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1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/proc_fs.h>
7#include <linux/smp.h>
8#include <linux/init.h>
9#include <linux/notifier.h>
10#include <linux/sched.h>
11#include <linux/unistd.h>
12#include <linux/cpu.h>
13#include <linux/oom.h>
14#include <linux/rcupdate.h>
15#include <linux/export.h>
16#include <linux/bug.h>
17#include <linux/kthread.h>
18#include <linux/stop_machine.h>
19#include <linux/mutex.h>
20#include <linux/gfp.h>
21#include <linux/suspend.h>
22#include <linux/lockdep.h>
23#include <linux/tick.h>
24#include <linux/irq.h>
25#include <linux/smpboot.h>
26#include <linux/relay.h>
27#include <linux/slab.h>
28
29#include <trace/events/power.h>
30#define CREATE_TRACE_POINTS
31#include <trace/events/cpuhp.h>
32
33#include "smpboot.h"
34
35/**
36 * cpuhp_cpu_state - Per cpu hotplug state storage
37 * @state: The current cpu state
38 * @target: The target state
39 * @thread: Pointer to the hotplug thread
40 * @should_run: Thread should execute
41 * @rollback: Perform a rollback
42 * @single: Single callback invocation
43 * @bringup: Single callback bringup or teardown selector
44 * @cb_state: The state for a single callback (install/uninstall)
45 * @result: Result of the operation
46 * @done: Signal completion to the issuer of the task
47 */
48struct cpuhp_cpu_state {
49 enum cpuhp_state state;
50 enum cpuhp_state target;
51#ifdef CONFIG_SMP
52 struct task_struct *thread;
53 bool should_run;
54 bool rollback;
55 bool single;
56 bool bringup;
57 struct hlist_node *node;
58 enum cpuhp_state cb_state;
59 int result;
60 struct completion done;
61#endif
62};
63
64static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
65
66/**
67 * cpuhp_step - Hotplug state machine step
68 * @name: Name of the step
69 * @startup: Startup function of the step
70 * @teardown: Teardown function of the step
71 * @skip_onerr: Do not invoke the functions on error rollback
72 * Will go away once the notifiers are gone
73 * @cant_stop: Bringup/teardown can't be stopped at this step
74 */
75struct cpuhp_step {
76 const char *name;
77 union {
78 int (*single)(unsigned int cpu);
79 int (*multi)(unsigned int cpu,
80 struct hlist_node *node);
81 } startup;
82 union {
83 int (*single)(unsigned int cpu);
84 int (*multi)(unsigned int cpu,
85 struct hlist_node *node);
86 } teardown;
87 struct hlist_head list;
88 bool skip_onerr;
89 bool cant_stop;
90 bool multi_instance;
91};
92
93static DEFINE_MUTEX(cpuhp_state_mutex);
94static struct cpuhp_step cpuhp_bp_states[];
95static struct cpuhp_step cpuhp_ap_states[];
96
97static bool cpuhp_is_ap_state(enum cpuhp_state state)
98{
99 /*
100 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
101 * purposes as that state is handled explicitly in cpu_down.
102 */
103 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
104}
105
106static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
107{
108 struct cpuhp_step *sp;
109
110 sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
111 return sp + state;
112}
113
114/**
115 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
116 * @cpu: The cpu for which the callback should be invoked
117 * @step: The step in the state machine
118 * @bringup: True if the bringup callback should be invoked
119 *
120 * Called from cpu hotplug and from the state register machinery.
121 */
122static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
123 bool bringup, struct hlist_node *node)
124{
125 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
126 struct cpuhp_step *step = cpuhp_get_step(state);
127 int (*cbm)(unsigned int cpu, struct hlist_node *node);
128 int (*cb)(unsigned int cpu);
129 int ret, cnt;
130
131 if (!step->multi_instance) {
132 cb = bringup ? step->startup.single : step->teardown.single;
133 if (!cb)
134 return 0;
135 trace_cpuhp_enter(cpu, st->target, state, cb);
136 ret = cb(cpu);
137 trace_cpuhp_exit(cpu, st->state, state, ret);
138 return ret;
139 }
140 cbm = bringup ? step->startup.multi : step->teardown.multi;
141 if (!cbm)
142 return 0;
143
144 /* Single invocation for instance add/remove */
145 if (node) {
146 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
147 ret = cbm(cpu, node);
148 trace_cpuhp_exit(cpu, st->state, state, ret);
149 return ret;
150 }
151
152 /* State transition. Invoke on all instances */
153 cnt = 0;
154 hlist_for_each(node, &step->list) {
155 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
156 ret = cbm(cpu, node);
157 trace_cpuhp_exit(cpu, st->state, state, ret);
158 if (ret)
159 goto err;
160 cnt++;
161 }
162 return 0;
163err:
164 /* Rollback the instances if one failed */
165 cbm = !bringup ? step->startup.multi : step->teardown.multi;
166 if (!cbm)
167 return ret;
168
169 hlist_for_each(node, &step->list) {
170 if (!cnt--)
171 break;
172 cbm(cpu, node);
173 }
174 return ret;
175}
176
177#ifdef CONFIG_SMP
178/* Serializes the updates to cpu_online_mask, cpu_present_mask */
179static DEFINE_MUTEX(cpu_add_remove_lock);
180bool cpuhp_tasks_frozen;
181EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
182
183/*
184 * The following two APIs (cpu_maps_update_begin/done) must be used when
185 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
186 */
187void cpu_maps_update_begin(void)
188{
189 mutex_lock(&cpu_add_remove_lock);
190}
191
192void cpu_maps_update_done(void)
193{
194 mutex_unlock(&cpu_add_remove_lock);
195}
196
197/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
198 * Should always be manipulated under cpu_add_remove_lock
199 */
200static int cpu_hotplug_disabled;
201
202#ifdef CONFIG_HOTPLUG_CPU
203
204static struct {
205 struct task_struct *active_writer;
206 /* wait queue to wake up the active_writer */
207 wait_queue_head_t wq;
208 /* verifies that no writer will get active while readers are active */
209 struct mutex lock;
210 /*
211 * Also blocks the new readers during
212 * an ongoing cpu hotplug operation.
213 */
214 atomic_t refcount;
215
216#ifdef CONFIG_DEBUG_LOCK_ALLOC
217 struct lockdep_map dep_map;
218#endif
219} cpu_hotplug = {
220 .active_writer = NULL,
221 .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
222 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
223#ifdef CONFIG_DEBUG_LOCK_ALLOC
224 .dep_map = STATIC_LOCKDEP_MAP_INIT("cpu_hotplug.dep_map", &cpu_hotplug.dep_map),
225#endif
226};
227
228/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
229#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
230#define cpuhp_lock_acquire_tryread() \
231 lock_map_acquire_tryread(&cpu_hotplug.dep_map)
232#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
233#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
234
235
236void get_online_cpus(void)
237{
238 might_sleep();
239 if (cpu_hotplug.active_writer == current)
240 return;
241 cpuhp_lock_acquire_read();
242 mutex_lock(&cpu_hotplug.lock);
243 atomic_inc(&cpu_hotplug.refcount);
244 mutex_unlock(&cpu_hotplug.lock);
245}
246EXPORT_SYMBOL_GPL(get_online_cpus);
247
248void put_online_cpus(void)
249{
250 int refcount;
251
252 if (cpu_hotplug.active_writer == current)
253 return;
254
255 refcount = atomic_dec_return(&cpu_hotplug.refcount);
256 if (WARN_ON(refcount < 0)) /* try to fix things up */
257 atomic_inc(&cpu_hotplug.refcount);
258
259 if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
260 wake_up(&cpu_hotplug.wq);
261
262 cpuhp_lock_release();
263
264}
265EXPORT_SYMBOL_GPL(put_online_cpus);
266
267/*
268 * This ensures that the hotplug operation can begin only when the
269 * refcount goes to zero.
270 *
271 * Note that during a cpu-hotplug operation, the new readers, if any,
272 * will be blocked by the cpu_hotplug.lock
273 *
274 * Since cpu_hotplug_begin() is always called after invoking
275 * cpu_maps_update_begin(), we can be sure that only one writer is active.
276 *
277 * Note that theoretically, there is a possibility of a livelock:
278 * - Refcount goes to zero, last reader wakes up the sleeping
279 * writer.
280 * - Last reader unlocks the cpu_hotplug.lock.
281 * - A new reader arrives at this moment, bumps up the refcount.
282 * - The writer acquires the cpu_hotplug.lock finds the refcount
283 * non zero and goes to sleep again.
284 *
285 * However, this is very difficult to achieve in practice since
286 * get_online_cpus() not an api which is called all that often.
287 *
288 */
289void cpu_hotplug_begin(void)
290{
291 DEFINE_WAIT(wait);
292
293 cpu_hotplug.active_writer = current;
294 cpuhp_lock_acquire();
295
296 for (;;) {
297 mutex_lock(&cpu_hotplug.lock);
298 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
299 if (likely(!atomic_read(&cpu_hotplug.refcount)))
300 break;
301 mutex_unlock(&cpu_hotplug.lock);
302 schedule();
303 }
304 finish_wait(&cpu_hotplug.wq, &wait);
305}
306
307void cpu_hotplug_done(void)
308{
309 cpu_hotplug.active_writer = NULL;
310 mutex_unlock(&cpu_hotplug.lock);
311 cpuhp_lock_release();
312}
313
314/*
315 * Wait for currently running CPU hotplug operations to complete (if any) and
316 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
317 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
318 * hotplug path before performing hotplug operations. So acquiring that lock
319 * guarantees mutual exclusion from any currently running hotplug operations.
320 */
321void cpu_hotplug_disable(void)
322{
323 cpu_maps_update_begin();
324 cpu_hotplug_disabled++;
325 cpu_maps_update_done();
326}
327EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
328
329static void __cpu_hotplug_enable(void)
330{
331 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
332 return;
333 cpu_hotplug_disabled--;
334}
335
336void cpu_hotplug_enable(void)
337{
338 cpu_maps_update_begin();
339 __cpu_hotplug_enable();
340 cpu_maps_update_done();
341}
342EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
343#endif /* CONFIG_HOTPLUG_CPU */
344
345/* Notifier wrappers for transitioning to state machine */
346
347static int bringup_wait_for_ap(unsigned int cpu)
348{
349 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
350
351 wait_for_completion(&st->done);
352 return st->result;
353}
354
355static int bringup_cpu(unsigned int cpu)
356{
357 struct task_struct *idle = idle_thread_get(cpu);
358 int ret;
359
360 /*
361 * Some architectures have to walk the irq descriptors to
362 * setup the vector space for the cpu which comes online.
363 * Prevent irq alloc/free across the bringup.
364 */
365 irq_lock_sparse();
366
367 /* Arch-specific enabling code. */
368 ret = __cpu_up(cpu, idle);
369 irq_unlock_sparse();
370 if (ret)
371 return ret;
372 ret = bringup_wait_for_ap(cpu);
373 BUG_ON(!cpu_online(cpu));
374 return ret;
375}
376
377/*
378 * Hotplug state machine related functions
379 */
380static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
381{
382 for (st->state++; st->state < st->target; st->state++) {
383 struct cpuhp_step *step = cpuhp_get_step(st->state);
384
385 if (!step->skip_onerr)
386 cpuhp_invoke_callback(cpu, st->state, true, NULL);
387 }
388}
389
390static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
391 enum cpuhp_state target)
392{
393 enum cpuhp_state prev_state = st->state;
394 int ret = 0;
395
396 for (; st->state > target; st->state--) {
397 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL);
398 if (ret) {
399 st->target = prev_state;
400 undo_cpu_down(cpu, st);
401 break;
402 }
403 }
404 return ret;
405}
406
407static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
408{
409 for (st->state--; st->state > st->target; st->state--) {
410 struct cpuhp_step *step = cpuhp_get_step(st->state);
411
412 if (!step->skip_onerr)
413 cpuhp_invoke_callback(cpu, st->state, false, NULL);
414 }
415}
416
417static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
418 enum cpuhp_state target)
419{
420 enum cpuhp_state prev_state = st->state;
421 int ret = 0;
422
423 while (st->state < target) {
424 st->state++;
425 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL);
426 if (ret) {
427 st->target = prev_state;
428 undo_cpu_up(cpu, st);
429 break;
430 }
431 }
432 return ret;
433}
434
435/*
436 * The cpu hotplug threads manage the bringup and teardown of the cpus
437 */
438static void cpuhp_create(unsigned int cpu)
439{
440 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
441
442 init_completion(&st->done);
443}
444
445static int cpuhp_should_run(unsigned int cpu)
446{
447 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
448
449 return st->should_run;
450}
451
452/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
453static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
454{
455 enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
456
457 return cpuhp_down_callbacks(cpu, st, target);
458}
459
460/* Execute the online startup callbacks. Used to be CPU_ONLINE */
461static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
462{
463 return cpuhp_up_callbacks(cpu, st, st->target);
464}
465
466/*
467 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
468 * callbacks when a state gets [un]installed at runtime.
469 */
470static void cpuhp_thread_fun(unsigned int cpu)
471{
472 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
473 int ret = 0;
474
475 /*
476 * Paired with the mb() in cpuhp_kick_ap_work and
477 * cpuhp_invoke_ap_callback, so the work set is consistent visible.
478 */
479 smp_mb();
480 if (!st->should_run)
481 return;
482
483 st->should_run = false;
484
485 /* Single callback invocation for [un]install ? */
486 if (st->single) {
487 if (st->cb_state < CPUHP_AP_ONLINE) {
488 local_irq_disable();
489 ret = cpuhp_invoke_callback(cpu, st->cb_state,
490 st->bringup, st->node);
491 local_irq_enable();
492 } else {
493 ret = cpuhp_invoke_callback(cpu, st->cb_state,
494 st->bringup, st->node);
495 }
496 } else if (st->rollback) {
497 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
498
499 undo_cpu_down(cpu, st);
500 st->rollback = false;
501 } else {
502 /* Cannot happen .... */
503 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
504
505 /* Regular hotplug work */
506 if (st->state < st->target)
507 ret = cpuhp_ap_online(cpu, st);
508 else if (st->state > st->target)
509 ret = cpuhp_ap_offline(cpu, st);
510 }
511 st->result = ret;
512 complete(&st->done);
513}
514
515/* Invoke a single callback on a remote cpu */
516static int
517cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
518 struct hlist_node *node)
519{
520 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
521
522 if (!cpu_online(cpu))
523 return 0;
524
525 /*
526 * If we are up and running, use the hotplug thread. For early calls
527 * we invoke the thread function directly.
528 */
529 if (!st->thread)
530 return cpuhp_invoke_callback(cpu, state, bringup, node);
531
532 st->cb_state = state;
533 st->single = true;
534 st->bringup = bringup;
535 st->node = node;
536
537 /*
538 * Make sure the above stores are visible before should_run becomes
539 * true. Paired with the mb() above in cpuhp_thread_fun()
540 */
541 smp_mb();
542 st->should_run = true;
543 wake_up_process(st->thread);
544 wait_for_completion(&st->done);
545 return st->result;
546}
547
548/* Regular hotplug invocation of the AP hotplug thread */
549static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
550{
551 st->result = 0;
552 st->single = false;
553 /*
554 * Make sure the above stores are visible before should_run becomes
555 * true. Paired with the mb() above in cpuhp_thread_fun()
556 */
557 smp_mb();
558 st->should_run = true;
559 wake_up_process(st->thread);
560}
561
562static int cpuhp_kick_ap_work(unsigned int cpu)
563{
564 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
565 enum cpuhp_state state = st->state;
566
567 trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
568 __cpuhp_kick_ap_work(st);
569 wait_for_completion(&st->done);
570 trace_cpuhp_exit(cpu, st->state, state, st->result);
571 return st->result;
572}
573
574static struct smp_hotplug_thread cpuhp_threads = {
575 .store = &cpuhp_state.thread,
576 .create = &cpuhp_create,
577 .thread_should_run = cpuhp_should_run,
578 .thread_fn = cpuhp_thread_fun,
579 .thread_comm = "cpuhp/%u",
580 .selfparking = true,
581};
582
583void __init cpuhp_threads_init(void)
584{
585 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
586 kthread_unpark(this_cpu_read(cpuhp_state.thread));
587}
588
589#ifdef CONFIG_HOTPLUG_CPU
590/**
591 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
592 * @cpu: a CPU id
593 *
594 * This function walks all processes, finds a valid mm struct for each one and
595 * then clears a corresponding bit in mm's cpumask. While this all sounds
596 * trivial, there are various non-obvious corner cases, which this function
597 * tries to solve in a safe manner.
598 *
599 * Also note that the function uses a somewhat relaxed locking scheme, so it may
600 * be called only for an already offlined CPU.
601 */
602void clear_tasks_mm_cpumask(int cpu)
603{
604 struct task_struct *p;
605
606 /*
607 * This function is called after the cpu is taken down and marked
608 * offline, so its not like new tasks will ever get this cpu set in
609 * their mm mask. -- Peter Zijlstra
610 * Thus, we may use rcu_read_lock() here, instead of grabbing
611 * full-fledged tasklist_lock.
612 */
613 WARN_ON(cpu_online(cpu));
614 rcu_read_lock();
615 for_each_process(p) {
616 struct task_struct *t;
617
618 /*
619 * Main thread might exit, but other threads may still have
620 * a valid mm. Find one.
621 */
622 t = find_lock_task_mm(p);
623 if (!t)
624 continue;
625 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
626 task_unlock(t);
627 }
628 rcu_read_unlock();
629}
630
631static inline void check_for_tasks(int dead_cpu)
632{
633 struct task_struct *g, *p;
634
635 read_lock(&tasklist_lock);
636 for_each_process_thread(g, p) {
637 if (!p->on_rq)
638 continue;
639 /*
640 * We do the check with unlocked task_rq(p)->lock.
641 * Order the reading to do not warn about a task,
642 * which was running on this cpu in the past, and
643 * it's just been woken on another cpu.
644 */
645 rmb();
646 if (task_cpu(p) != dead_cpu)
647 continue;
648
649 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
650 p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
651 }
652 read_unlock(&tasklist_lock);
653}
654
655/* Take this CPU down. */
656static int take_cpu_down(void *_param)
657{
658 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
659 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
660 int err, cpu = smp_processor_id();
661
662 /* Ensure this CPU doesn't handle any more interrupts. */
663 err = __cpu_disable();
664 if (err < 0)
665 return err;
666
667 /*
668 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
669 * do this step again.
670 */
671 WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
672 st->state--;
673 /* Invoke the former CPU_DYING callbacks */
674 for (; st->state > target; st->state--)
675 cpuhp_invoke_callback(cpu, st->state, false, NULL);
676
677 /* Give up timekeeping duties */
678 tick_handover_do_timer();
679 /* Park the stopper thread */
680 stop_machine_park(cpu);
681 return 0;
682}
683
684static int takedown_cpu(unsigned int cpu)
685{
686 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
687 int err;
688
689 /* Park the smpboot threads */
690 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
691 smpboot_park_threads(cpu);
692
693 /*
694 * Prevent irq alloc/free while the dying cpu reorganizes the
695 * interrupt affinities.
696 */
697 irq_lock_sparse();
698
699 /*
700 * So now all preempt/rcu users must observe !cpu_active().
701 */
702 err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
703 if (err) {
704 /* CPU refused to die */
705 irq_unlock_sparse();
706 /* Unpark the hotplug thread so we can rollback there */
707 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
708 return err;
709 }
710 BUG_ON(cpu_online(cpu));
711
712 /*
713 * The CPUHP_AP_SCHED_MIGRATE_DYING callback will have removed all
714 * runnable tasks from the cpu, there's only the idle task left now
715 * that the migration thread is done doing the stop_machine thing.
716 *
717 * Wait for the stop thread to go away.
718 */
719 wait_for_completion(&st->done);
720 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
721
722 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
723 irq_unlock_sparse();
724
725 hotplug_cpu__broadcast_tick_pull(cpu);
726 /* This actually kills the CPU. */
727 __cpu_die(cpu);
728
729 tick_cleanup_dead_cpu(cpu);
730 return 0;
731}
732
733static void cpuhp_complete_idle_dead(void *arg)
734{
735 struct cpuhp_cpu_state *st = arg;
736
737 complete(&st->done);
738}
739
740void cpuhp_report_idle_dead(void)
741{
742 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
743
744 BUG_ON(st->state != CPUHP_AP_OFFLINE);
745 rcu_report_dead(smp_processor_id());
746 st->state = CPUHP_AP_IDLE_DEAD;
747 /*
748 * We cannot call complete after rcu_report_dead() so we delegate it
749 * to an online cpu.
750 */
751 smp_call_function_single(cpumask_first(cpu_online_mask),
752 cpuhp_complete_idle_dead, st, 0);
753}
754
755#else
756#define takedown_cpu NULL
757#endif
758
759#ifdef CONFIG_HOTPLUG_CPU
760
761/* Requires cpu_add_remove_lock to be held */
762static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
763 enum cpuhp_state target)
764{
765 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
766 int prev_state, ret = 0;
767
768 if (num_online_cpus() == 1)
769 return -EBUSY;
770
771 if (!cpu_present(cpu))
772 return -EINVAL;
773
774 cpu_hotplug_begin();
775
776 cpuhp_tasks_frozen = tasks_frozen;
777
778 prev_state = st->state;
779 st->target = target;
780 /*
781 * If the current CPU state is in the range of the AP hotplug thread,
782 * then we need to kick the thread.
783 */
784 if (st->state > CPUHP_TEARDOWN_CPU) {
785 ret = cpuhp_kick_ap_work(cpu);
786 /*
787 * The AP side has done the error rollback already. Just
788 * return the error code..
789 */
790 if (ret)
791 goto out;
792
793 /*
794 * We might have stopped still in the range of the AP hotplug
795 * thread. Nothing to do anymore.
796 */
797 if (st->state > CPUHP_TEARDOWN_CPU)
798 goto out;
799 }
800 /*
801 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
802 * to do the further cleanups.
803 */
804 ret = cpuhp_down_callbacks(cpu, st, target);
805 if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
806 st->target = prev_state;
807 st->rollback = true;
808 cpuhp_kick_ap_work(cpu);
809 }
810
811out:
812 cpu_hotplug_done();
813 return ret;
814}
815
816static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
817{
818 int err;
819
820 cpu_maps_update_begin();
821
822 if (cpu_hotplug_disabled) {
823 err = -EBUSY;
824 goto out;
825 }
826
827 err = _cpu_down(cpu, 0, target);
828
829out:
830 cpu_maps_update_done();
831 return err;
832}
833int cpu_down(unsigned int cpu)
834{
835 return do_cpu_down(cpu, CPUHP_OFFLINE);
836}
837EXPORT_SYMBOL(cpu_down);
838#endif /*CONFIG_HOTPLUG_CPU*/
839
840/**
841 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
842 * @cpu: cpu that just started
843 *
844 * It must be called by the arch code on the new cpu, before the new cpu
845 * enables interrupts and before the "boot" cpu returns from __cpu_up().
846 */
847void notify_cpu_starting(unsigned int cpu)
848{
849 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
850 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
851
852 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
853 while (st->state < target) {
854 st->state++;
855 cpuhp_invoke_callback(cpu, st->state, true, NULL);
856 }
857}
858
859/*
860 * Called from the idle task. We need to set active here, so we can kick off
861 * the stopper thread and unpark the smpboot threads. If the target state is
862 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
863 * cpu further.
864 */
865void cpuhp_online_idle(enum cpuhp_state state)
866{
867 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
868 unsigned int cpu = smp_processor_id();
869
870 /* Happens for the boot cpu */
871 if (state != CPUHP_AP_ONLINE_IDLE)
872 return;
873
874 st->state = CPUHP_AP_ONLINE_IDLE;
875
876 /* Unpark the stopper thread and the hotplug thread of this cpu */
877 stop_machine_unpark(cpu);
878 kthread_unpark(st->thread);
879
880 /* Should we go further up ? */
881 if (st->target > CPUHP_AP_ONLINE_IDLE)
882 __cpuhp_kick_ap_work(st);
883 else
884 complete(&st->done);
885}
886
887/* Requires cpu_add_remove_lock to be held */
888static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
889{
890 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
891 struct task_struct *idle;
892 int ret = 0;
893
894 cpu_hotplug_begin();
895
896 if (!cpu_present(cpu)) {
897 ret = -EINVAL;
898 goto out;
899 }
900
901 /*
902 * The caller of do_cpu_up might have raced with another
903 * caller. Ignore it for now.
904 */
905 if (st->state >= target)
906 goto out;
907
908 if (st->state == CPUHP_OFFLINE) {
909 /* Let it fail before we try to bring the cpu up */
910 idle = idle_thread_get(cpu);
911 if (IS_ERR(idle)) {
912 ret = PTR_ERR(idle);
913 goto out;
914 }
915 }
916
917 cpuhp_tasks_frozen = tasks_frozen;
918
919 st->target = target;
920 /*
921 * If the current CPU state is in the range of the AP hotplug thread,
922 * then we need to kick the thread once more.
923 */
924 if (st->state > CPUHP_BRINGUP_CPU) {
925 ret = cpuhp_kick_ap_work(cpu);
926 /*
927 * The AP side has done the error rollback already. Just
928 * return the error code..
929 */
930 if (ret)
931 goto out;
932 }
933
934 /*
935 * Try to reach the target state. We max out on the BP at
936 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
937 * responsible for bringing it up to the target state.
938 */
939 target = min((int)target, CPUHP_BRINGUP_CPU);
940 ret = cpuhp_up_callbacks(cpu, st, target);
941out:
942 cpu_hotplug_done();
943 return ret;
944}
945
946static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
947{
948 int err = 0;
949
950 if (!cpu_possible(cpu)) {
951 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
952 cpu);
953#if defined(CONFIG_IA64)
954 pr_err("please check additional_cpus= boot parameter\n");
955#endif
956 return -EINVAL;
957 }
958
959 err = try_online_node(cpu_to_node(cpu));
960 if (err)
961 return err;
962
963 cpu_maps_update_begin();
964
965 if (cpu_hotplug_disabled) {
966 err = -EBUSY;
967 goto out;
968 }
969
970 err = _cpu_up(cpu, 0, target);
971out:
972 cpu_maps_update_done();
973 return err;
974}
975
976int cpu_up(unsigned int cpu)
977{
978 return do_cpu_up(cpu, CPUHP_ONLINE);
979}
980EXPORT_SYMBOL_GPL(cpu_up);
981
982#ifdef CONFIG_PM_SLEEP_SMP
983static cpumask_var_t frozen_cpus;
984
985int freeze_secondary_cpus(int primary)
986{
987 int cpu, error = 0;
988
989 cpu_maps_update_begin();
990 if (!cpu_online(primary))
991 primary = cpumask_first(cpu_online_mask);
992 /*
993 * We take down all of the non-boot CPUs in one shot to avoid races
994 * with the userspace trying to use the CPU hotplug at the same time
995 */
996 cpumask_clear(frozen_cpus);
997
998 pr_info("Disabling non-boot CPUs ...\n");
999 for_each_online_cpu(cpu) {
1000 if (cpu == primary)
1001 continue;
1002 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1003 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1004 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1005 if (!error)
1006 cpumask_set_cpu(cpu, frozen_cpus);
1007 else {
1008 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1009 break;
1010 }
1011 }
1012
1013 if (!error)
1014 BUG_ON(num_online_cpus() > 1);
1015 else
1016 pr_err("Non-boot CPUs are not disabled\n");
1017
1018 /*
1019 * Make sure the CPUs won't be enabled by someone else. We need to do
1020 * this even in case of failure as all disable_nonboot_cpus() users are
1021 * supposed to do enable_nonboot_cpus() on the failure path.
1022 */
1023 cpu_hotplug_disabled++;
1024
1025 cpu_maps_update_done();
1026 return error;
1027}
1028
1029void __weak arch_enable_nonboot_cpus_begin(void)
1030{
1031}
1032
1033void __weak arch_enable_nonboot_cpus_end(void)
1034{
1035}
1036
1037void enable_nonboot_cpus(void)
1038{
1039 int cpu, error;
1040
1041 /* Allow everyone to use the CPU hotplug again */
1042 cpu_maps_update_begin();
1043 __cpu_hotplug_enable();
1044 if (cpumask_empty(frozen_cpus))
1045 goto out;
1046
1047 pr_info("Enabling non-boot CPUs ...\n");
1048
1049 arch_enable_nonboot_cpus_begin();
1050
1051 for_each_cpu(cpu, frozen_cpus) {
1052 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1053 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1054 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1055 if (!error) {
1056 pr_info("CPU%d is up\n", cpu);
1057 continue;
1058 }
1059 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1060 }
1061
1062 arch_enable_nonboot_cpus_end();
1063
1064 cpumask_clear(frozen_cpus);
1065out:
1066 cpu_maps_update_done();
1067}
1068
1069static int __init alloc_frozen_cpus(void)
1070{
1071 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1072 return -ENOMEM;
1073 return 0;
1074}
1075core_initcall(alloc_frozen_cpus);
1076
1077/*
1078 * When callbacks for CPU hotplug notifications are being executed, we must
1079 * ensure that the state of the system with respect to the tasks being frozen
1080 * or not, as reported by the notification, remains unchanged *throughout the
1081 * duration* of the execution of the callbacks.
1082 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1083 *
1084 * This synchronization is implemented by mutually excluding regular CPU
1085 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1086 * Hibernate notifications.
1087 */
1088static int
1089cpu_hotplug_pm_callback(struct notifier_block *nb,
1090 unsigned long action, void *ptr)
1091{
1092 switch (action) {
1093
1094 case PM_SUSPEND_PREPARE:
1095 case PM_HIBERNATION_PREPARE:
1096 cpu_hotplug_disable();
1097 break;
1098
1099 case PM_POST_SUSPEND:
1100 case PM_POST_HIBERNATION:
1101 cpu_hotplug_enable();
1102 break;
1103
1104 default:
1105 return NOTIFY_DONE;
1106 }
1107
1108 return NOTIFY_OK;
1109}
1110
1111
1112static int __init cpu_hotplug_pm_sync_init(void)
1113{
1114 /*
1115 * cpu_hotplug_pm_callback has higher priority than x86
1116 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1117 * to disable cpu hotplug to avoid cpu hotplug race.
1118 */
1119 pm_notifier(cpu_hotplug_pm_callback, 0);
1120 return 0;
1121}
1122core_initcall(cpu_hotplug_pm_sync_init);
1123
1124#endif /* CONFIG_PM_SLEEP_SMP */
1125
1126#endif /* CONFIG_SMP */
1127
1128/* Boot processor state steps */
1129static struct cpuhp_step cpuhp_bp_states[] = {
1130 [CPUHP_OFFLINE] = {
1131 .name = "offline",
1132 .startup.single = NULL,
1133 .teardown.single = NULL,
1134 },
1135#ifdef CONFIG_SMP
1136 [CPUHP_CREATE_THREADS]= {
1137 .name = "threads:prepare",
1138 .startup.single = smpboot_create_threads,
1139 .teardown.single = NULL,
1140 .cant_stop = true,
1141 },
1142 [CPUHP_PERF_PREPARE] = {
1143 .name = "perf:prepare",
1144 .startup.single = perf_event_init_cpu,
1145 .teardown.single = perf_event_exit_cpu,
1146 },
1147 [CPUHP_WORKQUEUE_PREP] = {
1148 .name = "workqueue:prepare",
1149 .startup.single = workqueue_prepare_cpu,
1150 .teardown.single = NULL,
1151 },
1152 [CPUHP_HRTIMERS_PREPARE] = {
1153 .name = "hrtimers:prepare",
1154 .startup.single = hrtimers_prepare_cpu,
1155 .teardown.single = hrtimers_dead_cpu,
1156 },
1157 [CPUHP_SMPCFD_PREPARE] = {
1158 .name = "smpcfd:prepare",
1159 .startup.single = smpcfd_prepare_cpu,
1160 .teardown.single = smpcfd_dead_cpu,
1161 },
1162 [CPUHP_RELAY_PREPARE] = {
1163 .name = "relay:prepare",
1164 .startup.single = relay_prepare_cpu,
1165 .teardown.single = NULL,
1166 },
1167 [CPUHP_SLAB_PREPARE] = {
1168 .name = "slab:prepare",
1169 .startup.single = slab_prepare_cpu,
1170 .teardown.single = slab_dead_cpu,
1171 },
1172 [CPUHP_RCUTREE_PREP] = {
1173 .name = "RCU/tree:prepare",
1174 .startup.single = rcutree_prepare_cpu,
1175 .teardown.single = rcutree_dead_cpu,
1176 },
1177 /*
1178 * On the tear-down path, timers_dead_cpu() must be invoked
1179 * before blk_mq_queue_reinit_notify() from notify_dead(),
1180 * otherwise a RCU stall occurs.
1181 */
1182 [CPUHP_TIMERS_DEAD] = {
1183 .name = "timers:dead",
1184 .startup.single = NULL,
1185 .teardown.single = timers_dead_cpu,
1186 },
1187 /* Kicks the plugged cpu into life */
1188 [CPUHP_BRINGUP_CPU] = {
1189 .name = "cpu:bringup",
1190 .startup.single = bringup_cpu,
1191 .teardown.single = NULL,
1192 .cant_stop = true,
1193 },
1194 [CPUHP_AP_SMPCFD_DYING] = {
1195 .name = "smpcfd:dying",
1196 .startup.single = NULL,
1197 .teardown.single = smpcfd_dying_cpu,
1198 },
1199 /*
1200 * Handled on controll processor until the plugged processor manages
1201 * this itself.
1202 */
1203 [CPUHP_TEARDOWN_CPU] = {
1204 .name = "cpu:teardown",
1205 .startup.single = NULL,
1206 .teardown.single = takedown_cpu,
1207 .cant_stop = true,
1208 },
1209#else
1210 [CPUHP_BRINGUP_CPU] = { },
1211#endif
1212};
1213
1214/* Application processor state steps */
1215static struct cpuhp_step cpuhp_ap_states[] = {
1216#ifdef CONFIG_SMP
1217 /* Final state before CPU kills itself */
1218 [CPUHP_AP_IDLE_DEAD] = {
1219 .name = "idle:dead",
1220 },
1221 /*
1222 * Last state before CPU enters the idle loop to die. Transient state
1223 * for synchronization.
1224 */
1225 [CPUHP_AP_OFFLINE] = {
1226 .name = "ap:offline",
1227 .cant_stop = true,
1228 },
1229 /* First state is scheduler control. Interrupts are disabled */
1230 [CPUHP_AP_SCHED_STARTING] = {
1231 .name = "sched:starting",
1232 .startup.single = sched_cpu_starting,
1233 .teardown.single = sched_cpu_dying,
1234 },
1235 [CPUHP_AP_RCUTREE_DYING] = {
1236 .name = "RCU/tree:dying",
1237 .startup.single = NULL,
1238 .teardown.single = rcutree_dying_cpu,
1239 },
1240 /* Entry state on starting. Interrupts enabled from here on. Transient
1241 * state for synchronsization */
1242 [CPUHP_AP_ONLINE] = {
1243 .name = "ap:online",
1244 },
1245 /* Handle smpboot threads park/unpark */
1246 [CPUHP_AP_SMPBOOT_THREADS] = {
1247 .name = "smpboot/threads:online",
1248 .startup.single = smpboot_unpark_threads,
1249 .teardown.single = NULL,
1250 },
1251 [CPUHP_AP_PERF_ONLINE] = {
1252 .name = "perf:online",
1253 .startup.single = perf_event_init_cpu,
1254 .teardown.single = perf_event_exit_cpu,
1255 },
1256 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1257 .name = "workqueue:online",
1258 .startup.single = workqueue_online_cpu,
1259 .teardown.single = workqueue_offline_cpu,
1260 },
1261 [CPUHP_AP_RCUTREE_ONLINE] = {
1262 .name = "RCU/tree:online",
1263 .startup.single = rcutree_online_cpu,
1264 .teardown.single = rcutree_offline_cpu,
1265 },
1266#endif
1267 /*
1268 * The dynamically registered state space is here
1269 */
1270
1271#ifdef CONFIG_SMP
1272 /* Last state is scheduler control setting the cpu active */
1273 [CPUHP_AP_ACTIVE] = {
1274 .name = "sched:active",
1275 .startup.single = sched_cpu_activate,
1276 .teardown.single = sched_cpu_deactivate,
1277 },
1278#endif
1279
1280 /* CPU is fully up and running. */
1281 [CPUHP_ONLINE] = {
1282 .name = "online",
1283 .startup.single = NULL,
1284 .teardown.single = NULL,
1285 },
1286};
1287
1288/* Sanity check for callbacks */
1289static int cpuhp_cb_check(enum cpuhp_state state)
1290{
1291 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1292 return -EINVAL;
1293 return 0;
1294}
1295
1296/*
1297 * Returns a free for dynamic slot assignment of the Online state. The states
1298 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1299 * by having no name assigned.
1300 */
1301static int cpuhp_reserve_state(enum cpuhp_state state)
1302{
1303 enum cpuhp_state i, end;
1304 struct cpuhp_step *step;
1305
1306 switch (state) {
1307 case CPUHP_AP_ONLINE_DYN:
1308 step = cpuhp_ap_states + CPUHP_AP_ONLINE_DYN;
1309 end = CPUHP_AP_ONLINE_DYN_END;
1310 break;
1311 case CPUHP_BP_PREPARE_DYN:
1312 step = cpuhp_bp_states + CPUHP_BP_PREPARE_DYN;
1313 end = CPUHP_BP_PREPARE_DYN_END;
1314 break;
1315 default:
1316 return -EINVAL;
1317 }
1318
1319 for (i = state; i <= end; i++, step++) {
1320 if (!step->name)
1321 return i;
1322 }
1323 WARN(1, "No more dynamic states available for CPU hotplug\n");
1324 return -ENOSPC;
1325}
1326
1327static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1328 int (*startup)(unsigned int cpu),
1329 int (*teardown)(unsigned int cpu),
1330 bool multi_instance)
1331{
1332 /* (Un)Install the callbacks for further cpu hotplug operations */
1333 struct cpuhp_step *sp;
1334 int ret = 0;
1335
1336 mutex_lock(&cpuhp_state_mutex);
1337
1338 if (state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN) {
1339 ret = cpuhp_reserve_state(state);
1340 if (ret < 0)
1341 goto out;
1342 state = ret;
1343 }
1344 sp = cpuhp_get_step(state);
1345 if (name && sp->name) {
1346 ret = -EBUSY;
1347 goto out;
1348 }
1349 sp->startup.single = startup;
1350 sp->teardown.single = teardown;
1351 sp->name = name;
1352 sp->multi_instance = multi_instance;
1353 INIT_HLIST_HEAD(&sp->list);
1354out:
1355 mutex_unlock(&cpuhp_state_mutex);
1356 return ret;
1357}
1358
1359static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1360{
1361 return cpuhp_get_step(state)->teardown.single;
1362}
1363
1364/*
1365 * Call the startup/teardown function for a step either on the AP or
1366 * on the current CPU.
1367 */
1368static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1369 struct hlist_node *node)
1370{
1371 struct cpuhp_step *sp = cpuhp_get_step(state);
1372 int ret;
1373
1374 if ((bringup && !sp->startup.single) ||
1375 (!bringup && !sp->teardown.single))
1376 return 0;
1377 /*
1378 * The non AP bound callbacks can fail on bringup. On teardown
1379 * e.g. module removal we crash for now.
1380 */
1381#ifdef CONFIG_SMP
1382 if (cpuhp_is_ap_state(state))
1383 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1384 else
1385 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1386#else
1387 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1388#endif
1389 BUG_ON(ret && !bringup);
1390 return ret;
1391}
1392
1393/*
1394 * Called from __cpuhp_setup_state on a recoverable failure.
1395 *
1396 * Note: The teardown callbacks for rollback are not allowed to fail!
1397 */
1398static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1399 struct hlist_node *node)
1400{
1401 int cpu;
1402
1403 /* Roll back the already executed steps on the other cpus */
1404 for_each_present_cpu(cpu) {
1405 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1406 int cpustate = st->state;
1407
1408 if (cpu >= failedcpu)
1409 break;
1410
1411 /* Did we invoke the startup call on that cpu ? */
1412 if (cpustate >= state)
1413 cpuhp_issue_call(cpu, state, false, node);
1414 }
1415}
1416
1417int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1418 bool invoke)
1419{
1420 struct cpuhp_step *sp;
1421 int cpu;
1422 int ret;
1423
1424 sp = cpuhp_get_step(state);
1425 if (sp->multi_instance == false)
1426 return -EINVAL;
1427
1428 get_online_cpus();
1429
1430 if (!invoke || !sp->startup.multi)
1431 goto add_node;
1432
1433 /*
1434 * Try to call the startup callback for each present cpu
1435 * depending on the hotplug state of the cpu.
1436 */
1437 for_each_present_cpu(cpu) {
1438 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1439 int cpustate = st->state;
1440
1441 if (cpustate < state)
1442 continue;
1443
1444 ret = cpuhp_issue_call(cpu, state, true, node);
1445 if (ret) {
1446 if (sp->teardown.multi)
1447 cpuhp_rollback_install(cpu, state, node);
1448 goto err;
1449 }
1450 }
1451add_node:
1452 ret = 0;
1453 mutex_lock(&cpuhp_state_mutex);
1454 hlist_add_head(node, &sp->list);
1455 mutex_unlock(&cpuhp_state_mutex);
1456
1457err:
1458 put_online_cpus();
1459 return ret;
1460}
1461EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1462
1463/**
1464 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1465 * @state: The state to setup
1466 * @invoke: If true, the startup function is invoked for cpus where
1467 * cpu state >= @state
1468 * @startup: startup callback function
1469 * @teardown: teardown callback function
1470 * @multi_instance: State is set up for multiple instances which get
1471 * added afterwards.
1472 *
1473 * Returns:
1474 * On success:
1475 * Positive state number if @state is CPUHP_AP_ONLINE_DYN
1476 * 0 for all other states
1477 * On failure: proper (negative) error code
1478 */
1479int __cpuhp_setup_state(enum cpuhp_state state,
1480 const char *name, bool invoke,
1481 int (*startup)(unsigned int cpu),
1482 int (*teardown)(unsigned int cpu),
1483 bool multi_instance)
1484{
1485 int cpu, ret = 0;
1486 bool dynstate;
1487
1488 if (cpuhp_cb_check(state) || !name)
1489 return -EINVAL;
1490
1491 get_online_cpus();
1492
1493 ret = cpuhp_store_callbacks(state, name, startup, teardown,
1494 multi_instance);
1495
1496 dynstate = state == CPUHP_AP_ONLINE_DYN;
1497 if (ret > 0 && dynstate) {
1498 state = ret;
1499 ret = 0;
1500 }
1501
1502 if (ret || !invoke || !startup)
1503 goto out;
1504
1505 /*
1506 * Try to call the startup callback for each present cpu
1507 * depending on the hotplug state of the cpu.
1508 */
1509 for_each_present_cpu(cpu) {
1510 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1511 int cpustate = st->state;
1512
1513 if (cpustate < state)
1514 continue;
1515
1516 ret = cpuhp_issue_call(cpu, state, true, NULL);
1517 if (ret) {
1518 if (teardown)
1519 cpuhp_rollback_install(cpu, state, NULL);
1520 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1521 goto out;
1522 }
1523 }
1524out:
1525 put_online_cpus();
1526 /*
1527 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1528 * dynamically allocated state in case of success.
1529 */
1530 if (!ret && dynstate)
1531 return state;
1532 return ret;
1533}
1534EXPORT_SYMBOL(__cpuhp_setup_state);
1535
1536int __cpuhp_state_remove_instance(enum cpuhp_state state,
1537 struct hlist_node *node, bool invoke)
1538{
1539 struct cpuhp_step *sp = cpuhp_get_step(state);
1540 int cpu;
1541
1542 BUG_ON(cpuhp_cb_check(state));
1543
1544 if (!sp->multi_instance)
1545 return -EINVAL;
1546
1547 get_online_cpus();
1548 if (!invoke || !cpuhp_get_teardown_cb(state))
1549 goto remove;
1550 /*
1551 * Call the teardown callback for each present cpu depending
1552 * on the hotplug state of the cpu. This function is not
1553 * allowed to fail currently!
1554 */
1555 for_each_present_cpu(cpu) {
1556 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1557 int cpustate = st->state;
1558
1559 if (cpustate >= state)
1560 cpuhp_issue_call(cpu, state, false, node);
1561 }
1562
1563remove:
1564 mutex_lock(&cpuhp_state_mutex);
1565 hlist_del(node);
1566 mutex_unlock(&cpuhp_state_mutex);
1567 put_online_cpus();
1568
1569 return 0;
1570}
1571EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1572/**
1573 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1574 * @state: The state to remove
1575 * @invoke: If true, the teardown function is invoked for cpus where
1576 * cpu state >= @state
1577 *
1578 * The teardown callback is currently not allowed to fail. Think
1579 * about module removal!
1580 */
1581void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1582{
1583 struct cpuhp_step *sp = cpuhp_get_step(state);
1584 int cpu;
1585
1586 BUG_ON(cpuhp_cb_check(state));
1587
1588 get_online_cpus();
1589
1590 if (sp->multi_instance) {
1591 WARN(!hlist_empty(&sp->list),
1592 "Error: Removing state %d which has instances left.\n",
1593 state);
1594 goto remove;
1595 }
1596
1597 if (!invoke || !cpuhp_get_teardown_cb(state))
1598 goto remove;
1599
1600 /*
1601 * Call the teardown callback for each present cpu depending
1602 * on the hotplug state of the cpu. This function is not
1603 * allowed to fail currently!
1604 */
1605 for_each_present_cpu(cpu) {
1606 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1607 int cpustate = st->state;
1608
1609 if (cpustate >= state)
1610 cpuhp_issue_call(cpu, state, false, NULL);
1611 }
1612remove:
1613 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1614 put_online_cpus();
1615}
1616EXPORT_SYMBOL(__cpuhp_remove_state);
1617
1618#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1619static ssize_t show_cpuhp_state(struct device *dev,
1620 struct device_attribute *attr, char *buf)
1621{
1622 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1623
1624 return sprintf(buf, "%d\n", st->state);
1625}
1626static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1627
1628static ssize_t write_cpuhp_target(struct device *dev,
1629 struct device_attribute *attr,
1630 const char *buf, size_t count)
1631{
1632 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1633 struct cpuhp_step *sp;
1634 int target, ret;
1635
1636 ret = kstrtoint(buf, 10, &target);
1637 if (ret)
1638 return ret;
1639
1640#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1641 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1642 return -EINVAL;
1643#else
1644 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1645 return -EINVAL;
1646#endif
1647
1648 ret = lock_device_hotplug_sysfs();
1649 if (ret)
1650 return ret;
1651
1652 mutex_lock(&cpuhp_state_mutex);
1653 sp = cpuhp_get_step(target);
1654 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1655 mutex_unlock(&cpuhp_state_mutex);
1656 if (ret)
1657 return ret;
1658
1659 if (st->state < target)
1660 ret = do_cpu_up(dev->id, target);
1661 else
1662 ret = do_cpu_down(dev->id, target);
1663
1664 unlock_device_hotplug();
1665 return ret ? ret : count;
1666}
1667
1668static ssize_t show_cpuhp_target(struct device *dev,
1669 struct device_attribute *attr, char *buf)
1670{
1671 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1672
1673 return sprintf(buf, "%d\n", st->target);
1674}
1675static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1676
1677static struct attribute *cpuhp_cpu_attrs[] = {
1678 &dev_attr_state.attr,
1679 &dev_attr_target.attr,
1680 NULL
1681};
1682
1683static struct attribute_group cpuhp_cpu_attr_group = {
1684 .attrs = cpuhp_cpu_attrs,
1685 .name = "hotplug",
1686 NULL
1687};
1688
1689static ssize_t show_cpuhp_states(struct device *dev,
1690 struct device_attribute *attr, char *buf)
1691{
1692 ssize_t cur, res = 0;
1693 int i;
1694
1695 mutex_lock(&cpuhp_state_mutex);
1696 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1697 struct cpuhp_step *sp = cpuhp_get_step(i);
1698
1699 if (sp->name) {
1700 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1701 buf += cur;
1702 res += cur;
1703 }
1704 }
1705 mutex_unlock(&cpuhp_state_mutex);
1706 return res;
1707}
1708static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1709
1710static struct attribute *cpuhp_cpu_root_attrs[] = {
1711 &dev_attr_states.attr,
1712 NULL
1713};
1714
1715static struct attribute_group cpuhp_cpu_root_attr_group = {
1716 .attrs = cpuhp_cpu_root_attrs,
1717 .name = "hotplug",
1718 NULL
1719};
1720
1721static int __init cpuhp_sysfs_init(void)
1722{
1723 int cpu, ret;
1724
1725 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1726 &cpuhp_cpu_root_attr_group);
1727 if (ret)
1728 return ret;
1729
1730 for_each_possible_cpu(cpu) {
1731 struct device *dev = get_cpu_device(cpu);
1732
1733 if (!dev)
1734 continue;
1735 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1736 if (ret)
1737 return ret;
1738 }
1739 return 0;
1740}
1741device_initcall(cpuhp_sysfs_init);
1742#endif
1743
1744/*
1745 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1746 * represents all NR_CPUS bits binary values of 1<<nr.
1747 *
1748 * It is used by cpumask_of() to get a constant address to a CPU
1749 * mask value that has a single bit set only.
1750 */
1751
1752/* cpu_bit_bitmap[0] is empty - so we can back into it */
1753#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
1754#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1755#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1756#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1757
1758const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1759
1760 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
1761 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
1762#if BITS_PER_LONG > 32
1763 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
1764 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
1765#endif
1766};
1767EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1768
1769const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1770EXPORT_SYMBOL(cpu_all_bits);
1771
1772#ifdef CONFIG_INIT_ALL_POSSIBLE
1773struct cpumask __cpu_possible_mask __read_mostly
1774 = {CPU_BITS_ALL};
1775#else
1776struct cpumask __cpu_possible_mask __read_mostly;
1777#endif
1778EXPORT_SYMBOL(__cpu_possible_mask);
1779
1780struct cpumask __cpu_online_mask __read_mostly;
1781EXPORT_SYMBOL(__cpu_online_mask);
1782
1783struct cpumask __cpu_present_mask __read_mostly;
1784EXPORT_SYMBOL(__cpu_present_mask);
1785
1786struct cpumask __cpu_active_mask __read_mostly;
1787EXPORT_SYMBOL(__cpu_active_mask);
1788
1789void init_cpu_present(const struct cpumask *src)
1790{
1791 cpumask_copy(&__cpu_present_mask, src);
1792}
1793
1794void init_cpu_possible(const struct cpumask *src)
1795{
1796 cpumask_copy(&__cpu_possible_mask, src);
1797}
1798
1799void init_cpu_online(const struct cpumask *src)
1800{
1801 cpumask_copy(&__cpu_online_mask, src);
1802}
1803
1804/*
1805 * Activate the first processor.
1806 */
1807void __init boot_cpu_init(void)
1808{
1809 int cpu = smp_processor_id();
1810
1811 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1812 set_cpu_online(cpu, true);
1813 set_cpu_active(cpu, true);
1814 set_cpu_present(cpu, true);
1815 set_cpu_possible(cpu, true);
1816}
1817
1818/*
1819 * Must be called _AFTER_ setting up the per_cpu areas
1820 */
1821void __init boot_cpu_state_init(void)
1822{
1823 per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1824}
1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/sched/mm.h>
7#include <linux/proc_fs.h>
8#include <linux/smp.h>
9#include <linux/init.h>
10#include <linux/notifier.h>
11#include <linux/sched/signal.h>
12#include <linux/sched/hotplug.h>
13#include <linux/sched/isolation.h>
14#include <linux/sched/task.h>
15#include <linux/sched/smt.h>
16#include <linux/unistd.h>
17#include <linux/cpu.h>
18#include <linux/oom.h>
19#include <linux/rcupdate.h>
20#include <linux/export.h>
21#include <linux/bug.h>
22#include <linux/kthread.h>
23#include <linux/stop_machine.h>
24#include <linux/mutex.h>
25#include <linux/gfp.h>
26#include <linux/suspend.h>
27#include <linux/lockdep.h>
28#include <linux/tick.h>
29#include <linux/irq.h>
30#include <linux/nmi.h>
31#include <linux/smpboot.h>
32#include <linux/relay.h>
33#include <linux/slab.h>
34#include <linux/scs.h>
35#include <linux/percpu-rwsem.h>
36#include <linux/cpuset.h>
37#include <linux/random.h>
38#include <linux/cc_platform.h>
39
40#include <trace/events/power.h>
41#define CREATE_TRACE_POINTS
42#include <trace/events/cpuhp.h>
43
44#include "smpboot.h"
45
46/**
47 * struct cpuhp_cpu_state - Per cpu hotplug state storage
48 * @state: The current cpu state
49 * @target: The target state
50 * @fail: Current CPU hotplug callback state
51 * @thread: Pointer to the hotplug thread
52 * @should_run: Thread should execute
53 * @rollback: Perform a rollback
54 * @single: Single callback invocation
55 * @bringup: Single callback bringup or teardown selector
56 * @cpu: CPU number
57 * @node: Remote CPU node; for multi-instance, do a
58 * single entry callback for install/remove
59 * @last: For multi-instance rollback, remember how far we got
60 * @cb_state: The state for a single callback (install/uninstall)
61 * @result: Result of the operation
62 * @done_up: Signal completion to the issuer of the task for cpu-up
63 * @done_down: Signal completion to the issuer of the task for cpu-down
64 */
65struct cpuhp_cpu_state {
66 enum cpuhp_state state;
67 enum cpuhp_state target;
68 enum cpuhp_state fail;
69#ifdef CONFIG_SMP
70 struct task_struct *thread;
71 bool should_run;
72 bool rollback;
73 bool single;
74 bool bringup;
75 struct hlist_node *node;
76 struct hlist_node *last;
77 enum cpuhp_state cb_state;
78 int result;
79 struct completion done_up;
80 struct completion done_down;
81#endif
82};
83
84static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
85 .fail = CPUHP_INVALID,
86};
87
88#ifdef CONFIG_SMP
89cpumask_t cpus_booted_once_mask;
90#endif
91
92#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
93static struct lockdep_map cpuhp_state_up_map =
94 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
95static struct lockdep_map cpuhp_state_down_map =
96 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
97
98
99static inline void cpuhp_lock_acquire(bool bringup)
100{
101 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
102}
103
104static inline void cpuhp_lock_release(bool bringup)
105{
106 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
107}
108#else
109
110static inline void cpuhp_lock_acquire(bool bringup) { }
111static inline void cpuhp_lock_release(bool bringup) { }
112
113#endif
114
115/**
116 * struct cpuhp_step - Hotplug state machine step
117 * @name: Name of the step
118 * @startup: Startup function of the step
119 * @teardown: Teardown function of the step
120 * @cant_stop: Bringup/teardown can't be stopped at this step
121 * @multi_instance: State has multiple instances which get added afterwards
122 */
123struct cpuhp_step {
124 const char *name;
125 union {
126 int (*single)(unsigned int cpu);
127 int (*multi)(unsigned int cpu,
128 struct hlist_node *node);
129 } startup;
130 union {
131 int (*single)(unsigned int cpu);
132 int (*multi)(unsigned int cpu,
133 struct hlist_node *node);
134 } teardown;
135 /* private: */
136 struct hlist_head list;
137 /* public: */
138 bool cant_stop;
139 bool multi_instance;
140};
141
142static DEFINE_MUTEX(cpuhp_state_mutex);
143static struct cpuhp_step cpuhp_hp_states[];
144
145static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
146{
147 return cpuhp_hp_states + state;
148}
149
150static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
151{
152 return bringup ? !step->startup.single : !step->teardown.single;
153}
154
155/**
156 * cpuhp_invoke_callback - Invoke the callbacks for a given state
157 * @cpu: The cpu for which the callback should be invoked
158 * @state: The state to do callbacks for
159 * @bringup: True if the bringup callback should be invoked
160 * @node: For multi-instance, do a single entry callback for install/remove
161 * @lastp: For multi-instance rollback, remember how far we got
162 *
163 * Called from cpu hotplug and from the state register machinery.
164 *
165 * Return: %0 on success or a negative errno code
166 */
167static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
168 bool bringup, struct hlist_node *node,
169 struct hlist_node **lastp)
170{
171 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
172 struct cpuhp_step *step = cpuhp_get_step(state);
173 int (*cbm)(unsigned int cpu, struct hlist_node *node);
174 int (*cb)(unsigned int cpu);
175 int ret, cnt;
176
177 if (st->fail == state) {
178 st->fail = CPUHP_INVALID;
179 return -EAGAIN;
180 }
181
182 if (cpuhp_step_empty(bringup, step)) {
183 WARN_ON_ONCE(1);
184 return 0;
185 }
186
187 if (!step->multi_instance) {
188 WARN_ON_ONCE(lastp && *lastp);
189 cb = bringup ? step->startup.single : step->teardown.single;
190
191 trace_cpuhp_enter(cpu, st->target, state, cb);
192 ret = cb(cpu);
193 trace_cpuhp_exit(cpu, st->state, state, ret);
194 return ret;
195 }
196 cbm = bringup ? step->startup.multi : step->teardown.multi;
197
198 /* Single invocation for instance add/remove */
199 if (node) {
200 WARN_ON_ONCE(lastp && *lastp);
201 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
202 ret = cbm(cpu, node);
203 trace_cpuhp_exit(cpu, st->state, state, ret);
204 return ret;
205 }
206
207 /* State transition. Invoke on all instances */
208 cnt = 0;
209 hlist_for_each(node, &step->list) {
210 if (lastp && node == *lastp)
211 break;
212
213 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
214 ret = cbm(cpu, node);
215 trace_cpuhp_exit(cpu, st->state, state, ret);
216 if (ret) {
217 if (!lastp)
218 goto err;
219
220 *lastp = node;
221 return ret;
222 }
223 cnt++;
224 }
225 if (lastp)
226 *lastp = NULL;
227 return 0;
228err:
229 /* Rollback the instances if one failed */
230 cbm = !bringup ? step->startup.multi : step->teardown.multi;
231 if (!cbm)
232 return ret;
233
234 hlist_for_each(node, &step->list) {
235 if (!cnt--)
236 break;
237
238 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
239 ret = cbm(cpu, node);
240 trace_cpuhp_exit(cpu, st->state, state, ret);
241 /*
242 * Rollback must not fail,
243 */
244 WARN_ON_ONCE(ret);
245 }
246 return ret;
247}
248
249#ifdef CONFIG_SMP
250static bool cpuhp_is_ap_state(enum cpuhp_state state)
251{
252 /*
253 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
254 * purposes as that state is handled explicitly in cpu_down.
255 */
256 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
257}
258
259static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
260{
261 struct completion *done = bringup ? &st->done_up : &st->done_down;
262 wait_for_completion(done);
263}
264
265static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
266{
267 struct completion *done = bringup ? &st->done_up : &st->done_down;
268 complete(done);
269}
270
271/*
272 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
273 */
274static bool cpuhp_is_atomic_state(enum cpuhp_state state)
275{
276 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
277}
278
279/* Serializes the updates to cpu_online_mask, cpu_present_mask */
280static DEFINE_MUTEX(cpu_add_remove_lock);
281bool cpuhp_tasks_frozen;
282EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
283
284/*
285 * The following two APIs (cpu_maps_update_begin/done) must be used when
286 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
287 */
288void cpu_maps_update_begin(void)
289{
290 mutex_lock(&cpu_add_remove_lock);
291}
292
293void cpu_maps_update_done(void)
294{
295 mutex_unlock(&cpu_add_remove_lock);
296}
297
298/*
299 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
300 * Should always be manipulated under cpu_add_remove_lock
301 */
302static int cpu_hotplug_disabled;
303
304#ifdef CONFIG_HOTPLUG_CPU
305
306DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
307
308void cpus_read_lock(void)
309{
310 percpu_down_read(&cpu_hotplug_lock);
311}
312EXPORT_SYMBOL_GPL(cpus_read_lock);
313
314int cpus_read_trylock(void)
315{
316 return percpu_down_read_trylock(&cpu_hotplug_lock);
317}
318EXPORT_SYMBOL_GPL(cpus_read_trylock);
319
320void cpus_read_unlock(void)
321{
322 percpu_up_read(&cpu_hotplug_lock);
323}
324EXPORT_SYMBOL_GPL(cpus_read_unlock);
325
326void cpus_write_lock(void)
327{
328 percpu_down_write(&cpu_hotplug_lock);
329}
330
331void cpus_write_unlock(void)
332{
333 percpu_up_write(&cpu_hotplug_lock);
334}
335
336void lockdep_assert_cpus_held(void)
337{
338 /*
339 * We can't have hotplug operations before userspace starts running,
340 * and some init codepaths will knowingly not take the hotplug lock.
341 * This is all valid, so mute lockdep until it makes sense to report
342 * unheld locks.
343 */
344 if (system_state < SYSTEM_RUNNING)
345 return;
346
347 percpu_rwsem_assert_held(&cpu_hotplug_lock);
348}
349
350#ifdef CONFIG_LOCKDEP
351int lockdep_is_cpus_held(void)
352{
353 return percpu_rwsem_is_held(&cpu_hotplug_lock);
354}
355#endif
356
357static void lockdep_acquire_cpus_lock(void)
358{
359 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
360}
361
362static void lockdep_release_cpus_lock(void)
363{
364 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
365}
366
367/*
368 * Wait for currently running CPU hotplug operations to complete (if any) and
369 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
370 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
371 * hotplug path before performing hotplug operations. So acquiring that lock
372 * guarantees mutual exclusion from any currently running hotplug operations.
373 */
374void cpu_hotplug_disable(void)
375{
376 cpu_maps_update_begin();
377 cpu_hotplug_disabled++;
378 cpu_maps_update_done();
379}
380EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
381
382static void __cpu_hotplug_enable(void)
383{
384 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
385 return;
386 cpu_hotplug_disabled--;
387}
388
389void cpu_hotplug_enable(void)
390{
391 cpu_maps_update_begin();
392 __cpu_hotplug_enable();
393 cpu_maps_update_done();
394}
395EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
396
397#else
398
399static void lockdep_acquire_cpus_lock(void)
400{
401}
402
403static void lockdep_release_cpus_lock(void)
404{
405}
406
407#endif /* CONFIG_HOTPLUG_CPU */
408
409/*
410 * Architectures that need SMT-specific errata handling during SMT hotplug
411 * should override this.
412 */
413void __weak arch_smt_update(void) { }
414
415#ifdef CONFIG_HOTPLUG_SMT
416enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
417
418void __init cpu_smt_disable(bool force)
419{
420 if (!cpu_smt_possible())
421 return;
422
423 if (force) {
424 pr_info("SMT: Force disabled\n");
425 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
426 } else {
427 pr_info("SMT: disabled\n");
428 cpu_smt_control = CPU_SMT_DISABLED;
429 }
430}
431
432/*
433 * The decision whether SMT is supported can only be done after the full
434 * CPU identification. Called from architecture code.
435 */
436void __init cpu_smt_check_topology(void)
437{
438 if (!topology_smt_supported())
439 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
440}
441
442static int __init smt_cmdline_disable(char *str)
443{
444 cpu_smt_disable(str && !strcmp(str, "force"));
445 return 0;
446}
447early_param("nosmt", smt_cmdline_disable);
448
449static inline bool cpu_smt_allowed(unsigned int cpu)
450{
451 if (cpu_smt_control == CPU_SMT_ENABLED)
452 return true;
453
454 if (topology_is_primary_thread(cpu))
455 return true;
456
457 /*
458 * On x86 it's required to boot all logical CPUs at least once so
459 * that the init code can get a chance to set CR4.MCE on each
460 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
461 * core will shutdown the machine.
462 */
463 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
464}
465
466/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
467bool cpu_smt_possible(void)
468{
469 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
470 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
471}
472EXPORT_SYMBOL_GPL(cpu_smt_possible);
473#else
474static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
475#endif
476
477static inline enum cpuhp_state
478cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
479{
480 enum cpuhp_state prev_state = st->state;
481 bool bringup = st->state < target;
482
483 st->rollback = false;
484 st->last = NULL;
485
486 st->target = target;
487 st->single = false;
488 st->bringup = bringup;
489 if (cpu_dying(cpu) != !bringup)
490 set_cpu_dying(cpu, !bringup);
491
492 return prev_state;
493}
494
495static inline void
496cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
497 enum cpuhp_state prev_state)
498{
499 bool bringup = !st->bringup;
500
501 st->target = prev_state;
502
503 /*
504 * Already rolling back. No need invert the bringup value or to change
505 * the current state.
506 */
507 if (st->rollback)
508 return;
509
510 st->rollback = true;
511
512 /*
513 * If we have st->last we need to undo partial multi_instance of this
514 * state first. Otherwise start undo at the previous state.
515 */
516 if (!st->last) {
517 if (st->bringup)
518 st->state--;
519 else
520 st->state++;
521 }
522
523 st->bringup = bringup;
524 if (cpu_dying(cpu) != !bringup)
525 set_cpu_dying(cpu, !bringup);
526}
527
528/* Regular hotplug invocation of the AP hotplug thread */
529static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
530{
531 if (!st->single && st->state == st->target)
532 return;
533
534 st->result = 0;
535 /*
536 * Make sure the above stores are visible before should_run becomes
537 * true. Paired with the mb() above in cpuhp_thread_fun()
538 */
539 smp_mb();
540 st->should_run = true;
541 wake_up_process(st->thread);
542 wait_for_ap_thread(st, st->bringup);
543}
544
545static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
546 enum cpuhp_state target)
547{
548 enum cpuhp_state prev_state;
549 int ret;
550
551 prev_state = cpuhp_set_state(cpu, st, target);
552 __cpuhp_kick_ap(st);
553 if ((ret = st->result)) {
554 cpuhp_reset_state(cpu, st, prev_state);
555 __cpuhp_kick_ap(st);
556 }
557
558 return ret;
559}
560
561static int bringup_wait_for_ap(unsigned int cpu)
562{
563 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
564
565 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
566 wait_for_ap_thread(st, true);
567 if (WARN_ON_ONCE((!cpu_online(cpu))))
568 return -ECANCELED;
569
570 /* Unpark the hotplug thread of the target cpu */
571 kthread_unpark(st->thread);
572
573 /*
574 * SMT soft disabling on X86 requires to bring the CPU out of the
575 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
576 * CPU marked itself as booted_once in notify_cpu_starting() so the
577 * cpu_smt_allowed() check will now return false if this is not the
578 * primary sibling.
579 */
580 if (!cpu_smt_allowed(cpu))
581 return -ECANCELED;
582
583 if (st->target <= CPUHP_AP_ONLINE_IDLE)
584 return 0;
585
586 return cpuhp_kick_ap(cpu, st, st->target);
587}
588
589static int bringup_cpu(unsigned int cpu)
590{
591 struct task_struct *idle = idle_thread_get(cpu);
592 int ret;
593
594 /*
595 * Reset stale stack state from the last time this CPU was online.
596 */
597 scs_task_reset(idle);
598 kasan_unpoison_task_stack(idle);
599
600 /*
601 * Some architectures have to walk the irq descriptors to
602 * setup the vector space for the cpu which comes online.
603 * Prevent irq alloc/free across the bringup.
604 */
605 irq_lock_sparse();
606
607 /* Arch-specific enabling code. */
608 ret = __cpu_up(cpu, idle);
609 irq_unlock_sparse();
610 if (ret)
611 return ret;
612 return bringup_wait_for_ap(cpu);
613}
614
615static int finish_cpu(unsigned int cpu)
616{
617 struct task_struct *idle = idle_thread_get(cpu);
618 struct mm_struct *mm = idle->active_mm;
619
620 /*
621 * idle_task_exit() will have switched to &init_mm, now
622 * clean up any remaining active_mm state.
623 */
624 if (mm != &init_mm)
625 idle->active_mm = &init_mm;
626 mmdrop(mm);
627 return 0;
628}
629
630/*
631 * Hotplug state machine related functions
632 */
633
634/*
635 * Get the next state to run. Empty ones will be skipped. Returns true if a
636 * state must be run.
637 *
638 * st->state will be modified ahead of time, to match state_to_run, as if it
639 * has already ran.
640 */
641static bool cpuhp_next_state(bool bringup,
642 enum cpuhp_state *state_to_run,
643 struct cpuhp_cpu_state *st,
644 enum cpuhp_state target)
645{
646 do {
647 if (bringup) {
648 if (st->state >= target)
649 return false;
650
651 *state_to_run = ++st->state;
652 } else {
653 if (st->state <= target)
654 return false;
655
656 *state_to_run = st->state--;
657 }
658
659 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
660 break;
661 } while (true);
662
663 return true;
664}
665
666static int __cpuhp_invoke_callback_range(bool bringup,
667 unsigned int cpu,
668 struct cpuhp_cpu_state *st,
669 enum cpuhp_state target,
670 bool nofail)
671{
672 enum cpuhp_state state;
673 int ret = 0;
674
675 while (cpuhp_next_state(bringup, &state, st, target)) {
676 int err;
677
678 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
679 if (!err)
680 continue;
681
682 if (nofail) {
683 pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
684 cpu, bringup ? "UP" : "DOWN",
685 cpuhp_get_step(st->state)->name,
686 st->state, err);
687 ret = -1;
688 } else {
689 ret = err;
690 break;
691 }
692 }
693
694 return ret;
695}
696
697static inline int cpuhp_invoke_callback_range(bool bringup,
698 unsigned int cpu,
699 struct cpuhp_cpu_state *st,
700 enum cpuhp_state target)
701{
702 return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
703}
704
705static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
706 unsigned int cpu,
707 struct cpuhp_cpu_state *st,
708 enum cpuhp_state target)
709{
710 __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
711}
712
713static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
714{
715 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
716 return true;
717 /*
718 * When CPU hotplug is disabled, then taking the CPU down is not
719 * possible because takedown_cpu() and the architecture and
720 * subsystem specific mechanisms are not available. So the CPU
721 * which would be completely unplugged again needs to stay around
722 * in the current state.
723 */
724 return st->state <= CPUHP_BRINGUP_CPU;
725}
726
727static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
728 enum cpuhp_state target)
729{
730 enum cpuhp_state prev_state = st->state;
731 int ret = 0;
732
733 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
734 if (ret) {
735 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
736 ret, cpu, cpuhp_get_step(st->state)->name,
737 st->state);
738
739 cpuhp_reset_state(cpu, st, prev_state);
740 if (can_rollback_cpu(st))
741 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
742 prev_state));
743 }
744 return ret;
745}
746
747/*
748 * The cpu hotplug threads manage the bringup and teardown of the cpus
749 */
750static int cpuhp_should_run(unsigned int cpu)
751{
752 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
753
754 return st->should_run;
755}
756
757/*
758 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
759 * callbacks when a state gets [un]installed at runtime.
760 *
761 * Each invocation of this function by the smpboot thread does a single AP
762 * state callback.
763 *
764 * It has 3 modes of operation:
765 * - single: runs st->cb_state
766 * - up: runs ++st->state, while st->state < st->target
767 * - down: runs st->state--, while st->state > st->target
768 *
769 * When complete or on error, should_run is cleared and the completion is fired.
770 */
771static void cpuhp_thread_fun(unsigned int cpu)
772{
773 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
774 bool bringup = st->bringup;
775 enum cpuhp_state state;
776
777 if (WARN_ON_ONCE(!st->should_run))
778 return;
779
780 /*
781 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
782 * that if we see ->should_run we also see the rest of the state.
783 */
784 smp_mb();
785
786 /*
787 * The BP holds the hotplug lock, but we're now running on the AP,
788 * ensure that anybody asserting the lock is held, will actually find
789 * it so.
790 */
791 lockdep_acquire_cpus_lock();
792 cpuhp_lock_acquire(bringup);
793
794 if (st->single) {
795 state = st->cb_state;
796 st->should_run = false;
797 } else {
798 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
799 if (!st->should_run)
800 goto end;
801 }
802
803 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
804
805 if (cpuhp_is_atomic_state(state)) {
806 local_irq_disable();
807 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
808 local_irq_enable();
809
810 /*
811 * STARTING/DYING must not fail!
812 */
813 WARN_ON_ONCE(st->result);
814 } else {
815 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
816 }
817
818 if (st->result) {
819 /*
820 * If we fail on a rollback, we're up a creek without no
821 * paddle, no way forward, no way back. We loose, thanks for
822 * playing.
823 */
824 WARN_ON_ONCE(st->rollback);
825 st->should_run = false;
826 }
827
828end:
829 cpuhp_lock_release(bringup);
830 lockdep_release_cpus_lock();
831
832 if (!st->should_run)
833 complete_ap_thread(st, bringup);
834}
835
836/* Invoke a single callback on a remote cpu */
837static int
838cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
839 struct hlist_node *node)
840{
841 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
842 int ret;
843
844 if (!cpu_online(cpu))
845 return 0;
846
847 cpuhp_lock_acquire(false);
848 cpuhp_lock_release(false);
849
850 cpuhp_lock_acquire(true);
851 cpuhp_lock_release(true);
852
853 /*
854 * If we are up and running, use the hotplug thread. For early calls
855 * we invoke the thread function directly.
856 */
857 if (!st->thread)
858 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
859
860 st->rollback = false;
861 st->last = NULL;
862
863 st->node = node;
864 st->bringup = bringup;
865 st->cb_state = state;
866 st->single = true;
867
868 __cpuhp_kick_ap(st);
869
870 /*
871 * If we failed and did a partial, do a rollback.
872 */
873 if ((ret = st->result) && st->last) {
874 st->rollback = true;
875 st->bringup = !bringup;
876
877 __cpuhp_kick_ap(st);
878 }
879
880 /*
881 * Clean up the leftovers so the next hotplug operation wont use stale
882 * data.
883 */
884 st->node = st->last = NULL;
885 return ret;
886}
887
888static int cpuhp_kick_ap_work(unsigned int cpu)
889{
890 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
891 enum cpuhp_state prev_state = st->state;
892 int ret;
893
894 cpuhp_lock_acquire(false);
895 cpuhp_lock_release(false);
896
897 cpuhp_lock_acquire(true);
898 cpuhp_lock_release(true);
899
900 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
901 ret = cpuhp_kick_ap(cpu, st, st->target);
902 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
903
904 return ret;
905}
906
907static struct smp_hotplug_thread cpuhp_threads = {
908 .store = &cpuhp_state.thread,
909 .thread_should_run = cpuhp_should_run,
910 .thread_fn = cpuhp_thread_fun,
911 .thread_comm = "cpuhp/%u",
912 .selfparking = true,
913};
914
915static __init void cpuhp_init_state(void)
916{
917 struct cpuhp_cpu_state *st;
918 int cpu;
919
920 for_each_possible_cpu(cpu) {
921 st = per_cpu_ptr(&cpuhp_state, cpu);
922 init_completion(&st->done_up);
923 init_completion(&st->done_down);
924 }
925}
926
927void __init cpuhp_threads_init(void)
928{
929 cpuhp_init_state();
930 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
931 kthread_unpark(this_cpu_read(cpuhp_state.thread));
932}
933
934/*
935 *
936 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
937 * protected region.
938 *
939 * The operation is still serialized against concurrent CPU hotplug via
940 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
941 * serialized against other hotplug related activity like adding or
942 * removing of state callbacks and state instances, which invoke either the
943 * startup or the teardown callback of the affected state.
944 *
945 * This is required for subsystems which are unfixable vs. CPU hotplug and
946 * evade lock inversion problems by scheduling work which has to be
947 * completed _before_ cpu_up()/_cpu_down() returns.
948 *
949 * Don't even think about adding anything to this for any new code or even
950 * drivers. It's only purpose is to keep existing lock order trainwrecks
951 * working.
952 *
953 * For cpu_down() there might be valid reasons to finish cleanups which are
954 * not required to be done under cpu_hotplug_lock, but that's a different
955 * story and would be not invoked via this.
956 */
957static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
958{
959 /*
960 * cpusets delegate hotplug operations to a worker to "solve" the
961 * lock order problems. Wait for the worker, but only if tasks are
962 * _not_ frozen (suspend, hibernate) as that would wait forever.
963 *
964 * The wait is required because otherwise the hotplug operation
965 * returns with inconsistent state, which could even be observed in
966 * user space when a new CPU is brought up. The CPU plug uevent
967 * would be delivered and user space reacting on it would fail to
968 * move tasks to the newly plugged CPU up to the point where the
969 * work has finished because up to that point the newly plugged CPU
970 * is not assignable in cpusets/cgroups. On unplug that's not
971 * necessarily a visible issue, but it is still inconsistent state,
972 * which is the real problem which needs to be "fixed". This can't
973 * prevent the transient state between scheduling the work and
974 * returning from waiting for it.
975 */
976 if (!tasks_frozen)
977 cpuset_wait_for_hotplug();
978}
979
980#ifdef CONFIG_HOTPLUG_CPU
981#ifndef arch_clear_mm_cpumask_cpu
982#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
983#endif
984
985/**
986 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
987 * @cpu: a CPU id
988 *
989 * This function walks all processes, finds a valid mm struct for each one and
990 * then clears a corresponding bit in mm's cpumask. While this all sounds
991 * trivial, there are various non-obvious corner cases, which this function
992 * tries to solve in a safe manner.
993 *
994 * Also note that the function uses a somewhat relaxed locking scheme, so it may
995 * be called only for an already offlined CPU.
996 */
997void clear_tasks_mm_cpumask(int cpu)
998{
999 struct task_struct *p;
1000
1001 /*
1002 * This function is called after the cpu is taken down and marked
1003 * offline, so its not like new tasks will ever get this cpu set in
1004 * their mm mask. -- Peter Zijlstra
1005 * Thus, we may use rcu_read_lock() here, instead of grabbing
1006 * full-fledged tasklist_lock.
1007 */
1008 WARN_ON(cpu_online(cpu));
1009 rcu_read_lock();
1010 for_each_process(p) {
1011 struct task_struct *t;
1012
1013 /*
1014 * Main thread might exit, but other threads may still have
1015 * a valid mm. Find one.
1016 */
1017 t = find_lock_task_mm(p);
1018 if (!t)
1019 continue;
1020 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1021 task_unlock(t);
1022 }
1023 rcu_read_unlock();
1024}
1025
1026/* Take this CPU down. */
1027static int take_cpu_down(void *_param)
1028{
1029 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1030 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1031 int err, cpu = smp_processor_id();
1032
1033 /* Ensure this CPU doesn't handle any more interrupts. */
1034 err = __cpu_disable();
1035 if (err < 0)
1036 return err;
1037
1038 /*
1039 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1040 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1041 */
1042 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1043
1044 /*
1045 * Invoke the former CPU_DYING callbacks. DYING must not fail!
1046 */
1047 cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1048
1049 /* Give up timekeeping duties */
1050 tick_handover_do_timer();
1051 /* Remove CPU from timer broadcasting */
1052 tick_offline_cpu(cpu);
1053 /* Park the stopper thread */
1054 stop_machine_park(cpu);
1055 return 0;
1056}
1057
1058static int takedown_cpu(unsigned int cpu)
1059{
1060 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1061 int err;
1062
1063 /* Park the smpboot threads */
1064 kthread_park(st->thread);
1065
1066 /*
1067 * Prevent irq alloc/free while the dying cpu reorganizes the
1068 * interrupt affinities.
1069 */
1070 irq_lock_sparse();
1071
1072 /*
1073 * So now all preempt/rcu users must observe !cpu_active().
1074 */
1075 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1076 if (err) {
1077 /* CPU refused to die */
1078 irq_unlock_sparse();
1079 /* Unpark the hotplug thread so we can rollback there */
1080 kthread_unpark(st->thread);
1081 return err;
1082 }
1083 BUG_ON(cpu_online(cpu));
1084
1085 /*
1086 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1087 * all runnable tasks from the CPU, there's only the idle task left now
1088 * that the migration thread is done doing the stop_machine thing.
1089 *
1090 * Wait for the stop thread to go away.
1091 */
1092 wait_for_ap_thread(st, false);
1093 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1094
1095 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1096 irq_unlock_sparse();
1097
1098 hotplug_cpu__broadcast_tick_pull(cpu);
1099 /* This actually kills the CPU. */
1100 __cpu_die(cpu);
1101
1102 tick_cleanup_dead_cpu(cpu);
1103 rcutree_migrate_callbacks(cpu);
1104 return 0;
1105}
1106
1107static void cpuhp_complete_idle_dead(void *arg)
1108{
1109 struct cpuhp_cpu_state *st = arg;
1110
1111 complete_ap_thread(st, false);
1112}
1113
1114void cpuhp_report_idle_dead(void)
1115{
1116 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1117
1118 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1119 rcu_report_dead(smp_processor_id());
1120 st->state = CPUHP_AP_IDLE_DEAD;
1121 /*
1122 * We cannot call complete after rcu_report_dead() so we delegate it
1123 * to an online cpu.
1124 */
1125 smp_call_function_single(cpumask_first(cpu_online_mask),
1126 cpuhp_complete_idle_dead, st, 0);
1127}
1128
1129static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1130 enum cpuhp_state target)
1131{
1132 enum cpuhp_state prev_state = st->state;
1133 int ret = 0;
1134
1135 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1136 if (ret) {
1137 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1138 ret, cpu, cpuhp_get_step(st->state)->name,
1139 st->state);
1140
1141 cpuhp_reset_state(cpu, st, prev_state);
1142
1143 if (st->state < prev_state)
1144 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1145 prev_state));
1146 }
1147
1148 return ret;
1149}
1150
1151/* Requires cpu_add_remove_lock to be held */
1152static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1153 enum cpuhp_state target)
1154{
1155 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1156 int prev_state, ret = 0;
1157
1158 if (num_online_cpus() == 1)
1159 return -EBUSY;
1160
1161 if (!cpu_present(cpu))
1162 return -EINVAL;
1163
1164 cpus_write_lock();
1165
1166 cpuhp_tasks_frozen = tasks_frozen;
1167
1168 prev_state = cpuhp_set_state(cpu, st, target);
1169 /*
1170 * If the current CPU state is in the range of the AP hotplug thread,
1171 * then we need to kick the thread.
1172 */
1173 if (st->state > CPUHP_TEARDOWN_CPU) {
1174 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1175 ret = cpuhp_kick_ap_work(cpu);
1176 /*
1177 * The AP side has done the error rollback already. Just
1178 * return the error code..
1179 */
1180 if (ret)
1181 goto out;
1182
1183 /*
1184 * We might have stopped still in the range of the AP hotplug
1185 * thread. Nothing to do anymore.
1186 */
1187 if (st->state > CPUHP_TEARDOWN_CPU)
1188 goto out;
1189
1190 st->target = target;
1191 }
1192 /*
1193 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1194 * to do the further cleanups.
1195 */
1196 ret = cpuhp_down_callbacks(cpu, st, target);
1197 if (ret && st->state < prev_state) {
1198 if (st->state == CPUHP_TEARDOWN_CPU) {
1199 cpuhp_reset_state(cpu, st, prev_state);
1200 __cpuhp_kick_ap(st);
1201 } else {
1202 WARN(1, "DEAD callback error for CPU%d", cpu);
1203 }
1204 }
1205
1206out:
1207 cpus_write_unlock();
1208 /*
1209 * Do post unplug cleanup. This is still protected against
1210 * concurrent CPU hotplug via cpu_add_remove_lock.
1211 */
1212 lockup_detector_cleanup();
1213 arch_smt_update();
1214 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1215 return ret;
1216}
1217
1218static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1219{
1220 /*
1221 * If the platform does not support hotplug, report it explicitly to
1222 * differentiate it from a transient offlining failure.
1223 */
1224 if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1225 return -EOPNOTSUPP;
1226 if (cpu_hotplug_disabled)
1227 return -EBUSY;
1228 return _cpu_down(cpu, 0, target);
1229}
1230
1231static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1232{
1233 int err;
1234
1235 cpu_maps_update_begin();
1236 err = cpu_down_maps_locked(cpu, target);
1237 cpu_maps_update_done();
1238 return err;
1239}
1240
1241/**
1242 * cpu_device_down - Bring down a cpu device
1243 * @dev: Pointer to the cpu device to offline
1244 *
1245 * This function is meant to be used by device core cpu subsystem only.
1246 *
1247 * Other subsystems should use remove_cpu() instead.
1248 *
1249 * Return: %0 on success or a negative errno code
1250 */
1251int cpu_device_down(struct device *dev)
1252{
1253 return cpu_down(dev->id, CPUHP_OFFLINE);
1254}
1255
1256int remove_cpu(unsigned int cpu)
1257{
1258 int ret;
1259
1260 lock_device_hotplug();
1261 ret = device_offline(get_cpu_device(cpu));
1262 unlock_device_hotplug();
1263
1264 return ret;
1265}
1266EXPORT_SYMBOL_GPL(remove_cpu);
1267
1268void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1269{
1270 unsigned int cpu;
1271 int error;
1272
1273 cpu_maps_update_begin();
1274
1275 /*
1276 * Make certain the cpu I'm about to reboot on is online.
1277 *
1278 * This is inline to what migrate_to_reboot_cpu() already do.
1279 */
1280 if (!cpu_online(primary_cpu))
1281 primary_cpu = cpumask_first(cpu_online_mask);
1282
1283 for_each_online_cpu(cpu) {
1284 if (cpu == primary_cpu)
1285 continue;
1286
1287 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1288 if (error) {
1289 pr_err("Failed to offline CPU%d - error=%d",
1290 cpu, error);
1291 break;
1292 }
1293 }
1294
1295 /*
1296 * Ensure all but the reboot CPU are offline.
1297 */
1298 BUG_ON(num_online_cpus() > 1);
1299
1300 /*
1301 * Make sure the CPUs won't be enabled by someone else after this
1302 * point. Kexec will reboot to a new kernel shortly resetting
1303 * everything along the way.
1304 */
1305 cpu_hotplug_disabled++;
1306
1307 cpu_maps_update_done();
1308}
1309
1310#else
1311#define takedown_cpu NULL
1312#endif /*CONFIG_HOTPLUG_CPU*/
1313
1314/**
1315 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1316 * @cpu: cpu that just started
1317 *
1318 * It must be called by the arch code on the new cpu, before the new cpu
1319 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1320 */
1321void notify_cpu_starting(unsigned int cpu)
1322{
1323 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1324 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1325
1326 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1327 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1328
1329 /*
1330 * STARTING must not fail!
1331 */
1332 cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1333}
1334
1335/*
1336 * Called from the idle task. Wake up the controlling task which brings the
1337 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1338 * online bringup to the hotplug thread.
1339 */
1340void cpuhp_online_idle(enum cpuhp_state state)
1341{
1342 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1343
1344 /* Happens for the boot cpu */
1345 if (state != CPUHP_AP_ONLINE_IDLE)
1346 return;
1347
1348 /*
1349 * Unpart the stopper thread before we start the idle loop (and start
1350 * scheduling); this ensures the stopper task is always available.
1351 */
1352 stop_machine_unpark(smp_processor_id());
1353
1354 st->state = CPUHP_AP_ONLINE_IDLE;
1355 complete_ap_thread(st, true);
1356}
1357
1358/* Requires cpu_add_remove_lock to be held */
1359static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1360{
1361 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1362 struct task_struct *idle;
1363 int ret = 0;
1364
1365 cpus_write_lock();
1366
1367 if (!cpu_present(cpu)) {
1368 ret = -EINVAL;
1369 goto out;
1370 }
1371
1372 /*
1373 * The caller of cpu_up() might have raced with another
1374 * caller. Nothing to do.
1375 */
1376 if (st->state >= target)
1377 goto out;
1378
1379 if (st->state == CPUHP_OFFLINE) {
1380 /* Let it fail before we try to bring the cpu up */
1381 idle = idle_thread_get(cpu);
1382 if (IS_ERR(idle)) {
1383 ret = PTR_ERR(idle);
1384 goto out;
1385 }
1386 }
1387
1388 cpuhp_tasks_frozen = tasks_frozen;
1389
1390 cpuhp_set_state(cpu, st, target);
1391 /*
1392 * If the current CPU state is in the range of the AP hotplug thread,
1393 * then we need to kick the thread once more.
1394 */
1395 if (st->state > CPUHP_BRINGUP_CPU) {
1396 ret = cpuhp_kick_ap_work(cpu);
1397 /*
1398 * The AP side has done the error rollback already. Just
1399 * return the error code..
1400 */
1401 if (ret)
1402 goto out;
1403 }
1404
1405 /*
1406 * Try to reach the target state. We max out on the BP at
1407 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1408 * responsible for bringing it up to the target state.
1409 */
1410 target = min((int)target, CPUHP_BRINGUP_CPU);
1411 ret = cpuhp_up_callbacks(cpu, st, target);
1412out:
1413 cpus_write_unlock();
1414 arch_smt_update();
1415 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1416 return ret;
1417}
1418
1419static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1420{
1421 int err = 0;
1422
1423 if (!cpu_possible(cpu)) {
1424 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1425 cpu);
1426#if defined(CONFIG_IA64)
1427 pr_err("please check additional_cpus= boot parameter\n");
1428#endif
1429 return -EINVAL;
1430 }
1431
1432 err = try_online_node(cpu_to_node(cpu));
1433 if (err)
1434 return err;
1435
1436 cpu_maps_update_begin();
1437
1438 if (cpu_hotplug_disabled) {
1439 err = -EBUSY;
1440 goto out;
1441 }
1442 if (!cpu_smt_allowed(cpu)) {
1443 err = -EPERM;
1444 goto out;
1445 }
1446
1447 err = _cpu_up(cpu, 0, target);
1448out:
1449 cpu_maps_update_done();
1450 return err;
1451}
1452
1453/**
1454 * cpu_device_up - Bring up a cpu device
1455 * @dev: Pointer to the cpu device to online
1456 *
1457 * This function is meant to be used by device core cpu subsystem only.
1458 *
1459 * Other subsystems should use add_cpu() instead.
1460 *
1461 * Return: %0 on success or a negative errno code
1462 */
1463int cpu_device_up(struct device *dev)
1464{
1465 return cpu_up(dev->id, CPUHP_ONLINE);
1466}
1467
1468int add_cpu(unsigned int cpu)
1469{
1470 int ret;
1471
1472 lock_device_hotplug();
1473 ret = device_online(get_cpu_device(cpu));
1474 unlock_device_hotplug();
1475
1476 return ret;
1477}
1478EXPORT_SYMBOL_GPL(add_cpu);
1479
1480/**
1481 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1482 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1483 *
1484 * On some architectures like arm64, we can hibernate on any CPU, but on
1485 * wake up the CPU we hibernated on might be offline as a side effect of
1486 * using maxcpus= for example.
1487 *
1488 * Return: %0 on success or a negative errno code
1489 */
1490int bringup_hibernate_cpu(unsigned int sleep_cpu)
1491{
1492 int ret;
1493
1494 if (!cpu_online(sleep_cpu)) {
1495 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1496 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1497 if (ret) {
1498 pr_err("Failed to bring hibernate-CPU up!\n");
1499 return ret;
1500 }
1501 }
1502 return 0;
1503}
1504
1505void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1506{
1507 unsigned int cpu;
1508
1509 for_each_present_cpu(cpu) {
1510 if (num_online_cpus() >= setup_max_cpus)
1511 break;
1512 if (!cpu_online(cpu))
1513 cpu_up(cpu, CPUHP_ONLINE);
1514 }
1515}
1516
1517#ifdef CONFIG_PM_SLEEP_SMP
1518static cpumask_var_t frozen_cpus;
1519
1520int freeze_secondary_cpus(int primary)
1521{
1522 int cpu, error = 0;
1523
1524 cpu_maps_update_begin();
1525 if (primary == -1) {
1526 primary = cpumask_first(cpu_online_mask);
1527 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1528 primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1529 } else {
1530 if (!cpu_online(primary))
1531 primary = cpumask_first(cpu_online_mask);
1532 }
1533
1534 /*
1535 * We take down all of the non-boot CPUs in one shot to avoid races
1536 * with the userspace trying to use the CPU hotplug at the same time
1537 */
1538 cpumask_clear(frozen_cpus);
1539
1540 pr_info("Disabling non-boot CPUs ...\n");
1541 for_each_online_cpu(cpu) {
1542 if (cpu == primary)
1543 continue;
1544
1545 if (pm_wakeup_pending()) {
1546 pr_info("Wakeup pending. Abort CPU freeze\n");
1547 error = -EBUSY;
1548 break;
1549 }
1550
1551 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1552 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1553 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1554 if (!error)
1555 cpumask_set_cpu(cpu, frozen_cpus);
1556 else {
1557 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1558 break;
1559 }
1560 }
1561
1562 if (!error)
1563 BUG_ON(num_online_cpus() > 1);
1564 else
1565 pr_err("Non-boot CPUs are not disabled\n");
1566
1567 /*
1568 * Make sure the CPUs won't be enabled by someone else. We need to do
1569 * this even in case of failure as all freeze_secondary_cpus() users are
1570 * supposed to do thaw_secondary_cpus() on the failure path.
1571 */
1572 cpu_hotplug_disabled++;
1573
1574 cpu_maps_update_done();
1575 return error;
1576}
1577
1578void __weak arch_thaw_secondary_cpus_begin(void)
1579{
1580}
1581
1582void __weak arch_thaw_secondary_cpus_end(void)
1583{
1584}
1585
1586void thaw_secondary_cpus(void)
1587{
1588 int cpu, error;
1589
1590 /* Allow everyone to use the CPU hotplug again */
1591 cpu_maps_update_begin();
1592 __cpu_hotplug_enable();
1593 if (cpumask_empty(frozen_cpus))
1594 goto out;
1595
1596 pr_info("Enabling non-boot CPUs ...\n");
1597
1598 arch_thaw_secondary_cpus_begin();
1599
1600 for_each_cpu(cpu, frozen_cpus) {
1601 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1602 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1603 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1604 if (!error) {
1605 pr_info("CPU%d is up\n", cpu);
1606 continue;
1607 }
1608 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1609 }
1610
1611 arch_thaw_secondary_cpus_end();
1612
1613 cpumask_clear(frozen_cpus);
1614out:
1615 cpu_maps_update_done();
1616}
1617
1618static int __init alloc_frozen_cpus(void)
1619{
1620 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1621 return -ENOMEM;
1622 return 0;
1623}
1624core_initcall(alloc_frozen_cpus);
1625
1626/*
1627 * When callbacks for CPU hotplug notifications are being executed, we must
1628 * ensure that the state of the system with respect to the tasks being frozen
1629 * or not, as reported by the notification, remains unchanged *throughout the
1630 * duration* of the execution of the callbacks.
1631 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1632 *
1633 * This synchronization is implemented by mutually excluding regular CPU
1634 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1635 * Hibernate notifications.
1636 */
1637static int
1638cpu_hotplug_pm_callback(struct notifier_block *nb,
1639 unsigned long action, void *ptr)
1640{
1641 switch (action) {
1642
1643 case PM_SUSPEND_PREPARE:
1644 case PM_HIBERNATION_PREPARE:
1645 cpu_hotplug_disable();
1646 break;
1647
1648 case PM_POST_SUSPEND:
1649 case PM_POST_HIBERNATION:
1650 cpu_hotplug_enable();
1651 break;
1652
1653 default:
1654 return NOTIFY_DONE;
1655 }
1656
1657 return NOTIFY_OK;
1658}
1659
1660
1661static int __init cpu_hotplug_pm_sync_init(void)
1662{
1663 /*
1664 * cpu_hotplug_pm_callback has higher priority than x86
1665 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1666 * to disable cpu hotplug to avoid cpu hotplug race.
1667 */
1668 pm_notifier(cpu_hotplug_pm_callback, 0);
1669 return 0;
1670}
1671core_initcall(cpu_hotplug_pm_sync_init);
1672
1673#endif /* CONFIG_PM_SLEEP_SMP */
1674
1675int __boot_cpu_id;
1676
1677#endif /* CONFIG_SMP */
1678
1679/* Boot processor state steps */
1680static struct cpuhp_step cpuhp_hp_states[] = {
1681 [CPUHP_OFFLINE] = {
1682 .name = "offline",
1683 .startup.single = NULL,
1684 .teardown.single = NULL,
1685 },
1686#ifdef CONFIG_SMP
1687 [CPUHP_CREATE_THREADS]= {
1688 .name = "threads:prepare",
1689 .startup.single = smpboot_create_threads,
1690 .teardown.single = NULL,
1691 .cant_stop = true,
1692 },
1693 [CPUHP_PERF_PREPARE] = {
1694 .name = "perf:prepare",
1695 .startup.single = perf_event_init_cpu,
1696 .teardown.single = perf_event_exit_cpu,
1697 },
1698 [CPUHP_RANDOM_PREPARE] = {
1699 .name = "random:prepare",
1700 .startup.single = random_prepare_cpu,
1701 .teardown.single = NULL,
1702 },
1703 [CPUHP_WORKQUEUE_PREP] = {
1704 .name = "workqueue:prepare",
1705 .startup.single = workqueue_prepare_cpu,
1706 .teardown.single = NULL,
1707 },
1708 [CPUHP_HRTIMERS_PREPARE] = {
1709 .name = "hrtimers:prepare",
1710 .startup.single = hrtimers_prepare_cpu,
1711 .teardown.single = hrtimers_dead_cpu,
1712 },
1713 [CPUHP_SMPCFD_PREPARE] = {
1714 .name = "smpcfd:prepare",
1715 .startup.single = smpcfd_prepare_cpu,
1716 .teardown.single = smpcfd_dead_cpu,
1717 },
1718 [CPUHP_RELAY_PREPARE] = {
1719 .name = "relay:prepare",
1720 .startup.single = relay_prepare_cpu,
1721 .teardown.single = NULL,
1722 },
1723 [CPUHP_SLAB_PREPARE] = {
1724 .name = "slab:prepare",
1725 .startup.single = slab_prepare_cpu,
1726 .teardown.single = slab_dead_cpu,
1727 },
1728 [CPUHP_RCUTREE_PREP] = {
1729 .name = "RCU/tree:prepare",
1730 .startup.single = rcutree_prepare_cpu,
1731 .teardown.single = rcutree_dead_cpu,
1732 },
1733 /*
1734 * On the tear-down path, timers_dead_cpu() must be invoked
1735 * before blk_mq_queue_reinit_notify() from notify_dead(),
1736 * otherwise a RCU stall occurs.
1737 */
1738 [CPUHP_TIMERS_PREPARE] = {
1739 .name = "timers:prepare",
1740 .startup.single = timers_prepare_cpu,
1741 .teardown.single = timers_dead_cpu,
1742 },
1743 /* Kicks the plugged cpu into life */
1744 [CPUHP_BRINGUP_CPU] = {
1745 .name = "cpu:bringup",
1746 .startup.single = bringup_cpu,
1747 .teardown.single = finish_cpu,
1748 .cant_stop = true,
1749 },
1750 /* Final state before CPU kills itself */
1751 [CPUHP_AP_IDLE_DEAD] = {
1752 .name = "idle:dead",
1753 },
1754 /*
1755 * Last state before CPU enters the idle loop to die. Transient state
1756 * for synchronization.
1757 */
1758 [CPUHP_AP_OFFLINE] = {
1759 .name = "ap:offline",
1760 .cant_stop = true,
1761 },
1762 /* First state is scheduler control. Interrupts are disabled */
1763 [CPUHP_AP_SCHED_STARTING] = {
1764 .name = "sched:starting",
1765 .startup.single = sched_cpu_starting,
1766 .teardown.single = sched_cpu_dying,
1767 },
1768 [CPUHP_AP_RCUTREE_DYING] = {
1769 .name = "RCU/tree:dying",
1770 .startup.single = NULL,
1771 .teardown.single = rcutree_dying_cpu,
1772 },
1773 [CPUHP_AP_SMPCFD_DYING] = {
1774 .name = "smpcfd:dying",
1775 .startup.single = NULL,
1776 .teardown.single = smpcfd_dying_cpu,
1777 },
1778 /* Entry state on starting. Interrupts enabled from here on. Transient
1779 * state for synchronsization */
1780 [CPUHP_AP_ONLINE] = {
1781 .name = "ap:online",
1782 },
1783 /*
1784 * Handled on control processor until the plugged processor manages
1785 * this itself.
1786 */
1787 [CPUHP_TEARDOWN_CPU] = {
1788 .name = "cpu:teardown",
1789 .startup.single = NULL,
1790 .teardown.single = takedown_cpu,
1791 .cant_stop = true,
1792 },
1793
1794 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
1795 .name = "sched:waitempty",
1796 .startup.single = NULL,
1797 .teardown.single = sched_cpu_wait_empty,
1798 },
1799
1800 /* Handle smpboot threads park/unpark */
1801 [CPUHP_AP_SMPBOOT_THREADS] = {
1802 .name = "smpboot/threads:online",
1803 .startup.single = smpboot_unpark_threads,
1804 .teardown.single = smpboot_park_threads,
1805 },
1806 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1807 .name = "irq/affinity:online",
1808 .startup.single = irq_affinity_online_cpu,
1809 .teardown.single = NULL,
1810 },
1811 [CPUHP_AP_PERF_ONLINE] = {
1812 .name = "perf:online",
1813 .startup.single = perf_event_init_cpu,
1814 .teardown.single = perf_event_exit_cpu,
1815 },
1816 [CPUHP_AP_WATCHDOG_ONLINE] = {
1817 .name = "lockup_detector:online",
1818 .startup.single = lockup_detector_online_cpu,
1819 .teardown.single = lockup_detector_offline_cpu,
1820 },
1821 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1822 .name = "workqueue:online",
1823 .startup.single = workqueue_online_cpu,
1824 .teardown.single = workqueue_offline_cpu,
1825 },
1826 [CPUHP_AP_RANDOM_ONLINE] = {
1827 .name = "random:online",
1828 .startup.single = random_online_cpu,
1829 .teardown.single = NULL,
1830 },
1831 [CPUHP_AP_RCUTREE_ONLINE] = {
1832 .name = "RCU/tree:online",
1833 .startup.single = rcutree_online_cpu,
1834 .teardown.single = rcutree_offline_cpu,
1835 },
1836#endif
1837 /*
1838 * The dynamically registered state space is here
1839 */
1840
1841#ifdef CONFIG_SMP
1842 /* Last state is scheduler control setting the cpu active */
1843 [CPUHP_AP_ACTIVE] = {
1844 .name = "sched:active",
1845 .startup.single = sched_cpu_activate,
1846 .teardown.single = sched_cpu_deactivate,
1847 },
1848#endif
1849
1850 /* CPU is fully up and running. */
1851 [CPUHP_ONLINE] = {
1852 .name = "online",
1853 .startup.single = NULL,
1854 .teardown.single = NULL,
1855 },
1856};
1857
1858/* Sanity check for callbacks */
1859static int cpuhp_cb_check(enum cpuhp_state state)
1860{
1861 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1862 return -EINVAL;
1863 return 0;
1864}
1865
1866/*
1867 * Returns a free for dynamic slot assignment of the Online state. The states
1868 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1869 * by having no name assigned.
1870 */
1871static int cpuhp_reserve_state(enum cpuhp_state state)
1872{
1873 enum cpuhp_state i, end;
1874 struct cpuhp_step *step;
1875
1876 switch (state) {
1877 case CPUHP_AP_ONLINE_DYN:
1878 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1879 end = CPUHP_AP_ONLINE_DYN_END;
1880 break;
1881 case CPUHP_BP_PREPARE_DYN:
1882 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1883 end = CPUHP_BP_PREPARE_DYN_END;
1884 break;
1885 default:
1886 return -EINVAL;
1887 }
1888
1889 for (i = state; i <= end; i++, step++) {
1890 if (!step->name)
1891 return i;
1892 }
1893 WARN(1, "No more dynamic states available for CPU hotplug\n");
1894 return -ENOSPC;
1895}
1896
1897static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1898 int (*startup)(unsigned int cpu),
1899 int (*teardown)(unsigned int cpu),
1900 bool multi_instance)
1901{
1902 /* (Un)Install the callbacks for further cpu hotplug operations */
1903 struct cpuhp_step *sp;
1904 int ret = 0;
1905
1906 /*
1907 * If name is NULL, then the state gets removed.
1908 *
1909 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1910 * the first allocation from these dynamic ranges, so the removal
1911 * would trigger a new allocation and clear the wrong (already
1912 * empty) state, leaving the callbacks of the to be cleared state
1913 * dangling, which causes wreckage on the next hotplug operation.
1914 */
1915 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1916 state == CPUHP_BP_PREPARE_DYN)) {
1917 ret = cpuhp_reserve_state(state);
1918 if (ret < 0)
1919 return ret;
1920 state = ret;
1921 }
1922 sp = cpuhp_get_step(state);
1923 if (name && sp->name)
1924 return -EBUSY;
1925
1926 sp->startup.single = startup;
1927 sp->teardown.single = teardown;
1928 sp->name = name;
1929 sp->multi_instance = multi_instance;
1930 INIT_HLIST_HEAD(&sp->list);
1931 return ret;
1932}
1933
1934static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1935{
1936 return cpuhp_get_step(state)->teardown.single;
1937}
1938
1939/*
1940 * Call the startup/teardown function for a step either on the AP or
1941 * on the current CPU.
1942 */
1943static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1944 struct hlist_node *node)
1945{
1946 struct cpuhp_step *sp = cpuhp_get_step(state);
1947 int ret;
1948
1949 /*
1950 * If there's nothing to do, we done.
1951 * Relies on the union for multi_instance.
1952 */
1953 if (cpuhp_step_empty(bringup, sp))
1954 return 0;
1955 /*
1956 * The non AP bound callbacks can fail on bringup. On teardown
1957 * e.g. module removal we crash for now.
1958 */
1959#ifdef CONFIG_SMP
1960 if (cpuhp_is_ap_state(state))
1961 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1962 else
1963 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1964#else
1965 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1966#endif
1967 BUG_ON(ret && !bringup);
1968 return ret;
1969}
1970
1971/*
1972 * Called from __cpuhp_setup_state on a recoverable failure.
1973 *
1974 * Note: The teardown callbacks for rollback are not allowed to fail!
1975 */
1976static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1977 struct hlist_node *node)
1978{
1979 int cpu;
1980
1981 /* Roll back the already executed steps on the other cpus */
1982 for_each_present_cpu(cpu) {
1983 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1984 int cpustate = st->state;
1985
1986 if (cpu >= failedcpu)
1987 break;
1988
1989 /* Did we invoke the startup call on that cpu ? */
1990 if (cpustate >= state)
1991 cpuhp_issue_call(cpu, state, false, node);
1992 }
1993}
1994
1995int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1996 struct hlist_node *node,
1997 bool invoke)
1998{
1999 struct cpuhp_step *sp;
2000 int cpu;
2001 int ret;
2002
2003 lockdep_assert_cpus_held();
2004
2005 sp = cpuhp_get_step(state);
2006 if (sp->multi_instance == false)
2007 return -EINVAL;
2008
2009 mutex_lock(&cpuhp_state_mutex);
2010
2011 if (!invoke || !sp->startup.multi)
2012 goto add_node;
2013
2014 /*
2015 * Try to call the startup callback for each present cpu
2016 * depending on the hotplug state of the cpu.
2017 */
2018 for_each_present_cpu(cpu) {
2019 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2020 int cpustate = st->state;
2021
2022 if (cpustate < state)
2023 continue;
2024
2025 ret = cpuhp_issue_call(cpu, state, true, node);
2026 if (ret) {
2027 if (sp->teardown.multi)
2028 cpuhp_rollback_install(cpu, state, node);
2029 goto unlock;
2030 }
2031 }
2032add_node:
2033 ret = 0;
2034 hlist_add_head(node, &sp->list);
2035unlock:
2036 mutex_unlock(&cpuhp_state_mutex);
2037 return ret;
2038}
2039
2040int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2041 bool invoke)
2042{
2043 int ret;
2044
2045 cpus_read_lock();
2046 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2047 cpus_read_unlock();
2048 return ret;
2049}
2050EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2051
2052/**
2053 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2054 * @state: The state to setup
2055 * @name: Name of the step
2056 * @invoke: If true, the startup function is invoked for cpus where
2057 * cpu state >= @state
2058 * @startup: startup callback function
2059 * @teardown: teardown callback function
2060 * @multi_instance: State is set up for multiple instances which get
2061 * added afterwards.
2062 *
2063 * The caller needs to hold cpus read locked while calling this function.
2064 * Return:
2065 * On success:
2066 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2067 * 0 for all other states
2068 * On failure: proper (negative) error code
2069 */
2070int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2071 const char *name, bool invoke,
2072 int (*startup)(unsigned int cpu),
2073 int (*teardown)(unsigned int cpu),
2074 bool multi_instance)
2075{
2076 int cpu, ret = 0;
2077 bool dynstate;
2078
2079 lockdep_assert_cpus_held();
2080
2081 if (cpuhp_cb_check(state) || !name)
2082 return -EINVAL;
2083
2084 mutex_lock(&cpuhp_state_mutex);
2085
2086 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2087 multi_instance);
2088
2089 dynstate = state == CPUHP_AP_ONLINE_DYN;
2090 if (ret > 0 && dynstate) {
2091 state = ret;
2092 ret = 0;
2093 }
2094
2095 if (ret || !invoke || !startup)
2096 goto out;
2097
2098 /*
2099 * Try to call the startup callback for each present cpu
2100 * depending on the hotplug state of the cpu.
2101 */
2102 for_each_present_cpu(cpu) {
2103 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2104 int cpustate = st->state;
2105
2106 if (cpustate < state)
2107 continue;
2108
2109 ret = cpuhp_issue_call(cpu, state, true, NULL);
2110 if (ret) {
2111 if (teardown)
2112 cpuhp_rollback_install(cpu, state, NULL);
2113 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2114 goto out;
2115 }
2116 }
2117out:
2118 mutex_unlock(&cpuhp_state_mutex);
2119 /*
2120 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2121 * dynamically allocated state in case of success.
2122 */
2123 if (!ret && dynstate)
2124 return state;
2125 return ret;
2126}
2127EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2128
2129int __cpuhp_setup_state(enum cpuhp_state state,
2130 const char *name, bool invoke,
2131 int (*startup)(unsigned int cpu),
2132 int (*teardown)(unsigned int cpu),
2133 bool multi_instance)
2134{
2135 int ret;
2136
2137 cpus_read_lock();
2138 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2139 teardown, multi_instance);
2140 cpus_read_unlock();
2141 return ret;
2142}
2143EXPORT_SYMBOL(__cpuhp_setup_state);
2144
2145int __cpuhp_state_remove_instance(enum cpuhp_state state,
2146 struct hlist_node *node, bool invoke)
2147{
2148 struct cpuhp_step *sp = cpuhp_get_step(state);
2149 int cpu;
2150
2151 BUG_ON(cpuhp_cb_check(state));
2152
2153 if (!sp->multi_instance)
2154 return -EINVAL;
2155
2156 cpus_read_lock();
2157 mutex_lock(&cpuhp_state_mutex);
2158
2159 if (!invoke || !cpuhp_get_teardown_cb(state))
2160 goto remove;
2161 /*
2162 * Call the teardown callback for each present cpu depending
2163 * on the hotplug state of the cpu. This function is not
2164 * allowed to fail currently!
2165 */
2166 for_each_present_cpu(cpu) {
2167 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2168 int cpustate = st->state;
2169
2170 if (cpustate >= state)
2171 cpuhp_issue_call(cpu, state, false, node);
2172 }
2173
2174remove:
2175 hlist_del(node);
2176 mutex_unlock(&cpuhp_state_mutex);
2177 cpus_read_unlock();
2178
2179 return 0;
2180}
2181EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2182
2183/**
2184 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2185 * @state: The state to remove
2186 * @invoke: If true, the teardown function is invoked for cpus where
2187 * cpu state >= @state
2188 *
2189 * The caller needs to hold cpus read locked while calling this function.
2190 * The teardown callback is currently not allowed to fail. Think
2191 * about module removal!
2192 */
2193void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2194{
2195 struct cpuhp_step *sp = cpuhp_get_step(state);
2196 int cpu;
2197
2198 BUG_ON(cpuhp_cb_check(state));
2199
2200 lockdep_assert_cpus_held();
2201
2202 mutex_lock(&cpuhp_state_mutex);
2203 if (sp->multi_instance) {
2204 WARN(!hlist_empty(&sp->list),
2205 "Error: Removing state %d which has instances left.\n",
2206 state);
2207 goto remove;
2208 }
2209
2210 if (!invoke || !cpuhp_get_teardown_cb(state))
2211 goto remove;
2212
2213 /*
2214 * Call the teardown callback for each present cpu depending
2215 * on the hotplug state of the cpu. This function is not
2216 * allowed to fail currently!
2217 */
2218 for_each_present_cpu(cpu) {
2219 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2220 int cpustate = st->state;
2221
2222 if (cpustate >= state)
2223 cpuhp_issue_call(cpu, state, false, NULL);
2224 }
2225remove:
2226 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2227 mutex_unlock(&cpuhp_state_mutex);
2228}
2229EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2230
2231void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2232{
2233 cpus_read_lock();
2234 __cpuhp_remove_state_cpuslocked(state, invoke);
2235 cpus_read_unlock();
2236}
2237EXPORT_SYMBOL(__cpuhp_remove_state);
2238
2239#ifdef CONFIG_HOTPLUG_SMT
2240static void cpuhp_offline_cpu_device(unsigned int cpu)
2241{
2242 struct device *dev = get_cpu_device(cpu);
2243
2244 dev->offline = true;
2245 /* Tell user space about the state change */
2246 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2247}
2248
2249static void cpuhp_online_cpu_device(unsigned int cpu)
2250{
2251 struct device *dev = get_cpu_device(cpu);
2252
2253 dev->offline = false;
2254 /* Tell user space about the state change */
2255 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2256}
2257
2258int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2259{
2260 int cpu, ret = 0;
2261
2262 cpu_maps_update_begin();
2263 for_each_online_cpu(cpu) {
2264 if (topology_is_primary_thread(cpu))
2265 continue;
2266 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2267 if (ret)
2268 break;
2269 /*
2270 * As this needs to hold the cpu maps lock it's impossible
2271 * to call device_offline() because that ends up calling
2272 * cpu_down() which takes cpu maps lock. cpu maps lock
2273 * needs to be held as this might race against in kernel
2274 * abusers of the hotplug machinery (thermal management).
2275 *
2276 * So nothing would update device:offline state. That would
2277 * leave the sysfs entry stale and prevent onlining after
2278 * smt control has been changed to 'off' again. This is
2279 * called under the sysfs hotplug lock, so it is properly
2280 * serialized against the regular offline usage.
2281 */
2282 cpuhp_offline_cpu_device(cpu);
2283 }
2284 if (!ret)
2285 cpu_smt_control = ctrlval;
2286 cpu_maps_update_done();
2287 return ret;
2288}
2289
2290int cpuhp_smt_enable(void)
2291{
2292 int cpu, ret = 0;
2293
2294 cpu_maps_update_begin();
2295 cpu_smt_control = CPU_SMT_ENABLED;
2296 for_each_present_cpu(cpu) {
2297 /* Skip online CPUs and CPUs on offline nodes */
2298 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2299 continue;
2300 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2301 if (ret)
2302 break;
2303 /* See comment in cpuhp_smt_disable() */
2304 cpuhp_online_cpu_device(cpu);
2305 }
2306 cpu_maps_update_done();
2307 return ret;
2308}
2309#endif
2310
2311#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2312static ssize_t state_show(struct device *dev,
2313 struct device_attribute *attr, char *buf)
2314{
2315 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2316
2317 return sprintf(buf, "%d\n", st->state);
2318}
2319static DEVICE_ATTR_RO(state);
2320
2321static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2322 const char *buf, size_t count)
2323{
2324 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2325 struct cpuhp_step *sp;
2326 int target, ret;
2327
2328 ret = kstrtoint(buf, 10, &target);
2329 if (ret)
2330 return ret;
2331
2332#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2333 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2334 return -EINVAL;
2335#else
2336 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2337 return -EINVAL;
2338#endif
2339
2340 ret = lock_device_hotplug_sysfs();
2341 if (ret)
2342 return ret;
2343
2344 mutex_lock(&cpuhp_state_mutex);
2345 sp = cpuhp_get_step(target);
2346 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2347 mutex_unlock(&cpuhp_state_mutex);
2348 if (ret)
2349 goto out;
2350
2351 if (st->state < target)
2352 ret = cpu_up(dev->id, target);
2353 else if (st->state > target)
2354 ret = cpu_down(dev->id, target);
2355 else if (WARN_ON(st->target != target))
2356 st->target = target;
2357out:
2358 unlock_device_hotplug();
2359 return ret ? ret : count;
2360}
2361
2362static ssize_t target_show(struct device *dev,
2363 struct device_attribute *attr, char *buf)
2364{
2365 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2366
2367 return sprintf(buf, "%d\n", st->target);
2368}
2369static DEVICE_ATTR_RW(target);
2370
2371static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2372 const char *buf, size_t count)
2373{
2374 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2375 struct cpuhp_step *sp;
2376 int fail, ret;
2377
2378 ret = kstrtoint(buf, 10, &fail);
2379 if (ret)
2380 return ret;
2381
2382 if (fail == CPUHP_INVALID) {
2383 st->fail = fail;
2384 return count;
2385 }
2386
2387 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2388 return -EINVAL;
2389
2390 /*
2391 * Cannot fail STARTING/DYING callbacks.
2392 */
2393 if (cpuhp_is_atomic_state(fail))
2394 return -EINVAL;
2395
2396 /*
2397 * DEAD callbacks cannot fail...
2398 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2399 * triggering STARTING callbacks, a failure in this state would
2400 * hinder rollback.
2401 */
2402 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2403 return -EINVAL;
2404
2405 /*
2406 * Cannot fail anything that doesn't have callbacks.
2407 */
2408 mutex_lock(&cpuhp_state_mutex);
2409 sp = cpuhp_get_step(fail);
2410 if (!sp->startup.single && !sp->teardown.single)
2411 ret = -EINVAL;
2412 mutex_unlock(&cpuhp_state_mutex);
2413 if (ret)
2414 return ret;
2415
2416 st->fail = fail;
2417
2418 return count;
2419}
2420
2421static ssize_t fail_show(struct device *dev,
2422 struct device_attribute *attr, char *buf)
2423{
2424 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2425
2426 return sprintf(buf, "%d\n", st->fail);
2427}
2428
2429static DEVICE_ATTR_RW(fail);
2430
2431static struct attribute *cpuhp_cpu_attrs[] = {
2432 &dev_attr_state.attr,
2433 &dev_attr_target.attr,
2434 &dev_attr_fail.attr,
2435 NULL
2436};
2437
2438static const struct attribute_group cpuhp_cpu_attr_group = {
2439 .attrs = cpuhp_cpu_attrs,
2440 .name = "hotplug",
2441 NULL
2442};
2443
2444static ssize_t states_show(struct device *dev,
2445 struct device_attribute *attr, char *buf)
2446{
2447 ssize_t cur, res = 0;
2448 int i;
2449
2450 mutex_lock(&cpuhp_state_mutex);
2451 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2452 struct cpuhp_step *sp = cpuhp_get_step(i);
2453
2454 if (sp->name) {
2455 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2456 buf += cur;
2457 res += cur;
2458 }
2459 }
2460 mutex_unlock(&cpuhp_state_mutex);
2461 return res;
2462}
2463static DEVICE_ATTR_RO(states);
2464
2465static struct attribute *cpuhp_cpu_root_attrs[] = {
2466 &dev_attr_states.attr,
2467 NULL
2468};
2469
2470static const struct attribute_group cpuhp_cpu_root_attr_group = {
2471 .attrs = cpuhp_cpu_root_attrs,
2472 .name = "hotplug",
2473 NULL
2474};
2475
2476#ifdef CONFIG_HOTPLUG_SMT
2477
2478static ssize_t
2479__store_smt_control(struct device *dev, struct device_attribute *attr,
2480 const char *buf, size_t count)
2481{
2482 int ctrlval, ret;
2483
2484 if (sysfs_streq(buf, "on"))
2485 ctrlval = CPU_SMT_ENABLED;
2486 else if (sysfs_streq(buf, "off"))
2487 ctrlval = CPU_SMT_DISABLED;
2488 else if (sysfs_streq(buf, "forceoff"))
2489 ctrlval = CPU_SMT_FORCE_DISABLED;
2490 else
2491 return -EINVAL;
2492
2493 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2494 return -EPERM;
2495
2496 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2497 return -ENODEV;
2498
2499 ret = lock_device_hotplug_sysfs();
2500 if (ret)
2501 return ret;
2502
2503 if (ctrlval != cpu_smt_control) {
2504 switch (ctrlval) {
2505 case CPU_SMT_ENABLED:
2506 ret = cpuhp_smt_enable();
2507 break;
2508 case CPU_SMT_DISABLED:
2509 case CPU_SMT_FORCE_DISABLED:
2510 ret = cpuhp_smt_disable(ctrlval);
2511 break;
2512 }
2513 }
2514
2515 unlock_device_hotplug();
2516 return ret ? ret : count;
2517}
2518
2519#else /* !CONFIG_HOTPLUG_SMT */
2520static ssize_t
2521__store_smt_control(struct device *dev, struct device_attribute *attr,
2522 const char *buf, size_t count)
2523{
2524 return -ENODEV;
2525}
2526#endif /* CONFIG_HOTPLUG_SMT */
2527
2528static const char *smt_states[] = {
2529 [CPU_SMT_ENABLED] = "on",
2530 [CPU_SMT_DISABLED] = "off",
2531 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2532 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2533 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2534};
2535
2536static ssize_t control_show(struct device *dev,
2537 struct device_attribute *attr, char *buf)
2538{
2539 const char *state = smt_states[cpu_smt_control];
2540
2541 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2542}
2543
2544static ssize_t control_store(struct device *dev, struct device_attribute *attr,
2545 const char *buf, size_t count)
2546{
2547 return __store_smt_control(dev, attr, buf, count);
2548}
2549static DEVICE_ATTR_RW(control);
2550
2551static ssize_t active_show(struct device *dev,
2552 struct device_attribute *attr, char *buf)
2553{
2554 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2555}
2556static DEVICE_ATTR_RO(active);
2557
2558static struct attribute *cpuhp_smt_attrs[] = {
2559 &dev_attr_control.attr,
2560 &dev_attr_active.attr,
2561 NULL
2562};
2563
2564static const struct attribute_group cpuhp_smt_attr_group = {
2565 .attrs = cpuhp_smt_attrs,
2566 .name = "smt",
2567 NULL
2568};
2569
2570static int __init cpu_smt_sysfs_init(void)
2571{
2572 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2573 &cpuhp_smt_attr_group);
2574}
2575
2576static int __init cpuhp_sysfs_init(void)
2577{
2578 int cpu, ret;
2579
2580 ret = cpu_smt_sysfs_init();
2581 if (ret)
2582 return ret;
2583
2584 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2585 &cpuhp_cpu_root_attr_group);
2586 if (ret)
2587 return ret;
2588
2589 for_each_possible_cpu(cpu) {
2590 struct device *dev = get_cpu_device(cpu);
2591
2592 if (!dev)
2593 continue;
2594 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2595 if (ret)
2596 return ret;
2597 }
2598 return 0;
2599}
2600device_initcall(cpuhp_sysfs_init);
2601#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2602
2603/*
2604 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2605 * represents all NR_CPUS bits binary values of 1<<nr.
2606 *
2607 * It is used by cpumask_of() to get a constant address to a CPU
2608 * mask value that has a single bit set only.
2609 */
2610
2611/* cpu_bit_bitmap[0] is empty - so we can back into it */
2612#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2613#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2614#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2615#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2616
2617const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2618
2619 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2620 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2621#if BITS_PER_LONG > 32
2622 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2623 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2624#endif
2625};
2626EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2627
2628const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2629EXPORT_SYMBOL(cpu_all_bits);
2630
2631#ifdef CONFIG_INIT_ALL_POSSIBLE
2632struct cpumask __cpu_possible_mask __read_mostly
2633 = {CPU_BITS_ALL};
2634#else
2635struct cpumask __cpu_possible_mask __read_mostly;
2636#endif
2637EXPORT_SYMBOL(__cpu_possible_mask);
2638
2639struct cpumask __cpu_online_mask __read_mostly;
2640EXPORT_SYMBOL(__cpu_online_mask);
2641
2642struct cpumask __cpu_present_mask __read_mostly;
2643EXPORT_SYMBOL(__cpu_present_mask);
2644
2645struct cpumask __cpu_active_mask __read_mostly;
2646EXPORT_SYMBOL(__cpu_active_mask);
2647
2648struct cpumask __cpu_dying_mask __read_mostly;
2649EXPORT_SYMBOL(__cpu_dying_mask);
2650
2651atomic_t __num_online_cpus __read_mostly;
2652EXPORT_SYMBOL(__num_online_cpus);
2653
2654void init_cpu_present(const struct cpumask *src)
2655{
2656 cpumask_copy(&__cpu_present_mask, src);
2657}
2658
2659void init_cpu_possible(const struct cpumask *src)
2660{
2661 cpumask_copy(&__cpu_possible_mask, src);
2662}
2663
2664void init_cpu_online(const struct cpumask *src)
2665{
2666 cpumask_copy(&__cpu_online_mask, src);
2667}
2668
2669void set_cpu_online(unsigned int cpu, bool online)
2670{
2671 /*
2672 * atomic_inc/dec() is required to handle the horrid abuse of this
2673 * function by the reboot and kexec code which invoke it from
2674 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2675 * regular CPU hotplug is properly serialized.
2676 *
2677 * Note, that the fact that __num_online_cpus is of type atomic_t
2678 * does not protect readers which are not serialized against
2679 * concurrent hotplug operations.
2680 */
2681 if (online) {
2682 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2683 atomic_inc(&__num_online_cpus);
2684 } else {
2685 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2686 atomic_dec(&__num_online_cpus);
2687 }
2688}
2689
2690/*
2691 * Activate the first processor.
2692 */
2693void __init boot_cpu_init(void)
2694{
2695 int cpu = smp_processor_id();
2696
2697 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2698 set_cpu_online(cpu, true);
2699 set_cpu_active(cpu, true);
2700 set_cpu_present(cpu, true);
2701 set_cpu_possible(cpu, true);
2702
2703#ifdef CONFIG_SMP
2704 __boot_cpu_id = cpu;
2705#endif
2706}
2707
2708/*
2709 * Must be called _AFTER_ setting up the per_cpu areas
2710 */
2711void __init boot_cpu_hotplug_init(void)
2712{
2713#ifdef CONFIG_SMP
2714 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2715#endif
2716 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2717 this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
2718}
2719
2720/*
2721 * These are used for a global "mitigations=" cmdline option for toggling
2722 * optional CPU mitigations.
2723 */
2724enum cpu_mitigations {
2725 CPU_MITIGATIONS_OFF,
2726 CPU_MITIGATIONS_AUTO,
2727 CPU_MITIGATIONS_AUTO_NOSMT,
2728};
2729
2730static enum cpu_mitigations cpu_mitigations __ro_after_init =
2731 CPU_MITIGATIONS_AUTO;
2732
2733static int __init mitigations_parse_cmdline(char *arg)
2734{
2735 if (!strcmp(arg, "off"))
2736 cpu_mitigations = CPU_MITIGATIONS_OFF;
2737 else if (!strcmp(arg, "auto"))
2738 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2739 else if (!strcmp(arg, "auto,nosmt"))
2740 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2741 else
2742 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2743 arg);
2744
2745 return 0;
2746}
2747early_param("mitigations", mitigations_parse_cmdline);
2748
2749/* mitigations=off */
2750bool cpu_mitigations_off(void)
2751{
2752 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2753}
2754EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2755
2756/* mitigations=auto,nosmt */
2757bool cpu_mitigations_auto_nosmt(void)
2758{
2759 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2760}
2761EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);