while, fold any nr_active delta we
8866 * might have. Called from the CPU stopper task after ensuring that the
8867 * stopper is the last running task on the CPU, so nr_active count is
8868 * stable. We need to take the teardown thread which is calling this into
8869 * account, so we hand in adjust = 1 to the load calculation.
8870 *
8871 * Also see the comment "Global load-average calculations".
8872 */
8873static void calc_load_migrate(struct rq *rq)
8874{
8875 long delta = calc_load_fold_active(rq, 1);
8876
8877 if (delta)
8878 atomic_long_add(delta, &calc_load_tasks);
8879}
8880
8881static void dump_rq_tasks(struct rq *rq, const char *loglvl)
8882{
8883 struct task_struct *g, *p;
8884 int cpu = cpu_of(rq);
8885
8886 lockdep_assert_rq_held(rq);
8887
8888 printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running);
8889 for_each_process_thread(g, p) {
8890 if (task_cpu(p) != cpu)
8891 continue;
8892
8893 if (!task_on_rq_queued(p))
8894 continue;
8895
8896 printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
8897 }
8898}
8899
8900int sched_cpu_dying(unsigned int cpu)
8901{
8902 struct rq *rq = cpu_rq(cpu);
8903 struct rq_flags rf;
8904
8905 /* Handle pending wakeups and then migrate everything off */
8906 sched_tick_stop(cpu);
8907
8908 rq_lock_irqsave(rq, &rf);
8909 if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
8910 WARN(true, "Dying CPU not properly vacated!");
8911 dump_rq_tasks(rq, KERN_WARNING);
8912 }
8913 rq_unlock_irqrestore(rq, &rf);
8914
8915 calc_load_migrate(rq);
8916 update_max_interval();
8917 hrtick_clear(rq);
8918 sched_core_cpu_dying(cpu);
8919 return 0;
8920}
8921#endif
8922
8923void __init sched_init_smp(void)
8924{
8925 sched_init_numa();
8926
8927 /*
8928 * There's no userspace yet to cause hotplug operations; hence all the
8929 * CPU masks are stable and all blatant races in the below code cannot
8930 * happen.
8931 */
8932 mutex_lock(&sched_domains_mutex);
8933 sched_init_domains(cpu_active_mask);
8934 mutex_unlock(&sched_domains_mutex);
8935
8936 /* Move init over to a non-isolated CPU */
8937 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
8938 BUG();
8939 current->flags &= ~PF_NO_SETAFFINITY;
8940 sched_init_granularity();
8941
8942 init_sched_rt_class();
8943 init_sched_dl_class();
8944
8945 sched_smp_initialized = true;
8946}
8947
8948static int __init migration_init(void)
8949{
8950 sched_cpu_starting(smp_processor_id());
8951 return 0;
8952}
8953early_initcall(migration_init);
8954
8955#else
8956void __init sched_init_smp(void)
8957{
8958 sched_init_granularity();
8959}
8960#endif /* CONFIG_SMP */
8961
8962int in_sched_functions(unsigned long addr)
8963{
8964 return in_lock_functions(addr) ||
8965 (addr >= (unsigned long)__sched_text_start
8966 && addr < (unsigned long)__sched_text_end);
8967}
8968
8969#ifdef CONFIG_CGROUP_SCHED
8970/*
8971 * Default task group.
8972 * Every task in system belongs to this group at bootup.
8973 */
8974struct task_group root_task_group;
8975LIST_HEAD(task_groups);
8976
8977/* Cacheline aligned slab cache for task_group */
8978static struct kmem_cache *task_group_cache __read_mostly;
8979#endif
8980
8981DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
8982DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
8983
8984void __init sched_init(void)
8985{
8986 unsigned long ptr = 0;
8987 int i;
8988
8989 /* Make sure the linker didn't screw up */
8990 BUG_ON(&idle_sched_class + 1 != &fair_sched_class ||
8991 &fair_sched_class + 1 != &rt_sched_class ||
8992 &rt_sched_class + 1 != &dl_sched_class);
8993#ifdef CONFIG_SMP
8994 BUG_ON(&dl_sched_class + 1 != &stop_sched_class);
8995#endif
8996
8997 wait_bit_init();
8998
8999#ifdef CONFIG_FAIR_GROUP_SCHED
9000 ptr += 2 * nr_cpu_ids * sizeof(void **);
9001#endif
9002#ifdef CONFIG_RT_GROUP_SCHED
9003 ptr += 2 * nr_cpu_ids * sizeof(void **);
9004#endif
9005 if (ptr) {
9006 ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT);
9007
9008#ifdef CONFIG_FAIR_GROUP_SCHED
9009 root_task_group.se = (struct sched_entity **)ptr;
9010 ptr += nr_cpu_ids * sizeof(void **);
9011
9012 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
9013 ptr += nr_cpu_ids * sizeof(void **);
9014
9015 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
9016 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
9017#endif /* CONFIG_FAIR_GROUP_SCHED */
9018#ifdef CONFIG_RT_GROUP_SCHED
9019 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
9020 ptr += nr_cpu_ids * sizeof(void **);
9021
9022 root_task_group.rt_rq = (struct rt_rq **)ptr;
9023 ptr += nr_cpu_ids * sizeof(void **);
9024
9025#endif /* CONFIG_RT_GROUP_SCHED */
9026 }
9027#ifdef CONFIG_CPUMASK_OFFSTACK
9028 for_each_possible_cpu(i) {
9029 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
9030 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
9031 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
9032 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
9033 }
9034#endif /* CONFIG_CPUMASK_OFFSTACK */
9035
9036 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
9037 init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
9038
9039#ifdef CONFIG_SMP
9040 init_defrootdomain();
9041#endif
9042
9043#ifdef CONFIG_RT_GROUP_SCHED
9044 init_rt_bandwidth(&root_task_group.rt_bandwidth,
9045 global_rt_period(), global_rt_runtime());
9046#endif /* CONFIG_RT_GROUP_SCHED */
9047
9048#ifdef CONFIG_CGROUP_SCHED
9049 task_group_cache = KMEM_CACHE(task_group, 0);
9050
9051 list_add(&root_task_group.list, &task_groups);
9052 INIT_LIST_HEAD(&root_task_group.children);
9053 INIT_LIST_HEAD(&root_task_group.siblings);
9054 autogroup_init(&init_task);
9055#endif /* CONFIG_CGROUP_SCHED */
9056
9057 for_each_possible_cpu(i) {
9058 struct rq *rq;
9059
9060 rq = cpu_rq(i);
9061 raw_spin_lock_init(&rq->__lock);
9062 rq->nr_running = 0;
9063 rq->calc_load_active = 0;
9064 rq->calc_load_update = jiffies + LOAD_FREQ;
9065 init_cfs_rq(&rq->cfs);
9066 init_rt_rq(&rq->rt);
9067 init_dl_rq(&rq->dl);
9068#ifdef CONFIG_FAIR_GROUP_SCHED
9069 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
9070 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
9071 /*
9072 * How much CPU bandwidth does root_task_group get?
9073 *
9074 * In case of task-groups formed thr' the cgroup filesystem, it
9075 * gets 100% of the CPU resources in the system. This overall
9076 * system CPU resource is divided among the tasks of
9077 * root_task_group and its child task-groups in a fair manner,
9078 * based on each entity's (task or task-group's) weight
9079 * (se->load.weight).
9080 *
9081 * In other words, if root_task_group has 10 tasks of weight
9082 * 1024) and two child groups A0 and A1 (of weight 1024 each),
9083 * then A0's share of the CPU resource is:
9084 *
9085 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
9086 *
9087 * We achieve this by letting root_task_group's tasks sit
9088 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
9089 */
9090 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
9091#endif /* CONFIG_FAIR_GROUP_SCHED */
9092
9093 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
9094#ifdef CONFIG_RT_GROUP_SCHED
9095 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
9096#endif
9097#ifdef CONFIG_SMP
9098 rq->sd = NULL;
9099 rq->rd = NULL;
9100 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
9101 rq->balance_callback = &balance_push_callback;
9102 rq->active_balance = 0;
9103 rq->next_balance = jiffies;
9104 rq->push_cpu = 0;
9105 rq->cpu = i;
9106 rq->online = 0;
9107 rq->idle_stamp = 0;
9108 rq->avg_idle = 2*sysctl_sched_migration_cost;
9109 rq->wake_stamp = jiffies;
9110 rq->wake_avg_idle = rq->avg_idle;
9111 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
9112
9113 INIT_LIST_HEAD(&rq->cfs_tasks);
9114
9115 rq_attach_root(rq, &def_root_domain);
9116#ifdef CONFIG_NO_HZ_COMMON
9117 rq->last_blocked_load_update_tick = jiffies;
9118 atomic_set(&rq->nohz_flags, 0);
9119
9120 INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq);
9121#endif
9122#ifdef CONFIG_HOTPLUG_CPU
9123 rcuwait_init(&rq->hotplug_wait);
9124#endif
9125#endif /* CONFIG_SMP */
9126 hrtick_rq_init(rq);
9127 atomic_set(&rq->nr_iowait, 0);
9128
9129#ifdef CONFIG_SCHED_CORE
9130 rq->core = rq;
9131 rq->core_pick = NULL;
9132 rq->core_enabled = 0;
9133 rq->core_tree = RB_ROOT;
9134 rq->core_forceidle = false;
9135
9136 rq->core_cookie = 0UL;
9137#endif
9138 }
9139
9140 set_load_weight(&init_task, false);
9141
9142 /*
9143 * The boot idle thread does lazy MMU switching as well:
9144 */
9145 mmgrab(&init_mm);
9146 enter_lazy_tlb(&init_mm, current);
9147
9148 /*
9149 * Make us the idle thread. Technically, schedule() should not be
9150 * called from this thread, however somewhere below it might be,
9151 * but because we are the idle thread, we just pick up running again
9152 * when this runqueue becomes "idle".
9153 */
9154 init_idle(current, smp_processor_id());
9155
9156 calc_load_update = jiffies + LOAD_FREQ;
9157
9158#ifdef CONFIG_SMP
9159 idle_thread_set_boot_cpu();
9160 balance_push_set(smp_processor_id(), false);
9161#endif
9162 init_sched_fair_class();
9163
9164 psi_init();
9165
9166 init_uclamp();
9167
9168 scheduler_running = 1;
9169}
9170
9171#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
9172static inline int preempt_count_equals(int preempt_offset)
9173{
9174 int nested = preempt_count() + rcu_preempt_depth();
9175
9176 return (nested == preempt_offset);
9177}
9178
9179void __might_sleep(const char *file, int line, int preempt_offset)
9180{
9181 unsigned int state = get_current_state();
9182 /*
9183 * Blocking primitives will set (and therefore destroy) current->state,
9184 * since we will exit with TASK_RUNNING make sure we enter with it,
9185 * otherwise we will destroy state.
9186 */
9187 WARN_ONCE(state != TASK_RUNNING && current->task_state_change,
9188 "do not call blocking ops when !TASK_RUNNING; "
9189 "state=%x set at [<%p>] %pS\n", state,
9190 (void *)current->task_state_change,
9191 (void *)current->task_state_change);
9192
9193 ___might_sleep(file, line, preempt_offset);
9194}
9195EXPORT_SYMBOL(__might_sleep);
9196
9197void ___might_sleep(const char *file, int line, int preempt_offset)
9198{
9199 /* Ratelimiting timestamp: */
9200 static unsigned long prev_jiffy;
9201
9202 unsigned long preempt_disable_ip;
9203
9204 /* WARN_ON_ONCE() by default, no rate limit required: */
9205 rcu_sleep_check();
9206
9207 if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
9208 !is_idle_task(current) && !current->non_block_count) ||
9209 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
9210 oops_in_progress)
9211 return;
9212
9213 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
9214 return;
9215 prev_jiffy = jiffies;
9216
9217 /* Save this before calling printk(), since that will clobber it: */
9218 preempt_disable_ip = get_preempt_disable_ip(current);
9219
9220 printk(KERN_ERR
9221 "BUG: sleeping function called from invalid context at %s:%d\n",
9222 file, line);
9223 printk(KERN_ERR
9224 "in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
9225 in_atomic(), irqs_disabled(), current->non_block_count,
9226 current->pid, current->comm);
9227
9228 if (task_stack_end_corrupted(current))
9229 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
9230
9231 debug_show_held_locks(current);
9232 if (irqs_disabled())
9233 print_irqtrace_events(current);
9234 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
9235 && !preempt_count_equals(preempt_offset)) {
9236 pr_err("Preemption disabled at:");
9237 print_ip_sym(KERN_ERR, preempt_disable_ip);
9238 }
9239 dump_stack();
9240 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
9241}
9242EXPORT_SYMBOL(___might_sleep);
9243
9244void __cant_sleep(const char *file, int line, int preempt_offset)
9245{
9246 static unsigned long prev_jiffy;
9247
9248 if (irqs_disabled())
9249 return;
9250
9251 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
9252 return;
9253
9254 if (preempt_count() > preempt_offset)
9255 return;
9256
9257 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
9258 return;
9259 prev_jiffy = jiffies;
9260
9261 printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
9262 printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
9263 in_atomic(), irqs_disabled(),
9264 current->pid, current->comm);
9265
9266 debug_show_held_locks(current);
9267 dump_stack();
9268 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
9269}
9270EXPORT_SYMBOL_GPL(__cant_sleep);
9271
9272#ifdef CONFIG_SMP
9273void __cant_migrate(const char *file, int line)
9274{
9275 static unsigned long prev_jiffy;
9276
9277 if (irqs_disabled())
9278 return;
9279
9280 if (is_migration_disabled(current))
9281 return;
9282
9283 if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
9284 return;
9285
9286 if (preempt_count() > 0)
9287 return;
9288
9289 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
9290 return;
9291 prev_jiffy = jiffies;
9292
9293 pr_err("BUG: assuming non migratable context at %s:%d\n", file, line);
9294 pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n",
9295 in_atomic(), irqs_disabled(), is_migration_disabled(current),
9296 current->pid, current->comm);
9297
9298 debug_show_held_locks(current);
9299 dump_stack();
9300 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
9301}
9302EXPORT_SYMBOL_GPL(__cant_migrate);
9303#endif
9304#endif
9305
9306#ifdef CONFIG_MAGIC_SYSRQ
9307void normalize_rt_tasks(void)
9308{
9309 struct task_struct *g, *p;
9310 struct sched_attr attr = {
9311 .sched_policy = SCHED_NORMAL,
9312 };
9313
9314 read_lock(&tasklist_lock);
9315 for_each_process_thread(g, p) {
9316 /*
9317 * Only normalize user tasks:
9318 */
9319 if (p->flags & PF_KTHREAD)
9320 continue;
9321
9322 p->se.exec_start = 0;
9323 schedstat_set(p->se.statistics.wait_start, 0);
9324 schedstat_set(p->se.statistics.sleep_start, 0);
9325 schedstat_set(p->se.statistics.block_start, 0);
9326
9327 if (!dl_task(p) && !rt_task(p)) {
9328 /*
9329 * Renice negative nice level userspace
9330 * tasks back to 0:
9331 */
9332 if (task_nice(p) < 0)
9333 set_user_nice(p, 0);
9334 continue;
9335 }
9336
9337 __sched_setscheduler(p, &attr, false, false);
9338 }
9339 read_unlock(&tasklist_lock);
9340}
9341
9342#endif /* CONFIG_MAGIC_SYSRQ */
9343
9344#if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
9345/*
9346 * These functions are only useful for the IA64 MCA handling, or kdb.
9347 *
9348 * They can only be called when the whole system has been
9349 * stopped - every CPU needs to be quiescent, and no scheduling
9350 * activity can take place. Using them for anything else would
9351 * be a serious bug, and as a result, they aren't even visible
9352 * under any other configuration.
9353 */
9354
9355/**
9356 * curr_task - return the current task for a given CPU.
9357 * @cpu: the processor in question.
9358 *
9359 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
9360 *
9361 * Return: The current task for @cpu.
9362 */
9363struct task_struct *curr_task(int cpu)
9364{
9365 return cpu_curr(cpu);
9366}
9367
9368#endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
9369
9370#ifdef CONFIG_IA64
9371/**
9372 * ia64_set_curr_task - set the current task for a given CPU.
9373 * @cpu: the processor in question.
9374 * @p: the task pointer to set.
9375 *
9376 * Description: This function must only be used when non-maskable interrupts
9377 * are serviced on a separate stack. It allows the architecture to switch the
9378 * notion of the current task on a CPU in a non-blocking manner. This function
9379 * must be called with all CPU's synchronized, and interrupts disabled, the
9380 * and caller must save the original value of the current task (see
9381 * curr_task() above) and restore that value before reenabling interrupts and
9382 * re-starting the system.
9383 *
9384 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
9385 */
9386void ia64_set_curr_task(int cpu, struct task_struct *p)
9387{
9388 cpu_curr(cpu) = p;
9389}
9390
9391#endif
9392
9393#ifdef CONFIG_CGROUP_SCHED
9394/* task_group_lock serializes the addition/removal of task groups */
9395static DEFINE_SPINLOCK(task_group_lock);
9396
9397static inline void alloc_uclamp_sched_group(struct task_group *tg,
9398 struct task_group *parent)
9399{
9400#ifdef CONFIG_UCLAMP_TASK_GROUP
9401 enum uclamp_id clamp_id;
9402
9403 for_each_clamp_id(clamp_id) {
9404 uclamp_se_set(&tg->uclamp_req[clamp_id],
9405 uclamp_none(clamp_id), false);
9406 tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
9407 }
9408#endif
9409}
9410
9411static void sched_free_group(struct task_group *tg)
9412{
9413 free_fair_sched_group(tg);
9414 free_rt_sched_group(tg);
9415 autogroup_free(tg);
9416 kmem_cache_free(task_group_cache, tg);
9417}
9418
9419/* allocate runqueue etc for a new task group */
9420struct task_group *sched_create_group(struct task_group *parent)
9421{
9422 struct task_group *tg;
9423
9424 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
9425 if (!tg)
9426 return ERR_PTR(-ENOMEM);
9427
9428 if (!alloc_fair_sched_group(tg, parent))
9429 goto err;
9430
9431 if (!alloc_rt_sched_group(tg, parent))
9432 goto err;
9433
9434 alloc_uclamp_sched_group(tg, parent);
9435
9436 return tg;
9437
9438err:
9439 sched_free_group(tg);
9440 return ERR_PTR(-ENOMEM);
9441}
9442
9443void sched_online_group(struct task_group *tg, struct task_group *parent)
9444{
9445 unsigned long flags;
9446
9447 spin_lock_irqsave(&task_group_lock, flags);
9448 list_add_rcu(&tg->list, &task_groups);
9449
9450 /* Root should already exist: */
9451 WARN_ON(!parent);
9452
9453 tg->parent = parent;
9454 INIT_LIST_HEAD(&tg->children);
9455 list_add_rcu(&tg->siblings, &parent->children);
9456 spin_unlock_irqrestore(&task_group_lock, flags);
9457
9458 online_fair_sched_group(tg);
9459}
9460
9461/* rcu callback to free various structures associated with a task group */
9462static void sched_free_group_rcu(struct rcu_head *rhp)
9463{
9464 /* Now it should be safe to free those cfs_rqs: */
9465 sched_free_group(container_of(rhp, struct task_group, rcu));
9466}
9467
9468void sched_destroy_group(struct task_group *tg)
9469{
9470 /* Wait for possible concurrent references to cfs_rqs complete: */
9471 call_rcu(&tg->rcu, sched_free_group_rcu);
9472}
9473
9474void sched_offline_group(struct task_group *tg)
9475{
9476 unsigned long flags;
9477
9478 /* End participation in shares distribution: */
9479 unregister_fair_sched_group(tg);
9480
9481 spin_lock_irqsave(&task_group_lock, flags);
9482 list_del_rcu(&tg->list);
9483 list_del_rcu(&tg->siblings);
9484 spin_unlock_irqrestore(&task_group_lock, flags);
9485}
9486
9487static void sched_change_group(struct task_struct *tsk, int type)
9488{
9489 struct task_group *tg;
9490
9491 /*
9492 * All callers are synchronized by task_rq_lock(); we do not use RCU
9493 * which is pointless here. Thus, we pass "true" to task_css_check()
9494 * to prevent lockdep warnings.
9495 */
9496 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
9497 struct task_group, css);
9498 tg = autogroup_task_group(tsk, tg);
9499 tsk->sched_task_group = tg;
9500
9501#ifdef CONFIG_FAIR_GROUP_SCHED
9502 if (tsk->sched_class->task_change_group)
9503 tsk->sched_class->task_change_group(tsk, type);
9504 else
9505#endif
9506 set_task_rq(tsk, task_cpu(tsk));
9507}
9508
9509/*
9510 * Change task's runqueue when it moves between groups.
9511 *
9512 * The caller of this function should have put the task in its new group by
9513 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
9514 * its new group.
9515 */
9516void sched_move_task(struct task_struct *tsk)
9517{
9518 int queued, running, queue_flags =
9519 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
9520 struct rq_flags rf;
9521 struct rq *rq;
9522
9523 rq = task_rq_lock(tsk, &rf);
9524 update_rq_clock(rq);
9525
9526 running = task_current(rq, tsk);
9527 queued = task_on_rq_queued(tsk);
9528
9529 if (queued)
9530 dequeue_task(rq, tsk, queue_flags);
9531 if (running)
9532 put_prev_task(rq, tsk);
9533
9534 sched_change_group(tsk, TASK_MOVE_GROUP);
9535
9536 if (queued)
9537 enqueue_task(rq, tsk, queue_flags);
9538 if (running) {
9539 set_next_task(rq, tsk);
9540 /*
9541 * After changing group, the running task may have joined a
9542 * throttled one but it's still the running task. Trigger a
9543 * resched to make sure that task can still run.
9544 */
9545 resched_curr(rq);
9546 }
9547
9548 task_rq_unlock(rq, tsk, &rf);
9549}
9550
9551static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
9552{
9553 return css ? container_of(css, struct task_group, css) : NULL;
9554}
9555
9556static struct cgroup_subsys_state *
9557cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
9558{
9559 struct task_group *parent = css_tg(parent_css);
9560 struct task_group *tg;
9561
9562 if (!parent) {
9563 /* This is early initialization for the top cgroup */
9564 return &root_task_group.css;
9565 }
9566
9567 tg = sched_create_group(parent);
9568 if (IS_ERR(tg))
9569 return ERR_PTR(-ENOMEM);
9570
9571 return &tg->css;
9572}
9573
9574/* Expose task group only after completing cgroup initialization */
9575static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
9576{
9577 struct task_group *tg = css_tg(css);
9578 struct task_group *parent = css_tg(css->parent);
9579
9580 if (parent)
9581 sched_online_group(tg, parent);
9582
9583#ifdef CONFIG_UCLAMP_TASK_GROUP
9584 /* Propagate the effective uclamp value for the new group */
9585 mutex_lock(&uclamp_mutex);
9586 rcu_read_lock();
9587 cpu_util_update_eff(css);
9588 rcu_read_unlock();
9589 mutex_unlock(&uclamp_mutex);
9590#endif
9591
9592 return 0;
9593}
9594
9595static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
9596{
9597 struct task_group *tg = css_tg(css);
9598
9599 sched_offline_group(tg);
9600}
9601
9602static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
9603{
9604 struct task_group *tg = css_tg(css);
9605
9606 /*
9607 * Relies on the RCU grace period between css_released() and this.
9608 */
9609 sched_free_group(tg);
9610}
9611
9612/*
9613 * This is called before wake_up_new_task(), therefore we really only
9614 * have to set its group bits, all the other stuff does not apply.
9615 */
9616static void cpu_cgroup_fork(struct task_struct *task)
9617{
9618 struct rq_flags rf;
9619 struct rq *rq;
9620
9621 rq = task_rq_lock(task, &rf);
9622
9623 update_rq_clock(rq);
9624 sched_change_group(task, TASK_SET_GROUP);
9625
9626 task_rq_unlock(rq, task, &rf);
9627}
9628
9629static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
9630{
9631 struct task_struct *task;
9632 struct cgroup_subsys_state *css;
9633 int ret = 0;
9634
9635 cgroup_taskset_for_each(task, css, tset) {
9636#ifdef CONFIG_RT_GROUP_SCHED
9637 if (!sched_rt_can_attach(css_tg(css), task))
9638 return -EINVAL;
9639#endif
9640 /*
9641 * Serialize against wake_up_new_task() such that if it's
9642 * running, we're sure to observe its full state.
9643 */
9644 raw_spin_lock_irq(&task->pi_lock);
9645 /*
9646 * Avoid calling sched_move_task() before wake_up_new_task()
9647 * has happened. This would lead to problems with PELT, due to
9648 * move wanting to detach+attach while we're not attached yet.
9649 */
9650 if (READ_ONCE(task->__state) == TASK_NEW)
9651 ret = -EINVAL;
9652 raw_spin_unlock_irq(&task->pi_lock);
9653
9654 if (ret)
9655 break;
9656 }
9657 return ret;
9658}
9659
9660static void cpu_cgroup_attach(struct cgroup_taskset *tset)
9661{
9662 struct task_struct *task;
9663 struct cgroup_subsys_state *css;
9664
9665 cgroup_taskset_for_each(task, css, tset)
9666 sched_move_task(task);
9667}
9668
9669#ifdef CONFIG_UCLAMP_TASK_GROUP
9670static void cpu_util_update_eff(struct cgroup_subsys_state *css)
9671{
9672 struct cgroup_subsys_state *top_css = css;
9673 struct uclamp_se *uc_parent = NULL;
9674 struct uclamp_se *uc_se = NULL;
9675 unsigned int eff[UCLAMP_CNT];
9676 enum uclamp_id clamp_id;
9677 unsigned int clamps;
9678
9679 lockdep_assert_held(&uclamp_mutex);
9680 SCHED_WARN_ON(!rcu_read_lock_held());
9681
9682 css_for_each_descendant_pre(css, top_css) {
9683 uc_parent = css_tg(css)->parent
9684 ? css_tg(css)->parent->uclamp : NULL;
9685
9686 for_each_clamp_id(clamp_id) {
9687 /* Assume effective clamps matches requested clamps */
9688 eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
9689 /* Cap effective clamps with parent's effective clamps */
9690 if (uc_parent &&
9691 eff[clamp_id] > uc_parent[clamp_id].value) {
9692 eff[clamp_id] = uc_parent[clamp_id].value;
9693 }
9694 }
9695 /* Ensure protection is always capped by limit */
9696 eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
9697
9698 /* Propagate most restrictive effective clamps */
9699 clamps = 0x0;
9700 uc_se = css_tg(css)->uclamp;
9701 for_each_clamp_id(clamp_id) {
9702 if (eff[clamp_id] == uc_se[clamp_id].value)
9703 continue;
9704 uc_se[clamp_id].value = eff[clamp_id];
9705 uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
9706 clamps |= (0x1 << clamp_id);
9707 }
9708 if (!clamps) {
9709 css = css_rightmost_descendant(css);
9710 continue;
9711 }
9712
9713 /* Immediately update descendants RUNNABLE tasks */
9714 uclamp_update_active_tasks(css);
9715 }
9716}
9717
9718/*
9719 * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
9720 * C expression. Since there is no way to convert a macro argument (N) into a
9721 * character constant, use two levels of macros.
9722 */
9723#define _POW10(exp) ((unsigned int)1e##exp)
9724#define POW10(exp) _POW10(exp)
9725
9726struct uclamp_request {
9727#define UCLAMP_PERCENT_SHIFT 2
9728#define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT))
9729 s64 percent;
9730 u64 util;
9731 int ret;
9732};
9733
9734static inline struct uclamp_request
9735capacity_from_percent(char *buf)
9736{
9737 struct uclamp_request req = {
9738 .percent = UCLAMP_PERCENT_SCALE,
9739 .util = SCHED_CAPACITY_SCALE,
9740 .ret = 0,
9741 };
9742
9743 buf = strim(buf);
9744 if (strcmp(buf, "max")) {
9745 req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT,
9746 &req.percent);
9747 if (req.ret)
9748 return req;
9749 if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
9750 req.ret = -ERANGE;
9751 return req;
9752 }
9753
9754 req.util = req.percent << SCHED_CAPACITY_SHIFT;
9755 req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE);
9756 }
9757
9758 return req;
9759}
9760
9761static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
9762 size_t nbytes, loff_t off,
9763 enum uclamp_id clamp_id)
9764{
9765 struct uclamp_request req;
9766 struct task_group *tg;
9767
9768 req = capacity_from_percent(buf);
9769 if (req.ret)
9770 return req.ret;
9771
9772 static_branch_enable(&sched_uclamp_used);
9773
9774 mutex_lock(&uclamp_mutex);
9775 rcu_read_lock();
9776
9777 tg = css_tg(of_css(of));
9778 if (tg->uclamp_req[clamp_id].value != req.util)
9779 uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false);
9780
9781 /*
9782 * Because of not recoverable conversion rounding we keep track of the
9783 * exact requested value
9784 */
9785 tg->uclamp_pct[clamp_id] = req.percent;
9786
9787 /* Update effective clamps to track the most restrictive value */
9788 cpu_util_update_eff(of_css(of));
9789
9790 rcu_read_unlock();
9791 mutex_unlock(&uclamp_mutex);
9792
9793 return nbytes;
9794}
9795
9796static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of,
9797 char *buf, size_t nbytes,
9798 loff_t off)
9799{
9800 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN);
9801}
9802
9803static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of,
9804 char *buf, size_t nbytes,
9805 loff_t off)
9806{
9807 return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX);
9808}
9809
9810static inline void cpu_uclamp_print(struct seq_file *sf,
9811 enum uclamp_id clamp_id)
9812{
9813 struct task_group *tg;
9814 u64 util_clamp;
9815 u64 percent;
9816 u32 rem;
9817
9818 rcu_read_lock();
9819 tg = css_tg(seq_css(sf));
9820 util_clamp = tg->uclamp_req[clamp_id].value;
9821 rcu_read_unlock();
9822
9823 if (util_clamp == SCHED_CAPACITY_SCALE) {
9824 seq_puts(sf, "max\n");
9825 return;
9826 }
9827
9828 percent = tg->uclamp_pct[clamp_id];
9829 percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem);
9830 seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem);
9831}
9832
9833static int cpu_uclamp_min_show(struct seq_file *sf, void *v)
9834{
9835 cpu_uclamp_print(sf, UCLAMP_MIN);
9836 return 0;
9837}
9838
9839static int cpu_uclamp_max_show(struct seq_file *sf, void *v)
9840{
9841 cpu_uclamp_print(sf, UCLAMP_MAX);
9842 return 0;
9843}
9844#endif /* CONFIG_UCLAMP_TASK_GROUP */
9845
9846#ifdef CONFIG_FAIR_GROUP_SCHED
9847static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
9848 struct cftype *cftype, u64 shareval)
9849{
9850 if (shareval > scale_load_down(ULONG_MAX))
9851 shareval = MAX_SHARES;
9852 return sched_group_set_shares(css_tg(css), scale_load(shareval));
9853}
9854
9855static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
9856 struct cftype *cft)
9857{
9858 struct task_group *tg = css_tg(css);
9859
9860 return (u64) scale_load_down(tg->shares);
9861}
9862
9863#ifdef CONFIG_CFS_BANDWIDTH
9864static DEFINE_MUTEX(cfs_constraints_mutex);
9865
9866const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
9867static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
9868/* More than 203 days if BW_SHIFT equals 20. */
9869static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC;
9870
9871static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
9872
9873static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota,
9874 u64 burst)
9875{
9876 int i, ret = 0, runtime_enabled, runtime_was_enabled;
9877 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
9878
9879 if (tg == &root_task_group)
9880 return -EINVAL;
9881
9882 /*
9883 * Ensure we have at some amount of bandwidth every period. This is
9884 * to prevent reaching a state of large arrears when throttled via
9885 * entity_tick() resulting in prolonged exit starvation.
9886 */
9887 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
9888 return -EINVAL;
9889
9890 /*
9891 * Likewise, bound things on the other side by preventing insane quota
9892 * periods. This also allows us to normalize in computing quota
9893 * feasibility.
9894 */
9895 if (period > max_cfs_quota_period)
9896 return -EINVAL;
9897
9898 /*
9899 * Bound quota to defend quota against overflow during bandwidth shift.
9900 */
9901 if (quota != RUNTIME_INF && quota > max_cfs_runtime)
9902 return -EINVAL;
9903
9904 if (quota != RUNTIME_INF && (burst > quota ||
9905 burst + quota > max_cfs_runtime))
9906 return -EINVAL;
9907
9908 /*
9909 * Prevent race between setting of cfs_rq->runtime_enabled and
9910 * unthrottle_offline_cfs_rqs().
9911 */
9912 get_online_cpus();
9913 mutex_lock(&cfs_constraints_mutex);
9914 ret = __cfs_schedulable(tg, period, quota);
9915 if (ret)
9916 goto out_unlock;
9917
9918 runtime_enabled = quota != RUNTIME_INF;
9919 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
9920 /*
9921 * If we need to toggle cfs_bandwidth_used, off->on must occur
9922 * before making related changes, and on->off must occur afterwards
9923 */
9924 if (runtime_enabled && !runtime_was_enabled)
9925 cfs_bandwidth_usage_inc();
9926 raw_spin_lock_irq(&cfs_b->lock);
9927 cfs_b->period = ns_to_ktime(period);
9928 cfs_b->quota = quota;
9929 cfs_b->burst = burst;
9930
9931 __refill_cfs_bandwidth_runtime(cfs_b);
9932
9933 /* Restart the period timer (if active) to handle new period expiry: */
9934 if (runtime_enabled)
9935 start_cfs_bandwidth(cfs_b);
9936
9937 raw_spin_unlock_irq(&cfs_b->lock);
9938
9939 for_each_online_cpu(i) {
9940 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
9941 struct rq *rq = cfs_rq->rq;
9942 struct rq_flags rf;
9943
9944 rq_lock_irq(rq, &rf);
9945 cfs_rq->runtime_enabled = runtime_enabled;
9946 cfs_rq->runtime_remaining = 0;
9947
9948 if (cfs_rq->throttled)
9949 unthrottle_cfs_rq(cfs_rq);
9950 rq_unlock_irq(rq, &rf);
9951 }
9952 if (runtime_was_enabled && !runtime_enabled)
9953 cfs_bandwidth_usage_dec();
9954out_unlock:
9955 mutex_unlock(&cfs_constraints_mutex);
9956 put_online_cpus();
9957
9958 return ret;
9959}
9960
9961static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
9962{
9963 u64 quota, period, burst;
9964
9965 period = ktime_to_ns(tg->cfs_bandwidth.period);
9966 burst = tg->cfs_bandwidth.burst;
9967 if (cfs_quota_us < 0)
9968 quota = RUNTIME_INF;
9969 else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC)
9970 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
9971 else
9972 return -EINVAL;
9973
9974 return tg_set_cfs_bandwidth(tg, period, quota, burst);
9975}
9976
9977static long tg_get_cfs_quota(struct task_group *tg)
9978{
9979 u64 quota_us;
9980
9981 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
9982 return -1;
9983
9984 quota_us = tg->cfs_bandwidth.quota;
9985 do_div(quota_us, NSEC_PER_USEC);
9986
9987 return quota_us;
9988}
9989
9990static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
9991{
9992 u64 quota, period, burst;
9993
9994 if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC)
9995 return -EINVAL;
9996
9997 period = (u64)cfs_period_us * NSEC_PER_USEC;
9998 quota = tg->cfs_bandwidth.quota;
9999 burst = tg->cfs_bandwidth.burst;
10000
10001 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10002}
10003
10004static long tg_get_cfs_period(struct task_group *tg)
10005{
10006 u64 cfs_period_us;
10007
10008 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
10009 do_div(cfs_period_us, NSEC_PER_USEC);
10010
10011 return cfs_period_us;
10012}
10013
10014static int tg_set_cfs_burst(struct task_group *tg, long cfs_burst_us)
10015{
10016 u64 quota, period, burst;
10017
10018 if ((u64)cfs_burst_us > U64_MAX / NSEC_PER_USEC)
10019 return -EINVAL;
10020
10021 burst = (u64)cfs_burst_us * NSEC_PER_USEC;
10022 period = ktime_to_ns(tg->cfs_bandwidth.period);
10023 quota = tg->cfs_bandwidth.quota;
10024
10025 return tg_set_cfs_bandwidth(tg, period, quota, burst);
10026}
10027
10028static long tg_get_cfs_burst(struct task_group *tg)
10029{
10030 u64 burst_us;
10031
10032 burst_us = tg->cfs_bandwidth.burst;
10033 do_div(burst_us, NSEC_PER_USEC);
10034
10035 return burst_us;
10036}
10037
10038static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
10039 struct cftype *cft)
10040{
10041 return tg_get_cfs_quota(css_tg(css));
10042}
10043
10044static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
10045 struct cftype *cftype, s64 cfs_quota_us)
10046{
10047 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
10048}
10049
10050static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
10051 struct cftype *cft)
10052{
10053 return tg_get_cfs_period(css_tg(css));
10054}
10055
10056static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
10057 struct cftype *cftype, u64 cfs_period_us)
10058{
10059 return tg_set_cfs_period(css_tg(css), cfs_period_us);
10060}
10061
10062static u64 cpu_cfs_burst_read_u64(struct cgroup_subsys_state *css,
10063 struct cftype *cft)
10064{
10065 return tg_get_cfs_burst(css_tg(css));
10066}
10067
10068static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state *css,
10069 struct cftype *cftype, u64 cfs_burst_us)
10070{
10071 return tg_set_cfs_burst(css_tg(css), cfs_burst_us);
10072}
10073
10074struct cfs_schedulable_data {
10075 struct task_group *tg;
10076 u64 period, quota;
10077};
10078
10079/*
10080 * normalize group quota/period to be quota/max_period
10081 * note: units are usecs
10082 */
10083static u64 normalize_cfs_quota(struct task_group *tg,
10084 struct cfs_schedulable_data *d)
10085{
10086 u64 quota, period;
10087
10088 if (tg == d->tg) {
10089 period = d->period;
10090 quota = d->quota;
10091 } else {
10092 period = tg_get_cfs_period(tg);
10093 quota = tg_get_cfs_quota(tg);
10094 }
10095
10096 /* note: these should typically be equivalent */
10097 if (quota == RUNTIME_INF || quota == -1)
10098 return RUNTIME_INF;
10099
10100 return to_ratio(period, quota);
10101}
10102
10103static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
10104{
10105 struct cfs_schedulable_data *d = data;
10106 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10107 s64 quota = 0, parent_quota = -1;
10108
10109 if (!tg->parent) {
10110 quota = RUNTIME_INF;
10111 } else {
10112 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
10113
10114 quota = normalize_cfs_quota(tg, d);
10115 parent_quota = parent_b->hierarchical_quota;
10116
10117 /*
10118 * Ensure max(child_quota) <= parent_quota. On cgroup2,
10119 * always take the min. On cgroup1, only inherit when no
10120 * limit is set:
10121 */
10122 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
10123 quota = min(quota, parent_quota);
10124 } else {
10125 if (quota == RUNTIME_INF)
10126 quota = parent_quota;
10127 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
10128 return -EINVAL;
10129 }
10130 }
10131 cfs_b->hierarchical_quota = quota;
10132
10133 return 0;
10134}
10135
10136static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
10137{
10138 int ret;
10139 struct cfs_schedulable_data data = {
10140 .tg = tg,
10141 .period = period,
10142 .quota = quota,
10143 };
10144
10145 if (quota != RUNTIME_INF) {
10146 do_div(data.period, NSEC_PER_USEC);
10147 do_div(data.quota, NSEC_PER_USEC);
10148 }
10149
10150 rcu_read_lock();
10151 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
10152 rcu_read_unlock();
10153
10154 return ret;
10155}
10156
10157static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
10158{
10159 struct task_group *tg = css_tg(seq_css(sf));
10160 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10161
10162 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
10163 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
10164 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
10165
10166 if (schedstat_enabled() && tg != &root_task_group) {
10167 u64 ws = 0;
10168 int i;
10169
10170 for_each_possible_cpu(i)
10171 ws += schedstat_val(tg->se[i]->statistics.wait_sum);
10172
10173 seq_printf(sf, "wait_sum %llu\n", ws);
10174 }
10175
10176 return 0;
10177}
10178#endif /* CONFIG_CFS_BANDWIDTH */
10179#endif /* CONFIG_FAIR_GROUP_SCHED */
10180
10181#ifdef CONFIG_RT_GROUP_SCHED
10182static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
10183 struct cftype *cft, s64 val)
10184{
10185 return sched_group_set_rt_runtime(css_tg(css), val);
10186}
10187
10188static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
10189 struct cftype *cft)
10190{
10191 return sched_group_rt_runtime(css_tg(css));
10192}
10193
10194static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
10195 struct cftype *cftype, u64 rt_period_us)
10196{
10197 return sched_group_set_rt_period(css_tg(css), rt_period_us);
10198}
10199
10200static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
10201 struct cftype *cft)
10202{
10203 return sched_group_rt_period(css_tg(css));
10204}
10205#endif /* CONFIG_RT_GROUP_SCHED */
10206
10207static struct cftype cpu_legacy_files[] = {
10208#ifdef CONFIG_FAIR_GROUP_SCHED
10209 {
10210 .name = "shares",
10211 .read_u64 = cpu_shares_read_u64,
10212 .write_u64 = cpu_shares_write_u64,
10213 },
10214#endif
10215#ifdef CONFIG_CFS_BANDWIDTH
10216 {
10217 .name = "cfs_quota_us",
10218 .read_s64 = cpu_cfs_quota_read_s64,
10219 .write_s64 = cpu_cfs_quota_write_s64,
10220 },
10221 {
10222 .name = "cfs_period_us",
10223 .read_u64 = cpu_cfs_period_read_u64,
10224 .write_u64 = cpu_cfs_period_write_u64,
10225 },
10226 {
10227 .name = "cfs_burst_us",
10228 .read_u64 = cpu_cfs_burst_read_u64,
10229 .write_u64 = cpu_cfs_burst_write_u64,
10230 },
10231 {
10232 .name = "stat",
10233 .seq_show = cpu_cfs_stat_show,
10234 },
10235#endif
10236#ifdef CONFIG_RT_GROUP_SCHED
10237 {
10238 .name = "rt_runtime_us",
10239 .read_s64 = cpu_rt_runtime_read,
10240 .write_s64 = cpu_rt_runtime_write,
10241 },
10242 {
10243 .name = "rt_period_us",
10244 .read_u64 = cpu_rt_period_read_uint,
10245 .write_u64 = cpu_rt_period_write_uint,
10246 },
10247#endif
10248#ifdef CONFIG_UCLAMP_TASK_GROUP
10249 {
10250 .name = "uclamp.min",
10251 .flags = CFTYPE_NOT_ON_ROOT,
10252 .seq_show = cpu_uclamp_min_show,
10253 .write = cpu_uclamp_min_write,
10254 },
10255 {
10256 .name = "uclamp.max",
10257 .flags = CFTYPE_NOT_ON_ROOT,
10258 .seq_show = cpu_uclamp_max_show,
10259 .write = cpu_uclamp_max_write,
10260 },
10261#endif
10262 { } /* Terminate */
10263};
10264
10265static int cpu_extra_stat_show(struct seq_file *sf,
10266 struct cgroup_subsys_state *css)
10267{
10268#ifdef CONFIG_CFS_BANDWIDTH
10269 {
10270 struct task_group *tg = css_tg(css);
10271 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
10272 u64 throttled_usec;
10273
10274 throttled_usec = cfs_b->throttled_time;
10275 do_div(throttled_usec, NSEC_PER_USEC);
10276
10277 seq_printf(sf, "nr_periods %d\n"
10278 "nr_throttled %d\n"
10279 "throttled_usec %llu\n",
10280 cfs_b->nr_periods, cfs_b->nr_throttled,
10281 throttled_usec);
10282 }
10283#endif
10284 return 0;
10285}
10286
10287#ifdef CONFIG_FAIR_GROUP_SCHED
10288static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
10289 struct cftype *cft)
10290{
10291 struct task_group *tg = css_tg(css);
10292 u64 weight = scale_load_down(tg->shares);
10293
10294 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
10295}
10296
10297static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
10298 struct cftype *cft, u64 weight)
10299{
10300 /*
10301 * cgroup weight knobs should use the common MIN, DFL and MAX
10302 * values which are 1, 100 and 10000 respectively. While it loses
10303 * a bit of range on both ends, it maps pretty well onto the shares
10304 * value used by scheduler and the round-trip conversions preserve
10305 * the original value over the entire range.
10306 */
10307 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
10308 return -ERANGE;
10309
10310 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
10311
10312 return sched_group_set_shares(css_tg(css), scale_load(weight));
10313}
10314
10315static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
10316 struct cftype *cft)
10317{
10318 unsigned long weight = scale_load_down(css_tg(css)->shares);
10319 int last_delta = INT_MAX;
10320 int prio, delta;
10321
10322 /* find the closest nice value to the current weight */
10323 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
10324 delta = abs(sched_prio_to_weight[prio] - weight);
10325 if (delta >= last_delta)
10326 break;
10327 last_delta = delta;
10328 }
10329
10330 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
10331}
10332
10333static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
10334 struct cftype *cft, s64 nice)
10335{
10336 unsigned long weight;
10337 int idx;
10338
10339 if (nice < MIN_NICE || nice > MAX_NICE)
10340 return -ERANGE;
10341
10342 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
10343 idx = array_index_nospec(idx, 40);
10344 weight = sched_prio_to_weight[idx];
10345
10346 return sched_group_set_shares(css_tg(css), scale_load(weight));
10347}
10348#endif
10349
10350static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
10351 long period, long quota)
10352{
10353 if (quota < 0)
10354 seq_puts(sf, "max");
10355 else
10356 seq_printf(sf, "%ld", quota);
10357
10358 seq_printf(sf, " %ld\n", period);
10359}
10360
10361/* caller should put the current value in *@periodp before calling */
10362static int __maybe_unused cpu_period_quota_parse(char *buf,
10363 u64 *periodp, u64 *quotap)
10364{
10365 char tok[21]; /* U64_MAX */
10366
10367 if (sscanf(buf, "%20s %llu", tok, periodp) < 1)
10368 return -EINVAL;
10369
10370 *periodp *= NSEC_PER_USEC;
10371
10372 if (sscanf(tok, "%llu", quotap))
10373 *quotap *= NSEC_PER_USEC;
10374 else if (!strcmp(tok, "max"))
10375 *quotap = RUNTIME_INF;
10376 else
10377 return -EINVAL;
10378
10379 return 0;
10380}
10381
10382#ifdef CONFIG_CFS_BANDWIDTH
10383static int cpu_max_show(struct seq_file *sf, void *v)
10384{
10385 struct task_group *tg = css_tg(seq_css(sf));
10386
10387 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
10388 return 0;
10389}
10390
10391static ssize_t cpu_max_write(struct kernfs_open_file *of,
10392 char *buf, size_t nbytes, loff_t off)
10393{
10394 struct task_group *tg = css_tg(of_css(of));
10395 u64 period = tg_get_cfs_period(tg);
10396 u64 burst = tg_get_cfs_burst(tg);
10397 u64 quota;
10398 int ret;
10399
10400 ret = cpu_period_quota_parse(buf, &period, "a);
10401 if (!ret)
10402 ret = tg_set_cfs_bandwidth(tg, period, quota, burst);
10403 return ret ?: nbytes;
10404}
10405#endif
10406
10407static struct cftype cpu_files[] = {
10408#ifdef CONFIG_FAIR_GROUP_SCHED
10409 {
10410 .name = "weight",
10411 .flags = CFTYPE_NOT_ON_ROOT,
10412 .read_u64 = cpu_weight_read_u64,
10413 .write_u64 = cpu_weight_write_u64,
10414 },
10415 {
10416 .name = "weight.nice",
10417 .flags = CFTYPE_NOT_ON_ROOT,
10418 .read_s64 = cpu_weight_nice_read_s64,
10419 .write_s64 = cpu_weight_nice_write_s64,
10420 },
10421#endif
10422#ifdef CONFIG_CFS_BANDWIDTH
10423 {
10424 .name = "max",
10425 .flags = CFTYPE_NOT_ON_ROOT,
10426 .seq_show = cpu_max_show,
10427 .write = cpu_max_write,
10428 },
10429 {
10430 .name = "max.burst",
10431 .flags = CFTYPE_NOT_ON_ROOT,
10432 .read_u64 = cpu_cfs_burst_read_u64,
10433 .write_u64 = cpu_cfs_burst_write_u64,
10434 },
10435#endif
10436#ifdef CONFIG_UCLAMP_TASK_GROUP
10437 {
10438 .name = "uclamp.min",
10439 .flags = CFTYPE_NOT_ON_ROOT,
10440 .seq_show = cpu_uclamp_min_show,
10441 .write = cpu_uclamp_min_write,
10442 },
10443 {
10444 .name = "uclamp.max",
10445 .flags = CFTYPE_NOT_ON_ROOT,
10446 .seq_show = cpu_uclamp_max_show,
10447 .write = cpu_uclamp_max_write,
10448 },
10449#endif
10450 { } /* terminate */
10451};
10452
10453struct cgroup_subsys cpu_cgrp_subsys = {
10454 .css_alloc = cpu_cgroup_css_alloc,
10455 .css_online = cpu_cgroup_css_online,
10456 .css_released = cpu_cgroup_css_released,
10457 .css_free = cpu_cgroup_css_free,
10458 .css_extra_stat_show = cpu_extra_stat_show,
10459 .fork = cpu_cgroup_fork,
10460 .can_attach = cpu_cgroup_can_attach,
10461 .attach = cpu_cgroup_attach,
10462 .legacy_cftypes = cpu_legacy_files,
10463 .dfl_cftypes = cpu_files,
10464 .early_init = true,
10465 .threaded = true,
10466};
10467
10468#endif /* CONFIG_CGROUP_SCHED */
10469
10470void dump_cpu_task(int cpu)
10471{
10472 pr_info("Task dump for CPU %d:\n", cpu);
10473 sched_show_task(cpu_curr(cpu));
10474}
10475
10476/*
10477 * Nice levels are multiplicative, with a gentle 10% change for every
10478 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
10479 * nice 1, it will get ~10% less CPU time than another CPU-bound task
10480 * that remained on nice 0.
10481 *
10482 * The "10% effect" is relative and cumulative: from _any_ nice level,
10483 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
10484 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
10485 * If a task goes up by ~10% and another task goes down by ~10% then
10486 * the relative distance between them is ~25%.)
10487 */
10488const int sched_prio_to_weight[40] = {
10489 /* -20 */ 88761, 71755, 56483, 46273, 36291,
10490 /* -15 */ 29154, 23254, 18705, 14949, 11916,
10491 /* -10 */ 9548, 7620, 6100, 4904, 3906,
10492 /* -5 */ 3121, 2501, 1991, 1586, 1277,
10493 /* 0 */ 1024, 820, 655, 526, 423,
10494 /* 5 */ 335, 272, 215, 172, 137,
10495 /* 10 */ 110, 87, 70, 56, 45,
10496 /* 15 */ 36, 29, 23, 18, 15,
10497};
10498
10499/*
10500 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
10501 *
10502 * In cases where the weight does not change often, we can use the
10503 * precalculated inverse to speed up arithmetics by turning divisions
10504 * into multiplications:
10505 */
10506const u32 sched_prio_to_wmult[40] = {
10507 /* -20 */ 48388, 59856, 76040, 92818, 118348,
10508 /* -15 */ 147320, 184698, 229616, 287308, 360437,
10509 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
10510 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
10511 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
10512 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
10513 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
10514 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
10515};
10516
10517void call_trace_sched_update_nr_running(struct rq *rq, int count)
10518{
10519 trace_sched_update_nr_running_tp(rq, count);
10520}