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1/*
2 * kernel/sched/core.c
3 *
4 * Core kernel scheduler code and related syscalls
5 *
6 * Copyright (C) 1991-2002 Linus Torvalds
7 */
8#include "sched.h"
9
10#include <linux/kthread.h>
11#include <linux/nospec.h>
12
13#include <asm/switch_to.h>
14#include <asm/tlb.h>
15
16#include "../workqueue_internal.h"
17#include "../smpboot.h"
18
19#define CREATE_TRACE_POINTS
20#include <trace/events/sched.h>
21
22DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
23
24#if defined(CONFIG_SCHED_DEBUG) && defined(HAVE_JUMP_LABEL)
25/*
26 * Debugging: various feature bits
27 *
28 * If SCHED_DEBUG is disabled, each compilation unit has its own copy of
29 * sysctl_sched_features, defined in sched.h, to allow constants propagation
30 * at compile time and compiler optimization based on features default.
31 */
32#define SCHED_FEAT(name, enabled) \
33 (1UL << __SCHED_FEAT_##name) * enabled |
34const_debug unsigned int sysctl_sched_features =
35#include "features.h"
36 0;
37#undef SCHED_FEAT
38#endif
39
40/*
41 * Number of tasks to iterate in a single balance run.
42 * Limited because this is done with IRQs disabled.
43 */
44const_debug unsigned int sysctl_sched_nr_migrate = 32;
45
46/*
47 * period over which we average the RT time consumption, measured
48 * in ms.
49 *
50 * default: 1s
51 */
52const_debug unsigned int sysctl_sched_time_avg = MSEC_PER_SEC;
53
54/*
55 * period over which we measure -rt task CPU usage in us.
56 * default: 1s
57 */
58unsigned int sysctl_sched_rt_period = 1000000;
59
60__read_mostly int scheduler_running;
61
62/*
63 * part of the period that we allow rt tasks to run in us.
64 * default: 0.95s
65 */
66int sysctl_sched_rt_runtime = 950000;
67
68/*
69 * __task_rq_lock - lock the rq @p resides on.
70 */
71struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
72 __acquires(rq->lock)
73{
74 struct rq *rq;
75
76 lockdep_assert_held(&p->pi_lock);
77
78 for (;;) {
79 rq = task_rq(p);
80 raw_spin_lock(&rq->lock);
81 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
82 rq_pin_lock(rq, rf);
83 return rq;
84 }
85 raw_spin_unlock(&rq->lock);
86
87 while (unlikely(task_on_rq_migrating(p)))
88 cpu_relax();
89 }
90}
91
92/*
93 * task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
94 */
95struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
96 __acquires(p->pi_lock)
97 __acquires(rq->lock)
98{
99 struct rq *rq;
100
101 for (;;) {
102 raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
103 rq = task_rq(p);
104 raw_spin_lock(&rq->lock);
105 /*
106 * move_queued_task() task_rq_lock()
107 *
108 * ACQUIRE (rq->lock)
109 * [S] ->on_rq = MIGRATING [L] rq = task_rq()
110 * WMB (__set_task_cpu()) ACQUIRE (rq->lock);
111 * [S] ->cpu = new_cpu [L] task_rq()
112 * [L] ->on_rq
113 * RELEASE (rq->lock)
114 *
115 * If we observe the old CPU in task_rq_lock, the acquire of
116 * the old rq->lock will fully serialize against the stores.
117 *
118 * If we observe the new CPU in task_rq_lock, the acquire will
119 * pair with the WMB to ensure we must then also see migrating.
120 */
121 if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
122 rq_pin_lock(rq, rf);
123 return rq;
124 }
125 raw_spin_unlock(&rq->lock);
126 raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
127
128 while (unlikely(task_on_rq_migrating(p)))
129 cpu_relax();
130 }
131}
132
133/*
134 * RQ-clock updating methods:
135 */
136
137static void update_rq_clock_task(struct rq *rq, s64 delta)
138{
139/*
140 * In theory, the compile should just see 0 here, and optimize out the call
141 * to sched_rt_avg_update. But I don't trust it...
142 */
143#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
144 s64 steal = 0, irq_delta = 0;
145#endif
146#ifdef CONFIG_IRQ_TIME_ACCOUNTING
147 irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
148
149 /*
150 * Since irq_time is only updated on {soft,}irq_exit, we might run into
151 * this case when a previous update_rq_clock() happened inside a
152 * {soft,}irq region.
153 *
154 * When this happens, we stop ->clock_task and only update the
155 * prev_irq_time stamp to account for the part that fit, so that a next
156 * update will consume the rest. This ensures ->clock_task is
157 * monotonic.
158 *
159 * It does however cause some slight miss-attribution of {soft,}irq
160 * time, a more accurate solution would be to update the irq_time using
161 * the current rq->clock timestamp, except that would require using
162 * atomic ops.
163 */
164 if (irq_delta > delta)
165 irq_delta = delta;
166
167 rq->prev_irq_time += irq_delta;
168 delta -= irq_delta;
169#endif
170#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
171 if (static_key_false((¶virt_steal_rq_enabled))) {
172 steal = paravirt_steal_clock(cpu_of(rq));
173 steal -= rq->prev_steal_time_rq;
174
175 if (unlikely(steal > delta))
176 steal = delta;
177
178 rq->prev_steal_time_rq += steal;
179 delta -= steal;
180 }
181#endif
182
183 rq->clock_task += delta;
184
185#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)
186 if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY))
187 sched_rt_avg_update(rq, irq_delta + steal);
188#endif
189}
190
191void update_rq_clock(struct rq *rq)
192{
193 s64 delta;
194
195 lockdep_assert_held(&rq->lock);
196
197 if (rq->clock_update_flags & RQCF_ACT_SKIP)
198 return;
199
200#ifdef CONFIG_SCHED_DEBUG
201 if (sched_feat(WARN_DOUBLE_CLOCK))
202 SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED);
203 rq->clock_update_flags |= RQCF_UPDATED;
204#endif
205
206 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
207 if (delta < 0)
208 return;
209 rq->clock += delta;
210 update_rq_clock_task(rq, delta);
211}
212
213
214#ifdef CONFIG_SCHED_HRTICK
215/*
216 * Use HR-timers to deliver accurate preemption points.
217 */
218
219static void hrtick_clear(struct rq *rq)
220{
221 if (hrtimer_active(&rq->hrtick_timer))
222 hrtimer_cancel(&rq->hrtick_timer);
223}
224
225/*
226 * High-resolution timer tick.
227 * Runs from hardirq context with interrupts disabled.
228 */
229static enum hrtimer_restart hrtick(struct hrtimer *timer)
230{
231 struct rq *rq = container_of(timer, struct rq, hrtick_timer);
232 struct rq_flags rf;
233
234 WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
235
236 rq_lock(rq, &rf);
237 update_rq_clock(rq);
238 rq->curr->sched_class->task_tick(rq, rq->curr, 1);
239 rq_unlock(rq, &rf);
240
241 return HRTIMER_NORESTART;
242}
243
244#ifdef CONFIG_SMP
245
246static void __hrtick_restart(struct rq *rq)
247{
248 struct hrtimer *timer = &rq->hrtick_timer;
249
250 hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
251}
252
253/*
254 * called from hardirq (IPI) context
255 */
256static void __hrtick_start(void *arg)
257{
258 struct rq *rq = arg;
259 struct rq_flags rf;
260
261 rq_lock(rq, &rf);
262 __hrtick_restart(rq);
263 rq->hrtick_csd_pending = 0;
264 rq_unlock(rq, &rf);
265}
266
267/*
268 * Called to set the hrtick timer state.
269 *
270 * called with rq->lock held and irqs disabled
271 */
272void hrtick_start(struct rq *rq, u64 delay)
273{
274 struct hrtimer *timer = &rq->hrtick_timer;
275 ktime_t time;
276 s64 delta;
277
278 /*
279 * Don't schedule slices shorter than 10000ns, that just
280 * doesn't make sense and can cause timer DoS.
281 */
282 delta = max_t(s64, delay, 10000LL);
283 time = ktime_add_ns(timer->base->get_time(), delta);
284
285 hrtimer_set_expires(timer, time);
286
287 if (rq == this_rq()) {
288 __hrtick_restart(rq);
289 } else if (!rq->hrtick_csd_pending) {
290 smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
291 rq->hrtick_csd_pending = 1;
292 }
293}
294
295#else
296/*
297 * Called to set the hrtick timer state.
298 *
299 * called with rq->lock held and irqs disabled
300 */
301void hrtick_start(struct rq *rq, u64 delay)
302{
303 /*
304 * Don't schedule slices shorter than 10000ns, that just
305 * doesn't make sense. Rely on vruntime for fairness.
306 */
307 delay = max_t(u64, delay, 10000LL);
308 hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
309 HRTIMER_MODE_REL_PINNED);
310}
311#endif /* CONFIG_SMP */
312
313static void hrtick_rq_init(struct rq *rq)
314{
315#ifdef CONFIG_SMP
316 rq->hrtick_csd_pending = 0;
317
318 rq->hrtick_csd.flags = 0;
319 rq->hrtick_csd.func = __hrtick_start;
320 rq->hrtick_csd.info = rq;
321#endif
322
323 hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
324 rq->hrtick_timer.function = hrtick;
325}
326#else /* CONFIG_SCHED_HRTICK */
327static inline void hrtick_clear(struct rq *rq)
328{
329}
330
331static inline void hrtick_rq_init(struct rq *rq)
332{
333}
334#endif /* CONFIG_SCHED_HRTICK */
335
336/*
337 * cmpxchg based fetch_or, macro so it works for different integer types
338 */
339#define fetch_or(ptr, mask) \
340 ({ \
341 typeof(ptr) _ptr = (ptr); \
342 typeof(mask) _mask = (mask); \
343 typeof(*_ptr) _old, _val = *_ptr; \
344 \
345 for (;;) { \
346 _old = cmpxchg(_ptr, _val, _val | _mask); \
347 if (_old == _val) \
348 break; \
349 _val = _old; \
350 } \
351 _old; \
352})
353
354#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
355/*
356 * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
357 * this avoids any races wrt polling state changes and thereby avoids
358 * spurious IPIs.
359 */
360static bool set_nr_and_not_polling(struct task_struct *p)
361{
362 struct thread_info *ti = task_thread_info(p);
363 return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
364}
365
366/*
367 * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
368 *
369 * If this returns true, then the idle task promises to call
370 * sched_ttwu_pending() and reschedule soon.
371 */
372static bool set_nr_if_polling(struct task_struct *p)
373{
374 struct thread_info *ti = task_thread_info(p);
375 typeof(ti->flags) old, val = READ_ONCE(ti->flags);
376
377 for (;;) {
378 if (!(val & _TIF_POLLING_NRFLAG))
379 return false;
380 if (val & _TIF_NEED_RESCHED)
381 return true;
382 old = cmpxchg(&ti->flags, val, val | _TIF_NEED_RESCHED);
383 if (old == val)
384 break;
385 val = old;
386 }
387 return true;
388}
389
390#else
391static bool set_nr_and_not_polling(struct task_struct *p)
392{
393 set_tsk_need_resched(p);
394 return true;
395}
396
397#ifdef CONFIG_SMP
398static bool set_nr_if_polling(struct task_struct *p)
399{
400 return false;
401}
402#endif
403#endif
404
405void wake_q_add(struct wake_q_head *head, struct task_struct *task)
406{
407 struct wake_q_node *node = &task->wake_q;
408
409 /*
410 * Atomically grab the task, if ->wake_q is !nil already it means
411 * its already queued (either by us or someone else) and will get the
412 * wakeup due to that.
413 *
414 * This cmpxchg() implies a full barrier, which pairs with the write
415 * barrier implied by the wakeup in wake_up_q().
416 */
417 if (cmpxchg(&node->next, NULL, WAKE_Q_TAIL))
418 return;
419
420 get_task_struct(task);
421
422 /*
423 * The head is context local, there can be no concurrency.
424 */
425 *head->lastp = node;
426 head->lastp = &node->next;
427}
428
429void wake_up_q(struct wake_q_head *head)
430{
431 struct wake_q_node *node = head->first;
432
433 while (node != WAKE_Q_TAIL) {
434 struct task_struct *task;
435
436 task = container_of(node, struct task_struct, wake_q);
437 BUG_ON(!task);
438 /* Task can safely be re-inserted now: */
439 node = node->next;
440 task->wake_q.next = NULL;
441
442 /*
443 * wake_up_process() implies a wmb() to pair with the queueing
444 * in wake_q_add() so as not to miss wakeups.
445 */
446 wake_up_process(task);
447 put_task_struct(task);
448 }
449}
450
451/*
452 * resched_curr - mark rq's current task 'to be rescheduled now'.
453 *
454 * On UP this means the setting of the need_resched flag, on SMP it
455 * might also involve a cross-CPU call to trigger the scheduler on
456 * the target CPU.
457 */
458void resched_curr(struct rq *rq)
459{
460 struct task_struct *curr = rq->curr;
461 int cpu;
462
463 lockdep_assert_held(&rq->lock);
464
465 if (test_tsk_need_resched(curr))
466 return;
467
468 cpu = cpu_of(rq);
469
470 if (cpu == smp_processor_id()) {
471 set_tsk_need_resched(curr);
472 set_preempt_need_resched();
473 return;
474 }
475
476 if (set_nr_and_not_polling(curr))
477 smp_send_reschedule(cpu);
478 else
479 trace_sched_wake_idle_without_ipi(cpu);
480}
481
482void resched_cpu(int cpu)
483{
484 struct rq *rq = cpu_rq(cpu);
485 unsigned long flags;
486
487 raw_spin_lock_irqsave(&rq->lock, flags);
488 if (cpu_online(cpu) || cpu == smp_processor_id())
489 resched_curr(rq);
490 raw_spin_unlock_irqrestore(&rq->lock, flags);
491}
492
493#ifdef CONFIG_SMP
494#ifdef CONFIG_NO_HZ_COMMON
495/*
496 * In the semi idle case, use the nearest busy CPU for migrating timers
497 * from an idle CPU. This is good for power-savings.
498 *
499 * We don't do similar optimization for completely idle system, as
500 * selecting an idle CPU will add more delays to the timers than intended
501 * (as that CPU's timer base may not be uptodate wrt jiffies etc).
502 */
503int get_nohz_timer_target(void)
504{
505 int i, cpu = smp_processor_id();
506 struct sched_domain *sd;
507
508 if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER))
509 return cpu;
510
511 rcu_read_lock();
512 for_each_domain(cpu, sd) {
513 for_each_cpu(i, sched_domain_span(sd)) {
514 if (cpu == i)
515 continue;
516
517 if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) {
518 cpu = i;
519 goto unlock;
520 }
521 }
522 }
523
524 if (!housekeeping_cpu(cpu, HK_FLAG_TIMER))
525 cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
526unlock:
527 rcu_read_unlock();
528 return cpu;
529}
530
531/*
532 * When add_timer_on() enqueues a timer into the timer wheel of an
533 * idle CPU then this timer might expire before the next timer event
534 * which is scheduled to wake up that CPU. In case of a completely
535 * idle system the next event might even be infinite time into the
536 * future. wake_up_idle_cpu() ensures that the CPU is woken up and
537 * leaves the inner idle loop so the newly added timer is taken into
538 * account when the CPU goes back to idle and evaluates the timer
539 * wheel for the next timer event.
540 */
541static void wake_up_idle_cpu(int cpu)
542{
543 struct rq *rq = cpu_rq(cpu);
544
545 if (cpu == smp_processor_id())
546 return;
547
548 if (set_nr_and_not_polling(rq->idle))
549 smp_send_reschedule(cpu);
550 else
551 trace_sched_wake_idle_without_ipi(cpu);
552}
553
554static bool wake_up_full_nohz_cpu(int cpu)
555{
556 /*
557 * We just need the target to call irq_exit() and re-evaluate
558 * the next tick. The nohz full kick at least implies that.
559 * If needed we can still optimize that later with an
560 * empty IRQ.
561 */
562 if (cpu_is_offline(cpu))
563 return true; /* Don't try to wake offline CPUs. */
564 if (tick_nohz_full_cpu(cpu)) {
565 if (cpu != smp_processor_id() ||
566 tick_nohz_tick_stopped())
567 tick_nohz_full_kick_cpu(cpu);
568 return true;
569 }
570
571 return false;
572}
573
574/*
575 * Wake up the specified CPU. If the CPU is going offline, it is the
576 * caller's responsibility to deal with the lost wakeup, for example,
577 * by hooking into the CPU_DEAD notifier like timers and hrtimers do.
578 */
579void wake_up_nohz_cpu(int cpu)
580{
581 if (!wake_up_full_nohz_cpu(cpu))
582 wake_up_idle_cpu(cpu);
583}
584
585static inline bool got_nohz_idle_kick(void)
586{
587 int cpu = smp_processor_id();
588
589 if (!(atomic_read(nohz_flags(cpu)) & NOHZ_KICK_MASK))
590 return false;
591
592 if (idle_cpu(cpu) && !need_resched())
593 return true;
594
595 /*
596 * We can't run Idle Load Balance on this CPU for this time so we
597 * cancel it and clear NOHZ_BALANCE_KICK
598 */
599 atomic_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
600 return false;
601}
602
603#else /* CONFIG_NO_HZ_COMMON */
604
605static inline bool got_nohz_idle_kick(void)
606{
607 return false;
608}
609
610#endif /* CONFIG_NO_HZ_COMMON */
611
612#ifdef CONFIG_NO_HZ_FULL
613bool sched_can_stop_tick(struct rq *rq)
614{
615 int fifo_nr_running;
616
617 /* Deadline tasks, even if single, need the tick */
618 if (rq->dl.dl_nr_running)
619 return false;
620
621 /*
622 * If there are more than one RR tasks, we need the tick to effect the
623 * actual RR behaviour.
624 */
625 if (rq->rt.rr_nr_running) {
626 if (rq->rt.rr_nr_running == 1)
627 return true;
628 else
629 return false;
630 }
631
632 /*
633 * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
634 * forced preemption between FIFO tasks.
635 */
636 fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running;
637 if (fifo_nr_running)
638 return true;
639
640 /*
641 * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left;
642 * if there's more than one we need the tick for involuntary
643 * preemption.
644 */
645 if (rq->nr_running > 1)
646 return false;
647
648 return true;
649}
650#endif /* CONFIG_NO_HZ_FULL */
651
652void sched_avg_update(struct rq *rq)
653{
654 s64 period = sched_avg_period();
655
656 while ((s64)(rq_clock(rq) - rq->age_stamp) > period) {
657 /*
658 * Inline assembly required to prevent the compiler
659 * optimising this loop into a divmod call.
660 * See __iter_div_u64_rem() for another example of this.
661 */
662 asm("" : "+rm" (rq->age_stamp));
663 rq->age_stamp += period;
664 rq->rt_avg /= 2;
665 }
666}
667
668#endif /* CONFIG_SMP */
669
670#if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \
671 (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH)))
672/*
673 * Iterate task_group tree rooted at *from, calling @down when first entering a
674 * node and @up when leaving it for the final time.
675 *
676 * Caller must hold rcu_lock or sufficient equivalent.
677 */
678int walk_tg_tree_from(struct task_group *from,
679 tg_visitor down, tg_visitor up, void *data)
680{
681 struct task_group *parent, *child;
682 int ret;
683
684 parent = from;
685
686down:
687 ret = (*down)(parent, data);
688 if (ret)
689 goto out;
690 list_for_each_entry_rcu(child, &parent->children, siblings) {
691 parent = child;
692 goto down;
693
694up:
695 continue;
696 }
697 ret = (*up)(parent, data);
698 if (ret || parent == from)
699 goto out;
700
701 child = parent;
702 parent = parent->parent;
703 if (parent)
704 goto up;
705out:
706 return ret;
707}
708
709int tg_nop(struct task_group *tg, void *data)
710{
711 return 0;
712}
713#endif
714
715static void set_load_weight(struct task_struct *p, bool update_load)
716{
717 int prio = p->static_prio - MAX_RT_PRIO;
718 struct load_weight *load = &p->se.load;
719
720 /*
721 * SCHED_IDLE tasks get minimal weight:
722 */
723 if (idle_policy(p->policy)) {
724 load->weight = scale_load(WEIGHT_IDLEPRIO);
725 load->inv_weight = WMULT_IDLEPRIO;
726 return;
727 }
728
729 /*
730 * SCHED_OTHER tasks have to update their load when changing their
731 * weight
732 */
733 if (update_load && p->sched_class == &fair_sched_class) {
734 reweight_task(p, prio);
735 } else {
736 load->weight = scale_load(sched_prio_to_weight[prio]);
737 load->inv_weight = sched_prio_to_wmult[prio];
738 }
739}
740
741static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
742{
743 if (!(flags & ENQUEUE_NOCLOCK))
744 update_rq_clock(rq);
745
746 if (!(flags & ENQUEUE_RESTORE))
747 sched_info_queued(rq, p);
748
749 p->sched_class->enqueue_task(rq, p, flags);
750}
751
752static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
753{
754 if (!(flags & DEQUEUE_NOCLOCK))
755 update_rq_clock(rq);
756
757 if (!(flags & DEQUEUE_SAVE))
758 sched_info_dequeued(rq, p);
759
760 p->sched_class->dequeue_task(rq, p, flags);
761}
762
763void activate_task(struct rq *rq, struct task_struct *p, int flags)
764{
765 if (task_contributes_to_load(p))
766 rq->nr_uninterruptible--;
767
768 enqueue_task(rq, p, flags);
769}
770
771void deactivate_task(struct rq *rq, struct task_struct *p, int flags)
772{
773 if (task_contributes_to_load(p))
774 rq->nr_uninterruptible++;
775
776 dequeue_task(rq, p, flags);
777}
778
779/*
780 * __normal_prio - return the priority that is based on the static prio
781 */
782static inline int __normal_prio(struct task_struct *p)
783{
784 return p->static_prio;
785}
786
787/*
788 * Calculate the expected normal priority: i.e. priority
789 * without taking RT-inheritance into account. Might be
790 * boosted by interactivity modifiers. Changes upon fork,
791 * setprio syscalls, and whenever the interactivity
792 * estimator recalculates.
793 */
794static inline int normal_prio(struct task_struct *p)
795{
796 int prio;
797
798 if (task_has_dl_policy(p))
799 prio = MAX_DL_PRIO-1;
800 else if (task_has_rt_policy(p))
801 prio = MAX_RT_PRIO-1 - p->rt_priority;
802 else
803 prio = __normal_prio(p);
804 return prio;
805}
806
807/*
808 * Calculate the current priority, i.e. the priority
809 * taken into account by the scheduler. This value might
810 * be boosted by RT tasks, or might be boosted by
811 * interactivity modifiers. Will be RT if the task got
812 * RT-boosted. If not then it returns p->normal_prio.
813 */
814static int effective_prio(struct task_struct *p)
815{
816 p->normal_prio = normal_prio(p);
817 /*
818 * If we are RT tasks or we were boosted to RT priority,
819 * keep the priority unchanged. Otherwise, update priority
820 * to the normal priority:
821 */
822 if (!rt_prio(p->prio))
823 return p->normal_prio;
824 return p->prio;
825}
826
827/**
828 * task_curr - is this task currently executing on a CPU?
829 * @p: the task in question.
830 *
831 * Return: 1 if the task is currently executing. 0 otherwise.
832 */
833inline int task_curr(const struct task_struct *p)
834{
835 return cpu_curr(task_cpu(p)) == p;
836}
837
838/*
839 * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock,
840 * use the balance_callback list if you want balancing.
841 *
842 * this means any call to check_class_changed() must be followed by a call to
843 * balance_callback().
844 */
845static inline void check_class_changed(struct rq *rq, struct task_struct *p,
846 const struct sched_class *prev_class,
847 int oldprio)
848{
849 if (prev_class != p->sched_class) {
850 if (prev_class->switched_from)
851 prev_class->switched_from(rq, p);
852
853 p->sched_class->switched_to(rq, p);
854 } else if (oldprio != p->prio || dl_task(p))
855 p->sched_class->prio_changed(rq, p, oldprio);
856}
857
858void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags)
859{
860 const struct sched_class *class;
861
862 if (p->sched_class == rq->curr->sched_class) {
863 rq->curr->sched_class->check_preempt_curr(rq, p, flags);
864 } else {
865 for_each_class(class) {
866 if (class == rq->curr->sched_class)
867 break;
868 if (class == p->sched_class) {
869 resched_curr(rq);
870 break;
871 }
872 }
873 }
874
875 /*
876 * A queue event has occurred, and we're going to schedule. In
877 * this case, we can save a useless back to back clock update.
878 */
879 if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr))
880 rq_clock_skip_update(rq);
881}
882
883#ifdef CONFIG_SMP
884
885static inline bool is_per_cpu_kthread(struct task_struct *p)
886{
887 if (!(p->flags & PF_KTHREAD))
888 return false;
889
890 if (p->nr_cpus_allowed != 1)
891 return false;
892
893 return true;
894}
895
896/*
897 * Per-CPU kthreads are allowed to run on !actie && online CPUs, see
898 * __set_cpus_allowed_ptr() and select_fallback_rq().
899 */
900static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
901{
902 if (!cpumask_test_cpu(cpu, &p->cpus_allowed))
903 return false;
904
905 if (is_per_cpu_kthread(p))
906 return cpu_online(cpu);
907
908 return cpu_active(cpu);
909}
910
911/*
912 * This is how migration works:
913 *
914 * 1) we invoke migration_cpu_stop() on the target CPU using
915 * stop_one_cpu().
916 * 2) stopper starts to run (implicitly forcing the migrated thread
917 * off the CPU)
918 * 3) it checks whether the migrated task is still in the wrong runqueue.
919 * 4) if it's in the wrong runqueue then the migration thread removes
920 * it and puts it into the right queue.
921 * 5) stopper completes and stop_one_cpu() returns and the migration
922 * is done.
923 */
924
925/*
926 * move_queued_task - move a queued task to new rq.
927 *
928 * Returns (locked) new rq. Old rq's lock is released.
929 */
930static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
931 struct task_struct *p, int new_cpu)
932{
933 lockdep_assert_held(&rq->lock);
934
935 p->on_rq = TASK_ON_RQ_MIGRATING;
936 dequeue_task(rq, p, DEQUEUE_NOCLOCK);
937 set_task_cpu(p, new_cpu);
938 rq_unlock(rq, rf);
939
940 rq = cpu_rq(new_cpu);
941
942 rq_lock(rq, rf);
943 BUG_ON(task_cpu(p) != new_cpu);
944 enqueue_task(rq, p, 0);
945 p->on_rq = TASK_ON_RQ_QUEUED;
946 check_preempt_curr(rq, p, 0);
947
948 return rq;
949}
950
951struct migration_arg {
952 struct task_struct *task;
953 int dest_cpu;
954};
955
956/*
957 * Move (not current) task off this CPU, onto the destination CPU. We're doing
958 * this because either it can't run here any more (set_cpus_allowed()
959 * away from this CPU, or CPU going down), or because we're
960 * attempting to rebalance this task on exec (sched_exec).
961 *
962 * So we race with normal scheduler movements, but that's OK, as long
963 * as the task is no longer on this CPU.
964 */
965static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf,
966 struct task_struct *p, int dest_cpu)
967{
968 /* Affinity changed (again). */
969 if (!is_cpu_allowed(p, dest_cpu))
970 return rq;
971
972 update_rq_clock(rq);
973 rq = move_queued_task(rq, rf, p, dest_cpu);
974
975 return rq;
976}
977
978/*
979 * migration_cpu_stop - this will be executed by a highprio stopper thread
980 * and performs thread migration by bumping thread off CPU then
981 * 'pushing' onto another runqueue.
982 */
983static int migration_cpu_stop(void *data)
984{
985 struct migration_arg *arg = data;
986 struct task_struct *p = arg->task;
987 struct rq *rq = this_rq();
988 struct rq_flags rf;
989
990 /*
991 * The original target CPU might have gone down and we might
992 * be on another CPU but it doesn't matter.
993 */
994 local_irq_disable();
995 /*
996 * We need to explicitly wake pending tasks before running
997 * __migrate_task() such that we will not miss enforcing cpus_allowed
998 * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
999 */
1000 sched_ttwu_pending();
1001
1002 raw_spin_lock(&p->pi_lock);
1003 rq_lock(rq, &rf);
1004 /*
1005 * If task_rq(p) != rq, it cannot be migrated here, because we're
1006 * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
1007 * we're holding p->pi_lock.
1008 */
1009 if (task_rq(p) == rq) {
1010 if (task_on_rq_queued(p))
1011 rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
1012 else
1013 p->wake_cpu = arg->dest_cpu;
1014 }
1015 rq_unlock(rq, &rf);
1016 raw_spin_unlock(&p->pi_lock);
1017
1018 local_irq_enable();
1019 return 0;
1020}
1021
1022/*
1023 * sched_class::set_cpus_allowed must do the below, but is not required to
1024 * actually call this function.
1025 */
1026void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask)
1027{
1028 cpumask_copy(&p->cpus_allowed, new_mask);
1029 p->nr_cpus_allowed = cpumask_weight(new_mask);
1030}
1031
1032void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
1033{
1034 struct rq *rq = task_rq(p);
1035 bool queued, running;
1036
1037 lockdep_assert_held(&p->pi_lock);
1038
1039 queued = task_on_rq_queued(p);
1040 running = task_current(rq, p);
1041
1042 if (queued) {
1043 /*
1044 * Because __kthread_bind() calls this on blocked tasks without
1045 * holding rq->lock.
1046 */
1047 lockdep_assert_held(&rq->lock);
1048 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
1049 }
1050 if (running)
1051 put_prev_task(rq, p);
1052
1053 p->sched_class->set_cpus_allowed(p, new_mask);
1054
1055 if (queued)
1056 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
1057 if (running)
1058 set_curr_task(rq, p);
1059}
1060
1061/*
1062 * Change a given task's CPU affinity. Migrate the thread to a
1063 * proper CPU and schedule it away if the CPU it's executing on
1064 * is removed from the allowed bitmask.
1065 *
1066 * NOTE: the caller must have a valid reference to the task, the
1067 * task must not exit() & deallocate itself prematurely. The
1068 * call is not atomic; no spinlocks may be held.
1069 */
1070static int __set_cpus_allowed_ptr(struct task_struct *p,
1071 const struct cpumask *new_mask, bool check)
1072{
1073 const struct cpumask *cpu_valid_mask = cpu_active_mask;
1074 unsigned int dest_cpu;
1075 struct rq_flags rf;
1076 struct rq *rq;
1077 int ret = 0;
1078
1079 rq = task_rq_lock(p, &rf);
1080 update_rq_clock(rq);
1081
1082 if (p->flags & PF_KTHREAD) {
1083 /*
1084 * Kernel threads are allowed on online && !active CPUs
1085 */
1086 cpu_valid_mask = cpu_online_mask;
1087 }
1088
1089 /*
1090 * Must re-check here, to close a race against __kthread_bind(),
1091 * sched_setaffinity() is not guaranteed to observe the flag.
1092 */
1093 if (check && (p->flags & PF_NO_SETAFFINITY)) {
1094 ret = -EINVAL;
1095 goto out;
1096 }
1097
1098 if (cpumask_equal(&p->cpus_allowed, new_mask))
1099 goto out;
1100
1101 if (!cpumask_intersects(new_mask, cpu_valid_mask)) {
1102 ret = -EINVAL;
1103 goto out;
1104 }
1105
1106 do_set_cpus_allowed(p, new_mask);
1107
1108 if (p->flags & PF_KTHREAD) {
1109 /*
1110 * For kernel threads that do indeed end up on online &&
1111 * !active we want to ensure they are strict per-CPU threads.
1112 */
1113 WARN_ON(cpumask_intersects(new_mask, cpu_online_mask) &&
1114 !cpumask_intersects(new_mask, cpu_active_mask) &&
1115 p->nr_cpus_allowed != 1);
1116 }
1117
1118 /* Can the task run on the task's current CPU? If so, we're done */
1119 if (cpumask_test_cpu(task_cpu(p), new_mask))
1120 goto out;
1121
1122 dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask);
1123 if (task_running(rq, p) || p->state == TASK_WAKING) {
1124 struct migration_arg arg = { p, dest_cpu };
1125 /* Need help from migration thread: drop lock and wait. */
1126 task_rq_unlock(rq, p, &rf);
1127 stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
1128 tlb_migrate_finish(p->mm);
1129 return 0;
1130 } else if (task_on_rq_queued(p)) {
1131 /*
1132 * OK, since we're going to drop the lock immediately
1133 * afterwards anyway.
1134 */
1135 rq = move_queued_task(rq, &rf, p, dest_cpu);
1136 }
1137out:
1138 task_rq_unlock(rq, p, &rf);
1139
1140 return ret;
1141}
1142
1143int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
1144{
1145 return __set_cpus_allowed_ptr(p, new_mask, false);
1146}
1147EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
1148
1149void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
1150{
1151#ifdef CONFIG_SCHED_DEBUG
1152 /*
1153 * We should never call set_task_cpu() on a blocked task,
1154 * ttwu() will sort out the placement.
1155 */
1156 WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
1157 !p->on_rq);
1158
1159 /*
1160 * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
1161 * because schedstat_wait_{start,end} rebase migrating task's wait_start
1162 * time relying on p->on_rq.
1163 */
1164 WARN_ON_ONCE(p->state == TASK_RUNNING &&
1165 p->sched_class == &fair_sched_class &&
1166 (p->on_rq && !task_on_rq_migrating(p)));
1167
1168#ifdef CONFIG_LOCKDEP
1169 /*
1170 * The caller should hold either p->pi_lock or rq->lock, when changing
1171 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
1172 *
1173 * sched_move_task() holds both and thus holding either pins the cgroup,
1174 * see task_group().
1175 *
1176 * Furthermore, all task_rq users should acquire both locks, see
1177 * task_rq_lock().
1178 */
1179 WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
1180 lockdep_is_held(&task_rq(p)->lock)));
1181#endif
1182 /*
1183 * Clearly, migrating tasks to offline CPUs is a fairly daft thing.
1184 */
1185 WARN_ON_ONCE(!cpu_online(new_cpu));
1186#endif
1187
1188 trace_sched_migrate_task(p, new_cpu);
1189
1190 if (task_cpu(p) != new_cpu) {
1191 if (p->sched_class->migrate_task_rq)
1192 p->sched_class->migrate_task_rq(p);
1193 p->se.nr_migrations++;
1194 perf_event_task_migrate(p);
1195 }
1196
1197 __set_task_cpu(p, new_cpu);
1198}
1199
1200static void __migrate_swap_task(struct task_struct *p, int cpu)
1201{
1202 if (task_on_rq_queued(p)) {
1203 struct rq *src_rq, *dst_rq;
1204 struct rq_flags srf, drf;
1205
1206 src_rq = task_rq(p);
1207 dst_rq = cpu_rq(cpu);
1208
1209 rq_pin_lock(src_rq, &srf);
1210 rq_pin_lock(dst_rq, &drf);
1211
1212 p->on_rq = TASK_ON_RQ_MIGRATING;
1213 deactivate_task(src_rq, p, 0);
1214 set_task_cpu(p, cpu);
1215 activate_task(dst_rq, p, 0);
1216 p->on_rq = TASK_ON_RQ_QUEUED;
1217 check_preempt_curr(dst_rq, p, 0);
1218
1219 rq_unpin_lock(dst_rq, &drf);
1220 rq_unpin_lock(src_rq, &srf);
1221
1222 } else {
1223 /*
1224 * Task isn't running anymore; make it appear like we migrated
1225 * it before it went to sleep. This means on wakeup we make the
1226 * previous CPU our target instead of where it really is.
1227 */
1228 p->wake_cpu = cpu;
1229 }
1230}
1231
1232struct migration_swap_arg {
1233 struct task_struct *src_task, *dst_task;
1234 int src_cpu, dst_cpu;
1235};
1236
1237static int migrate_swap_stop(void *data)
1238{
1239 struct migration_swap_arg *arg = data;
1240 struct rq *src_rq, *dst_rq;
1241 int ret = -EAGAIN;
1242
1243 if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu))
1244 return -EAGAIN;
1245
1246 src_rq = cpu_rq(arg->src_cpu);
1247 dst_rq = cpu_rq(arg->dst_cpu);
1248
1249 double_raw_lock(&arg->src_task->pi_lock,
1250 &arg->dst_task->pi_lock);
1251 double_rq_lock(src_rq, dst_rq);
1252
1253 if (task_cpu(arg->dst_task) != arg->dst_cpu)
1254 goto unlock;
1255
1256 if (task_cpu(arg->src_task) != arg->src_cpu)
1257 goto unlock;
1258
1259 if (!cpumask_test_cpu(arg->dst_cpu, &arg->src_task->cpus_allowed))
1260 goto unlock;
1261
1262 if (!cpumask_test_cpu(arg->src_cpu, &arg->dst_task->cpus_allowed))
1263 goto unlock;
1264
1265 __migrate_swap_task(arg->src_task, arg->dst_cpu);
1266 __migrate_swap_task(arg->dst_task, arg->src_cpu);
1267
1268 ret = 0;
1269
1270unlock:
1271 double_rq_unlock(src_rq, dst_rq);
1272 raw_spin_unlock(&arg->dst_task->pi_lock);
1273 raw_spin_unlock(&arg->src_task->pi_lock);
1274
1275 return ret;
1276}
1277
1278/*
1279 * Cross migrate two tasks
1280 */
1281int migrate_swap(struct task_struct *cur, struct task_struct *p)
1282{
1283 struct migration_swap_arg arg;
1284 int ret = -EINVAL;
1285
1286 arg = (struct migration_swap_arg){
1287 .src_task = cur,
1288 .src_cpu = task_cpu(cur),
1289 .dst_task = p,
1290 .dst_cpu = task_cpu(p),
1291 };
1292
1293 if (arg.src_cpu == arg.dst_cpu)
1294 goto out;
1295
1296 /*
1297 * These three tests are all lockless; this is OK since all of them
1298 * will be re-checked with proper locks held further down the line.
1299 */
1300 if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu))
1301 goto out;
1302
1303 if (!cpumask_test_cpu(arg.dst_cpu, &arg.src_task->cpus_allowed))
1304 goto out;
1305
1306 if (!cpumask_test_cpu(arg.src_cpu, &arg.dst_task->cpus_allowed))
1307 goto out;
1308
1309 trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu);
1310 ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg);
1311
1312out:
1313 return ret;
1314}
1315
1316/*
1317 * wait_task_inactive - wait for a thread to unschedule.
1318 *
1319 * If @match_state is nonzero, it's the @p->state value just checked and
1320 * not expected to change. If it changes, i.e. @p might have woken up,
1321 * then return zero. When we succeed in waiting for @p to be off its CPU,
1322 * we return a positive number (its total switch count). If a second call
1323 * a short while later returns the same number, the caller can be sure that
1324 * @p has remained unscheduled the whole time.
1325 *
1326 * The caller must ensure that the task *will* unschedule sometime soon,
1327 * else this function might spin for a *long* time. This function can't
1328 * be called with interrupts off, or it may introduce deadlock with
1329 * smp_call_function() if an IPI is sent by the same process we are
1330 * waiting to become inactive.
1331 */
1332unsigned long wait_task_inactive(struct task_struct *p, long match_state)
1333{
1334 int running, queued;
1335 struct rq_flags rf;
1336 unsigned long ncsw;
1337 struct rq *rq;
1338
1339 for (;;) {
1340 /*
1341 * We do the initial early heuristics without holding
1342 * any task-queue locks at all. We'll only try to get
1343 * the runqueue lock when things look like they will
1344 * work out!
1345 */
1346 rq = task_rq(p);
1347
1348 /*
1349 * If the task is actively running on another CPU
1350 * still, just relax and busy-wait without holding
1351 * any locks.
1352 *
1353 * NOTE! Since we don't hold any locks, it's not
1354 * even sure that "rq" stays as the right runqueue!
1355 * But we don't care, since "task_running()" will
1356 * return false if the runqueue has changed and p
1357 * is actually now running somewhere else!
1358 */
1359 while (task_running(rq, p)) {
1360 if (match_state && unlikely(p->state != match_state))
1361 return 0;
1362 cpu_relax();
1363 }
1364
1365 /*
1366 * Ok, time to look more closely! We need the rq
1367 * lock now, to be *sure*. If we're wrong, we'll
1368 * just go back and repeat.
1369 */
1370 rq = task_rq_lock(p, &rf);
1371 trace_sched_wait_task(p);
1372 running = task_running(rq, p);
1373 queued = task_on_rq_queued(p);
1374 ncsw = 0;
1375 if (!match_state || p->state == match_state)
1376 ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
1377 task_rq_unlock(rq, p, &rf);
1378
1379 /*
1380 * If it changed from the expected state, bail out now.
1381 */
1382 if (unlikely(!ncsw))
1383 break;
1384
1385 /*
1386 * Was it really running after all now that we
1387 * checked with the proper locks actually held?
1388 *
1389 * Oops. Go back and try again..
1390 */
1391 if (unlikely(running)) {
1392 cpu_relax();
1393 continue;
1394 }
1395
1396 /*
1397 * It's not enough that it's not actively running,
1398 * it must be off the runqueue _entirely_, and not
1399 * preempted!
1400 *
1401 * So if it was still runnable (but just not actively
1402 * running right now), it's preempted, and we should
1403 * yield - it could be a while.
1404 */
1405 if (unlikely(queued)) {
1406 ktime_t to = NSEC_PER_SEC / HZ;
1407
1408 set_current_state(TASK_UNINTERRUPTIBLE);
1409 schedule_hrtimeout(&to, HRTIMER_MODE_REL);
1410 continue;
1411 }
1412
1413 /*
1414 * Ahh, all good. It wasn't running, and it wasn't
1415 * runnable, which means that it will never become
1416 * running in the future either. We're all done!
1417 */
1418 break;
1419 }
1420
1421 return ncsw;
1422}
1423
1424/***
1425 * kick_process - kick a running thread to enter/exit the kernel
1426 * @p: the to-be-kicked thread
1427 *
1428 * Cause a process which is running on another CPU to enter
1429 * kernel-mode, without any delay. (to get signals handled.)
1430 *
1431 * NOTE: this function doesn't have to take the runqueue lock,
1432 * because all it wants to ensure is that the remote task enters
1433 * the kernel. If the IPI races and the task has been migrated
1434 * to another CPU then no harm is done and the purpose has been
1435 * achieved as well.
1436 */
1437void kick_process(struct task_struct *p)
1438{
1439 int cpu;
1440
1441 preempt_disable();
1442 cpu = task_cpu(p);
1443 if ((cpu != smp_processor_id()) && task_curr(p))
1444 smp_send_reschedule(cpu);
1445 preempt_enable();
1446}
1447EXPORT_SYMBOL_GPL(kick_process);
1448
1449/*
1450 * ->cpus_allowed is protected by both rq->lock and p->pi_lock
1451 *
1452 * A few notes on cpu_active vs cpu_online:
1453 *
1454 * - cpu_active must be a subset of cpu_online
1455 *
1456 * - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
1457 * see __set_cpus_allowed_ptr(). At this point the newly online
1458 * CPU isn't yet part of the sched domains, and balancing will not
1459 * see it.
1460 *
1461 * - on CPU-down we clear cpu_active() to mask the sched domains and
1462 * avoid the load balancer to place new tasks on the to be removed
1463 * CPU. Existing tasks will remain running there and will be taken
1464 * off.
1465 *
1466 * This means that fallback selection must not select !active CPUs.
1467 * And can assume that any active CPU must be online. Conversely
1468 * select_task_rq() below may allow selection of !active CPUs in order
1469 * to satisfy the above rules.
1470 */
1471static int select_fallback_rq(int cpu, struct task_struct *p)
1472{
1473 int nid = cpu_to_node(cpu);
1474 const struct cpumask *nodemask = NULL;
1475 enum { cpuset, possible, fail } state = cpuset;
1476 int dest_cpu;
1477
1478 /*
1479 * If the node that the CPU is on has been offlined, cpu_to_node()
1480 * will return -1. There is no CPU on the node, and we should
1481 * select the CPU on the other node.
1482 */
1483 if (nid != -1) {
1484 nodemask = cpumask_of_node(nid);
1485
1486 /* Look for allowed, online CPU in same node. */
1487 for_each_cpu(dest_cpu, nodemask) {
1488 if (!cpu_active(dest_cpu))
1489 continue;
1490 if (cpumask_test_cpu(dest_cpu, &p->cpus_allowed))
1491 return dest_cpu;
1492 }
1493 }
1494
1495 for (;;) {
1496 /* Any allowed, online CPU? */
1497 for_each_cpu(dest_cpu, &p->cpus_allowed) {
1498 if (!is_cpu_allowed(p, dest_cpu))
1499 continue;
1500
1501 goto out;
1502 }
1503
1504 /* No more Mr. Nice Guy. */
1505 switch (state) {
1506 case cpuset:
1507 if (IS_ENABLED(CONFIG_CPUSETS)) {
1508 cpuset_cpus_allowed_fallback(p);
1509 state = possible;
1510 break;
1511 }
1512 /* Fall-through */
1513 case possible:
1514 do_set_cpus_allowed(p, cpu_possible_mask);
1515 state = fail;
1516 break;
1517
1518 case fail:
1519 BUG();
1520 break;
1521 }
1522 }
1523
1524out:
1525 if (state != cpuset) {
1526 /*
1527 * Don't tell them about moving exiting tasks or
1528 * kernel threads (both mm NULL), since they never
1529 * leave kernel.
1530 */
1531 if (p->mm && printk_ratelimit()) {
1532 printk_deferred("process %d (%s) no longer affine to cpu%d\n",
1533 task_pid_nr(p), p->comm, cpu);
1534 }
1535 }
1536
1537 return dest_cpu;
1538}
1539
1540/*
1541 * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable.
1542 */
1543static inline
1544int select_task_rq(struct task_struct *p, int cpu, int sd_flags, int wake_flags)
1545{
1546 lockdep_assert_held(&p->pi_lock);
1547
1548 if (p->nr_cpus_allowed > 1)
1549 cpu = p->sched_class->select_task_rq(p, cpu, sd_flags, wake_flags);
1550 else
1551 cpu = cpumask_any(&p->cpus_allowed);
1552
1553 /*
1554 * In order not to call set_task_cpu() on a blocking task we need
1555 * to rely on ttwu() to place the task on a valid ->cpus_allowed
1556 * CPU.
1557 *
1558 * Since this is common to all placement strategies, this lives here.
1559 *
1560 * [ this allows ->select_task() to simply return task_cpu(p) and
1561 * not worry about this generic constraint ]
1562 */
1563 if (unlikely(!is_cpu_allowed(p, cpu)))
1564 cpu = select_fallback_rq(task_cpu(p), p);
1565
1566 return cpu;
1567}
1568
1569static void update_avg(u64 *avg, u64 sample)
1570{
1571 s64 diff = sample - *avg;
1572 *avg += diff >> 3;
1573}
1574
1575void sched_set_stop_task(int cpu, struct task_struct *stop)
1576{
1577 struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
1578 struct task_struct *old_stop = cpu_rq(cpu)->stop;
1579
1580 if (stop) {
1581 /*
1582 * Make it appear like a SCHED_FIFO task, its something
1583 * userspace knows about and won't get confused about.
1584 *
1585 * Also, it will make PI more or less work without too
1586 * much confusion -- but then, stop work should not
1587 * rely on PI working anyway.
1588 */
1589 sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m);
1590
1591 stop->sched_class = &stop_sched_class;
1592 }
1593
1594 cpu_rq(cpu)->stop = stop;
1595
1596 if (old_stop) {
1597 /*
1598 * Reset it back to a normal scheduling class so that
1599 * it can die in pieces.
1600 */
1601 old_stop->sched_class = &rt_sched_class;
1602 }
1603}
1604
1605#else
1606
1607static inline int __set_cpus_allowed_ptr(struct task_struct *p,
1608 const struct cpumask *new_mask, bool check)
1609{
1610 return set_cpus_allowed_ptr(p, new_mask);
1611}
1612
1613#endif /* CONFIG_SMP */
1614
1615static void
1616ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
1617{
1618 struct rq *rq;
1619
1620 if (!schedstat_enabled())
1621 return;
1622
1623 rq = this_rq();
1624
1625#ifdef CONFIG_SMP
1626 if (cpu == rq->cpu) {
1627 __schedstat_inc(rq->ttwu_local);
1628 __schedstat_inc(p->se.statistics.nr_wakeups_local);
1629 } else {
1630 struct sched_domain *sd;
1631
1632 __schedstat_inc(p->se.statistics.nr_wakeups_remote);
1633 rcu_read_lock();
1634 for_each_domain(rq->cpu, sd) {
1635 if (cpumask_test_cpu(cpu, sched_domain_span(sd))) {
1636 __schedstat_inc(sd->ttwu_wake_remote);
1637 break;
1638 }
1639 }
1640 rcu_read_unlock();
1641 }
1642
1643 if (wake_flags & WF_MIGRATED)
1644 __schedstat_inc(p->se.statistics.nr_wakeups_migrate);
1645#endif /* CONFIG_SMP */
1646
1647 __schedstat_inc(rq->ttwu_count);
1648 __schedstat_inc(p->se.statistics.nr_wakeups);
1649
1650 if (wake_flags & WF_SYNC)
1651 __schedstat_inc(p->se.statistics.nr_wakeups_sync);
1652}
1653
1654static inline void ttwu_activate(struct rq *rq, struct task_struct *p, int en_flags)
1655{
1656 activate_task(rq, p, en_flags);
1657 p->on_rq = TASK_ON_RQ_QUEUED;
1658
1659 /* If a worker is waking up, notify the workqueue: */
1660 if (p->flags & PF_WQ_WORKER)
1661 wq_worker_waking_up(p, cpu_of(rq));
1662}
1663
1664/*
1665 * Mark the task runnable and perform wakeup-preemption.
1666 */
1667static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
1668 struct rq_flags *rf)
1669{
1670 check_preempt_curr(rq, p, wake_flags);
1671 p->state = TASK_RUNNING;
1672 trace_sched_wakeup(p);
1673
1674#ifdef CONFIG_SMP
1675 if (p->sched_class->task_woken) {
1676 /*
1677 * Our task @p is fully woken up and running; so its safe to
1678 * drop the rq->lock, hereafter rq is only used for statistics.
1679 */
1680 rq_unpin_lock(rq, rf);
1681 p->sched_class->task_woken(rq, p);
1682 rq_repin_lock(rq, rf);
1683 }
1684
1685 if (rq->idle_stamp) {
1686 u64 delta = rq_clock(rq) - rq->idle_stamp;
1687 u64 max = 2*rq->max_idle_balance_cost;
1688
1689 update_avg(&rq->avg_idle, delta);
1690
1691 if (rq->avg_idle > max)
1692 rq->avg_idle = max;
1693
1694 rq->idle_stamp = 0;
1695 }
1696#endif
1697}
1698
1699static void
1700ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags,
1701 struct rq_flags *rf)
1702{
1703 int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK;
1704
1705 lockdep_assert_held(&rq->lock);
1706
1707#ifdef CONFIG_SMP
1708 if (p->sched_contributes_to_load)
1709 rq->nr_uninterruptible--;
1710
1711 if (wake_flags & WF_MIGRATED)
1712 en_flags |= ENQUEUE_MIGRATED;
1713#endif
1714
1715 ttwu_activate(rq, p, en_flags);
1716 ttwu_do_wakeup(rq, p, wake_flags, rf);
1717}
1718
1719/*
1720 * Called in case the task @p isn't fully descheduled from its runqueue,
1721 * in this case we must do a remote wakeup. Its a 'light' wakeup though,
1722 * since all we need to do is flip p->state to TASK_RUNNING, since
1723 * the task is still ->on_rq.
1724 */
1725static int ttwu_remote(struct task_struct *p, int wake_flags)
1726{
1727 struct rq_flags rf;
1728 struct rq *rq;
1729 int ret = 0;
1730
1731 rq = __task_rq_lock(p, &rf);
1732 if (task_on_rq_queued(p)) {
1733 /* check_preempt_curr() may use rq clock */
1734 update_rq_clock(rq);
1735 ttwu_do_wakeup(rq, p, wake_flags, &rf);
1736 ret = 1;
1737 }
1738 __task_rq_unlock(rq, &rf);
1739
1740 return ret;
1741}
1742
1743#ifdef CONFIG_SMP
1744void sched_ttwu_pending(void)
1745{
1746 struct rq *rq = this_rq();
1747 struct llist_node *llist = llist_del_all(&rq->wake_list);
1748 struct task_struct *p, *t;
1749 struct rq_flags rf;
1750
1751 if (!llist)
1752 return;
1753
1754 rq_lock_irqsave(rq, &rf);
1755 update_rq_clock(rq);
1756
1757 llist_for_each_entry_safe(p, t, llist, wake_entry)
1758 ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf);
1759
1760 rq_unlock_irqrestore(rq, &rf);
1761}
1762
1763void scheduler_ipi(void)
1764{
1765 /*
1766 * Fold TIF_NEED_RESCHED into the preempt_count; anybody setting
1767 * TIF_NEED_RESCHED remotely (for the first time) will also send
1768 * this IPI.
1769 */
1770 preempt_fold_need_resched();
1771
1772 if (llist_empty(&this_rq()->wake_list) && !got_nohz_idle_kick())
1773 return;
1774
1775 /*
1776 * Not all reschedule IPI handlers call irq_enter/irq_exit, since
1777 * traditionally all their work was done from the interrupt return
1778 * path. Now that we actually do some work, we need to make sure
1779 * we do call them.
1780 *
1781 * Some archs already do call them, luckily irq_enter/exit nest
1782 * properly.
1783 *
1784 * Arguably we should visit all archs and update all handlers,
1785 * however a fair share of IPIs are still resched only so this would
1786 * somewhat pessimize the simple resched case.
1787 */
1788 irq_enter();
1789 sched_ttwu_pending();
1790
1791 /*
1792 * Check if someone kicked us for doing the nohz idle load balance.
1793 */
1794 if (unlikely(got_nohz_idle_kick())) {
1795 this_rq()->idle_balance = 1;
1796 raise_softirq_irqoff(SCHED_SOFTIRQ);
1797 }
1798 irq_exit();
1799}
1800
1801static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
1802{
1803 struct rq *rq = cpu_rq(cpu);
1804
1805 p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
1806
1807 if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
1808 if (!set_nr_if_polling(rq->idle))
1809 smp_send_reschedule(cpu);
1810 else
1811 trace_sched_wake_idle_without_ipi(cpu);
1812 }
1813}
1814
1815void wake_up_if_idle(int cpu)
1816{
1817 struct rq *rq = cpu_rq(cpu);
1818 struct rq_flags rf;
1819
1820 rcu_read_lock();
1821
1822 if (!is_idle_task(rcu_dereference(rq->curr)))
1823 goto out;
1824
1825 if (set_nr_if_polling(rq->idle)) {
1826 trace_sched_wake_idle_without_ipi(cpu);
1827 } else {
1828 rq_lock_irqsave(rq, &rf);
1829 if (is_idle_task(rq->curr))
1830 smp_send_reschedule(cpu);
1831 /* Else CPU is not idle, do nothing here: */
1832 rq_unlock_irqrestore(rq, &rf);
1833 }
1834
1835out:
1836 rcu_read_unlock();
1837}
1838
1839bool cpus_share_cache(int this_cpu, int that_cpu)
1840{
1841 return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
1842}
1843#endif /* CONFIG_SMP */
1844
1845static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
1846{
1847 struct rq *rq = cpu_rq(cpu);
1848 struct rq_flags rf;
1849
1850#if defined(CONFIG_SMP)
1851 if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
1852 sched_clock_cpu(cpu); /* Sync clocks across CPUs */
1853 ttwu_queue_remote(p, cpu, wake_flags);
1854 return;
1855 }
1856#endif
1857
1858 rq_lock(rq, &rf);
1859 update_rq_clock(rq);
1860 ttwu_do_activate(rq, p, wake_flags, &rf);
1861 rq_unlock(rq, &rf);
1862}
1863
1864/*
1865 * Notes on Program-Order guarantees on SMP systems.
1866 *
1867 * MIGRATION
1868 *
1869 * The basic program-order guarantee on SMP systems is that when a task [t]
1870 * migrates, all its activity on its old CPU [c0] happens-before any subsequent
1871 * execution on its new CPU [c1].
1872 *
1873 * For migration (of runnable tasks) this is provided by the following means:
1874 *
1875 * A) UNLOCK of the rq(c0)->lock scheduling out task t
1876 * B) migration for t is required to synchronize *both* rq(c0)->lock and
1877 * rq(c1)->lock (if not at the same time, then in that order).
1878 * C) LOCK of the rq(c1)->lock scheduling in task
1879 *
1880 * Transitivity guarantees that B happens after A and C after B.
1881 * Note: we only require RCpc transitivity.
1882 * Note: the CPU doing B need not be c0 or c1
1883 *
1884 * Example:
1885 *
1886 * CPU0 CPU1 CPU2
1887 *
1888 * LOCK rq(0)->lock
1889 * sched-out X
1890 * sched-in Y
1891 * UNLOCK rq(0)->lock
1892 *
1893 * LOCK rq(0)->lock // orders against CPU0
1894 * dequeue X
1895 * UNLOCK rq(0)->lock
1896 *
1897 * LOCK rq(1)->lock
1898 * enqueue X
1899 * UNLOCK rq(1)->lock
1900 *
1901 * LOCK rq(1)->lock // orders against CPU2
1902 * sched-out Z
1903 * sched-in X
1904 * UNLOCK rq(1)->lock
1905 *
1906 *
1907 * BLOCKING -- aka. SLEEP + WAKEUP
1908 *
1909 * For blocking we (obviously) need to provide the same guarantee as for
1910 * migration. However the means are completely different as there is no lock
1911 * chain to provide order. Instead we do:
1912 *
1913 * 1) smp_store_release(X->on_cpu, 0)
1914 * 2) smp_cond_load_acquire(!X->on_cpu)
1915 *
1916 * Example:
1917 *
1918 * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
1919 *
1920 * LOCK rq(0)->lock LOCK X->pi_lock
1921 * dequeue X
1922 * sched-out X
1923 * smp_store_release(X->on_cpu, 0);
1924 *
1925 * smp_cond_load_acquire(&X->on_cpu, !VAL);
1926 * X->state = WAKING
1927 * set_task_cpu(X,2)
1928 *
1929 * LOCK rq(2)->lock
1930 * enqueue X
1931 * X->state = RUNNING
1932 * UNLOCK rq(2)->lock
1933 *
1934 * LOCK rq(2)->lock // orders against CPU1
1935 * sched-out Z
1936 * sched-in X
1937 * UNLOCK rq(2)->lock
1938 *
1939 * UNLOCK X->pi_lock
1940 * UNLOCK rq(0)->lock
1941 *
1942 *
1943 * However; for wakeups there is a second guarantee we must provide, namely we
1944 * must observe the state that lead to our wakeup. That is, not only must our
1945 * task observe its own prior state, it must also observe the stores prior to
1946 * its wakeup.
1947 *
1948 * This means that any means of doing remote wakeups must order the CPU doing
1949 * the wakeup against the CPU the task is going to end up running on. This,
1950 * however, is already required for the regular Program-Order guarantee above,
1951 * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
1952 *
1953 */
1954
1955/**
1956 * try_to_wake_up - wake up a thread
1957 * @p: the thread to be awakened
1958 * @state: the mask of task states that can be woken
1959 * @wake_flags: wake modifier flags (WF_*)
1960 *
1961 * If (@state & @p->state) @p->state = TASK_RUNNING.
1962 *
1963 * If the task was not queued/runnable, also place it back on a runqueue.
1964 *
1965 * Atomic against schedule() which would dequeue a task, also see
1966 * set_current_state().
1967 *
1968 * Return: %true if @p->state changes (an actual wakeup was done),
1969 * %false otherwise.
1970 */
1971static int
1972try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
1973{
1974 unsigned long flags;
1975 int cpu, success = 0;
1976
1977 /*
1978 * If we are going to wake up a thread waiting for CONDITION we
1979 * need to ensure that CONDITION=1 done by the caller can not be
1980 * reordered with p->state check below. This pairs with mb() in
1981 * set_current_state() the waiting thread does.
1982 */
1983 raw_spin_lock_irqsave(&p->pi_lock, flags);
1984 smp_mb__after_spinlock();
1985 if (!(p->state & state))
1986 goto out;
1987
1988 trace_sched_waking(p);
1989
1990 /* We're going to change ->state: */
1991 success = 1;
1992 cpu = task_cpu(p);
1993
1994 /*
1995 * Ensure we load p->on_rq _after_ p->state, otherwise it would
1996 * be possible to, falsely, observe p->on_rq == 0 and get stuck
1997 * in smp_cond_load_acquire() below.
1998 *
1999 * sched_ttwu_pending() try_to_wake_up()
2000 * [S] p->on_rq = 1; [L] P->state
2001 * UNLOCK rq->lock -----.
2002 * \
2003 * +--- RMB
2004 * schedule() /
2005 * LOCK rq->lock -----'
2006 * UNLOCK rq->lock
2007 *
2008 * [task p]
2009 * [S] p->state = UNINTERRUPTIBLE [L] p->on_rq
2010 *
2011 * Pairs with the UNLOCK+LOCK on rq->lock from the
2012 * last wakeup of our task and the schedule that got our task
2013 * current.
2014 */
2015 smp_rmb();
2016 if (p->on_rq && ttwu_remote(p, wake_flags))
2017 goto stat;
2018
2019#ifdef CONFIG_SMP
2020 /*
2021 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
2022 * possible to, falsely, observe p->on_cpu == 0.
2023 *
2024 * One must be running (->on_cpu == 1) in order to remove oneself
2025 * from the runqueue.
2026 *
2027 * [S] ->on_cpu = 1; [L] ->on_rq
2028 * UNLOCK rq->lock
2029 * RMB
2030 * LOCK rq->lock
2031 * [S] ->on_rq = 0; [L] ->on_cpu
2032 *
2033 * Pairs with the full barrier implied in the UNLOCK+LOCK on rq->lock
2034 * from the consecutive calls to schedule(); the first switching to our
2035 * task, the second putting it to sleep.
2036 */
2037 smp_rmb();
2038
2039 /*
2040 * If the owning (remote) CPU is still in the middle of schedule() with
2041 * this task as prev, wait until its done referencing the task.
2042 *
2043 * Pairs with the smp_store_release() in finish_task().
2044 *
2045 * This ensures that tasks getting woken will be fully ordered against
2046 * their previous state and preserve Program Order.
2047 */
2048 smp_cond_load_acquire(&p->on_cpu, !VAL);
2049
2050 p->sched_contributes_to_load = !!task_contributes_to_load(p);
2051 p->state = TASK_WAKING;
2052
2053 if (p->in_iowait) {
2054 delayacct_blkio_end(p);
2055 atomic_dec(&task_rq(p)->nr_iowait);
2056 }
2057
2058 cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
2059 if (task_cpu(p) != cpu) {
2060 wake_flags |= WF_MIGRATED;
2061 set_task_cpu(p, cpu);
2062 }
2063
2064#else /* CONFIG_SMP */
2065
2066 if (p->in_iowait) {
2067 delayacct_blkio_end(p);
2068 atomic_dec(&task_rq(p)->nr_iowait);
2069 }
2070
2071#endif /* CONFIG_SMP */
2072
2073 ttwu_queue(p, cpu, wake_flags);
2074stat:
2075 ttwu_stat(p, cpu, wake_flags);
2076out:
2077 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2078
2079 return success;
2080}
2081
2082/**
2083 * try_to_wake_up_local - try to wake up a local task with rq lock held
2084 * @p: the thread to be awakened
2085 * @rf: request-queue flags for pinning
2086 *
2087 * Put @p on the run-queue if it's not already there. The caller must
2088 * ensure that this_rq() is locked, @p is bound to this_rq() and not
2089 * the current task.
2090 */
2091static void try_to_wake_up_local(struct task_struct *p, struct rq_flags *rf)
2092{
2093 struct rq *rq = task_rq(p);
2094
2095 if (WARN_ON_ONCE(rq != this_rq()) ||
2096 WARN_ON_ONCE(p == current))
2097 return;
2098
2099 lockdep_assert_held(&rq->lock);
2100
2101 if (!raw_spin_trylock(&p->pi_lock)) {
2102 /*
2103 * This is OK, because current is on_cpu, which avoids it being
2104 * picked for load-balance and preemption/IRQs are still
2105 * disabled avoiding further scheduler activity on it and we've
2106 * not yet picked a replacement task.
2107 */
2108 rq_unlock(rq, rf);
2109 raw_spin_lock(&p->pi_lock);
2110 rq_relock(rq, rf);
2111 }
2112
2113 if (!(p->state & TASK_NORMAL))
2114 goto out;
2115
2116 trace_sched_waking(p);
2117
2118 if (!task_on_rq_queued(p)) {
2119 if (p->in_iowait) {
2120 delayacct_blkio_end(p);
2121 atomic_dec(&rq->nr_iowait);
2122 }
2123 ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK);
2124 }
2125
2126 ttwu_do_wakeup(rq, p, 0, rf);
2127 ttwu_stat(p, smp_processor_id(), 0);
2128out:
2129 raw_spin_unlock(&p->pi_lock);
2130}
2131
2132/**
2133 * wake_up_process - Wake up a specific process
2134 * @p: The process to be woken up.
2135 *
2136 * Attempt to wake up the nominated process and move it to the set of runnable
2137 * processes.
2138 *
2139 * Return: 1 if the process was woken up, 0 if it was already running.
2140 *
2141 * It may be assumed that this function implies a write memory barrier before
2142 * changing the task state if and only if any tasks are woken up.
2143 */
2144int wake_up_process(struct task_struct *p)
2145{
2146 return try_to_wake_up(p, TASK_NORMAL, 0);
2147}
2148EXPORT_SYMBOL(wake_up_process);
2149
2150int wake_up_state(struct task_struct *p, unsigned int state)
2151{
2152 return try_to_wake_up(p, state, 0);
2153}
2154
2155/*
2156 * Perform scheduler related setup for a newly forked process p.
2157 * p is forked by current.
2158 *
2159 * __sched_fork() is basic setup used by init_idle() too:
2160 */
2161static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
2162{
2163 p->on_rq = 0;
2164
2165 p->se.on_rq = 0;
2166 p->se.exec_start = 0;
2167 p->se.sum_exec_runtime = 0;
2168 p->se.prev_sum_exec_runtime = 0;
2169 p->se.nr_migrations = 0;
2170 p->se.vruntime = 0;
2171 INIT_LIST_HEAD(&p->se.group_node);
2172
2173#ifdef CONFIG_FAIR_GROUP_SCHED
2174 p->se.cfs_rq = NULL;
2175#endif
2176
2177#ifdef CONFIG_SCHEDSTATS
2178 /* Even if schedstat is disabled, there should not be garbage */
2179 memset(&p->se.statistics, 0, sizeof(p->se.statistics));
2180#endif
2181
2182 RB_CLEAR_NODE(&p->dl.rb_node);
2183 init_dl_task_timer(&p->dl);
2184 init_dl_inactive_task_timer(&p->dl);
2185 __dl_clear_params(p);
2186
2187 INIT_LIST_HEAD(&p->rt.run_list);
2188 p->rt.timeout = 0;
2189 p->rt.time_slice = sched_rr_timeslice;
2190 p->rt.on_rq = 0;
2191 p->rt.on_list = 0;
2192
2193#ifdef CONFIG_PREEMPT_NOTIFIERS
2194 INIT_HLIST_HEAD(&p->preempt_notifiers);
2195#endif
2196
2197#ifdef CONFIG_NUMA_BALANCING
2198 if (p->mm && atomic_read(&p->mm->mm_users) == 1) {
2199 p->mm->numa_next_scan = jiffies + msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
2200 p->mm->numa_scan_seq = 0;
2201 }
2202
2203 if (clone_flags & CLONE_VM)
2204 p->numa_preferred_nid = current->numa_preferred_nid;
2205 else
2206 p->numa_preferred_nid = -1;
2207
2208 p->node_stamp = 0ULL;
2209 p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
2210 p->numa_scan_period = sysctl_numa_balancing_scan_delay;
2211 p->numa_work.next = &p->numa_work;
2212 p->numa_faults = NULL;
2213 p->last_task_numa_placement = 0;
2214 p->last_sum_exec_runtime = 0;
2215
2216 p->numa_group = NULL;
2217#endif /* CONFIG_NUMA_BALANCING */
2218}
2219
2220DEFINE_STATIC_KEY_FALSE(sched_numa_balancing);
2221
2222#ifdef CONFIG_NUMA_BALANCING
2223
2224void set_numabalancing_state(bool enabled)
2225{
2226 if (enabled)
2227 static_branch_enable(&sched_numa_balancing);
2228 else
2229 static_branch_disable(&sched_numa_balancing);
2230}
2231
2232#ifdef CONFIG_PROC_SYSCTL
2233int sysctl_numa_balancing(struct ctl_table *table, int write,
2234 void __user *buffer, size_t *lenp, loff_t *ppos)
2235{
2236 struct ctl_table t;
2237 int err;
2238 int state = static_branch_likely(&sched_numa_balancing);
2239
2240 if (write && !capable(CAP_SYS_ADMIN))
2241 return -EPERM;
2242
2243 t = *table;
2244 t.data = &state;
2245 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2246 if (err < 0)
2247 return err;
2248 if (write)
2249 set_numabalancing_state(state);
2250 return err;
2251}
2252#endif
2253#endif
2254
2255#ifdef CONFIG_SCHEDSTATS
2256
2257DEFINE_STATIC_KEY_FALSE(sched_schedstats);
2258static bool __initdata __sched_schedstats = false;
2259
2260static void set_schedstats(bool enabled)
2261{
2262 if (enabled)
2263 static_branch_enable(&sched_schedstats);
2264 else
2265 static_branch_disable(&sched_schedstats);
2266}
2267
2268void force_schedstat_enabled(void)
2269{
2270 if (!schedstat_enabled()) {
2271 pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
2272 static_branch_enable(&sched_schedstats);
2273 }
2274}
2275
2276static int __init setup_schedstats(char *str)
2277{
2278 int ret = 0;
2279 if (!str)
2280 goto out;
2281
2282 /*
2283 * This code is called before jump labels have been set up, so we can't
2284 * change the static branch directly just yet. Instead set a temporary
2285 * variable so init_schedstats() can do it later.
2286 */
2287 if (!strcmp(str, "enable")) {
2288 __sched_schedstats = true;
2289 ret = 1;
2290 } else if (!strcmp(str, "disable")) {
2291 __sched_schedstats = false;
2292 ret = 1;
2293 }
2294out:
2295 if (!ret)
2296 pr_warn("Unable to parse schedstats=\n");
2297
2298 return ret;
2299}
2300__setup("schedstats=", setup_schedstats);
2301
2302static void __init init_schedstats(void)
2303{
2304 set_schedstats(__sched_schedstats);
2305}
2306
2307#ifdef CONFIG_PROC_SYSCTL
2308int sysctl_schedstats(struct ctl_table *table, int write,
2309 void __user *buffer, size_t *lenp, loff_t *ppos)
2310{
2311 struct ctl_table t;
2312 int err;
2313 int state = static_branch_likely(&sched_schedstats);
2314
2315 if (write && !capable(CAP_SYS_ADMIN))
2316 return -EPERM;
2317
2318 t = *table;
2319 t.data = &state;
2320 err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
2321 if (err < 0)
2322 return err;
2323 if (write)
2324 set_schedstats(state);
2325 return err;
2326}
2327#endif /* CONFIG_PROC_SYSCTL */
2328#else /* !CONFIG_SCHEDSTATS */
2329static inline void init_schedstats(void) {}
2330#endif /* CONFIG_SCHEDSTATS */
2331
2332/*
2333 * fork()/clone()-time setup:
2334 */
2335int sched_fork(unsigned long clone_flags, struct task_struct *p)
2336{
2337 unsigned long flags;
2338 int cpu = get_cpu();
2339
2340 __sched_fork(clone_flags, p);
2341 /*
2342 * We mark the process as NEW here. This guarantees that
2343 * nobody will actually run it, and a signal or other external
2344 * event cannot wake it up and insert it on the runqueue either.
2345 */
2346 p->state = TASK_NEW;
2347
2348 /*
2349 * Make sure we do not leak PI boosting priority to the child.
2350 */
2351 p->prio = current->normal_prio;
2352
2353 /*
2354 * Revert to default priority/policy on fork if requested.
2355 */
2356 if (unlikely(p->sched_reset_on_fork)) {
2357 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
2358 p->policy = SCHED_NORMAL;
2359 p->static_prio = NICE_TO_PRIO(0);
2360 p->rt_priority = 0;
2361 } else if (PRIO_TO_NICE(p->static_prio) < 0)
2362 p->static_prio = NICE_TO_PRIO(0);
2363
2364 p->prio = p->normal_prio = __normal_prio(p);
2365 set_load_weight(p, false);
2366
2367 /*
2368 * We don't need the reset flag anymore after the fork. It has
2369 * fulfilled its duty:
2370 */
2371 p->sched_reset_on_fork = 0;
2372 }
2373
2374 if (dl_prio(p->prio)) {
2375 put_cpu();
2376 return -EAGAIN;
2377 } else if (rt_prio(p->prio)) {
2378 p->sched_class = &rt_sched_class;
2379 } else {
2380 p->sched_class = &fair_sched_class;
2381 }
2382
2383 init_entity_runnable_average(&p->se);
2384
2385 /*
2386 * The child is not yet in the pid-hash so no cgroup attach races,
2387 * and the cgroup is pinned to this child due to cgroup_fork()
2388 * is ran before sched_fork().
2389 *
2390 * Silence PROVE_RCU.
2391 */
2392 raw_spin_lock_irqsave(&p->pi_lock, flags);
2393 /*
2394 * We're setting the CPU for the first time, we don't migrate,
2395 * so use __set_task_cpu().
2396 */
2397 __set_task_cpu(p, cpu);
2398 if (p->sched_class->task_fork)
2399 p->sched_class->task_fork(p);
2400 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
2401
2402#ifdef CONFIG_SCHED_INFO
2403 if (likely(sched_info_on()))
2404 memset(&p->sched_info, 0, sizeof(p->sched_info));
2405#endif
2406#if defined(CONFIG_SMP)
2407 p->on_cpu = 0;
2408#endif
2409 init_task_preempt_count(p);
2410#ifdef CONFIG_SMP
2411 plist_node_init(&p->pushable_tasks, MAX_PRIO);
2412 RB_CLEAR_NODE(&p->pushable_dl_tasks);
2413#endif
2414
2415 put_cpu();
2416 return 0;
2417}
2418
2419unsigned long to_ratio(u64 period, u64 runtime)
2420{
2421 if (runtime == RUNTIME_INF)
2422 return BW_UNIT;
2423
2424 /*
2425 * Doing this here saves a lot of checks in all
2426 * the calling paths, and returning zero seems
2427 * safe for them anyway.
2428 */
2429 if (period == 0)
2430 return 0;
2431
2432 return div64_u64(runtime << BW_SHIFT, period);
2433}
2434
2435/*
2436 * wake_up_new_task - wake up a newly created task for the first time.
2437 *
2438 * This function will do some initial scheduler statistics housekeeping
2439 * that must be done for every newly created context, then puts the task
2440 * on the runqueue and wakes it.
2441 */
2442void wake_up_new_task(struct task_struct *p)
2443{
2444 struct rq_flags rf;
2445 struct rq *rq;
2446
2447 raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
2448 p->state = TASK_RUNNING;
2449#ifdef CONFIG_SMP
2450 /*
2451 * Fork balancing, do it here and not earlier because:
2452 * - cpus_allowed can change in the fork path
2453 * - any previously selected CPU might disappear through hotplug
2454 *
2455 * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
2456 * as we're not fully set-up yet.
2457 */
2458 p->recent_used_cpu = task_cpu(p);
2459 __set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
2460#endif
2461 rq = __task_rq_lock(p, &rf);
2462 update_rq_clock(rq);
2463 post_init_entity_util_avg(&p->se);
2464
2465 activate_task(rq, p, ENQUEUE_NOCLOCK);
2466 p->on_rq = TASK_ON_RQ_QUEUED;
2467 trace_sched_wakeup_new(p);
2468 check_preempt_curr(rq, p, WF_FORK);
2469#ifdef CONFIG_SMP
2470 if (p->sched_class->task_woken) {
2471 /*
2472 * Nothing relies on rq->lock after this, so its fine to
2473 * drop it.
2474 */
2475 rq_unpin_lock(rq, &rf);
2476 p->sched_class->task_woken(rq, p);
2477 rq_repin_lock(rq, &rf);
2478 }
2479#endif
2480 task_rq_unlock(rq, p, &rf);
2481}
2482
2483#ifdef CONFIG_PREEMPT_NOTIFIERS
2484
2485static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
2486
2487void preempt_notifier_inc(void)
2488{
2489 static_branch_inc(&preempt_notifier_key);
2490}
2491EXPORT_SYMBOL_GPL(preempt_notifier_inc);
2492
2493void preempt_notifier_dec(void)
2494{
2495 static_branch_dec(&preempt_notifier_key);
2496}
2497EXPORT_SYMBOL_GPL(preempt_notifier_dec);
2498
2499/**
2500 * preempt_notifier_register - tell me when current is being preempted & rescheduled
2501 * @notifier: notifier struct to register
2502 */
2503void preempt_notifier_register(struct preempt_notifier *notifier)
2504{
2505 if (!static_branch_unlikely(&preempt_notifier_key))
2506 WARN(1, "registering preempt_notifier while notifiers disabled\n");
2507
2508 hlist_add_head(¬ifier->link, ¤t->preempt_notifiers);
2509}
2510EXPORT_SYMBOL_GPL(preempt_notifier_register);
2511
2512/**
2513 * preempt_notifier_unregister - no longer interested in preemption notifications
2514 * @notifier: notifier struct to unregister
2515 *
2516 * This is *not* safe to call from within a preemption notifier.
2517 */
2518void preempt_notifier_unregister(struct preempt_notifier *notifier)
2519{
2520 hlist_del(¬ifier->link);
2521}
2522EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
2523
2524static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
2525{
2526 struct preempt_notifier *notifier;
2527
2528 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2529 notifier->ops->sched_in(notifier, raw_smp_processor_id());
2530}
2531
2532static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2533{
2534 if (static_branch_unlikely(&preempt_notifier_key))
2535 __fire_sched_in_preempt_notifiers(curr);
2536}
2537
2538static void
2539__fire_sched_out_preempt_notifiers(struct task_struct *curr,
2540 struct task_struct *next)
2541{
2542 struct preempt_notifier *notifier;
2543
2544 hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
2545 notifier->ops->sched_out(notifier, next);
2546}
2547
2548static __always_inline void
2549fire_sched_out_preempt_notifiers(struct task_struct *curr,
2550 struct task_struct *next)
2551{
2552 if (static_branch_unlikely(&preempt_notifier_key))
2553 __fire_sched_out_preempt_notifiers(curr, next);
2554}
2555
2556#else /* !CONFIG_PREEMPT_NOTIFIERS */
2557
2558static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
2559{
2560}
2561
2562static inline void
2563fire_sched_out_preempt_notifiers(struct task_struct *curr,
2564 struct task_struct *next)
2565{
2566}
2567
2568#endif /* CONFIG_PREEMPT_NOTIFIERS */
2569
2570static inline void prepare_task(struct task_struct *next)
2571{
2572#ifdef CONFIG_SMP
2573 /*
2574 * Claim the task as running, we do this before switching to it
2575 * such that any running task will have this set.
2576 */
2577 next->on_cpu = 1;
2578#endif
2579}
2580
2581static inline void finish_task(struct task_struct *prev)
2582{
2583#ifdef CONFIG_SMP
2584 /*
2585 * After ->on_cpu is cleared, the task can be moved to a different CPU.
2586 * We must ensure this doesn't happen until the switch is completely
2587 * finished.
2588 *
2589 * In particular, the load of prev->state in finish_task_switch() must
2590 * happen before this.
2591 *
2592 * Pairs with the smp_cond_load_acquire() in try_to_wake_up().
2593 */
2594 smp_store_release(&prev->on_cpu, 0);
2595#endif
2596}
2597
2598static inline void
2599prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf)
2600{
2601 /*
2602 * Since the runqueue lock will be released by the next
2603 * task (which is an invalid locking op but in the case
2604 * of the scheduler it's an obvious special-case), so we
2605 * do an early lockdep release here:
2606 */
2607 rq_unpin_lock(rq, rf);
2608 spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
2609#ifdef CONFIG_DEBUG_SPINLOCK
2610 /* this is a valid case when another task releases the spinlock */
2611 rq->lock.owner = next;
2612#endif
2613}
2614
2615static inline void finish_lock_switch(struct rq *rq)
2616{
2617 /*
2618 * If we are tracking spinlock dependencies then we have to
2619 * fix up the runqueue lock - which gets 'carried over' from
2620 * prev into current:
2621 */
2622 spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
2623 raw_spin_unlock_irq(&rq->lock);
2624}
2625
2626/*
2627 * NOP if the arch has not defined these:
2628 */
2629
2630#ifndef prepare_arch_switch
2631# define prepare_arch_switch(next) do { } while (0)
2632#endif
2633
2634#ifndef finish_arch_post_lock_switch
2635# define finish_arch_post_lock_switch() do { } while (0)
2636#endif
2637
2638/**
2639 * prepare_task_switch - prepare to switch tasks
2640 * @rq: the runqueue preparing to switch
2641 * @prev: the current task that is being switched out
2642 * @next: the task we are going to switch to.
2643 *
2644 * This is called with the rq lock held and interrupts off. It must
2645 * be paired with a subsequent finish_task_switch after the context
2646 * switch.
2647 *
2648 * prepare_task_switch sets up locking and calls architecture specific
2649 * hooks.
2650 */
2651static inline void
2652prepare_task_switch(struct rq *rq, struct task_struct *prev,
2653 struct task_struct *next)
2654{
2655 sched_info_switch(rq, prev, next);
2656 perf_event_task_sched_out(prev, next);
2657 fire_sched_out_preempt_notifiers(prev, next);
2658 prepare_task(next);
2659 prepare_arch_switch(next);
2660}
2661
2662/**
2663 * finish_task_switch - clean up after a task-switch
2664 * @prev: the thread we just switched away from.
2665 *
2666 * finish_task_switch must be called after the context switch, paired
2667 * with a prepare_task_switch call before the context switch.
2668 * finish_task_switch will reconcile locking set up by prepare_task_switch,
2669 * and do any other architecture-specific cleanup actions.
2670 *
2671 * Note that we may have delayed dropping an mm in context_switch(). If
2672 * so, we finish that here outside of the runqueue lock. (Doing it
2673 * with the lock held can cause deadlocks; see schedule() for
2674 * details.)
2675 *
2676 * The context switch have flipped the stack from under us and restored the
2677 * local variables which were saved when this task called schedule() in the
2678 * past. prev == current is still correct but we need to recalculate this_rq
2679 * because prev may have moved to another CPU.
2680 */
2681static struct rq *finish_task_switch(struct task_struct *prev)
2682 __releases(rq->lock)
2683{
2684 struct rq *rq = this_rq();
2685 struct mm_struct *mm = rq->prev_mm;
2686 long prev_state;
2687
2688 /*
2689 * The previous task will have left us with a preempt_count of 2
2690 * because it left us after:
2691 *
2692 * schedule()
2693 * preempt_disable(); // 1
2694 * __schedule()
2695 * raw_spin_lock_irq(&rq->lock) // 2
2696 *
2697 * Also, see FORK_PREEMPT_COUNT.
2698 */
2699 if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
2700 "corrupted preempt_count: %s/%d/0x%x\n",
2701 current->comm, current->pid, preempt_count()))
2702 preempt_count_set(FORK_PREEMPT_COUNT);
2703
2704 rq->prev_mm = NULL;
2705
2706 /*
2707 * A task struct has one reference for the use as "current".
2708 * If a task dies, then it sets TASK_DEAD in tsk->state and calls
2709 * schedule one last time. The schedule call will never return, and
2710 * the scheduled task must drop that reference.
2711 *
2712 * We must observe prev->state before clearing prev->on_cpu (in
2713 * finish_task), otherwise a concurrent wakeup can get prev
2714 * running on another CPU and we could rave with its RUNNING -> DEAD
2715 * transition, resulting in a double drop.
2716 */
2717 prev_state = prev->state;
2718 vtime_task_switch(prev);
2719 perf_event_task_sched_in(prev, current);
2720 finish_task(prev);
2721 finish_lock_switch(rq);
2722 finish_arch_post_lock_switch();
2723
2724 fire_sched_in_preempt_notifiers(current);
2725 /*
2726 * When switching through a kernel thread, the loop in
2727 * membarrier_{private,global}_expedited() may have observed that
2728 * kernel thread and not issued an IPI. It is therefore possible to
2729 * schedule between user->kernel->user threads without passing though
2730 * switch_mm(). Membarrier requires a barrier after storing to
2731 * rq->curr, before returning to userspace, so provide them here:
2732 *
2733 * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
2734 * provided by mmdrop(),
2735 * - a sync_core for SYNC_CORE.
2736 */
2737 if (mm) {
2738 membarrier_mm_sync_core_before_usermode(mm);
2739 mmdrop(mm);
2740 }
2741 if (unlikely(prev_state & (TASK_DEAD|TASK_PARKED))) {
2742 switch (prev_state) {
2743 case TASK_DEAD:
2744 if (prev->sched_class->task_dead)
2745 prev->sched_class->task_dead(prev);
2746
2747 /*
2748 * Remove function-return probe instances associated with this
2749 * task and put them back on the free list.
2750 */
2751 kprobe_flush_task(prev);
2752
2753 /* Task is done with its stack. */
2754 put_task_stack(prev);
2755
2756 put_task_struct(prev);
2757 break;
2758
2759 case TASK_PARKED:
2760 kthread_park_complete(prev);
2761 break;
2762 }
2763 }
2764
2765 tick_nohz_task_switch();
2766 return rq;
2767}
2768
2769#ifdef CONFIG_SMP
2770
2771/* rq->lock is NOT held, but preemption is disabled */
2772static void __balance_callback(struct rq *rq)
2773{
2774 struct callback_head *head, *next;
2775 void (*func)(struct rq *rq);
2776 unsigned long flags;
2777
2778 raw_spin_lock_irqsave(&rq->lock, flags);
2779 head = rq->balance_callback;
2780 rq->balance_callback = NULL;
2781 while (head) {
2782 func = (void (*)(struct rq *))head->func;
2783 next = head->next;
2784 head->next = NULL;
2785 head = next;
2786
2787 func(rq);
2788 }
2789 raw_spin_unlock_irqrestore(&rq->lock, flags);
2790}
2791
2792static inline void balance_callback(struct rq *rq)
2793{
2794 if (unlikely(rq->balance_callback))
2795 __balance_callback(rq);
2796}
2797
2798#else
2799
2800static inline void balance_callback(struct rq *rq)
2801{
2802}
2803
2804#endif
2805
2806/**
2807 * schedule_tail - first thing a freshly forked thread must call.
2808 * @prev: the thread we just switched away from.
2809 */
2810asmlinkage __visible void schedule_tail(struct task_struct *prev)
2811 __releases(rq->lock)
2812{
2813 struct rq *rq;
2814
2815 /*
2816 * New tasks start with FORK_PREEMPT_COUNT, see there and
2817 * finish_task_switch() for details.
2818 *
2819 * finish_task_switch() will drop rq->lock() and lower preempt_count
2820 * and the preempt_enable() will end up enabling preemption (on
2821 * PREEMPT_COUNT kernels).
2822 */
2823
2824 rq = finish_task_switch(prev);
2825 balance_callback(rq);
2826 preempt_enable();
2827
2828 if (current->set_child_tid)
2829 put_user(task_pid_vnr(current), current->set_child_tid);
2830}
2831
2832/*
2833 * context_switch - switch to the new MM and the new thread's register state.
2834 */
2835static __always_inline struct rq *
2836context_switch(struct rq *rq, struct task_struct *prev,
2837 struct task_struct *next, struct rq_flags *rf)
2838{
2839 struct mm_struct *mm, *oldmm;
2840
2841 prepare_task_switch(rq, prev, next);
2842
2843 mm = next->mm;
2844 oldmm = prev->active_mm;
2845 /*
2846 * For paravirt, this is coupled with an exit in switch_to to
2847 * combine the page table reload and the switch backend into
2848 * one hypercall.
2849 */
2850 arch_start_context_switch(prev);
2851
2852 /*
2853 * If mm is non-NULL, we pass through switch_mm(). If mm is
2854 * NULL, we will pass through mmdrop() in finish_task_switch().
2855 * Both of these contain the full memory barrier required by
2856 * membarrier after storing to rq->curr, before returning to
2857 * user-space.
2858 */
2859 if (!mm) {
2860 next->active_mm = oldmm;
2861 mmgrab(oldmm);
2862 enter_lazy_tlb(oldmm, next);
2863 } else
2864 switch_mm_irqs_off(oldmm, mm, next);
2865
2866 if (!prev->mm) {
2867 prev->active_mm = NULL;
2868 rq->prev_mm = oldmm;
2869 }
2870
2871 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
2872
2873 prepare_lock_switch(rq, next, rf);
2874
2875 /* Here we just switch the register state and the stack. */
2876 switch_to(prev, next, prev);
2877 barrier();
2878
2879 return finish_task_switch(prev);
2880}
2881
2882/*
2883 * nr_running and nr_context_switches:
2884 *
2885 * externally visible scheduler statistics: current number of runnable
2886 * threads, total number of context switches performed since bootup.
2887 */
2888unsigned long nr_running(void)
2889{
2890 unsigned long i, sum = 0;
2891
2892 for_each_online_cpu(i)
2893 sum += cpu_rq(i)->nr_running;
2894
2895 return sum;
2896}
2897
2898/*
2899 * Check if only the current task is running on the CPU.
2900 *
2901 * Caution: this function does not check that the caller has disabled
2902 * preemption, thus the result might have a time-of-check-to-time-of-use
2903 * race. The caller is responsible to use it correctly, for example:
2904 *
2905 * - from a non-preemptable section (of course)
2906 *
2907 * - from a thread that is bound to a single CPU
2908 *
2909 * - in a loop with very short iterations (e.g. a polling loop)
2910 */
2911bool single_task_running(void)
2912{
2913 return raw_rq()->nr_running == 1;
2914}
2915EXPORT_SYMBOL(single_task_running);
2916
2917unsigned long long nr_context_switches(void)
2918{
2919 int i;
2920 unsigned long long sum = 0;
2921
2922 for_each_possible_cpu(i)
2923 sum += cpu_rq(i)->nr_switches;
2924
2925 return sum;
2926}
2927
2928/*
2929 * IO-wait accounting, and how its mostly bollocks (on SMP).
2930 *
2931 * The idea behind IO-wait account is to account the idle time that we could
2932 * have spend running if it were not for IO. That is, if we were to improve the
2933 * storage performance, we'd have a proportional reduction in IO-wait time.
2934 *
2935 * This all works nicely on UP, where, when a task blocks on IO, we account
2936 * idle time as IO-wait, because if the storage were faster, it could've been
2937 * running and we'd not be idle.
2938 *
2939 * This has been extended to SMP, by doing the same for each CPU. This however
2940 * is broken.
2941 *
2942 * Imagine for instance the case where two tasks block on one CPU, only the one
2943 * CPU will have IO-wait accounted, while the other has regular idle. Even
2944 * though, if the storage were faster, both could've ran at the same time,
2945 * utilising both CPUs.
2946 *
2947 * This means, that when looking globally, the current IO-wait accounting on
2948 * SMP is a lower bound, by reason of under accounting.
2949 *
2950 * Worse, since the numbers are provided per CPU, they are sometimes
2951 * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
2952 * associated with any one particular CPU, it can wake to another CPU than it
2953 * blocked on. This means the per CPU IO-wait number is meaningless.
2954 *
2955 * Task CPU affinities can make all that even more 'interesting'.
2956 */
2957
2958unsigned long nr_iowait(void)
2959{
2960 unsigned long i, sum = 0;
2961
2962 for_each_possible_cpu(i)
2963 sum += atomic_read(&cpu_rq(i)->nr_iowait);
2964
2965 return sum;
2966}
2967
2968/*
2969 * Consumers of these two interfaces, like for example the cpufreq menu
2970 * governor are using nonsensical data. Boosting frequency for a CPU that has
2971 * IO-wait which might not even end up running the task when it does become
2972 * runnable.
2973 */
2974
2975unsigned long nr_iowait_cpu(int cpu)
2976{
2977 struct rq *this = cpu_rq(cpu);
2978 return atomic_read(&this->nr_iowait);
2979}
2980
2981void get_iowait_load(unsigned long *nr_waiters, unsigned long *load)
2982{
2983 struct rq *rq = this_rq();
2984 *nr_waiters = atomic_read(&rq->nr_iowait);
2985 *load = rq->load.weight;
2986}
2987
2988#ifdef CONFIG_SMP
2989
2990/*
2991 * sched_exec - execve() is a valuable balancing opportunity, because at
2992 * this point the task has the smallest effective memory and cache footprint.
2993 */
2994void sched_exec(void)
2995{
2996 struct task_struct *p = current;
2997 unsigned long flags;
2998 int dest_cpu;
2999
3000 raw_spin_lock_irqsave(&p->pi_lock, flags);
3001 dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), SD_BALANCE_EXEC, 0);
3002 if (dest_cpu == smp_processor_id())
3003 goto unlock;
3004
3005 if (likely(cpu_active(dest_cpu))) {
3006 struct migration_arg arg = { p, dest_cpu };
3007
3008 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3009 stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
3010 return;
3011 }
3012unlock:
3013 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
3014}
3015
3016#endif
3017
3018DEFINE_PER_CPU(struct kernel_stat, kstat);
3019DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
3020
3021EXPORT_PER_CPU_SYMBOL(kstat);
3022EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
3023
3024/*
3025 * The function fair_sched_class.update_curr accesses the struct curr
3026 * and its field curr->exec_start; when called from task_sched_runtime(),
3027 * we observe a high rate of cache misses in practice.
3028 * Prefetching this data results in improved performance.
3029 */
3030static inline void prefetch_curr_exec_start(struct task_struct *p)
3031{
3032#ifdef CONFIG_FAIR_GROUP_SCHED
3033 struct sched_entity *curr = (&p->se)->cfs_rq->curr;
3034#else
3035 struct sched_entity *curr = (&task_rq(p)->cfs)->curr;
3036#endif
3037 prefetch(curr);
3038 prefetch(&curr->exec_start);
3039}
3040
3041/*
3042 * Return accounted runtime for the task.
3043 * In case the task is currently running, return the runtime plus current's
3044 * pending runtime that have not been accounted yet.
3045 */
3046unsigned long long task_sched_runtime(struct task_struct *p)
3047{
3048 struct rq_flags rf;
3049 struct rq *rq;
3050 u64 ns;
3051
3052#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
3053 /*
3054 * 64-bit doesn't need locks to atomically read a 64-bit value.
3055 * So we have a optimization chance when the task's delta_exec is 0.
3056 * Reading ->on_cpu is racy, but this is ok.
3057 *
3058 * If we race with it leaving CPU, we'll take a lock. So we're correct.
3059 * If we race with it entering CPU, unaccounted time is 0. This is
3060 * indistinguishable from the read occurring a few cycles earlier.
3061 * If we see ->on_cpu without ->on_rq, the task is leaving, and has
3062 * been accounted, so we're correct here as well.
3063 */
3064 if (!p->on_cpu || !task_on_rq_queued(p))
3065 return p->se.sum_exec_runtime;
3066#endif
3067
3068 rq = task_rq_lock(p, &rf);
3069 /*
3070 * Must be ->curr _and_ ->on_rq. If dequeued, we would
3071 * project cycles that may never be accounted to this
3072 * thread, breaking clock_gettime().
3073 */
3074 if (task_current(rq, p) && task_on_rq_queued(p)) {
3075 prefetch_curr_exec_start(p);
3076 update_rq_clock(rq);
3077 p->sched_class->update_curr(rq);
3078 }
3079 ns = p->se.sum_exec_runtime;
3080 task_rq_unlock(rq, p, &rf);
3081
3082 return ns;
3083}
3084
3085/*
3086 * This function gets called by the timer code, with HZ frequency.
3087 * We call it with interrupts disabled.
3088 */
3089void scheduler_tick(void)
3090{
3091 int cpu = smp_processor_id();
3092 struct rq *rq = cpu_rq(cpu);
3093 struct task_struct *curr = rq->curr;
3094 struct rq_flags rf;
3095
3096 sched_clock_tick();
3097
3098 rq_lock(rq, &rf);
3099
3100 update_rq_clock(rq);
3101 curr->sched_class->task_tick(rq, curr, 0);
3102 cpu_load_update_active(rq);
3103 calc_global_load_tick(rq);
3104
3105 rq_unlock(rq, &rf);
3106
3107 perf_event_task_tick();
3108
3109#ifdef CONFIG_SMP
3110 rq->idle_balance = idle_cpu(cpu);
3111 trigger_load_balance(rq);
3112#endif
3113}
3114
3115#ifdef CONFIG_NO_HZ_FULL
3116
3117struct tick_work {
3118 int cpu;
3119 struct delayed_work work;
3120};
3121
3122static struct tick_work __percpu *tick_work_cpu;
3123
3124static void sched_tick_remote(struct work_struct *work)
3125{
3126 struct delayed_work *dwork = to_delayed_work(work);
3127 struct tick_work *twork = container_of(dwork, struct tick_work, work);
3128 int cpu = twork->cpu;
3129 struct rq *rq = cpu_rq(cpu);
3130 struct rq_flags rf;
3131
3132 /*
3133 * Handle the tick only if it appears the remote CPU is running in full
3134 * dynticks mode. The check is racy by nature, but missing a tick or
3135 * having one too much is no big deal because the scheduler tick updates
3136 * statistics and checks timeslices in a time-independent way, regardless
3137 * of when exactly it is running.
3138 */
3139 if (!idle_cpu(cpu) && tick_nohz_tick_stopped_cpu(cpu)) {
3140 struct task_struct *curr;
3141 u64 delta;
3142
3143 rq_lock_irq(rq, &rf);
3144 update_rq_clock(rq);
3145 curr = rq->curr;
3146 delta = rq_clock_task(rq) - curr->se.exec_start;
3147
3148 /*
3149 * Make sure the next tick runs within a reasonable
3150 * amount of time.
3151 */
3152 WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
3153 curr->sched_class->task_tick(rq, curr, 0);
3154 rq_unlock_irq(rq, &rf);
3155 }
3156
3157 /*
3158 * Run the remote tick once per second (1Hz). This arbitrary
3159 * frequency is large enough to avoid overload but short enough
3160 * to keep scheduler internal stats reasonably up to date.
3161 */
3162 queue_delayed_work(system_unbound_wq, dwork, HZ);
3163}
3164
3165static void sched_tick_start(int cpu)
3166{
3167 struct tick_work *twork;
3168
3169 if (housekeeping_cpu(cpu, HK_FLAG_TICK))
3170 return;
3171
3172 WARN_ON_ONCE(!tick_work_cpu);
3173
3174 twork = per_cpu_ptr(tick_work_cpu, cpu);
3175 twork->cpu = cpu;
3176 INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
3177 queue_delayed_work(system_unbound_wq, &twork->work, HZ);
3178}
3179
3180#ifdef CONFIG_HOTPLUG_CPU
3181static void sched_tick_stop(int cpu)
3182{
3183 struct tick_work *twork;
3184
3185 if (housekeeping_cpu(cpu, HK_FLAG_TICK))
3186 return;
3187
3188 WARN_ON_ONCE(!tick_work_cpu);
3189
3190 twork = per_cpu_ptr(tick_work_cpu, cpu);
3191 cancel_delayed_work_sync(&twork->work);
3192}
3193#endif /* CONFIG_HOTPLUG_CPU */
3194
3195int __init sched_tick_offload_init(void)
3196{
3197 tick_work_cpu = alloc_percpu(struct tick_work);
3198 BUG_ON(!tick_work_cpu);
3199
3200 return 0;
3201}
3202
3203#else /* !CONFIG_NO_HZ_FULL */
3204static inline void sched_tick_start(int cpu) { }
3205static inline void sched_tick_stop(int cpu) { }
3206#endif
3207
3208#if defined(CONFIG_PREEMPT) && (defined(CONFIG_DEBUG_PREEMPT) || \
3209 defined(CONFIG_PREEMPT_TRACER))
3210/*
3211 * If the value passed in is equal to the current preempt count
3212 * then we just disabled preemption. Start timing the latency.
3213 */
3214static inline void preempt_latency_start(int val)
3215{
3216 if (preempt_count() == val) {
3217 unsigned long ip = get_lock_parent_ip();
3218#ifdef CONFIG_DEBUG_PREEMPT
3219 current->preempt_disable_ip = ip;
3220#endif
3221 trace_preempt_off(CALLER_ADDR0, ip);
3222 }
3223}
3224
3225void preempt_count_add(int val)
3226{
3227#ifdef CONFIG_DEBUG_PREEMPT
3228 /*
3229 * Underflow?
3230 */
3231 if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
3232 return;
3233#endif
3234 __preempt_count_add(val);
3235#ifdef CONFIG_DEBUG_PREEMPT
3236 /*
3237 * Spinlock count overflowing soon?
3238 */
3239 DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
3240 PREEMPT_MASK - 10);
3241#endif
3242 preempt_latency_start(val);
3243}
3244EXPORT_SYMBOL(preempt_count_add);
3245NOKPROBE_SYMBOL(preempt_count_add);
3246
3247/*
3248 * If the value passed in equals to the current preempt count
3249 * then we just enabled preemption. Stop timing the latency.
3250 */
3251static inline void preempt_latency_stop(int val)
3252{
3253 if (preempt_count() == val)
3254 trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
3255}
3256
3257void preempt_count_sub(int val)
3258{
3259#ifdef CONFIG_DEBUG_PREEMPT
3260 /*
3261 * Underflow?
3262 */
3263 if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
3264 return;
3265 /*
3266 * Is the spinlock portion underflowing?
3267 */
3268 if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
3269 !(preempt_count() & PREEMPT_MASK)))
3270 return;
3271#endif
3272
3273 preempt_latency_stop(val);
3274 __preempt_count_sub(val);
3275}
3276EXPORT_SYMBOL(preempt_count_sub);
3277NOKPROBE_SYMBOL(preempt_count_sub);
3278
3279#else
3280static inline void preempt_latency_start(int val) { }
3281static inline void preempt_latency_stop(int val) { }
3282#endif
3283
3284static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
3285{
3286#ifdef CONFIG_DEBUG_PREEMPT
3287 return p->preempt_disable_ip;
3288#else
3289 return 0;
3290#endif
3291}
3292
3293/*
3294 * Print scheduling while atomic bug:
3295 */
3296static noinline void __schedule_bug(struct task_struct *prev)
3297{
3298 /* Save this before calling printk(), since that will clobber it */
3299 unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
3300
3301 if (oops_in_progress)
3302 return;
3303
3304 printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
3305 prev->comm, prev->pid, preempt_count());
3306
3307 debug_show_held_locks(prev);
3308 print_modules();
3309 if (irqs_disabled())
3310 print_irqtrace_events(prev);
3311 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
3312 && in_atomic_preempt_off()) {
3313 pr_err("Preemption disabled at:");
3314 print_ip_sym(preempt_disable_ip);
3315 pr_cont("\n");
3316 }
3317 if (panic_on_warn)
3318 panic("scheduling while atomic\n");
3319
3320 dump_stack();
3321 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
3322}
3323
3324/*
3325 * Various schedule()-time debugging checks and statistics:
3326 */
3327static inline void schedule_debug(struct task_struct *prev)
3328{
3329#ifdef CONFIG_SCHED_STACK_END_CHECK
3330 if (task_stack_end_corrupted(prev))
3331 panic("corrupted stack end detected inside scheduler\n");
3332#endif
3333
3334 if (unlikely(in_atomic_preempt_off())) {
3335 __schedule_bug(prev);
3336 preempt_count_set(PREEMPT_DISABLED);
3337 }
3338 rcu_sleep_check();
3339
3340 profile_hit(SCHED_PROFILING, __builtin_return_address(0));
3341
3342 schedstat_inc(this_rq()->sched_count);
3343}
3344
3345/*
3346 * Pick up the highest-prio task:
3347 */
3348static inline struct task_struct *
3349pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
3350{
3351 const struct sched_class *class;
3352 struct task_struct *p;
3353
3354 /*
3355 * Optimization: we know that if all tasks are in the fair class we can
3356 * call that function directly, but only if the @prev task wasn't of a
3357 * higher scheduling class, because otherwise those loose the
3358 * opportunity to pull in more work from other CPUs.
3359 */
3360 if (likely((prev->sched_class == &idle_sched_class ||
3361 prev->sched_class == &fair_sched_class) &&
3362 rq->nr_running == rq->cfs.h_nr_running)) {
3363
3364 p = fair_sched_class.pick_next_task(rq, prev, rf);
3365 if (unlikely(p == RETRY_TASK))
3366 goto again;
3367
3368 /* Assumes fair_sched_class->next == idle_sched_class */
3369 if (unlikely(!p))
3370 p = idle_sched_class.pick_next_task(rq, prev, rf);
3371
3372 return p;
3373 }
3374
3375again:
3376 for_each_class(class) {
3377 p = class->pick_next_task(rq, prev, rf);
3378 if (p) {
3379 if (unlikely(p == RETRY_TASK))
3380 goto again;
3381 return p;
3382 }
3383 }
3384
3385 /* The idle class should always have a runnable task: */
3386 BUG();
3387}
3388
3389/*
3390 * __schedule() is the main scheduler function.
3391 *
3392 * The main means of driving the scheduler and thus entering this function are:
3393 *
3394 * 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
3395 *
3396 * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
3397 * paths. For example, see arch/x86/entry_64.S.
3398 *
3399 * To drive preemption between tasks, the scheduler sets the flag in timer
3400 * interrupt handler scheduler_tick().
3401 *
3402 * 3. Wakeups don't really cause entry into schedule(). They add a
3403 * task to the run-queue and that's it.
3404 *
3405 * Now, if the new task added to the run-queue preempts the current
3406 * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
3407 * called on the nearest possible occasion:
3408 *
3409 * - If the kernel is preemptible (CONFIG_PREEMPT=y):
3410 *
3411 * - in syscall or exception context, at the next outmost
3412 * preempt_enable(). (this might be as soon as the wake_up()'s
3413 * spin_unlock()!)
3414 *
3415 * - in IRQ context, return from interrupt-handler to
3416 * preemptible context
3417 *
3418 * - If the kernel is not preemptible (CONFIG_PREEMPT is not set)
3419 * then at the next:
3420 *
3421 * - cond_resched() call
3422 * - explicit schedule() call
3423 * - return from syscall or exception to user-space
3424 * - return from interrupt-handler to user-space
3425 *
3426 * WARNING: must be called with preemption disabled!
3427 */
3428static void __sched notrace __schedule(bool preempt)
3429{
3430 struct task_struct *prev, *next;
3431 unsigned long *switch_count;
3432 struct rq_flags rf;
3433 struct rq *rq;
3434 int cpu;
3435
3436 cpu = smp_processor_id();
3437 rq = cpu_rq(cpu);
3438 prev = rq->curr;
3439
3440 schedule_debug(prev);
3441
3442 if (sched_feat(HRTICK))
3443 hrtick_clear(rq);
3444
3445 local_irq_disable();
3446 rcu_note_context_switch(preempt);
3447
3448 /*
3449 * Make sure that signal_pending_state()->signal_pending() below
3450 * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
3451 * done by the caller to avoid the race with signal_wake_up().
3452 *
3453 * The membarrier system call requires a full memory barrier
3454 * after coming from user-space, before storing to rq->curr.
3455 */
3456 rq_lock(rq, &rf);
3457 smp_mb__after_spinlock();
3458
3459 /* Promote REQ to ACT */
3460 rq->clock_update_flags <<= 1;
3461 update_rq_clock(rq);
3462
3463 switch_count = &prev->nivcsw;
3464 if (!preempt && prev->state) {
3465 if (unlikely(signal_pending_state(prev->state, prev))) {
3466 prev->state = TASK_RUNNING;
3467 } else {
3468 deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK);
3469 prev->on_rq = 0;
3470
3471 if (prev->in_iowait) {
3472 atomic_inc(&rq->nr_iowait);
3473 delayacct_blkio_start();
3474 }
3475
3476 /*
3477 * If a worker went to sleep, notify and ask workqueue
3478 * whether it wants to wake up a task to maintain
3479 * concurrency.
3480 */
3481 if (prev->flags & PF_WQ_WORKER) {
3482 struct task_struct *to_wakeup;
3483
3484 to_wakeup = wq_worker_sleeping(prev);
3485 if (to_wakeup)
3486 try_to_wake_up_local(to_wakeup, &rf);
3487 }
3488 }
3489 switch_count = &prev->nvcsw;
3490 }
3491
3492 next = pick_next_task(rq, prev, &rf);
3493 clear_tsk_need_resched(prev);
3494 clear_preempt_need_resched();
3495
3496 if (likely(prev != next)) {
3497 rq->nr_switches++;
3498 rq->curr = next;
3499 /*
3500 * The membarrier system call requires each architecture
3501 * to have a full memory barrier after updating
3502 * rq->curr, before returning to user-space.
3503 *
3504 * Here are the schemes providing that barrier on the
3505 * various architectures:
3506 * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
3507 * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
3508 * - finish_lock_switch() for weakly-ordered
3509 * architectures where spin_unlock is a full barrier,
3510 * - switch_to() for arm64 (weakly-ordered, spin_unlock
3511 * is a RELEASE barrier),
3512 */
3513 ++*switch_count;
3514
3515 trace_sched_switch(preempt, prev, next);
3516
3517 /* Also unlocks the rq: */
3518 rq = context_switch(rq, prev, next, &rf);
3519 } else {
3520 rq->clock_update_flags &= ~(RQCF_ACT_SKIP|RQCF_REQ_SKIP);
3521 rq_unlock_irq(rq, &rf);
3522 }
3523
3524 balance_callback(rq);
3525}
3526
3527void __noreturn do_task_dead(void)
3528{
3529 /* Causes final put_task_struct in finish_task_switch(): */
3530 set_special_state(TASK_DEAD);
3531
3532 /* Tell freezer to ignore us: */
3533 current->flags |= PF_NOFREEZE;
3534
3535 __schedule(false);
3536 BUG();
3537
3538 /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
3539 for (;;)
3540 cpu_relax();
3541}
3542
3543static inline void sched_submit_work(struct task_struct *tsk)
3544{
3545 if (!tsk->state || tsk_is_pi_blocked(tsk))
3546 return;
3547 /*
3548 * If we are going to sleep and we have plugged IO queued,
3549 * make sure to submit it to avoid deadlocks.
3550 */
3551 if (blk_needs_flush_plug(tsk))
3552 blk_schedule_flush_plug(tsk);
3553}
3554
3555asmlinkage __visible void __sched schedule(void)
3556{
3557 struct task_struct *tsk = current;
3558
3559 sched_submit_work(tsk);
3560 do {
3561 preempt_disable();
3562 __schedule(false);
3563 sched_preempt_enable_no_resched();
3564 } while (need_resched());
3565}
3566EXPORT_SYMBOL(schedule);
3567
3568/*
3569 * synchronize_rcu_tasks() makes sure that no task is stuck in preempted
3570 * state (have scheduled out non-voluntarily) by making sure that all
3571 * tasks have either left the run queue or have gone into user space.
3572 * As idle tasks do not do either, they must not ever be preempted
3573 * (schedule out non-voluntarily).
3574 *
3575 * schedule_idle() is similar to schedule_preempt_disable() except that it
3576 * never enables preemption because it does not call sched_submit_work().
3577 */
3578void __sched schedule_idle(void)
3579{
3580 /*
3581 * As this skips calling sched_submit_work(), which the idle task does
3582 * regardless because that function is a nop when the task is in a
3583 * TASK_RUNNING state, make sure this isn't used someplace that the
3584 * current task can be in any other state. Note, idle is always in the
3585 * TASK_RUNNING state.
3586 */
3587 WARN_ON_ONCE(current->state);
3588 do {
3589 __schedule(false);
3590 } while (need_resched());
3591}
3592
3593#ifdef CONFIG_CONTEXT_TRACKING
3594asmlinkage __visible void __sched schedule_user(void)
3595{
3596 /*
3597 * If we come here after a random call to set_need_resched(),
3598 * or we have been woken up remotely but the IPI has not yet arrived,
3599 * we haven't yet exited the RCU idle mode. Do it here manually until
3600 * we find a better solution.
3601 *
3602 * NB: There are buggy callers of this function. Ideally we
3603 * should warn if prev_state != CONTEXT_USER, but that will trigger
3604 * too frequently to make sense yet.
3605 */
3606 enum ctx_state prev_state = exception_enter();
3607 schedule();
3608 exception_exit(prev_state);
3609}
3610#endif
3611
3612/**
3613 * schedule_preempt_disabled - called with preemption disabled
3614 *
3615 * Returns with preemption disabled. Note: preempt_count must be 1
3616 */
3617void __sched schedule_preempt_disabled(void)
3618{
3619 sched_preempt_enable_no_resched();
3620 schedule();
3621 preempt_disable();
3622}
3623
3624static void __sched notrace preempt_schedule_common(void)
3625{
3626 do {
3627 /*
3628 * Because the function tracer can trace preempt_count_sub()
3629 * and it also uses preempt_enable/disable_notrace(), if
3630 * NEED_RESCHED is set, the preempt_enable_notrace() called
3631 * by the function tracer will call this function again and
3632 * cause infinite recursion.
3633 *
3634 * Preemption must be disabled here before the function
3635 * tracer can trace. Break up preempt_disable() into two
3636 * calls. One to disable preemption without fear of being
3637 * traced. The other to still record the preemption latency,
3638 * which can also be traced by the function tracer.
3639 */
3640 preempt_disable_notrace();
3641 preempt_latency_start(1);
3642 __schedule(true);
3643 preempt_latency_stop(1);
3644 preempt_enable_no_resched_notrace();
3645
3646 /*
3647 * Check again in case we missed a preemption opportunity
3648 * between schedule and now.
3649 */
3650 } while (need_resched());
3651}
3652
3653#ifdef CONFIG_PREEMPT
3654/*
3655 * this is the entry point to schedule() from in-kernel preemption
3656 * off of preempt_enable. Kernel preemptions off return from interrupt
3657 * occur there and call schedule directly.
3658 */
3659asmlinkage __visible void __sched notrace preempt_schedule(void)
3660{
3661 /*
3662 * If there is a non-zero preempt_count or interrupts are disabled,
3663 * we do not want to preempt the current task. Just return..
3664 */
3665 if (likely(!preemptible()))
3666 return;
3667
3668 preempt_schedule_common();
3669}
3670NOKPROBE_SYMBOL(preempt_schedule);
3671EXPORT_SYMBOL(preempt_schedule);
3672
3673/**
3674 * preempt_schedule_notrace - preempt_schedule called by tracing
3675 *
3676 * The tracing infrastructure uses preempt_enable_notrace to prevent
3677 * recursion and tracing preempt enabling caused by the tracing
3678 * infrastructure itself. But as tracing can happen in areas coming
3679 * from userspace or just about to enter userspace, a preempt enable
3680 * can occur before user_exit() is called. This will cause the scheduler
3681 * to be called when the system is still in usermode.
3682 *
3683 * To prevent this, the preempt_enable_notrace will use this function
3684 * instead of preempt_schedule() to exit user context if needed before
3685 * calling the scheduler.
3686 */
3687asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
3688{
3689 enum ctx_state prev_ctx;
3690
3691 if (likely(!preemptible()))
3692 return;
3693
3694 do {
3695 /*
3696 * Because the function tracer can trace preempt_count_sub()
3697 * and it also uses preempt_enable/disable_notrace(), if
3698 * NEED_RESCHED is set, the preempt_enable_notrace() called
3699 * by the function tracer will call this function again and
3700 * cause infinite recursion.
3701 *
3702 * Preemption must be disabled here before the function
3703 * tracer can trace. Break up preempt_disable() into two
3704 * calls. One to disable preemption without fear of being
3705 * traced. The other to still record the preemption latency,
3706 * which can also be traced by the function tracer.
3707 */
3708 preempt_disable_notrace();
3709 preempt_latency_start(1);
3710 /*
3711 * Needs preempt disabled in case user_exit() is traced
3712 * and the tracer calls preempt_enable_notrace() causing
3713 * an infinite recursion.
3714 */
3715 prev_ctx = exception_enter();
3716 __schedule(true);
3717 exception_exit(prev_ctx);
3718
3719 preempt_latency_stop(1);
3720 preempt_enable_no_resched_notrace();
3721 } while (need_resched());
3722}
3723EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
3724
3725#endif /* CONFIG_PREEMPT */
3726
3727/*
3728 * this is the entry point to schedule() from kernel preemption
3729 * off of irq context.
3730 * Note, that this is called and return with irqs disabled. This will
3731 * protect us against recursive calling from irq.
3732 */
3733asmlinkage __visible void __sched preempt_schedule_irq(void)
3734{
3735 enum ctx_state prev_state;
3736
3737 /* Catch callers which need to be fixed */
3738 BUG_ON(preempt_count() || !irqs_disabled());
3739
3740 prev_state = exception_enter();
3741
3742 do {
3743 preempt_disable();
3744 local_irq_enable();
3745 __schedule(true);
3746 local_irq_disable();
3747 sched_preempt_enable_no_resched();
3748 } while (need_resched());
3749
3750 exception_exit(prev_state);
3751}
3752
3753int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
3754 void *key)
3755{
3756 return try_to_wake_up(curr->private, mode, wake_flags);
3757}
3758EXPORT_SYMBOL(default_wake_function);
3759
3760#ifdef CONFIG_RT_MUTEXES
3761
3762static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
3763{
3764 if (pi_task)
3765 prio = min(prio, pi_task->prio);
3766
3767 return prio;
3768}
3769
3770static inline int rt_effective_prio(struct task_struct *p, int prio)
3771{
3772 struct task_struct *pi_task = rt_mutex_get_top_task(p);
3773
3774 return __rt_effective_prio(pi_task, prio);
3775}
3776
3777/*
3778 * rt_mutex_setprio - set the current priority of a task
3779 * @p: task to boost
3780 * @pi_task: donor task
3781 *
3782 * This function changes the 'effective' priority of a task. It does
3783 * not touch ->normal_prio like __setscheduler().
3784 *
3785 * Used by the rt_mutex code to implement priority inheritance
3786 * logic. Call site only calls if the priority of the task changed.
3787 */
3788void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
3789{
3790 int prio, oldprio, queued, running, queue_flag =
3791 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
3792 const struct sched_class *prev_class;
3793 struct rq_flags rf;
3794 struct rq *rq;
3795
3796 /* XXX used to be waiter->prio, not waiter->task->prio */
3797 prio = __rt_effective_prio(pi_task, p->normal_prio);
3798
3799 /*
3800 * If nothing changed; bail early.
3801 */
3802 if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio))
3803 return;
3804
3805 rq = __task_rq_lock(p, &rf);
3806 update_rq_clock(rq);
3807 /*
3808 * Set under pi_lock && rq->lock, such that the value can be used under
3809 * either lock.
3810 *
3811 * Note that there is loads of tricky to make this pointer cache work
3812 * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
3813 * ensure a task is de-boosted (pi_task is set to NULL) before the
3814 * task is allowed to run again (and can exit). This ensures the pointer
3815 * points to a blocked task -- which guaratees the task is present.
3816 */
3817 p->pi_top_task = pi_task;
3818
3819 /*
3820 * For FIFO/RR we only need to set prio, if that matches we're done.
3821 */
3822 if (prio == p->prio && !dl_prio(prio))
3823 goto out_unlock;
3824
3825 /*
3826 * Idle task boosting is a nono in general. There is one
3827 * exception, when PREEMPT_RT and NOHZ is active:
3828 *
3829 * The idle task calls get_next_timer_interrupt() and holds
3830 * the timer wheel base->lock on the CPU and another CPU wants
3831 * to access the timer (probably to cancel it). We can safely
3832 * ignore the boosting request, as the idle CPU runs this code
3833 * with interrupts disabled and will complete the lock
3834 * protected section without being interrupted. So there is no
3835 * real need to boost.
3836 */
3837 if (unlikely(p == rq->idle)) {
3838 WARN_ON(p != rq->curr);
3839 WARN_ON(p->pi_blocked_on);
3840 goto out_unlock;
3841 }
3842
3843 trace_sched_pi_setprio(p, pi_task);
3844 oldprio = p->prio;
3845
3846 if (oldprio == prio)
3847 queue_flag &= ~DEQUEUE_MOVE;
3848
3849 prev_class = p->sched_class;
3850 queued = task_on_rq_queued(p);
3851 running = task_current(rq, p);
3852 if (queued)
3853 dequeue_task(rq, p, queue_flag);
3854 if (running)
3855 put_prev_task(rq, p);
3856
3857 /*
3858 * Boosting condition are:
3859 * 1. -rt task is running and holds mutex A
3860 * --> -dl task blocks on mutex A
3861 *
3862 * 2. -dl task is running and holds mutex A
3863 * --> -dl task blocks on mutex A and could preempt the
3864 * running task
3865 */
3866 if (dl_prio(prio)) {
3867 if (!dl_prio(p->normal_prio) ||
3868 (pi_task && dl_entity_preempt(&pi_task->dl, &p->dl))) {
3869 p->dl.dl_boosted = 1;
3870 queue_flag |= ENQUEUE_REPLENISH;
3871 } else
3872 p->dl.dl_boosted = 0;
3873 p->sched_class = &dl_sched_class;
3874 } else if (rt_prio(prio)) {
3875 if (dl_prio(oldprio))
3876 p->dl.dl_boosted = 0;
3877 if (oldprio < prio)
3878 queue_flag |= ENQUEUE_HEAD;
3879 p->sched_class = &rt_sched_class;
3880 } else {
3881 if (dl_prio(oldprio))
3882 p->dl.dl_boosted = 0;
3883 if (rt_prio(oldprio))
3884 p->rt.timeout = 0;
3885 p->sched_class = &fair_sched_class;
3886 }
3887
3888 p->prio = prio;
3889
3890 if (queued)
3891 enqueue_task(rq, p, queue_flag);
3892 if (running)
3893 set_curr_task(rq, p);
3894
3895 check_class_changed(rq, p, prev_class, oldprio);
3896out_unlock:
3897 /* Avoid rq from going away on us: */
3898 preempt_disable();
3899 __task_rq_unlock(rq, &rf);
3900
3901 balance_callback(rq);
3902 preempt_enable();
3903}
3904#else
3905static inline int rt_effective_prio(struct task_struct *p, int prio)
3906{
3907 return prio;
3908}
3909#endif
3910
3911void set_user_nice(struct task_struct *p, long nice)
3912{
3913 bool queued, running;
3914 int old_prio, delta;
3915 struct rq_flags rf;
3916 struct rq *rq;
3917
3918 if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
3919 return;
3920 /*
3921 * We have to be careful, if called from sys_setpriority(),
3922 * the task might be in the middle of scheduling on another CPU.
3923 */
3924 rq = task_rq_lock(p, &rf);
3925 update_rq_clock(rq);
3926
3927 /*
3928 * The RT priorities are set via sched_setscheduler(), but we still
3929 * allow the 'normal' nice value to be set - but as expected
3930 * it wont have any effect on scheduling until the task is
3931 * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
3932 */
3933 if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
3934 p->static_prio = NICE_TO_PRIO(nice);
3935 goto out_unlock;
3936 }
3937 queued = task_on_rq_queued(p);
3938 running = task_current(rq, p);
3939 if (queued)
3940 dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
3941 if (running)
3942 put_prev_task(rq, p);
3943
3944 p->static_prio = NICE_TO_PRIO(nice);
3945 set_load_weight(p, true);
3946 old_prio = p->prio;
3947 p->prio = effective_prio(p);
3948 delta = p->prio - old_prio;
3949
3950 if (queued) {
3951 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
3952 /*
3953 * If the task increased its priority or is running and
3954 * lowered its priority, then reschedule its CPU:
3955 */
3956 if (delta < 0 || (delta > 0 && task_running(rq, p)))
3957 resched_curr(rq);
3958 }
3959 if (running)
3960 set_curr_task(rq, p);
3961out_unlock:
3962 task_rq_unlock(rq, p, &rf);
3963}
3964EXPORT_SYMBOL(set_user_nice);
3965
3966/*
3967 * can_nice - check if a task can reduce its nice value
3968 * @p: task
3969 * @nice: nice value
3970 */
3971int can_nice(const struct task_struct *p, const int nice)
3972{
3973 /* Convert nice value [19,-20] to rlimit style value [1,40]: */
3974 int nice_rlim = nice_to_rlimit(nice);
3975
3976 return (nice_rlim <= task_rlimit(p, RLIMIT_NICE) ||
3977 capable(CAP_SYS_NICE));
3978}
3979
3980#ifdef __ARCH_WANT_SYS_NICE
3981
3982/*
3983 * sys_nice - change the priority of the current process.
3984 * @increment: priority increment
3985 *
3986 * sys_setpriority is a more generic, but much slower function that
3987 * does similar things.
3988 */
3989SYSCALL_DEFINE1(nice, int, increment)
3990{
3991 long nice, retval;
3992
3993 /*
3994 * Setpriority might change our priority at the same moment.
3995 * We don't have to worry. Conceptually one call occurs first
3996 * and we have a single winner.
3997 */
3998 increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
3999 nice = task_nice(current) + increment;
4000
4001 nice = clamp_val(nice, MIN_NICE, MAX_NICE);
4002 if (increment < 0 && !can_nice(current, nice))
4003 return -EPERM;
4004
4005 retval = security_task_setnice(current, nice);
4006 if (retval)
4007 return retval;
4008
4009 set_user_nice(current, nice);
4010 return 0;
4011}
4012
4013#endif
4014
4015/**
4016 * task_prio - return the priority value of a given task.
4017 * @p: the task in question.
4018 *
4019 * Return: The priority value as seen by users in /proc.
4020 * RT tasks are offset by -200. Normal tasks are centered
4021 * around 0, value goes from -16 to +15.
4022 */
4023int task_prio(const struct task_struct *p)
4024{
4025 return p->prio - MAX_RT_PRIO;
4026}
4027
4028/**
4029 * idle_cpu - is a given CPU idle currently?
4030 * @cpu: the processor in question.
4031 *
4032 * Return: 1 if the CPU is currently idle. 0 otherwise.
4033 */
4034int idle_cpu(int cpu)
4035{
4036 struct rq *rq = cpu_rq(cpu);
4037
4038 if (rq->curr != rq->idle)
4039 return 0;
4040
4041 if (rq->nr_running)
4042 return 0;
4043
4044#ifdef CONFIG_SMP
4045 if (!llist_empty(&rq->wake_list))
4046 return 0;
4047#endif
4048
4049 return 1;
4050}
4051
4052/**
4053 * idle_task - return the idle task for a given CPU.
4054 * @cpu: the processor in question.
4055 *
4056 * Return: The idle task for the CPU @cpu.
4057 */
4058struct task_struct *idle_task(int cpu)
4059{
4060 return cpu_rq(cpu)->idle;
4061}
4062
4063/**
4064 * find_process_by_pid - find a process with a matching PID value.
4065 * @pid: the pid in question.
4066 *
4067 * The task of @pid, if found. %NULL otherwise.
4068 */
4069static struct task_struct *find_process_by_pid(pid_t pid)
4070{
4071 return pid ? find_task_by_vpid(pid) : current;
4072}
4073
4074/*
4075 * sched_setparam() passes in -1 for its policy, to let the functions
4076 * it calls know not to change it.
4077 */
4078#define SETPARAM_POLICY -1
4079
4080static void __setscheduler_params(struct task_struct *p,
4081 const struct sched_attr *attr)
4082{
4083 int policy = attr->sched_policy;
4084
4085 if (policy == SETPARAM_POLICY)
4086 policy = p->policy;
4087
4088 p->policy = policy;
4089
4090 if (dl_policy(policy))
4091 __setparam_dl(p, attr);
4092 else if (fair_policy(policy))
4093 p->static_prio = NICE_TO_PRIO(attr->sched_nice);
4094
4095 /*
4096 * __sched_setscheduler() ensures attr->sched_priority == 0 when
4097 * !rt_policy. Always setting this ensures that things like
4098 * getparam()/getattr() don't report silly values for !rt tasks.
4099 */
4100 p->rt_priority = attr->sched_priority;
4101 p->normal_prio = normal_prio(p);
4102 set_load_weight(p, true);
4103}
4104
4105/* Actually do priority change: must hold pi & rq lock. */
4106static void __setscheduler(struct rq *rq, struct task_struct *p,
4107 const struct sched_attr *attr, bool keep_boost)
4108{
4109 __setscheduler_params(p, attr);
4110
4111 /*
4112 * Keep a potential priority boosting if called from
4113 * sched_setscheduler().
4114 */
4115 p->prio = normal_prio(p);
4116 if (keep_boost)
4117 p->prio = rt_effective_prio(p, p->prio);
4118
4119 if (dl_prio(p->prio))
4120 p->sched_class = &dl_sched_class;
4121 else if (rt_prio(p->prio))
4122 p->sched_class = &rt_sched_class;
4123 else
4124 p->sched_class = &fair_sched_class;
4125}
4126
4127/*
4128 * Check the target process has a UID that matches the current process's:
4129 */
4130static bool check_same_owner(struct task_struct *p)
4131{
4132 const struct cred *cred = current_cred(), *pcred;
4133 bool match;
4134
4135 rcu_read_lock();
4136 pcred = __task_cred(p);
4137 match = (uid_eq(cred->euid, pcred->euid) ||
4138 uid_eq(cred->euid, pcred->uid));
4139 rcu_read_unlock();
4140 return match;
4141}
4142
4143static int __sched_setscheduler(struct task_struct *p,
4144 const struct sched_attr *attr,
4145 bool user, bool pi)
4146{
4147 int newprio = dl_policy(attr->sched_policy) ? MAX_DL_PRIO - 1 :
4148 MAX_RT_PRIO - 1 - attr->sched_priority;
4149 int retval, oldprio, oldpolicy = -1, queued, running;
4150 int new_effective_prio, policy = attr->sched_policy;
4151 const struct sched_class *prev_class;
4152 struct rq_flags rf;
4153 int reset_on_fork;
4154 int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
4155 struct rq *rq;
4156
4157 /* The pi code expects interrupts enabled */
4158 BUG_ON(pi && in_interrupt());
4159recheck:
4160 /* Double check policy once rq lock held: */
4161 if (policy < 0) {
4162 reset_on_fork = p->sched_reset_on_fork;
4163 policy = oldpolicy = p->policy;
4164 } else {
4165 reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
4166
4167 if (!valid_policy(policy))
4168 return -EINVAL;
4169 }
4170
4171 if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
4172 return -EINVAL;
4173
4174 /*
4175 * Valid priorities for SCHED_FIFO and SCHED_RR are
4176 * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL,
4177 * SCHED_BATCH and SCHED_IDLE is 0.
4178 */
4179 if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) ||
4180 (!p->mm && attr->sched_priority > MAX_RT_PRIO-1))
4181 return -EINVAL;
4182 if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
4183 (rt_policy(policy) != (attr->sched_priority != 0)))
4184 return -EINVAL;
4185
4186 /*
4187 * Allow unprivileged RT tasks to decrease priority:
4188 */
4189 if (user && !capable(CAP_SYS_NICE)) {
4190 if (fair_policy(policy)) {
4191 if (attr->sched_nice < task_nice(p) &&
4192 !can_nice(p, attr->sched_nice))
4193 return -EPERM;
4194 }
4195
4196 if (rt_policy(policy)) {
4197 unsigned long rlim_rtprio =
4198 task_rlimit(p, RLIMIT_RTPRIO);
4199
4200 /* Can't set/change the rt policy: */
4201 if (policy != p->policy && !rlim_rtprio)
4202 return -EPERM;
4203
4204 /* Can't increase priority: */
4205 if (attr->sched_priority > p->rt_priority &&
4206 attr->sched_priority > rlim_rtprio)
4207 return -EPERM;
4208 }
4209
4210 /*
4211 * Can't set/change SCHED_DEADLINE policy at all for now
4212 * (safest behavior); in the future we would like to allow
4213 * unprivileged DL tasks to increase their relative deadline
4214 * or reduce their runtime (both ways reducing utilization)
4215 */
4216 if (dl_policy(policy))
4217 return -EPERM;
4218
4219 /*
4220 * Treat SCHED_IDLE as nice 20. Only allow a switch to
4221 * SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
4222 */
4223 if (idle_policy(p->policy) && !idle_policy(policy)) {
4224 if (!can_nice(p, task_nice(p)))
4225 return -EPERM;
4226 }
4227
4228 /* Can't change other user's priorities: */
4229 if (!check_same_owner(p))
4230 return -EPERM;
4231
4232 /* Normal users shall not reset the sched_reset_on_fork flag: */
4233 if (p->sched_reset_on_fork && !reset_on_fork)
4234 return -EPERM;
4235 }
4236
4237 if (user) {
4238 if (attr->sched_flags & SCHED_FLAG_SUGOV)
4239 return -EINVAL;
4240
4241 retval = security_task_setscheduler(p);
4242 if (retval)
4243 return retval;
4244 }
4245
4246 /*
4247 * Make sure no PI-waiters arrive (or leave) while we are
4248 * changing the priority of the task:
4249 *
4250 * To be able to change p->policy safely, the appropriate
4251 * runqueue lock must be held.
4252 */
4253 rq = task_rq_lock(p, &rf);
4254 update_rq_clock(rq);
4255
4256 /*
4257 * Changing the policy of the stop threads its a very bad idea:
4258 */
4259 if (p == rq->stop) {
4260 task_rq_unlock(rq, p, &rf);
4261 return -EINVAL;
4262 }
4263
4264 /*
4265 * If not changing anything there's no need to proceed further,
4266 * but store a possible modification of reset_on_fork.
4267 */
4268 if (unlikely(policy == p->policy)) {
4269 if (fair_policy(policy) && attr->sched_nice != task_nice(p))
4270 goto change;
4271 if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
4272 goto change;
4273 if (dl_policy(policy) && dl_param_changed(p, attr))
4274 goto change;
4275
4276 p->sched_reset_on_fork = reset_on_fork;
4277 task_rq_unlock(rq, p, &rf);
4278 return 0;
4279 }
4280change:
4281
4282 if (user) {
4283#ifdef CONFIG_RT_GROUP_SCHED
4284 /*
4285 * Do not allow realtime tasks into groups that have no runtime
4286 * assigned.
4287 */
4288 if (rt_bandwidth_enabled() && rt_policy(policy) &&
4289 task_group(p)->rt_bandwidth.rt_runtime == 0 &&
4290 !task_group_is_autogroup(task_group(p))) {
4291 task_rq_unlock(rq, p, &rf);
4292 return -EPERM;
4293 }
4294#endif
4295#ifdef CONFIG_SMP
4296 if (dl_bandwidth_enabled() && dl_policy(policy) &&
4297 !(attr->sched_flags & SCHED_FLAG_SUGOV)) {
4298 cpumask_t *span = rq->rd->span;
4299
4300 /*
4301 * Don't allow tasks with an affinity mask smaller than
4302 * the entire root_domain to become SCHED_DEADLINE. We
4303 * will also fail if there's no bandwidth available.
4304 */
4305 if (!cpumask_subset(span, &p->cpus_allowed) ||
4306 rq->rd->dl_bw.bw == 0) {
4307 task_rq_unlock(rq, p, &rf);
4308 return -EPERM;
4309 }
4310 }
4311#endif
4312 }
4313
4314 /* Re-check policy now with rq lock held: */
4315 if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
4316 policy = oldpolicy = -1;
4317 task_rq_unlock(rq, p, &rf);
4318 goto recheck;
4319 }
4320
4321 /*
4322 * If setscheduling to SCHED_DEADLINE (or changing the parameters
4323 * of a SCHED_DEADLINE task) we need to check if enough bandwidth
4324 * is available.
4325 */
4326 if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
4327 task_rq_unlock(rq, p, &rf);
4328 return -EBUSY;
4329 }
4330
4331 p->sched_reset_on_fork = reset_on_fork;
4332 oldprio = p->prio;
4333
4334 if (pi) {
4335 /*
4336 * Take priority boosted tasks into account. If the new
4337 * effective priority is unchanged, we just store the new
4338 * normal parameters and do not touch the scheduler class and
4339 * the runqueue. This will be done when the task deboost
4340 * itself.
4341 */
4342 new_effective_prio = rt_effective_prio(p, newprio);
4343 if (new_effective_prio == oldprio)
4344 queue_flags &= ~DEQUEUE_MOVE;
4345 }
4346
4347 queued = task_on_rq_queued(p);
4348 running = task_current(rq, p);
4349 if (queued)
4350 dequeue_task(rq, p, queue_flags);
4351 if (running)
4352 put_prev_task(rq, p);
4353
4354 prev_class = p->sched_class;
4355 __setscheduler(rq, p, attr, pi);
4356
4357 if (queued) {
4358 /*
4359 * We enqueue to tail when the priority of a task is
4360 * increased (user space view).
4361 */
4362 if (oldprio < p->prio)
4363 queue_flags |= ENQUEUE_HEAD;
4364
4365 enqueue_task(rq, p, queue_flags);
4366 }
4367 if (running)
4368 set_curr_task(rq, p);
4369
4370 check_class_changed(rq, p, prev_class, oldprio);
4371
4372 /* Avoid rq from going away on us: */
4373 preempt_disable();
4374 task_rq_unlock(rq, p, &rf);
4375
4376 if (pi)
4377 rt_mutex_adjust_pi(p);
4378
4379 /* Run balance callbacks after we've adjusted the PI chain: */
4380 balance_callback(rq);
4381 preempt_enable();
4382
4383 return 0;
4384}
4385
4386static int _sched_setscheduler(struct task_struct *p, int policy,
4387 const struct sched_param *param, bool check)
4388{
4389 struct sched_attr attr = {
4390 .sched_policy = policy,
4391 .sched_priority = param->sched_priority,
4392 .sched_nice = PRIO_TO_NICE(p->static_prio),
4393 };
4394
4395 /* Fixup the legacy SCHED_RESET_ON_FORK hack. */
4396 if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
4397 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4398 policy &= ~SCHED_RESET_ON_FORK;
4399 attr.sched_policy = policy;
4400 }
4401
4402 return __sched_setscheduler(p, &attr, check, true);
4403}
4404/**
4405 * sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
4406 * @p: the task in question.
4407 * @policy: new policy.
4408 * @param: structure containing the new RT priority.
4409 *
4410 * Return: 0 on success. An error code otherwise.
4411 *
4412 * NOTE that the task may be already dead.
4413 */
4414int sched_setscheduler(struct task_struct *p, int policy,
4415 const struct sched_param *param)
4416{
4417 return _sched_setscheduler(p, policy, param, true);
4418}
4419EXPORT_SYMBOL_GPL(sched_setscheduler);
4420
4421int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
4422{
4423 return __sched_setscheduler(p, attr, true, true);
4424}
4425EXPORT_SYMBOL_GPL(sched_setattr);
4426
4427int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
4428{
4429 return __sched_setscheduler(p, attr, false, true);
4430}
4431
4432/**
4433 * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
4434 * @p: the task in question.
4435 * @policy: new policy.
4436 * @param: structure containing the new RT priority.
4437 *
4438 * Just like sched_setscheduler, only don't bother checking if the
4439 * current context has permission. For example, this is needed in
4440 * stop_machine(): we create temporary high priority worker threads,
4441 * but our caller might not have that capability.
4442 *
4443 * Return: 0 on success. An error code otherwise.
4444 */
4445int sched_setscheduler_nocheck(struct task_struct *p, int policy,
4446 const struct sched_param *param)
4447{
4448 return _sched_setscheduler(p, policy, param, false);
4449}
4450EXPORT_SYMBOL_GPL(sched_setscheduler_nocheck);
4451
4452static int
4453do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
4454{
4455 struct sched_param lparam;
4456 struct task_struct *p;
4457 int retval;
4458
4459 if (!param || pid < 0)
4460 return -EINVAL;
4461 if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
4462 return -EFAULT;
4463
4464 rcu_read_lock();
4465 retval = -ESRCH;
4466 p = find_process_by_pid(pid);
4467 if (p != NULL)
4468 retval = sched_setscheduler(p, policy, &lparam);
4469 rcu_read_unlock();
4470
4471 return retval;
4472}
4473
4474/*
4475 * Mimics kernel/events/core.c perf_copy_attr().
4476 */
4477static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
4478{
4479 u32 size;
4480 int ret;
4481
4482 if (!access_ok(VERIFY_WRITE, uattr, SCHED_ATTR_SIZE_VER0))
4483 return -EFAULT;
4484
4485 /* Zero the full structure, so that a short copy will be nice: */
4486 memset(attr, 0, sizeof(*attr));
4487
4488 ret = get_user(size, &uattr->size);
4489 if (ret)
4490 return ret;
4491
4492 /* Bail out on silly large: */
4493 if (size > PAGE_SIZE)
4494 goto err_size;
4495
4496 /* ABI compatibility quirk: */
4497 if (!size)
4498 size = SCHED_ATTR_SIZE_VER0;
4499
4500 if (size < SCHED_ATTR_SIZE_VER0)
4501 goto err_size;
4502
4503 /*
4504 * If we're handed a bigger struct than we know of,
4505 * ensure all the unknown bits are 0 - i.e. new
4506 * user-space does not rely on any kernel feature
4507 * extensions we dont know about yet.
4508 */
4509 if (size > sizeof(*attr)) {
4510 unsigned char __user *addr;
4511 unsigned char __user *end;
4512 unsigned char val;
4513
4514 addr = (void __user *)uattr + sizeof(*attr);
4515 end = (void __user *)uattr + size;
4516
4517 for (; addr < end; addr++) {
4518 ret = get_user(val, addr);
4519 if (ret)
4520 return ret;
4521 if (val)
4522 goto err_size;
4523 }
4524 size = sizeof(*attr);
4525 }
4526
4527 ret = copy_from_user(attr, uattr, size);
4528 if (ret)
4529 return -EFAULT;
4530
4531 /*
4532 * XXX: Do we want to be lenient like existing syscalls; or do we want
4533 * to be strict and return an error on out-of-bounds values?
4534 */
4535 attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
4536
4537 return 0;
4538
4539err_size:
4540 put_user(sizeof(*attr), &uattr->size);
4541 return -E2BIG;
4542}
4543
4544/**
4545 * sys_sched_setscheduler - set/change the scheduler policy and RT priority
4546 * @pid: the pid in question.
4547 * @policy: new policy.
4548 * @param: structure containing the new RT priority.
4549 *
4550 * Return: 0 on success. An error code otherwise.
4551 */
4552SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
4553{
4554 if (policy < 0)
4555 return -EINVAL;
4556
4557 return do_sched_setscheduler(pid, policy, param);
4558}
4559
4560/**
4561 * sys_sched_setparam - set/change the RT priority of a thread
4562 * @pid: the pid in question.
4563 * @param: structure containing the new RT priority.
4564 *
4565 * Return: 0 on success. An error code otherwise.
4566 */
4567SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
4568{
4569 return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
4570}
4571
4572/**
4573 * sys_sched_setattr - same as above, but with extended sched_attr
4574 * @pid: the pid in question.
4575 * @uattr: structure containing the extended parameters.
4576 * @flags: for future extension.
4577 */
4578SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
4579 unsigned int, flags)
4580{
4581 struct sched_attr attr;
4582 struct task_struct *p;
4583 int retval;
4584
4585 if (!uattr || pid < 0 || flags)
4586 return -EINVAL;
4587
4588 retval = sched_copy_attr(uattr, &attr);
4589 if (retval)
4590 return retval;
4591
4592 if ((int)attr.sched_policy < 0)
4593 return -EINVAL;
4594
4595 rcu_read_lock();
4596 retval = -ESRCH;
4597 p = find_process_by_pid(pid);
4598 if (p != NULL)
4599 retval = sched_setattr(p, &attr);
4600 rcu_read_unlock();
4601
4602 return retval;
4603}
4604
4605/**
4606 * sys_sched_getscheduler - get the policy (scheduling class) of a thread
4607 * @pid: the pid in question.
4608 *
4609 * Return: On success, the policy of the thread. Otherwise, a negative error
4610 * code.
4611 */
4612SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
4613{
4614 struct task_struct *p;
4615 int retval;
4616
4617 if (pid < 0)
4618 return -EINVAL;
4619
4620 retval = -ESRCH;
4621 rcu_read_lock();
4622 p = find_process_by_pid(pid);
4623 if (p) {
4624 retval = security_task_getscheduler(p);
4625 if (!retval)
4626 retval = p->policy
4627 | (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
4628 }
4629 rcu_read_unlock();
4630 return retval;
4631}
4632
4633/**
4634 * sys_sched_getparam - get the RT priority of a thread
4635 * @pid: the pid in question.
4636 * @param: structure containing the RT priority.
4637 *
4638 * Return: On success, 0 and the RT priority is in @param. Otherwise, an error
4639 * code.
4640 */
4641SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
4642{
4643 struct sched_param lp = { .sched_priority = 0 };
4644 struct task_struct *p;
4645 int retval;
4646
4647 if (!param || pid < 0)
4648 return -EINVAL;
4649
4650 rcu_read_lock();
4651 p = find_process_by_pid(pid);
4652 retval = -ESRCH;
4653 if (!p)
4654 goto out_unlock;
4655
4656 retval = security_task_getscheduler(p);
4657 if (retval)
4658 goto out_unlock;
4659
4660 if (task_has_rt_policy(p))
4661 lp.sched_priority = p->rt_priority;
4662 rcu_read_unlock();
4663
4664 /*
4665 * This one might sleep, we cannot do it with a spinlock held ...
4666 */
4667 retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
4668
4669 return retval;
4670
4671out_unlock:
4672 rcu_read_unlock();
4673 return retval;
4674}
4675
4676static int sched_read_attr(struct sched_attr __user *uattr,
4677 struct sched_attr *attr,
4678 unsigned int usize)
4679{
4680 int ret;
4681
4682 if (!access_ok(VERIFY_WRITE, uattr, usize))
4683 return -EFAULT;
4684
4685 /*
4686 * If we're handed a smaller struct than we know of,
4687 * ensure all the unknown bits are 0 - i.e. old
4688 * user-space does not get uncomplete information.
4689 */
4690 if (usize < sizeof(*attr)) {
4691 unsigned char *addr;
4692 unsigned char *end;
4693
4694 addr = (void *)attr + usize;
4695 end = (void *)attr + sizeof(*attr);
4696
4697 for (; addr < end; addr++) {
4698 if (*addr)
4699 return -EFBIG;
4700 }
4701
4702 attr->size = usize;
4703 }
4704
4705 ret = copy_to_user(uattr, attr, attr->size);
4706 if (ret)
4707 return -EFAULT;
4708
4709 return 0;
4710}
4711
4712/**
4713 * sys_sched_getattr - similar to sched_getparam, but with sched_attr
4714 * @pid: the pid in question.
4715 * @uattr: structure containing the extended parameters.
4716 * @size: sizeof(attr) for fwd/bwd comp.
4717 * @flags: for future extension.
4718 */
4719SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
4720 unsigned int, size, unsigned int, flags)
4721{
4722 struct sched_attr attr = {
4723 .size = sizeof(struct sched_attr),
4724 };
4725 struct task_struct *p;
4726 int retval;
4727
4728 if (!uattr || pid < 0 || size > PAGE_SIZE ||
4729 size < SCHED_ATTR_SIZE_VER0 || flags)
4730 return -EINVAL;
4731
4732 rcu_read_lock();
4733 p = find_process_by_pid(pid);
4734 retval = -ESRCH;
4735 if (!p)
4736 goto out_unlock;
4737
4738 retval = security_task_getscheduler(p);
4739 if (retval)
4740 goto out_unlock;
4741
4742 attr.sched_policy = p->policy;
4743 if (p->sched_reset_on_fork)
4744 attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
4745 if (task_has_dl_policy(p))
4746 __getparam_dl(p, &attr);
4747 else if (task_has_rt_policy(p))
4748 attr.sched_priority = p->rt_priority;
4749 else
4750 attr.sched_nice = task_nice(p);
4751
4752 rcu_read_unlock();
4753
4754 retval = sched_read_attr(uattr, &attr, size);
4755 return retval;
4756
4757out_unlock:
4758 rcu_read_unlock();
4759 return retval;
4760}
4761
4762long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
4763{
4764 cpumask_var_t cpus_allowed, new_mask;
4765 struct task_struct *p;
4766 int retval;
4767
4768 rcu_read_lock();
4769
4770 p = find_process_by_pid(pid);
4771 if (!p) {
4772 rcu_read_unlock();
4773 return -ESRCH;
4774 }
4775
4776 /* Prevent p going away */
4777 get_task_struct(p);
4778 rcu_read_unlock();
4779
4780 if (p->flags & PF_NO_SETAFFINITY) {
4781 retval = -EINVAL;
4782 goto out_put_task;
4783 }
4784 if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
4785 retval = -ENOMEM;
4786 goto out_put_task;
4787 }
4788 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
4789 retval = -ENOMEM;
4790 goto out_free_cpus_allowed;
4791 }
4792 retval = -EPERM;
4793 if (!check_same_owner(p)) {
4794 rcu_read_lock();
4795 if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
4796 rcu_read_unlock();
4797 goto out_free_new_mask;
4798 }
4799 rcu_read_unlock();
4800 }
4801
4802 retval = security_task_setscheduler(p);
4803 if (retval)
4804 goto out_free_new_mask;
4805
4806
4807 cpuset_cpus_allowed(p, cpus_allowed);
4808 cpumask_and(new_mask, in_mask, cpus_allowed);
4809
4810 /*
4811 * Since bandwidth control happens on root_domain basis,
4812 * if admission test is enabled, we only admit -deadline
4813 * tasks allowed to run on all the CPUs in the task's
4814 * root_domain.
4815 */
4816#ifdef CONFIG_SMP
4817 if (task_has_dl_policy(p) && dl_bandwidth_enabled()) {
4818 rcu_read_lock();
4819 if (!cpumask_subset(task_rq(p)->rd->span, new_mask)) {
4820 retval = -EBUSY;
4821 rcu_read_unlock();
4822 goto out_free_new_mask;
4823 }
4824 rcu_read_unlock();
4825 }
4826#endif
4827again:
4828 retval = __set_cpus_allowed_ptr(p, new_mask, true);
4829
4830 if (!retval) {
4831 cpuset_cpus_allowed(p, cpus_allowed);
4832 if (!cpumask_subset(new_mask, cpus_allowed)) {
4833 /*
4834 * We must have raced with a concurrent cpuset
4835 * update. Just reset the cpus_allowed to the
4836 * cpuset's cpus_allowed
4837 */
4838 cpumask_copy(new_mask, cpus_allowed);
4839 goto again;
4840 }
4841 }
4842out_free_new_mask:
4843 free_cpumask_var(new_mask);
4844out_free_cpus_allowed:
4845 free_cpumask_var(cpus_allowed);
4846out_put_task:
4847 put_task_struct(p);
4848 return retval;
4849}
4850
4851static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
4852 struct cpumask *new_mask)
4853{
4854 if (len < cpumask_size())
4855 cpumask_clear(new_mask);
4856 else if (len > cpumask_size())
4857 len = cpumask_size();
4858
4859 return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
4860}
4861
4862/**
4863 * sys_sched_setaffinity - set the CPU affinity of a process
4864 * @pid: pid of the process
4865 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4866 * @user_mask_ptr: user-space pointer to the new CPU mask
4867 *
4868 * Return: 0 on success. An error code otherwise.
4869 */
4870SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
4871 unsigned long __user *, user_mask_ptr)
4872{
4873 cpumask_var_t new_mask;
4874 int retval;
4875
4876 if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
4877 return -ENOMEM;
4878
4879 retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
4880 if (retval == 0)
4881 retval = sched_setaffinity(pid, new_mask);
4882 free_cpumask_var(new_mask);
4883 return retval;
4884}
4885
4886long sched_getaffinity(pid_t pid, struct cpumask *mask)
4887{
4888 struct task_struct *p;
4889 unsigned long flags;
4890 int retval;
4891
4892 rcu_read_lock();
4893
4894 retval = -ESRCH;
4895 p = find_process_by_pid(pid);
4896 if (!p)
4897 goto out_unlock;
4898
4899 retval = security_task_getscheduler(p);
4900 if (retval)
4901 goto out_unlock;
4902
4903 raw_spin_lock_irqsave(&p->pi_lock, flags);
4904 cpumask_and(mask, &p->cpus_allowed, cpu_active_mask);
4905 raw_spin_unlock_irqrestore(&p->pi_lock, flags);
4906
4907out_unlock:
4908 rcu_read_unlock();
4909
4910 return retval;
4911}
4912
4913/**
4914 * sys_sched_getaffinity - get the CPU affinity of a process
4915 * @pid: pid of the process
4916 * @len: length in bytes of the bitmask pointed to by user_mask_ptr
4917 * @user_mask_ptr: user-space pointer to hold the current CPU mask
4918 *
4919 * Return: size of CPU mask copied to user_mask_ptr on success. An
4920 * error code otherwise.
4921 */
4922SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
4923 unsigned long __user *, user_mask_ptr)
4924{
4925 int ret;
4926 cpumask_var_t mask;
4927
4928 if ((len * BITS_PER_BYTE) < nr_cpu_ids)
4929 return -EINVAL;
4930 if (len & (sizeof(unsigned long)-1))
4931 return -EINVAL;
4932
4933 if (!alloc_cpumask_var(&mask, GFP_KERNEL))
4934 return -ENOMEM;
4935
4936 ret = sched_getaffinity(pid, mask);
4937 if (ret == 0) {
4938 unsigned int retlen = min(len, cpumask_size());
4939
4940 if (copy_to_user(user_mask_ptr, mask, retlen))
4941 ret = -EFAULT;
4942 else
4943 ret = retlen;
4944 }
4945 free_cpumask_var(mask);
4946
4947 return ret;
4948}
4949
4950/**
4951 * sys_sched_yield - yield the current processor to other threads.
4952 *
4953 * This function yields the current CPU to other tasks. If there are no
4954 * other threads running on this CPU then this function will return.
4955 *
4956 * Return: 0.
4957 */
4958static void do_sched_yield(void)
4959{
4960 struct rq_flags rf;
4961 struct rq *rq;
4962
4963 local_irq_disable();
4964 rq = this_rq();
4965 rq_lock(rq, &rf);
4966
4967 schedstat_inc(rq->yld_count);
4968 current->sched_class->yield_task(rq);
4969
4970 /*
4971 * Since we are going to call schedule() anyway, there's
4972 * no need to preempt or enable interrupts:
4973 */
4974 preempt_disable();
4975 rq_unlock(rq, &rf);
4976 sched_preempt_enable_no_resched();
4977
4978 schedule();
4979}
4980
4981SYSCALL_DEFINE0(sched_yield)
4982{
4983 do_sched_yield();
4984 return 0;
4985}
4986
4987#ifndef CONFIG_PREEMPT
4988int __sched _cond_resched(void)
4989{
4990 if (should_resched(0)) {
4991 preempt_schedule_common();
4992 return 1;
4993 }
4994 rcu_all_qs();
4995 return 0;
4996}
4997EXPORT_SYMBOL(_cond_resched);
4998#endif
4999
5000/*
5001 * __cond_resched_lock() - if a reschedule is pending, drop the given lock,
5002 * call schedule, and on return reacquire the lock.
5003 *
5004 * This works OK both with and without CONFIG_PREEMPT. We do strange low-level
5005 * operations here to prevent schedule() from being called twice (once via
5006 * spin_unlock(), once by hand).
5007 */
5008int __cond_resched_lock(spinlock_t *lock)
5009{
5010 int resched = should_resched(PREEMPT_LOCK_OFFSET);
5011 int ret = 0;
5012
5013 lockdep_assert_held(lock);
5014
5015 if (spin_needbreak(lock) || resched) {
5016 spin_unlock(lock);
5017 if (resched)
5018 preempt_schedule_common();
5019 else
5020 cpu_relax();
5021 ret = 1;
5022 spin_lock(lock);
5023 }
5024 return ret;
5025}
5026EXPORT_SYMBOL(__cond_resched_lock);
5027
5028int __sched __cond_resched_softirq(void)
5029{
5030 BUG_ON(!in_softirq());
5031
5032 if (should_resched(SOFTIRQ_DISABLE_OFFSET)) {
5033 local_bh_enable();
5034 preempt_schedule_common();
5035 local_bh_disable();
5036 return 1;
5037 }
5038 return 0;
5039}
5040EXPORT_SYMBOL(__cond_resched_softirq);
5041
5042/**
5043 * yield - yield the current processor to other threads.
5044 *
5045 * Do not ever use this function, there's a 99% chance you're doing it wrong.
5046 *
5047 * The scheduler is at all times free to pick the calling task as the most
5048 * eligible task to run, if removing the yield() call from your code breaks
5049 * it, its already broken.
5050 *
5051 * Typical broken usage is:
5052 *
5053 * while (!event)
5054 * yield();
5055 *
5056 * where one assumes that yield() will let 'the other' process run that will
5057 * make event true. If the current task is a SCHED_FIFO task that will never
5058 * happen. Never use yield() as a progress guarantee!!
5059 *
5060 * If you want to use yield() to wait for something, use wait_event().
5061 * If you want to use yield() to be 'nice' for others, use cond_resched().
5062 * If you still want to use yield(), do not!
5063 */
5064void __sched yield(void)
5065{
5066 set_current_state(TASK_RUNNING);
5067 do_sched_yield();
5068}
5069EXPORT_SYMBOL(yield);
5070
5071/**
5072 * yield_to - yield the current processor to another thread in
5073 * your thread group, or accelerate that thread toward the
5074 * processor it's on.
5075 * @p: target task
5076 * @preempt: whether task preemption is allowed or not
5077 *
5078 * It's the caller's job to ensure that the target task struct
5079 * can't go away on us before we can do any checks.
5080 *
5081 * Return:
5082 * true (>0) if we indeed boosted the target task.
5083 * false (0) if we failed to boost the target.
5084 * -ESRCH if there's no task to yield to.
5085 */
5086int __sched yield_to(struct task_struct *p, bool preempt)
5087{
5088 struct task_struct *curr = current;
5089 struct rq *rq, *p_rq;
5090 unsigned long flags;
5091 int yielded = 0;
5092
5093 local_irq_save(flags);
5094 rq = this_rq();
5095
5096again:
5097 p_rq = task_rq(p);
5098 /*
5099 * If we're the only runnable task on the rq and target rq also
5100 * has only one task, there's absolutely no point in yielding.
5101 */
5102 if (rq->nr_running == 1 && p_rq->nr_running == 1) {
5103 yielded = -ESRCH;
5104 goto out_irq;
5105 }
5106
5107 double_rq_lock(rq, p_rq);
5108 if (task_rq(p) != p_rq) {
5109 double_rq_unlock(rq, p_rq);
5110 goto again;
5111 }
5112
5113 if (!curr->sched_class->yield_to_task)
5114 goto out_unlock;
5115
5116 if (curr->sched_class != p->sched_class)
5117 goto out_unlock;
5118
5119 if (task_running(p_rq, p) || p->state)
5120 goto out_unlock;
5121
5122 yielded = curr->sched_class->yield_to_task(rq, p, preempt);
5123 if (yielded) {
5124 schedstat_inc(rq->yld_count);
5125 /*
5126 * Make p's CPU reschedule; pick_next_entity takes care of
5127 * fairness.
5128 */
5129 if (preempt && rq != p_rq)
5130 resched_curr(p_rq);
5131 }
5132
5133out_unlock:
5134 double_rq_unlock(rq, p_rq);
5135out_irq:
5136 local_irq_restore(flags);
5137
5138 if (yielded > 0)
5139 schedule();
5140
5141 return yielded;
5142}
5143EXPORT_SYMBOL_GPL(yield_to);
5144
5145int io_schedule_prepare(void)
5146{
5147 int old_iowait = current->in_iowait;
5148
5149 current->in_iowait = 1;
5150 blk_schedule_flush_plug(current);
5151
5152 return old_iowait;
5153}
5154
5155void io_schedule_finish(int token)
5156{
5157 current->in_iowait = token;
5158}
5159
5160/*
5161 * This task is about to go to sleep on IO. Increment rq->nr_iowait so
5162 * that process accounting knows that this is a task in IO wait state.
5163 */
5164long __sched io_schedule_timeout(long timeout)
5165{
5166 int token;
5167 long ret;
5168
5169 token = io_schedule_prepare();
5170 ret = schedule_timeout(timeout);
5171 io_schedule_finish(token);
5172
5173 return ret;
5174}
5175EXPORT_SYMBOL(io_schedule_timeout);
5176
5177void io_schedule(void)
5178{
5179 int token;
5180
5181 token = io_schedule_prepare();
5182 schedule();
5183 io_schedule_finish(token);
5184}
5185EXPORT_SYMBOL(io_schedule);
5186
5187/**
5188 * sys_sched_get_priority_max - return maximum RT priority.
5189 * @policy: scheduling class.
5190 *
5191 * Return: On success, this syscall returns the maximum
5192 * rt_priority that can be used by a given scheduling class.
5193 * On failure, a negative error code is returned.
5194 */
5195SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
5196{
5197 int ret = -EINVAL;
5198
5199 switch (policy) {
5200 case SCHED_FIFO:
5201 case SCHED_RR:
5202 ret = MAX_USER_RT_PRIO-1;
5203 break;
5204 case SCHED_DEADLINE:
5205 case SCHED_NORMAL:
5206 case SCHED_BATCH:
5207 case SCHED_IDLE:
5208 ret = 0;
5209 break;
5210 }
5211 return ret;
5212}
5213
5214/**
5215 * sys_sched_get_priority_min - return minimum RT priority.
5216 * @policy: scheduling class.
5217 *
5218 * Return: On success, this syscall returns the minimum
5219 * rt_priority that can be used by a given scheduling class.
5220 * On failure, a negative error code is returned.
5221 */
5222SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
5223{
5224 int ret = -EINVAL;
5225
5226 switch (policy) {
5227 case SCHED_FIFO:
5228 case SCHED_RR:
5229 ret = 1;
5230 break;
5231 case SCHED_DEADLINE:
5232 case SCHED_NORMAL:
5233 case SCHED_BATCH:
5234 case SCHED_IDLE:
5235 ret = 0;
5236 }
5237 return ret;
5238}
5239
5240static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
5241{
5242 struct task_struct *p;
5243 unsigned int time_slice;
5244 struct rq_flags rf;
5245 struct rq *rq;
5246 int retval;
5247
5248 if (pid < 0)
5249 return -EINVAL;
5250
5251 retval = -ESRCH;
5252 rcu_read_lock();
5253 p = find_process_by_pid(pid);
5254 if (!p)
5255 goto out_unlock;
5256
5257 retval = security_task_getscheduler(p);
5258 if (retval)
5259 goto out_unlock;
5260
5261 rq = task_rq_lock(p, &rf);
5262 time_slice = 0;
5263 if (p->sched_class->get_rr_interval)
5264 time_slice = p->sched_class->get_rr_interval(rq, p);
5265 task_rq_unlock(rq, p, &rf);
5266
5267 rcu_read_unlock();
5268 jiffies_to_timespec64(time_slice, t);
5269 return 0;
5270
5271out_unlock:
5272 rcu_read_unlock();
5273 return retval;
5274}
5275
5276/**
5277 * sys_sched_rr_get_interval - return the default timeslice of a process.
5278 * @pid: pid of the process.
5279 * @interval: userspace pointer to the timeslice value.
5280 *
5281 * this syscall writes the default timeslice value of a given process
5282 * into the user-space timespec buffer. A value of '0' means infinity.
5283 *
5284 * Return: On success, 0 and the timeslice is in @interval. Otherwise,
5285 * an error code.
5286 */
5287SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
5288 struct timespec __user *, interval)
5289{
5290 struct timespec64 t;
5291 int retval = sched_rr_get_interval(pid, &t);
5292
5293 if (retval == 0)
5294 retval = put_timespec64(&t, interval);
5295
5296 return retval;
5297}
5298
5299#ifdef CONFIG_COMPAT
5300COMPAT_SYSCALL_DEFINE2(sched_rr_get_interval,
5301 compat_pid_t, pid,
5302 struct compat_timespec __user *, interval)
5303{
5304 struct timespec64 t;
5305 int retval = sched_rr_get_interval(pid, &t);
5306
5307 if (retval == 0)
5308 retval = compat_put_timespec64(&t, interval);
5309 return retval;
5310}
5311#endif
5312
5313void sched_show_task(struct task_struct *p)
5314{
5315 unsigned long free = 0;
5316 int ppid;
5317
5318 if (!try_get_task_stack(p))
5319 return;
5320
5321 printk(KERN_INFO "%-15.15s %c", p->comm, task_state_to_char(p));
5322
5323 if (p->state == TASK_RUNNING)
5324 printk(KERN_CONT " running task ");
5325#ifdef CONFIG_DEBUG_STACK_USAGE
5326 free = stack_not_used(p);
5327#endif
5328 ppid = 0;
5329 rcu_read_lock();
5330 if (pid_alive(p))
5331 ppid = task_pid_nr(rcu_dereference(p->real_parent));
5332 rcu_read_unlock();
5333 printk(KERN_CONT "%5lu %5d %6d 0x%08lx\n", free,
5334 task_pid_nr(p), ppid,
5335 (unsigned long)task_thread_info(p)->flags);
5336
5337 print_worker_info(KERN_INFO, p);
5338 show_stack(p, NULL);
5339 put_task_stack(p);
5340}
5341EXPORT_SYMBOL_GPL(sched_show_task);
5342
5343static inline bool
5344state_filter_match(unsigned long state_filter, struct task_struct *p)
5345{
5346 /* no filter, everything matches */
5347 if (!state_filter)
5348 return true;
5349
5350 /* filter, but doesn't match */
5351 if (!(p->state & state_filter))
5352 return false;
5353
5354 /*
5355 * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
5356 * TASK_KILLABLE).
5357 */
5358 if (state_filter == TASK_UNINTERRUPTIBLE && p->state == TASK_IDLE)
5359 return false;
5360
5361 return true;
5362}
5363
5364
5365void show_state_filter(unsigned long state_filter)
5366{
5367 struct task_struct *g, *p;
5368
5369#if BITS_PER_LONG == 32
5370 printk(KERN_INFO
5371 " task PC stack pid father\n");
5372#else
5373 printk(KERN_INFO
5374 " task PC stack pid father\n");
5375#endif
5376 rcu_read_lock();
5377 for_each_process_thread(g, p) {
5378 /*
5379 * reset the NMI-timeout, listing all files on a slow
5380 * console might take a lot of time:
5381 * Also, reset softlockup watchdogs on all CPUs, because
5382 * another CPU might be blocked waiting for us to process
5383 * an IPI.
5384 */
5385 touch_nmi_watchdog();
5386 touch_all_softlockup_watchdogs();
5387 if (state_filter_match(state_filter, p))
5388 sched_show_task(p);
5389 }
5390
5391#ifdef CONFIG_SCHED_DEBUG
5392 if (!state_filter)
5393 sysrq_sched_debug_show();
5394#endif
5395 rcu_read_unlock();
5396 /*
5397 * Only show locks if all tasks are dumped:
5398 */
5399 if (!state_filter)
5400 debug_show_all_locks();
5401}
5402
5403/**
5404 * init_idle - set up an idle thread for a given CPU
5405 * @idle: task in question
5406 * @cpu: CPU the idle task belongs to
5407 *
5408 * NOTE: this function does not set the idle thread's NEED_RESCHED
5409 * flag, to make booting more robust.
5410 */
5411void init_idle(struct task_struct *idle, int cpu)
5412{
5413 struct rq *rq = cpu_rq(cpu);
5414 unsigned long flags;
5415
5416 raw_spin_lock_irqsave(&idle->pi_lock, flags);
5417 raw_spin_lock(&rq->lock);
5418
5419 __sched_fork(0, idle);
5420 idle->state = TASK_RUNNING;
5421 idle->se.exec_start = sched_clock();
5422 idle->flags |= PF_IDLE;
5423
5424 kasan_unpoison_task_stack(idle);
5425
5426#ifdef CONFIG_SMP
5427 /*
5428 * Its possible that init_idle() gets called multiple times on a task,
5429 * in that case do_set_cpus_allowed() will not do the right thing.
5430 *
5431 * And since this is boot we can forgo the serialization.
5432 */
5433 set_cpus_allowed_common(idle, cpumask_of(cpu));
5434#endif
5435 /*
5436 * We're having a chicken and egg problem, even though we are
5437 * holding rq->lock, the CPU isn't yet set to this CPU so the
5438 * lockdep check in task_group() will fail.
5439 *
5440 * Similar case to sched_fork(). / Alternatively we could
5441 * use task_rq_lock() here and obtain the other rq->lock.
5442 *
5443 * Silence PROVE_RCU
5444 */
5445 rcu_read_lock();
5446 __set_task_cpu(idle, cpu);
5447 rcu_read_unlock();
5448
5449 rq->curr = rq->idle = idle;
5450 idle->on_rq = TASK_ON_RQ_QUEUED;
5451#ifdef CONFIG_SMP
5452 idle->on_cpu = 1;
5453#endif
5454 raw_spin_unlock(&rq->lock);
5455 raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
5456
5457 /* Set the preempt count _outside_ the spinlocks! */
5458 init_idle_preempt_count(idle, cpu);
5459
5460 /*
5461 * The idle tasks have their own, simple scheduling class:
5462 */
5463 idle->sched_class = &idle_sched_class;
5464 ftrace_graph_init_idle_task(idle, cpu);
5465 vtime_init_idle(idle, cpu);
5466#ifdef CONFIG_SMP
5467 sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
5468#endif
5469}
5470
5471#ifdef CONFIG_SMP
5472
5473int cpuset_cpumask_can_shrink(const struct cpumask *cur,
5474 const struct cpumask *trial)
5475{
5476 int ret = 1;
5477
5478 if (!cpumask_weight(cur))
5479 return ret;
5480
5481 ret = dl_cpuset_cpumask_can_shrink(cur, trial);
5482
5483 return ret;
5484}
5485
5486int task_can_attach(struct task_struct *p,
5487 const struct cpumask *cs_cpus_allowed)
5488{
5489 int ret = 0;
5490
5491 /*
5492 * Kthreads which disallow setaffinity shouldn't be moved
5493 * to a new cpuset; we don't want to change their CPU
5494 * affinity and isolating such threads by their set of
5495 * allowed nodes is unnecessary. Thus, cpusets are not
5496 * applicable for such threads. This prevents checking for
5497 * success of set_cpus_allowed_ptr() on all attached tasks
5498 * before cpus_allowed may be changed.
5499 */
5500 if (p->flags & PF_NO_SETAFFINITY) {
5501 ret = -EINVAL;
5502 goto out;
5503 }
5504
5505 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
5506 cs_cpus_allowed))
5507 ret = dl_task_can_attach(p, cs_cpus_allowed);
5508
5509out:
5510 return ret;
5511}
5512
5513bool sched_smp_initialized __read_mostly;
5514
5515#ifdef CONFIG_NUMA_BALANCING
5516/* Migrate current task p to target_cpu */
5517int migrate_task_to(struct task_struct *p, int target_cpu)
5518{
5519 struct migration_arg arg = { p, target_cpu };
5520 int curr_cpu = task_cpu(p);
5521
5522 if (curr_cpu == target_cpu)
5523 return 0;
5524
5525 if (!cpumask_test_cpu(target_cpu, &p->cpus_allowed))
5526 return -EINVAL;
5527
5528 /* TODO: This is not properly updating schedstats */
5529
5530 trace_sched_move_numa(p, curr_cpu, target_cpu);
5531 return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);
5532}
5533
5534/*
5535 * Requeue a task on a given node and accurately track the number of NUMA
5536 * tasks on the runqueues
5537 */
5538void sched_setnuma(struct task_struct *p, int nid)
5539{
5540 bool queued, running;
5541 struct rq_flags rf;
5542 struct rq *rq;
5543
5544 rq = task_rq_lock(p, &rf);
5545 queued = task_on_rq_queued(p);
5546 running = task_current(rq, p);
5547
5548 if (queued)
5549 dequeue_task(rq, p, DEQUEUE_SAVE);
5550 if (running)
5551 put_prev_task(rq, p);
5552
5553 p->numa_preferred_nid = nid;
5554
5555 if (queued)
5556 enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
5557 if (running)
5558 set_curr_task(rq, p);
5559 task_rq_unlock(rq, p, &rf);
5560}
5561#endif /* CONFIG_NUMA_BALANCING */
5562
5563#ifdef CONFIG_HOTPLUG_CPU
5564/*
5565 * Ensure that the idle task is using init_mm right before its CPU goes
5566 * offline.
5567 */
5568void idle_task_exit(void)
5569{
5570 struct mm_struct *mm = current->active_mm;
5571
5572 BUG_ON(cpu_online(smp_processor_id()));
5573
5574 if (mm != &init_mm) {
5575 switch_mm(mm, &init_mm, current);
5576 current->active_mm = &init_mm;
5577 finish_arch_post_lock_switch();
5578 }
5579 mmdrop(mm);
5580}
5581
5582/*
5583 * Since this CPU is going 'away' for a while, fold any nr_active delta
5584 * we might have. Assumes we're called after migrate_tasks() so that the
5585 * nr_active count is stable. We need to take the teardown thread which
5586 * is calling this into account, so we hand in adjust = 1 to the load
5587 * calculation.
5588 *
5589 * Also see the comment "Global load-average calculations".
5590 */
5591static void calc_load_migrate(struct rq *rq)
5592{
5593 long delta = calc_load_fold_active(rq, 1);
5594 if (delta)
5595 atomic_long_add(delta, &calc_load_tasks);
5596}
5597
5598static void put_prev_task_fake(struct rq *rq, struct task_struct *prev)
5599{
5600}
5601
5602static const struct sched_class fake_sched_class = {
5603 .put_prev_task = put_prev_task_fake,
5604};
5605
5606static struct task_struct fake_task = {
5607 /*
5608 * Avoid pull_{rt,dl}_task()
5609 */
5610 .prio = MAX_PRIO + 1,
5611 .sched_class = &fake_sched_class,
5612};
5613
5614/*
5615 * Migrate all tasks from the rq, sleeping tasks will be migrated by
5616 * try_to_wake_up()->select_task_rq().
5617 *
5618 * Called with rq->lock held even though we'er in stop_machine() and
5619 * there's no concurrency possible, we hold the required locks anyway
5620 * because of lock validation efforts.
5621 */
5622static void migrate_tasks(struct rq *dead_rq, struct rq_flags *rf)
5623{
5624 struct rq *rq = dead_rq;
5625 struct task_struct *next, *stop = rq->stop;
5626 struct rq_flags orf = *rf;
5627 int dest_cpu;
5628
5629 /*
5630 * Fudge the rq selection such that the below task selection loop
5631 * doesn't get stuck on the currently eligible stop task.
5632 *
5633 * We're currently inside stop_machine() and the rq is either stuck
5634 * in the stop_machine_cpu_stop() loop, or we're executing this code,
5635 * either way we should never end up calling schedule() until we're
5636 * done here.
5637 */
5638 rq->stop = NULL;
5639
5640 /*
5641 * put_prev_task() and pick_next_task() sched
5642 * class method both need to have an up-to-date
5643 * value of rq->clock[_task]
5644 */
5645 update_rq_clock(rq);
5646
5647 for (;;) {
5648 /*
5649 * There's this thread running, bail when that's the only
5650 * remaining thread:
5651 */
5652 if (rq->nr_running == 1)
5653 break;
5654
5655 /*
5656 * pick_next_task() assumes pinned rq->lock:
5657 */
5658 next = pick_next_task(rq, &fake_task, rf);
5659 BUG_ON(!next);
5660 put_prev_task(rq, next);
5661
5662 /*
5663 * Rules for changing task_struct::cpus_allowed are holding
5664 * both pi_lock and rq->lock, such that holding either
5665 * stabilizes the mask.
5666 *
5667 * Drop rq->lock is not quite as disastrous as it usually is
5668 * because !cpu_active at this point, which means load-balance
5669 * will not interfere. Also, stop-machine.
5670 */
5671 rq_unlock(rq, rf);
5672 raw_spin_lock(&next->pi_lock);
5673 rq_relock(rq, rf);
5674
5675 /*
5676 * Since we're inside stop-machine, _nothing_ should have
5677 * changed the task, WARN if weird stuff happened, because in
5678 * that case the above rq->lock drop is a fail too.
5679 */
5680 if (WARN_ON(task_rq(next) != rq || !task_on_rq_queued(next))) {
5681 raw_spin_unlock(&next->pi_lock);
5682 continue;
5683 }
5684
5685 /* Find suitable destination for @next, with force if needed. */
5686 dest_cpu = select_fallback_rq(dead_rq->cpu, next);
5687 rq = __migrate_task(rq, rf, next, dest_cpu);
5688 if (rq != dead_rq) {
5689 rq_unlock(rq, rf);
5690 rq = dead_rq;
5691 *rf = orf;
5692 rq_relock(rq, rf);
5693 }
5694 raw_spin_unlock(&next->pi_lock);
5695 }
5696
5697 rq->stop = stop;
5698}
5699#endif /* CONFIG_HOTPLUG_CPU */
5700
5701void set_rq_online(struct rq *rq)
5702{
5703 if (!rq->online) {
5704 const struct sched_class *class;
5705
5706 cpumask_set_cpu(rq->cpu, rq->rd->online);
5707 rq->online = 1;
5708
5709 for_each_class(class) {
5710 if (class->rq_online)
5711 class->rq_online(rq);
5712 }
5713 }
5714}
5715
5716void set_rq_offline(struct rq *rq)
5717{
5718 if (rq->online) {
5719 const struct sched_class *class;
5720
5721 for_each_class(class) {
5722 if (class->rq_offline)
5723 class->rq_offline(rq);
5724 }
5725
5726 cpumask_clear_cpu(rq->cpu, rq->rd->online);
5727 rq->online = 0;
5728 }
5729}
5730
5731static void set_cpu_rq_start_time(unsigned int cpu)
5732{
5733 struct rq *rq = cpu_rq(cpu);
5734
5735 rq->age_stamp = sched_clock_cpu(cpu);
5736}
5737
5738/*
5739 * used to mark begin/end of suspend/resume:
5740 */
5741static int num_cpus_frozen;
5742
5743/*
5744 * Update cpusets according to cpu_active mask. If cpusets are
5745 * disabled, cpuset_update_active_cpus() becomes a simple wrapper
5746 * around partition_sched_domains().
5747 *
5748 * If we come here as part of a suspend/resume, don't touch cpusets because we
5749 * want to restore it back to its original state upon resume anyway.
5750 */
5751static void cpuset_cpu_active(void)
5752{
5753 if (cpuhp_tasks_frozen) {
5754 /*
5755 * num_cpus_frozen tracks how many CPUs are involved in suspend
5756 * resume sequence. As long as this is not the last online
5757 * operation in the resume sequence, just build a single sched
5758 * domain, ignoring cpusets.
5759 */
5760 partition_sched_domains(1, NULL, NULL);
5761 if (--num_cpus_frozen)
5762 return;
5763 /*
5764 * This is the last CPU online operation. So fall through and
5765 * restore the original sched domains by considering the
5766 * cpuset configurations.
5767 */
5768 cpuset_force_rebuild();
5769 }
5770 cpuset_update_active_cpus();
5771}
5772
5773static int cpuset_cpu_inactive(unsigned int cpu)
5774{
5775 if (!cpuhp_tasks_frozen) {
5776 if (dl_cpu_busy(cpu))
5777 return -EBUSY;
5778 cpuset_update_active_cpus();
5779 } else {
5780 num_cpus_frozen++;
5781 partition_sched_domains(1, NULL, NULL);
5782 }
5783 return 0;
5784}
5785
5786int sched_cpu_activate(unsigned int cpu)
5787{
5788 struct rq *rq = cpu_rq(cpu);
5789 struct rq_flags rf;
5790
5791 set_cpu_active(cpu, true);
5792
5793 if (sched_smp_initialized) {
5794 sched_domains_numa_masks_set(cpu);
5795 cpuset_cpu_active();
5796 }
5797
5798 /*
5799 * Put the rq online, if not already. This happens:
5800 *
5801 * 1) In the early boot process, because we build the real domains
5802 * after all CPUs have been brought up.
5803 *
5804 * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
5805 * domains.
5806 */
5807 rq_lock_irqsave(rq, &rf);
5808 if (rq->rd) {
5809 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5810 set_rq_online(rq);
5811 }
5812 rq_unlock_irqrestore(rq, &rf);
5813
5814 update_max_interval();
5815
5816 return 0;
5817}
5818
5819int sched_cpu_deactivate(unsigned int cpu)
5820{
5821 int ret;
5822
5823 set_cpu_active(cpu, false);
5824 /*
5825 * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
5826 * users of this state to go away such that all new such users will
5827 * observe it.
5828 *
5829 * Do sync before park smpboot threads to take care the rcu boost case.
5830 */
5831 synchronize_rcu_mult(call_rcu, call_rcu_sched);
5832
5833 if (!sched_smp_initialized)
5834 return 0;
5835
5836 ret = cpuset_cpu_inactive(cpu);
5837 if (ret) {
5838 set_cpu_active(cpu, true);
5839 return ret;
5840 }
5841 sched_domains_numa_masks_clear(cpu);
5842 return 0;
5843}
5844
5845static void sched_rq_cpu_starting(unsigned int cpu)
5846{
5847 struct rq *rq = cpu_rq(cpu);
5848
5849 rq->calc_load_update = calc_load_update;
5850 update_max_interval();
5851}
5852
5853int sched_cpu_starting(unsigned int cpu)
5854{
5855 set_cpu_rq_start_time(cpu);
5856 sched_rq_cpu_starting(cpu);
5857 sched_tick_start(cpu);
5858 return 0;
5859}
5860
5861#ifdef CONFIG_HOTPLUG_CPU
5862int sched_cpu_dying(unsigned int cpu)
5863{
5864 struct rq *rq = cpu_rq(cpu);
5865 struct rq_flags rf;
5866
5867 /* Handle pending wakeups and then migrate everything off */
5868 sched_ttwu_pending();
5869 sched_tick_stop(cpu);
5870
5871 rq_lock_irqsave(rq, &rf);
5872 if (rq->rd) {
5873 BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
5874 set_rq_offline(rq);
5875 }
5876 migrate_tasks(rq, &rf);
5877 BUG_ON(rq->nr_running != 1);
5878 rq_unlock_irqrestore(rq, &rf);
5879
5880 calc_load_migrate(rq);
5881 update_max_interval();
5882 nohz_balance_exit_idle(rq);
5883 hrtick_clear(rq);
5884 return 0;
5885}
5886#endif
5887
5888#ifdef CONFIG_SCHED_SMT
5889DEFINE_STATIC_KEY_FALSE(sched_smt_present);
5890
5891static void sched_init_smt(void)
5892{
5893 /*
5894 * We've enumerated all CPUs and will assume that if any CPU
5895 * has SMT siblings, CPU0 will too.
5896 */
5897 if (cpumask_weight(cpu_smt_mask(0)) > 1)
5898 static_branch_enable(&sched_smt_present);
5899}
5900#else
5901static inline void sched_init_smt(void) { }
5902#endif
5903
5904void __init sched_init_smp(void)
5905{
5906 sched_init_numa();
5907
5908 /*
5909 * There's no userspace yet to cause hotplug operations; hence all the
5910 * CPU masks are stable and all blatant races in the below code cannot
5911 * happen.
5912 */
5913 mutex_lock(&sched_domains_mutex);
5914 sched_init_domains(cpu_active_mask);
5915 mutex_unlock(&sched_domains_mutex);
5916
5917 /* Move init over to a non-isolated CPU */
5918 if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
5919 BUG();
5920 sched_init_granularity();
5921
5922 init_sched_rt_class();
5923 init_sched_dl_class();
5924
5925 sched_init_smt();
5926
5927 sched_smp_initialized = true;
5928}
5929
5930static int __init migration_init(void)
5931{
5932 sched_rq_cpu_starting(smp_processor_id());
5933 return 0;
5934}
5935early_initcall(migration_init);
5936
5937#else
5938void __init sched_init_smp(void)
5939{
5940 sched_init_granularity();
5941}
5942#endif /* CONFIG_SMP */
5943
5944int in_sched_functions(unsigned long addr)
5945{
5946 return in_lock_functions(addr) ||
5947 (addr >= (unsigned long)__sched_text_start
5948 && addr < (unsigned long)__sched_text_end);
5949}
5950
5951#ifdef CONFIG_CGROUP_SCHED
5952/*
5953 * Default task group.
5954 * Every task in system belongs to this group at bootup.
5955 */
5956struct task_group root_task_group;
5957LIST_HEAD(task_groups);
5958
5959/* Cacheline aligned slab cache for task_group */
5960static struct kmem_cache *task_group_cache __read_mostly;
5961#endif
5962
5963DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
5964DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
5965
5966void __init sched_init(void)
5967{
5968 int i, j;
5969 unsigned long alloc_size = 0, ptr;
5970
5971 sched_clock_init();
5972 wait_bit_init();
5973
5974#ifdef CONFIG_FAIR_GROUP_SCHED
5975 alloc_size += 2 * nr_cpu_ids * sizeof(void **);
5976#endif
5977#ifdef CONFIG_RT_GROUP_SCHED
5978 alloc_size += 2 * nr_cpu_ids * sizeof(void **);
5979#endif
5980 if (alloc_size) {
5981 ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);
5982
5983#ifdef CONFIG_FAIR_GROUP_SCHED
5984 root_task_group.se = (struct sched_entity **)ptr;
5985 ptr += nr_cpu_ids * sizeof(void **);
5986
5987 root_task_group.cfs_rq = (struct cfs_rq **)ptr;
5988 ptr += nr_cpu_ids * sizeof(void **);
5989
5990#endif /* CONFIG_FAIR_GROUP_SCHED */
5991#ifdef CONFIG_RT_GROUP_SCHED
5992 root_task_group.rt_se = (struct sched_rt_entity **)ptr;
5993 ptr += nr_cpu_ids * sizeof(void **);
5994
5995 root_task_group.rt_rq = (struct rt_rq **)ptr;
5996 ptr += nr_cpu_ids * sizeof(void **);
5997
5998#endif /* CONFIG_RT_GROUP_SCHED */
5999 }
6000#ifdef CONFIG_CPUMASK_OFFSTACK
6001 for_each_possible_cpu(i) {
6002 per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
6003 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
6004 per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
6005 cpumask_size(), GFP_KERNEL, cpu_to_node(i));
6006 }
6007#endif /* CONFIG_CPUMASK_OFFSTACK */
6008
6009 init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
6010 init_dl_bandwidth(&def_dl_bandwidth, global_rt_period(), global_rt_runtime());
6011
6012#ifdef CONFIG_SMP
6013 init_defrootdomain();
6014#endif
6015
6016#ifdef CONFIG_RT_GROUP_SCHED
6017 init_rt_bandwidth(&root_task_group.rt_bandwidth,
6018 global_rt_period(), global_rt_runtime());
6019#endif /* CONFIG_RT_GROUP_SCHED */
6020
6021#ifdef CONFIG_CGROUP_SCHED
6022 task_group_cache = KMEM_CACHE(task_group, 0);
6023
6024 list_add(&root_task_group.list, &task_groups);
6025 INIT_LIST_HEAD(&root_task_group.children);
6026 INIT_LIST_HEAD(&root_task_group.siblings);
6027 autogroup_init(&init_task);
6028#endif /* CONFIG_CGROUP_SCHED */
6029
6030 for_each_possible_cpu(i) {
6031 struct rq *rq;
6032
6033 rq = cpu_rq(i);
6034 raw_spin_lock_init(&rq->lock);
6035 rq->nr_running = 0;
6036 rq->calc_load_active = 0;
6037 rq->calc_load_update = jiffies + LOAD_FREQ;
6038 init_cfs_rq(&rq->cfs);
6039 init_rt_rq(&rq->rt);
6040 init_dl_rq(&rq->dl);
6041#ifdef CONFIG_FAIR_GROUP_SCHED
6042 root_task_group.shares = ROOT_TASK_GROUP_LOAD;
6043 INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
6044 rq->tmp_alone_branch = &rq->leaf_cfs_rq_list;
6045 /*
6046 * How much CPU bandwidth does root_task_group get?
6047 *
6048 * In case of task-groups formed thr' the cgroup filesystem, it
6049 * gets 100% of the CPU resources in the system. This overall
6050 * system CPU resource is divided among the tasks of
6051 * root_task_group and its child task-groups in a fair manner,
6052 * based on each entity's (task or task-group's) weight
6053 * (se->load.weight).
6054 *
6055 * In other words, if root_task_group has 10 tasks of weight
6056 * 1024) and two child groups A0 and A1 (of weight 1024 each),
6057 * then A0's share of the CPU resource is:
6058 *
6059 * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33%
6060 *
6061 * We achieve this by letting root_task_group's tasks sit
6062 * directly in rq->cfs (i.e root_task_group->se[] = NULL).
6063 */
6064 init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
6065 init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
6066#endif /* CONFIG_FAIR_GROUP_SCHED */
6067
6068 rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime;
6069#ifdef CONFIG_RT_GROUP_SCHED
6070 init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL);
6071#endif
6072
6073 for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
6074 rq->cpu_load[j] = 0;
6075
6076#ifdef CONFIG_SMP
6077 rq->sd = NULL;
6078 rq->rd = NULL;
6079 rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
6080 rq->balance_callback = NULL;
6081 rq->active_balance = 0;
6082 rq->next_balance = jiffies;
6083 rq->push_cpu = 0;
6084 rq->cpu = i;
6085 rq->online = 0;
6086 rq->idle_stamp = 0;
6087 rq->avg_idle = 2*sysctl_sched_migration_cost;
6088 rq->max_idle_balance_cost = sysctl_sched_migration_cost;
6089
6090 INIT_LIST_HEAD(&rq->cfs_tasks);
6091
6092 rq_attach_root(rq, &def_root_domain);
6093#ifdef CONFIG_NO_HZ_COMMON
6094 rq->last_load_update_tick = jiffies;
6095 rq->last_blocked_load_update_tick = jiffies;
6096 atomic_set(&rq->nohz_flags, 0);
6097#endif
6098#endif /* CONFIG_SMP */
6099 hrtick_rq_init(rq);
6100 atomic_set(&rq->nr_iowait, 0);
6101 }
6102
6103 set_load_weight(&init_task, false);
6104
6105 /*
6106 * The boot idle thread does lazy MMU switching as well:
6107 */
6108 mmgrab(&init_mm);
6109 enter_lazy_tlb(&init_mm, current);
6110
6111 /*
6112 * Make us the idle thread. Technically, schedule() should not be
6113 * called from this thread, however somewhere below it might be,
6114 * but because we are the idle thread, we just pick up running again
6115 * when this runqueue becomes "idle".
6116 */
6117 init_idle(current, smp_processor_id());
6118
6119 calc_load_update = jiffies + LOAD_FREQ;
6120
6121#ifdef CONFIG_SMP
6122 idle_thread_set_boot_cpu();
6123 set_cpu_rq_start_time(smp_processor_id());
6124#endif
6125 init_sched_fair_class();
6126
6127 init_schedstats();
6128
6129 scheduler_running = 1;
6130}
6131
6132#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
6133static inline int preempt_count_equals(int preempt_offset)
6134{
6135 int nested = preempt_count() + rcu_preempt_depth();
6136
6137 return (nested == preempt_offset);
6138}
6139
6140void __might_sleep(const char *file, int line, int preempt_offset)
6141{
6142 /*
6143 * Blocking primitives will set (and therefore destroy) current->state,
6144 * since we will exit with TASK_RUNNING make sure we enter with it,
6145 * otherwise we will destroy state.
6146 */
6147 WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
6148 "do not call blocking ops when !TASK_RUNNING; "
6149 "state=%lx set at [<%p>] %pS\n",
6150 current->state,
6151 (void *)current->task_state_change,
6152 (void *)current->task_state_change);
6153
6154 ___might_sleep(file, line, preempt_offset);
6155}
6156EXPORT_SYMBOL(__might_sleep);
6157
6158void ___might_sleep(const char *file, int line, int preempt_offset)
6159{
6160 /* Ratelimiting timestamp: */
6161 static unsigned long prev_jiffy;
6162
6163 unsigned long preempt_disable_ip;
6164
6165 /* WARN_ON_ONCE() by default, no rate limit required: */
6166 rcu_sleep_check();
6167
6168 if ((preempt_count_equals(preempt_offset) && !irqs_disabled() &&
6169 !is_idle_task(current)) ||
6170 system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
6171 oops_in_progress)
6172 return;
6173
6174 if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
6175 return;
6176 prev_jiffy = jiffies;
6177
6178 /* Save this before calling printk(), since that will clobber it: */
6179 preempt_disable_ip = get_preempt_disable_ip(current);
6180
6181 printk(KERN_ERR
6182 "BUG: sleeping function called from invalid context at %s:%d\n",
6183 file, line);
6184 printk(KERN_ERR
6185 "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
6186 in_atomic(), irqs_disabled(),
6187 current->pid, current->comm);
6188
6189 if (task_stack_end_corrupted(current))
6190 printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");
6191
6192 debug_show_held_locks(current);
6193 if (irqs_disabled())
6194 print_irqtrace_events(current);
6195 if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
6196 && !preempt_count_equals(preempt_offset)) {
6197 pr_err("Preemption disabled at:");
6198 print_ip_sym(preempt_disable_ip);
6199 pr_cont("\n");
6200 }
6201 dump_stack();
6202 add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
6203}
6204EXPORT_SYMBOL(___might_sleep);
6205#endif
6206
6207#ifdef CONFIG_MAGIC_SYSRQ
6208void normalize_rt_tasks(void)
6209{
6210 struct task_struct *g, *p;
6211 struct sched_attr attr = {
6212 .sched_policy = SCHED_NORMAL,
6213 };
6214
6215 read_lock(&tasklist_lock);
6216 for_each_process_thread(g, p) {
6217 /*
6218 * Only normalize user tasks:
6219 */
6220 if (p->flags & PF_KTHREAD)
6221 continue;
6222
6223 p->se.exec_start = 0;
6224 schedstat_set(p->se.statistics.wait_start, 0);
6225 schedstat_set(p->se.statistics.sleep_start, 0);
6226 schedstat_set(p->se.statistics.block_start, 0);
6227
6228 if (!dl_task(p) && !rt_task(p)) {
6229 /*
6230 * Renice negative nice level userspace
6231 * tasks back to 0:
6232 */
6233 if (task_nice(p) < 0)
6234 set_user_nice(p, 0);
6235 continue;
6236 }
6237
6238 __sched_setscheduler(p, &attr, false, false);
6239 }
6240 read_unlock(&tasklist_lock);
6241}
6242
6243#endif /* CONFIG_MAGIC_SYSRQ */
6244
6245#if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
6246/*
6247 * These functions are only useful for the IA64 MCA handling, or kdb.
6248 *
6249 * They can only be called when the whole system has been
6250 * stopped - every CPU needs to be quiescent, and no scheduling
6251 * activity can take place. Using them for anything else would
6252 * be a serious bug, and as a result, they aren't even visible
6253 * under any other configuration.
6254 */
6255
6256/**
6257 * curr_task - return the current task for a given CPU.
6258 * @cpu: the processor in question.
6259 *
6260 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6261 *
6262 * Return: The current task for @cpu.
6263 */
6264struct task_struct *curr_task(int cpu)
6265{
6266 return cpu_curr(cpu);
6267}
6268
6269#endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
6270
6271#ifdef CONFIG_IA64
6272/**
6273 * set_curr_task - set the current task for a given CPU.
6274 * @cpu: the processor in question.
6275 * @p: the task pointer to set.
6276 *
6277 * Description: This function must only be used when non-maskable interrupts
6278 * are serviced on a separate stack. It allows the architecture to switch the
6279 * notion of the current task on a CPU in a non-blocking manner. This function
6280 * must be called with all CPU's synchronized, and interrupts disabled, the
6281 * and caller must save the original value of the current task (see
6282 * curr_task() above) and restore that value before reenabling interrupts and
6283 * re-starting the system.
6284 *
6285 * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
6286 */
6287void ia64_set_curr_task(int cpu, struct task_struct *p)
6288{
6289 cpu_curr(cpu) = p;
6290}
6291
6292#endif
6293
6294#ifdef CONFIG_CGROUP_SCHED
6295/* task_group_lock serializes the addition/removal of task groups */
6296static DEFINE_SPINLOCK(task_group_lock);
6297
6298static void sched_free_group(struct task_group *tg)
6299{
6300 free_fair_sched_group(tg);
6301 free_rt_sched_group(tg);
6302 autogroup_free(tg);
6303 kmem_cache_free(task_group_cache, tg);
6304}
6305
6306/* allocate runqueue etc for a new task group */
6307struct task_group *sched_create_group(struct task_group *parent)
6308{
6309 struct task_group *tg;
6310
6311 tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
6312 if (!tg)
6313 return ERR_PTR(-ENOMEM);
6314
6315 if (!alloc_fair_sched_group(tg, parent))
6316 goto err;
6317
6318 if (!alloc_rt_sched_group(tg, parent))
6319 goto err;
6320
6321 return tg;
6322
6323err:
6324 sched_free_group(tg);
6325 return ERR_PTR(-ENOMEM);
6326}
6327
6328void sched_online_group(struct task_group *tg, struct task_group *parent)
6329{
6330 unsigned long flags;
6331
6332 spin_lock_irqsave(&task_group_lock, flags);
6333 list_add_rcu(&tg->list, &task_groups);
6334
6335 /* Root should already exist: */
6336 WARN_ON(!parent);
6337
6338 tg->parent = parent;
6339 INIT_LIST_HEAD(&tg->children);
6340 list_add_rcu(&tg->siblings, &parent->children);
6341 spin_unlock_irqrestore(&task_group_lock, flags);
6342
6343 online_fair_sched_group(tg);
6344}
6345
6346/* rcu callback to free various structures associated with a task group */
6347static void sched_free_group_rcu(struct rcu_head *rhp)
6348{
6349 /* Now it should be safe to free those cfs_rqs: */
6350 sched_free_group(container_of(rhp, struct task_group, rcu));
6351}
6352
6353void sched_destroy_group(struct task_group *tg)
6354{
6355 /* Wait for possible concurrent references to cfs_rqs complete: */
6356 call_rcu(&tg->rcu, sched_free_group_rcu);
6357}
6358
6359void sched_offline_group(struct task_group *tg)
6360{
6361 unsigned long flags;
6362
6363 /* End participation in shares distribution: */
6364 unregister_fair_sched_group(tg);
6365
6366 spin_lock_irqsave(&task_group_lock, flags);
6367 list_del_rcu(&tg->list);
6368 list_del_rcu(&tg->siblings);
6369 spin_unlock_irqrestore(&task_group_lock, flags);
6370}
6371
6372static void sched_change_group(struct task_struct *tsk, int type)
6373{
6374 struct task_group *tg;
6375
6376 /*
6377 * All callers are synchronized by task_rq_lock(); we do not use RCU
6378 * which is pointless here. Thus, we pass "true" to task_css_check()
6379 * to prevent lockdep warnings.
6380 */
6381 tg = container_of(task_css_check(tsk, cpu_cgrp_id, true),
6382 struct task_group, css);
6383 tg = autogroup_task_group(tsk, tg);
6384 tsk->sched_task_group = tg;
6385
6386#ifdef CONFIG_FAIR_GROUP_SCHED
6387 if (tsk->sched_class->task_change_group)
6388 tsk->sched_class->task_change_group(tsk, type);
6389 else
6390#endif
6391 set_task_rq(tsk, task_cpu(tsk));
6392}
6393
6394/*
6395 * Change task's runqueue when it moves between groups.
6396 *
6397 * The caller of this function should have put the task in its new group by
6398 * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect
6399 * its new group.
6400 */
6401void sched_move_task(struct task_struct *tsk)
6402{
6403 int queued, running, queue_flags =
6404 DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
6405 struct rq_flags rf;
6406 struct rq *rq;
6407
6408 rq = task_rq_lock(tsk, &rf);
6409 update_rq_clock(rq);
6410
6411 running = task_current(rq, tsk);
6412 queued = task_on_rq_queued(tsk);
6413
6414 if (queued)
6415 dequeue_task(rq, tsk, queue_flags);
6416 if (running)
6417 put_prev_task(rq, tsk);
6418
6419 sched_change_group(tsk, TASK_MOVE_GROUP);
6420
6421 if (queued)
6422 enqueue_task(rq, tsk, queue_flags);
6423 if (running)
6424 set_curr_task(rq, tsk);
6425
6426 task_rq_unlock(rq, tsk, &rf);
6427}
6428
6429static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
6430{
6431 return css ? container_of(css, struct task_group, css) : NULL;
6432}
6433
6434static struct cgroup_subsys_state *
6435cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
6436{
6437 struct task_group *parent = css_tg(parent_css);
6438 struct task_group *tg;
6439
6440 if (!parent) {
6441 /* This is early initialization for the top cgroup */
6442 return &root_task_group.css;
6443 }
6444
6445 tg = sched_create_group(parent);
6446 if (IS_ERR(tg))
6447 return ERR_PTR(-ENOMEM);
6448
6449 return &tg->css;
6450}
6451
6452/* Expose task group only after completing cgroup initialization */
6453static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
6454{
6455 struct task_group *tg = css_tg(css);
6456 struct task_group *parent = css_tg(css->parent);
6457
6458 if (parent)
6459 sched_online_group(tg, parent);
6460 return 0;
6461}
6462
6463static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
6464{
6465 struct task_group *tg = css_tg(css);
6466
6467 sched_offline_group(tg);
6468}
6469
6470static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
6471{
6472 struct task_group *tg = css_tg(css);
6473
6474 /*
6475 * Relies on the RCU grace period between css_released() and this.
6476 */
6477 sched_free_group(tg);
6478}
6479
6480/*
6481 * This is called before wake_up_new_task(), therefore we really only
6482 * have to set its group bits, all the other stuff does not apply.
6483 */
6484static void cpu_cgroup_fork(struct task_struct *task)
6485{
6486 struct rq_flags rf;
6487 struct rq *rq;
6488
6489 rq = task_rq_lock(task, &rf);
6490
6491 update_rq_clock(rq);
6492 sched_change_group(task, TASK_SET_GROUP);
6493
6494 task_rq_unlock(rq, task, &rf);
6495}
6496
6497static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
6498{
6499 struct task_struct *task;
6500 struct cgroup_subsys_state *css;
6501 int ret = 0;
6502
6503 cgroup_taskset_for_each(task, css, tset) {
6504#ifdef CONFIG_RT_GROUP_SCHED
6505 if (!sched_rt_can_attach(css_tg(css), task))
6506 return -EINVAL;
6507#else
6508 /* We don't support RT-tasks being in separate groups */
6509 if (task->sched_class != &fair_sched_class)
6510 return -EINVAL;
6511#endif
6512 /*
6513 * Serialize against wake_up_new_task() such that if its
6514 * running, we're sure to observe its full state.
6515 */
6516 raw_spin_lock_irq(&task->pi_lock);
6517 /*
6518 * Avoid calling sched_move_task() before wake_up_new_task()
6519 * has happened. This would lead to problems with PELT, due to
6520 * move wanting to detach+attach while we're not attached yet.
6521 */
6522 if (task->state == TASK_NEW)
6523 ret = -EINVAL;
6524 raw_spin_unlock_irq(&task->pi_lock);
6525
6526 if (ret)
6527 break;
6528 }
6529 return ret;
6530}
6531
6532static void cpu_cgroup_attach(struct cgroup_taskset *tset)
6533{
6534 struct task_struct *task;
6535 struct cgroup_subsys_state *css;
6536
6537 cgroup_taskset_for_each(task, css, tset)
6538 sched_move_task(task);
6539}
6540
6541#ifdef CONFIG_FAIR_GROUP_SCHED
6542static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
6543 struct cftype *cftype, u64 shareval)
6544{
6545 return sched_group_set_shares(css_tg(css), scale_load(shareval));
6546}
6547
6548static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
6549 struct cftype *cft)
6550{
6551 struct task_group *tg = css_tg(css);
6552
6553 return (u64) scale_load_down(tg->shares);
6554}
6555
6556#ifdef CONFIG_CFS_BANDWIDTH
6557static DEFINE_MUTEX(cfs_constraints_mutex);
6558
6559const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */
6560const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */
6561
6562static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime);
6563
6564static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota)
6565{
6566 int i, ret = 0, runtime_enabled, runtime_was_enabled;
6567 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6568
6569 if (tg == &root_task_group)
6570 return -EINVAL;
6571
6572 /*
6573 * Ensure we have at some amount of bandwidth every period. This is
6574 * to prevent reaching a state of large arrears when throttled via
6575 * entity_tick() resulting in prolonged exit starvation.
6576 */
6577 if (quota < min_cfs_quota_period || period < min_cfs_quota_period)
6578 return -EINVAL;
6579
6580 /*
6581 * Likewise, bound things on the otherside by preventing insane quota
6582 * periods. This also allows us to normalize in computing quota
6583 * feasibility.
6584 */
6585 if (period > max_cfs_quota_period)
6586 return -EINVAL;
6587
6588 /*
6589 * Prevent race between setting of cfs_rq->runtime_enabled and
6590 * unthrottle_offline_cfs_rqs().
6591 */
6592 get_online_cpus();
6593 mutex_lock(&cfs_constraints_mutex);
6594 ret = __cfs_schedulable(tg, period, quota);
6595 if (ret)
6596 goto out_unlock;
6597
6598 runtime_enabled = quota != RUNTIME_INF;
6599 runtime_was_enabled = cfs_b->quota != RUNTIME_INF;
6600 /*
6601 * If we need to toggle cfs_bandwidth_used, off->on must occur
6602 * before making related changes, and on->off must occur afterwards
6603 */
6604 if (runtime_enabled && !runtime_was_enabled)
6605 cfs_bandwidth_usage_inc();
6606 raw_spin_lock_irq(&cfs_b->lock);
6607 cfs_b->period = ns_to_ktime(period);
6608 cfs_b->quota = quota;
6609
6610 __refill_cfs_bandwidth_runtime(cfs_b);
6611
6612 /* Restart the period timer (if active) to handle new period expiry: */
6613 if (runtime_enabled)
6614 start_cfs_bandwidth(cfs_b);
6615
6616 raw_spin_unlock_irq(&cfs_b->lock);
6617
6618 for_each_online_cpu(i) {
6619 struct cfs_rq *cfs_rq = tg->cfs_rq[i];
6620 struct rq *rq = cfs_rq->rq;
6621 struct rq_flags rf;
6622
6623 rq_lock_irq(rq, &rf);
6624 cfs_rq->runtime_enabled = runtime_enabled;
6625 cfs_rq->runtime_remaining = 0;
6626
6627 if (cfs_rq->throttled)
6628 unthrottle_cfs_rq(cfs_rq);
6629 rq_unlock_irq(rq, &rf);
6630 }
6631 if (runtime_was_enabled && !runtime_enabled)
6632 cfs_bandwidth_usage_dec();
6633out_unlock:
6634 mutex_unlock(&cfs_constraints_mutex);
6635 put_online_cpus();
6636
6637 return ret;
6638}
6639
6640int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us)
6641{
6642 u64 quota, period;
6643
6644 period = ktime_to_ns(tg->cfs_bandwidth.period);
6645 if (cfs_quota_us < 0)
6646 quota = RUNTIME_INF;
6647 else
6648 quota = (u64)cfs_quota_us * NSEC_PER_USEC;
6649
6650 return tg_set_cfs_bandwidth(tg, period, quota);
6651}
6652
6653long tg_get_cfs_quota(struct task_group *tg)
6654{
6655 u64 quota_us;
6656
6657 if (tg->cfs_bandwidth.quota == RUNTIME_INF)
6658 return -1;
6659
6660 quota_us = tg->cfs_bandwidth.quota;
6661 do_div(quota_us, NSEC_PER_USEC);
6662
6663 return quota_us;
6664}
6665
6666int tg_set_cfs_period(struct task_group *tg, long cfs_period_us)
6667{
6668 u64 quota, period;
6669
6670 period = (u64)cfs_period_us * NSEC_PER_USEC;
6671 quota = tg->cfs_bandwidth.quota;
6672
6673 return tg_set_cfs_bandwidth(tg, period, quota);
6674}
6675
6676long tg_get_cfs_period(struct task_group *tg)
6677{
6678 u64 cfs_period_us;
6679
6680 cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period);
6681 do_div(cfs_period_us, NSEC_PER_USEC);
6682
6683 return cfs_period_us;
6684}
6685
6686static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css,
6687 struct cftype *cft)
6688{
6689 return tg_get_cfs_quota(css_tg(css));
6690}
6691
6692static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css,
6693 struct cftype *cftype, s64 cfs_quota_us)
6694{
6695 return tg_set_cfs_quota(css_tg(css), cfs_quota_us);
6696}
6697
6698static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css,
6699 struct cftype *cft)
6700{
6701 return tg_get_cfs_period(css_tg(css));
6702}
6703
6704static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css,
6705 struct cftype *cftype, u64 cfs_period_us)
6706{
6707 return tg_set_cfs_period(css_tg(css), cfs_period_us);
6708}
6709
6710struct cfs_schedulable_data {
6711 struct task_group *tg;
6712 u64 period, quota;
6713};
6714
6715/*
6716 * normalize group quota/period to be quota/max_period
6717 * note: units are usecs
6718 */
6719static u64 normalize_cfs_quota(struct task_group *tg,
6720 struct cfs_schedulable_data *d)
6721{
6722 u64 quota, period;
6723
6724 if (tg == d->tg) {
6725 period = d->period;
6726 quota = d->quota;
6727 } else {
6728 period = tg_get_cfs_period(tg);
6729 quota = tg_get_cfs_quota(tg);
6730 }
6731
6732 /* note: these should typically be equivalent */
6733 if (quota == RUNTIME_INF || quota == -1)
6734 return RUNTIME_INF;
6735
6736 return to_ratio(period, quota);
6737}
6738
6739static int tg_cfs_schedulable_down(struct task_group *tg, void *data)
6740{
6741 struct cfs_schedulable_data *d = data;
6742 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6743 s64 quota = 0, parent_quota = -1;
6744
6745 if (!tg->parent) {
6746 quota = RUNTIME_INF;
6747 } else {
6748 struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth;
6749
6750 quota = normalize_cfs_quota(tg, d);
6751 parent_quota = parent_b->hierarchical_quota;
6752
6753 /*
6754 * Ensure max(child_quota) <= parent_quota. On cgroup2,
6755 * always take the min. On cgroup1, only inherit when no
6756 * limit is set:
6757 */
6758 if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) {
6759 quota = min(quota, parent_quota);
6760 } else {
6761 if (quota == RUNTIME_INF)
6762 quota = parent_quota;
6763 else if (parent_quota != RUNTIME_INF && quota > parent_quota)
6764 return -EINVAL;
6765 }
6766 }
6767 cfs_b->hierarchical_quota = quota;
6768
6769 return 0;
6770}
6771
6772static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota)
6773{
6774 int ret;
6775 struct cfs_schedulable_data data = {
6776 .tg = tg,
6777 .period = period,
6778 .quota = quota,
6779 };
6780
6781 if (quota != RUNTIME_INF) {
6782 do_div(data.period, NSEC_PER_USEC);
6783 do_div(data.quota, NSEC_PER_USEC);
6784 }
6785
6786 rcu_read_lock();
6787 ret = walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data);
6788 rcu_read_unlock();
6789
6790 return ret;
6791}
6792
6793static int cpu_cfs_stat_show(struct seq_file *sf, void *v)
6794{
6795 struct task_group *tg = css_tg(seq_css(sf));
6796 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6797
6798 seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods);
6799 seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled);
6800 seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time);
6801
6802 return 0;
6803}
6804#endif /* CONFIG_CFS_BANDWIDTH */
6805#endif /* CONFIG_FAIR_GROUP_SCHED */
6806
6807#ifdef CONFIG_RT_GROUP_SCHED
6808static int cpu_rt_runtime_write(struct cgroup_subsys_state *css,
6809 struct cftype *cft, s64 val)
6810{
6811 return sched_group_set_rt_runtime(css_tg(css), val);
6812}
6813
6814static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css,
6815 struct cftype *cft)
6816{
6817 return sched_group_rt_runtime(css_tg(css));
6818}
6819
6820static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css,
6821 struct cftype *cftype, u64 rt_period_us)
6822{
6823 return sched_group_set_rt_period(css_tg(css), rt_period_us);
6824}
6825
6826static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
6827 struct cftype *cft)
6828{
6829 return sched_group_rt_period(css_tg(css));
6830}
6831#endif /* CONFIG_RT_GROUP_SCHED */
6832
6833static struct cftype cpu_legacy_files[] = {
6834#ifdef CONFIG_FAIR_GROUP_SCHED
6835 {
6836 .name = "shares",
6837 .read_u64 = cpu_shares_read_u64,
6838 .write_u64 = cpu_shares_write_u64,
6839 },
6840#endif
6841#ifdef CONFIG_CFS_BANDWIDTH
6842 {
6843 .name = "cfs_quota_us",
6844 .read_s64 = cpu_cfs_quota_read_s64,
6845 .write_s64 = cpu_cfs_quota_write_s64,
6846 },
6847 {
6848 .name = "cfs_period_us",
6849 .read_u64 = cpu_cfs_period_read_u64,
6850 .write_u64 = cpu_cfs_period_write_u64,
6851 },
6852 {
6853 .name = "stat",
6854 .seq_show = cpu_cfs_stat_show,
6855 },
6856#endif
6857#ifdef CONFIG_RT_GROUP_SCHED
6858 {
6859 .name = "rt_runtime_us",
6860 .read_s64 = cpu_rt_runtime_read,
6861 .write_s64 = cpu_rt_runtime_write,
6862 },
6863 {
6864 .name = "rt_period_us",
6865 .read_u64 = cpu_rt_period_read_uint,
6866 .write_u64 = cpu_rt_period_write_uint,
6867 },
6868#endif
6869 { } /* Terminate */
6870};
6871
6872static int cpu_extra_stat_show(struct seq_file *sf,
6873 struct cgroup_subsys_state *css)
6874{
6875#ifdef CONFIG_CFS_BANDWIDTH
6876 {
6877 struct task_group *tg = css_tg(css);
6878 struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth;
6879 u64 throttled_usec;
6880
6881 throttled_usec = cfs_b->throttled_time;
6882 do_div(throttled_usec, NSEC_PER_USEC);
6883
6884 seq_printf(sf, "nr_periods %d\n"
6885 "nr_throttled %d\n"
6886 "throttled_usec %llu\n",
6887 cfs_b->nr_periods, cfs_b->nr_throttled,
6888 throttled_usec);
6889 }
6890#endif
6891 return 0;
6892}
6893
6894#ifdef CONFIG_FAIR_GROUP_SCHED
6895static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css,
6896 struct cftype *cft)
6897{
6898 struct task_group *tg = css_tg(css);
6899 u64 weight = scale_load_down(tg->shares);
6900
6901 return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024);
6902}
6903
6904static int cpu_weight_write_u64(struct cgroup_subsys_state *css,
6905 struct cftype *cft, u64 weight)
6906{
6907 /*
6908 * cgroup weight knobs should use the common MIN, DFL and MAX
6909 * values which are 1, 100 and 10000 respectively. While it loses
6910 * a bit of range on both ends, it maps pretty well onto the shares
6911 * value used by scheduler and the round-trip conversions preserve
6912 * the original value over the entire range.
6913 */
6914 if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX)
6915 return -ERANGE;
6916
6917 weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL);
6918
6919 return sched_group_set_shares(css_tg(css), scale_load(weight));
6920}
6921
6922static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css,
6923 struct cftype *cft)
6924{
6925 unsigned long weight = scale_load_down(css_tg(css)->shares);
6926 int last_delta = INT_MAX;
6927 int prio, delta;
6928
6929 /* find the closest nice value to the current weight */
6930 for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) {
6931 delta = abs(sched_prio_to_weight[prio] - weight);
6932 if (delta >= last_delta)
6933 break;
6934 last_delta = delta;
6935 }
6936
6937 return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO);
6938}
6939
6940static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css,
6941 struct cftype *cft, s64 nice)
6942{
6943 unsigned long weight;
6944 int idx;
6945
6946 if (nice < MIN_NICE || nice > MAX_NICE)
6947 return -ERANGE;
6948
6949 idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO;
6950 idx = array_index_nospec(idx, 40);
6951 weight = sched_prio_to_weight[idx];
6952
6953 return sched_group_set_shares(css_tg(css), scale_load(weight));
6954}
6955#endif
6956
6957static void __maybe_unused cpu_period_quota_print(struct seq_file *sf,
6958 long period, long quota)
6959{
6960 if (quota < 0)
6961 seq_puts(sf, "max");
6962 else
6963 seq_printf(sf, "%ld", quota);
6964
6965 seq_printf(sf, " %ld\n", period);
6966}
6967
6968/* caller should put the current value in *@periodp before calling */
6969static int __maybe_unused cpu_period_quota_parse(char *buf,
6970 u64 *periodp, u64 *quotap)
6971{
6972 char tok[21]; /* U64_MAX */
6973
6974 if (!sscanf(buf, "%s %llu", tok, periodp))
6975 return -EINVAL;
6976
6977 *periodp *= NSEC_PER_USEC;
6978
6979 if (sscanf(tok, "%llu", quotap))
6980 *quotap *= NSEC_PER_USEC;
6981 else if (!strcmp(tok, "max"))
6982 *quotap = RUNTIME_INF;
6983 else
6984 return -EINVAL;
6985
6986 return 0;
6987}
6988
6989#ifdef CONFIG_CFS_BANDWIDTH
6990static int cpu_max_show(struct seq_file *sf, void *v)
6991{
6992 struct task_group *tg = css_tg(seq_css(sf));
6993
6994 cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg));
6995 return 0;
6996}
6997
6998static ssize_t cpu_max_write(struct kernfs_open_file *of,
6999 char *buf, size_t nbytes, loff_t off)
7000{
7001 struct task_group *tg = css_tg(of_css(of));
7002 u64 period = tg_get_cfs_period(tg);
7003 u64 quota;
7004 int ret;
7005
7006 ret = cpu_period_quota_parse(buf, &period, "a);
7007 if (!ret)
7008 ret = tg_set_cfs_bandwidth(tg, period, quota);
7009 return ret ?: nbytes;
7010}
7011#endif
7012
7013static struct cftype cpu_files[] = {
7014#ifdef CONFIG_FAIR_GROUP_SCHED
7015 {
7016 .name = "weight",
7017 .flags = CFTYPE_NOT_ON_ROOT,
7018 .read_u64 = cpu_weight_read_u64,
7019 .write_u64 = cpu_weight_write_u64,
7020 },
7021 {
7022 .name = "weight.nice",
7023 .flags = CFTYPE_NOT_ON_ROOT,
7024 .read_s64 = cpu_weight_nice_read_s64,
7025 .write_s64 = cpu_weight_nice_write_s64,
7026 },
7027#endif
7028#ifdef CONFIG_CFS_BANDWIDTH
7029 {
7030 .name = "max",
7031 .flags = CFTYPE_NOT_ON_ROOT,
7032 .seq_show = cpu_max_show,
7033 .write = cpu_max_write,
7034 },
7035#endif
7036 { } /* terminate */
7037};
7038
7039struct cgroup_subsys cpu_cgrp_subsys = {
7040 .css_alloc = cpu_cgroup_css_alloc,
7041 .css_online = cpu_cgroup_css_online,
7042 .css_released = cpu_cgroup_css_released,
7043 .css_free = cpu_cgroup_css_free,
7044 .css_extra_stat_show = cpu_extra_stat_show,
7045 .fork = cpu_cgroup_fork,
7046 .can_attach = cpu_cgroup_can_attach,
7047 .attach = cpu_cgroup_attach,
7048 .legacy_cftypes = cpu_legacy_files,
7049 .dfl_cftypes = cpu_files,
7050 .early_init = true,
7051 .threaded = true,
7052};
7053
7054#endif /* CONFIG_CGROUP_SCHED */
7055
7056void dump_cpu_task(int cpu)
7057{
7058 pr_info("Task dump for CPU %d:\n", cpu);
7059 sched_show_task(cpu_curr(cpu));
7060}
7061
7062/*
7063 * Nice levels are multiplicative, with a gentle 10% change for every
7064 * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
7065 * nice 1, it will get ~10% less CPU time than another CPU-bound task
7066 * that remained on nice 0.
7067 *
7068 * The "10% effect" is relative and cumulative: from _any_ nice level,
7069 * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
7070 * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
7071 * If a task goes up by ~10% and another task goes down by ~10% then
7072 * the relative distance between them is ~25%.)
7073 */
7074const int sched_prio_to_weight[40] = {
7075 /* -20 */ 88761, 71755, 56483, 46273, 36291,
7076 /* -15 */ 29154, 23254, 18705, 14949, 11916,
7077 /* -10 */ 9548, 7620, 6100, 4904, 3906,
7078 /* -5 */ 3121, 2501, 1991, 1586, 1277,
7079 /* 0 */ 1024, 820, 655, 526, 423,
7080 /* 5 */ 335, 272, 215, 172, 137,
7081 /* 10 */ 110, 87, 70, 56, 45,
7082 /* 15 */ 36, 29, 23, 18, 15,
7083};
7084
7085/*
7086 * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
7087 *
7088 * In cases where the weight does not change often, we can use the
7089 * precalculated inverse to speed up arithmetics by turning divisions
7090 * into multiplications:
7091 */
7092const u32 sched_prio_to_wmult[40] = {
7093 /* -20 */ 48388, 59856, 76040, 92818, 118348,
7094 /* -15 */ 147320, 184698, 229616, 287308, 360437,
7095 /* -10 */ 449829, 563644, 704093, 875809, 1099582,
7096 /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
7097 /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
7098 /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
7099 /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
7100 /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
7101};
7102
7103#undef CREATE_TRACE_POINTS