Loading...
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
27#include <trace/events/power.h>
28#define CREATE_TRACE_POINTS
29#include <trace/events/cpuhp.h>
30
31#include "smpboot.h"
32
33/**
34 * cpuhp_cpu_state - Per cpu hotplug state storage
35 * @state: The current cpu state
36 * @target: The target state
37 * @thread: Pointer to the hotplug thread
38 * @should_run: Thread should execute
39 * @rollback: Perform a rollback
40 * @cb_stat: The state for a single callback (install/uninstall)
41 * @cb: Single callback function (install/uninstall)
42 * @result: Result of the operation
43 * @done: Signal completion to the issuer of the task
44 */
45struct cpuhp_cpu_state {
46 enum cpuhp_state state;
47 enum cpuhp_state target;
48#ifdef CONFIG_SMP
49 struct task_struct *thread;
50 bool should_run;
51 bool rollback;
52 enum cpuhp_state cb_state;
53 int (*cb)(unsigned int cpu);
54 int result;
55 struct completion done;
56#endif
57};
58
59static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
60
61/**
62 * cpuhp_step - Hotplug state machine step
63 * @name: Name of the step
64 * @startup: Startup function of the step
65 * @teardown: Teardown function of the step
66 * @skip_onerr: Do not invoke the functions on error rollback
67 * Will go away once the notifiers are gone
68 * @cant_stop: Bringup/teardown can't be stopped at this step
69 */
70struct cpuhp_step {
71 const char *name;
72 int (*startup)(unsigned int cpu);
73 int (*teardown)(unsigned int cpu);
74 bool skip_onerr;
75 bool cant_stop;
76};
77
78static DEFINE_MUTEX(cpuhp_state_mutex);
79static struct cpuhp_step cpuhp_bp_states[];
80static struct cpuhp_step cpuhp_ap_states[];
81
82/**
83 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
84 * @cpu: The cpu for which the callback should be invoked
85 * @step: The step in the state machine
86 * @cb: The callback function to invoke
87 *
88 * Called from cpu hotplug and from the state register machinery
89 */
90static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step,
91 int (*cb)(unsigned int))
92{
93 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
94 int ret = 0;
95
96 if (cb) {
97 trace_cpuhp_enter(cpu, st->target, step, cb);
98 ret = cb(cpu);
99 trace_cpuhp_exit(cpu, st->state, step, ret);
100 }
101 return ret;
102}
103
104#ifdef CONFIG_SMP
105/* Serializes the updates to cpu_online_mask, cpu_present_mask */
106static DEFINE_MUTEX(cpu_add_remove_lock);
107bool cpuhp_tasks_frozen;
108EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
109
110/*
111 * The following two APIs (cpu_maps_update_begin/done) must be used when
112 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
113 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
114 * hotplug callback (un)registration performed using __register_cpu_notifier()
115 * or __unregister_cpu_notifier().
116 */
117void cpu_maps_update_begin(void)
118{
119 mutex_lock(&cpu_add_remove_lock);
120}
121EXPORT_SYMBOL(cpu_notifier_register_begin);
122
123void cpu_maps_update_done(void)
124{
125 mutex_unlock(&cpu_add_remove_lock);
126}
127EXPORT_SYMBOL(cpu_notifier_register_done);
128
129static RAW_NOTIFIER_HEAD(cpu_chain);
130
131/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
132 * Should always be manipulated under cpu_add_remove_lock
133 */
134static int cpu_hotplug_disabled;
135
136#ifdef CONFIG_HOTPLUG_CPU
137
138static struct {
139 struct task_struct *active_writer;
140 /* wait queue to wake up the active_writer */
141 wait_queue_head_t wq;
142 /* verifies that no writer will get active while readers are active */
143 struct mutex lock;
144 /*
145 * Also blocks the new readers during
146 * an ongoing cpu hotplug operation.
147 */
148 atomic_t refcount;
149
150#ifdef CONFIG_DEBUG_LOCK_ALLOC
151 struct lockdep_map dep_map;
152#endif
153} cpu_hotplug = {
154 .active_writer = NULL,
155 .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
156 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
157#ifdef CONFIG_DEBUG_LOCK_ALLOC
158 .dep_map = {.name = "cpu_hotplug.lock" },
159#endif
160};
161
162/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
163#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
164#define cpuhp_lock_acquire_tryread() \
165 lock_map_acquire_tryread(&cpu_hotplug.dep_map)
166#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
167#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
168
169
170void get_online_cpus(void)
171{
172 might_sleep();
173 if (cpu_hotplug.active_writer == current)
174 return;
175 cpuhp_lock_acquire_read();
176 mutex_lock(&cpu_hotplug.lock);
177 atomic_inc(&cpu_hotplug.refcount);
178 mutex_unlock(&cpu_hotplug.lock);
179}
180EXPORT_SYMBOL_GPL(get_online_cpus);
181
182void put_online_cpus(void)
183{
184 int refcount;
185
186 if (cpu_hotplug.active_writer == current)
187 return;
188
189 refcount = atomic_dec_return(&cpu_hotplug.refcount);
190 if (WARN_ON(refcount < 0)) /* try to fix things up */
191 atomic_inc(&cpu_hotplug.refcount);
192
193 if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
194 wake_up(&cpu_hotplug.wq);
195
196 cpuhp_lock_release();
197
198}
199EXPORT_SYMBOL_GPL(put_online_cpus);
200
201/*
202 * This ensures that the hotplug operation can begin only when the
203 * refcount goes to zero.
204 *
205 * Note that during a cpu-hotplug operation, the new readers, if any,
206 * will be blocked by the cpu_hotplug.lock
207 *
208 * Since cpu_hotplug_begin() is always called after invoking
209 * cpu_maps_update_begin(), we can be sure that only one writer is active.
210 *
211 * Note that theoretically, there is a possibility of a livelock:
212 * - Refcount goes to zero, last reader wakes up the sleeping
213 * writer.
214 * - Last reader unlocks the cpu_hotplug.lock.
215 * - A new reader arrives at this moment, bumps up the refcount.
216 * - The writer acquires the cpu_hotplug.lock finds the refcount
217 * non zero and goes to sleep again.
218 *
219 * However, this is very difficult to achieve in practice since
220 * get_online_cpus() not an api which is called all that often.
221 *
222 */
223void cpu_hotplug_begin(void)
224{
225 DEFINE_WAIT(wait);
226
227 cpu_hotplug.active_writer = current;
228 cpuhp_lock_acquire();
229
230 for (;;) {
231 mutex_lock(&cpu_hotplug.lock);
232 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
233 if (likely(!atomic_read(&cpu_hotplug.refcount)))
234 break;
235 mutex_unlock(&cpu_hotplug.lock);
236 schedule();
237 }
238 finish_wait(&cpu_hotplug.wq, &wait);
239}
240
241void cpu_hotplug_done(void)
242{
243 cpu_hotplug.active_writer = NULL;
244 mutex_unlock(&cpu_hotplug.lock);
245 cpuhp_lock_release();
246}
247
248/*
249 * Wait for currently running CPU hotplug operations to complete (if any) and
250 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
251 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
252 * hotplug path before performing hotplug operations. So acquiring that lock
253 * guarantees mutual exclusion from any currently running hotplug operations.
254 */
255void cpu_hotplug_disable(void)
256{
257 cpu_maps_update_begin();
258 cpu_hotplug_disabled++;
259 cpu_maps_update_done();
260}
261EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
262
263void cpu_hotplug_enable(void)
264{
265 cpu_maps_update_begin();
266 WARN_ON(--cpu_hotplug_disabled < 0);
267 cpu_maps_update_done();
268}
269EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
270#endif /* CONFIG_HOTPLUG_CPU */
271
272/* Need to know about CPUs going up/down? */
273int register_cpu_notifier(struct notifier_block *nb)
274{
275 int ret;
276 cpu_maps_update_begin();
277 ret = raw_notifier_chain_register(&cpu_chain, nb);
278 cpu_maps_update_done();
279 return ret;
280}
281
282int __register_cpu_notifier(struct notifier_block *nb)
283{
284 return raw_notifier_chain_register(&cpu_chain, nb);
285}
286
287static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
288 int *nr_calls)
289{
290 unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
291 void *hcpu = (void *)(long)cpu;
292
293 int ret;
294
295 ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
296 nr_calls);
297
298 return notifier_to_errno(ret);
299}
300
301static int cpu_notify(unsigned long val, unsigned int cpu)
302{
303 return __cpu_notify(val, cpu, -1, NULL);
304}
305
306static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
307{
308 BUG_ON(cpu_notify(val, cpu));
309}
310
311/* Notifier wrappers for transitioning to state machine */
312static int notify_prepare(unsigned int cpu)
313{
314 int nr_calls = 0;
315 int ret;
316
317 ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
318 if (ret) {
319 nr_calls--;
320 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
321 __func__, cpu);
322 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
323 }
324 return ret;
325}
326
327static int notify_online(unsigned int cpu)
328{
329 cpu_notify(CPU_ONLINE, cpu);
330 return 0;
331}
332
333static int notify_starting(unsigned int cpu)
334{
335 cpu_notify(CPU_STARTING, cpu);
336 return 0;
337}
338
339static int bringup_wait_for_ap(unsigned int cpu)
340{
341 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
342
343 wait_for_completion(&st->done);
344 return st->result;
345}
346
347static int bringup_cpu(unsigned int cpu)
348{
349 struct task_struct *idle = idle_thread_get(cpu);
350 int ret;
351
352 /* Arch-specific enabling code. */
353 ret = __cpu_up(cpu, idle);
354 if (ret) {
355 cpu_notify(CPU_UP_CANCELED, cpu);
356 return ret;
357 }
358 ret = bringup_wait_for_ap(cpu);
359 BUG_ON(!cpu_online(cpu));
360 return ret;
361}
362
363/*
364 * Hotplug state machine related functions
365 */
366static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st,
367 struct cpuhp_step *steps)
368{
369 for (st->state++; st->state < st->target; st->state++) {
370 struct cpuhp_step *step = steps + st->state;
371
372 if (!step->skip_onerr)
373 cpuhp_invoke_callback(cpu, st->state, step->startup);
374 }
375}
376
377static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
378 struct cpuhp_step *steps, enum cpuhp_state target)
379{
380 enum cpuhp_state prev_state = st->state;
381 int ret = 0;
382
383 for (; st->state > target; st->state--) {
384 struct cpuhp_step *step = steps + st->state;
385
386 ret = cpuhp_invoke_callback(cpu, st->state, step->teardown);
387 if (ret) {
388 st->target = prev_state;
389 undo_cpu_down(cpu, st, steps);
390 break;
391 }
392 }
393 return ret;
394}
395
396static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st,
397 struct cpuhp_step *steps)
398{
399 for (st->state--; st->state > st->target; st->state--) {
400 struct cpuhp_step *step = steps + st->state;
401
402 if (!step->skip_onerr)
403 cpuhp_invoke_callback(cpu, st->state, step->teardown);
404 }
405}
406
407static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
408 struct cpuhp_step *steps, enum cpuhp_state target)
409{
410 enum cpuhp_state prev_state = st->state;
411 int ret = 0;
412
413 while (st->state < target) {
414 struct cpuhp_step *step;
415
416 st->state++;
417 step = steps + st->state;
418 ret = cpuhp_invoke_callback(cpu, st->state, step->startup);
419 if (ret) {
420 st->target = prev_state;
421 undo_cpu_up(cpu, st, steps);
422 break;
423 }
424 }
425 return ret;
426}
427
428/*
429 * The cpu hotplug threads manage the bringup and teardown of the cpus
430 */
431static void cpuhp_create(unsigned int cpu)
432{
433 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
434
435 init_completion(&st->done);
436}
437
438static int cpuhp_should_run(unsigned int cpu)
439{
440 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
441
442 return st->should_run;
443}
444
445/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
446static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
447{
448 enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
449
450 return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
451}
452
453/* Execute the online startup callbacks. Used to be CPU_ONLINE */
454static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
455{
456 return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);
457}
458
459/*
460 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
461 * callbacks when a state gets [un]installed at runtime.
462 */
463static void cpuhp_thread_fun(unsigned int cpu)
464{
465 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
466 int ret = 0;
467
468 /*
469 * Paired with the mb() in cpuhp_kick_ap_work and
470 * cpuhp_invoke_ap_callback, so the work set is consistent visible.
471 */
472 smp_mb();
473 if (!st->should_run)
474 return;
475
476 st->should_run = false;
477
478 /* Single callback invocation for [un]install ? */
479 if (st->cb) {
480 if (st->cb_state < CPUHP_AP_ONLINE) {
481 local_irq_disable();
482 ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
483 local_irq_enable();
484 } else {
485 ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
486 }
487 } else if (st->rollback) {
488 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
489
490 undo_cpu_down(cpu, st, cpuhp_ap_states);
491 /*
492 * This is a momentary workaround to keep the notifier users
493 * happy. Will go away once we got rid of the notifiers.
494 */
495 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
496 st->rollback = false;
497 } else {
498 /* Cannot happen .... */
499 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
500
501 /* Regular hotplug work */
502 if (st->state < st->target)
503 ret = cpuhp_ap_online(cpu, st);
504 else if (st->state > st->target)
505 ret = cpuhp_ap_offline(cpu, st);
506 }
507 st->result = ret;
508 complete(&st->done);
509}
510
511/* Invoke a single callback on a remote cpu */
512static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
513 int (*cb)(unsigned int))
514{
515 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
516
517 if (!cpu_online(cpu))
518 return 0;
519
520 st->cb_state = state;
521 st->cb = cb;
522 /*
523 * Make sure the above stores are visible before should_run becomes
524 * true. Paired with the mb() above in cpuhp_thread_fun()
525 */
526 smp_mb();
527 st->should_run = true;
528 wake_up_process(st->thread);
529 wait_for_completion(&st->done);
530 return st->result;
531}
532
533/* Regular hotplug invocation of the AP hotplug thread */
534static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
535{
536 st->result = 0;
537 st->cb = NULL;
538 /*
539 * Make sure the above stores are visible before should_run becomes
540 * true. Paired with the mb() above in cpuhp_thread_fun()
541 */
542 smp_mb();
543 st->should_run = true;
544 wake_up_process(st->thread);
545}
546
547static int cpuhp_kick_ap_work(unsigned int cpu)
548{
549 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
550 enum cpuhp_state state = st->state;
551
552 trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
553 __cpuhp_kick_ap_work(st);
554 wait_for_completion(&st->done);
555 trace_cpuhp_exit(cpu, st->state, state, st->result);
556 return st->result;
557}
558
559static struct smp_hotplug_thread cpuhp_threads = {
560 .store = &cpuhp_state.thread,
561 .create = &cpuhp_create,
562 .thread_should_run = cpuhp_should_run,
563 .thread_fn = cpuhp_thread_fun,
564 .thread_comm = "cpuhp/%u",
565 .selfparking = true,
566};
567
568void __init cpuhp_threads_init(void)
569{
570 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
571 kthread_unpark(this_cpu_read(cpuhp_state.thread));
572}
573
574#ifdef CONFIG_HOTPLUG_CPU
575EXPORT_SYMBOL(register_cpu_notifier);
576EXPORT_SYMBOL(__register_cpu_notifier);
577void unregister_cpu_notifier(struct notifier_block *nb)
578{
579 cpu_maps_update_begin();
580 raw_notifier_chain_unregister(&cpu_chain, nb);
581 cpu_maps_update_done();
582}
583EXPORT_SYMBOL(unregister_cpu_notifier);
584
585void __unregister_cpu_notifier(struct notifier_block *nb)
586{
587 raw_notifier_chain_unregister(&cpu_chain, nb);
588}
589EXPORT_SYMBOL(__unregister_cpu_notifier);
590
591/**
592 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
593 * @cpu: a CPU id
594 *
595 * This function walks all processes, finds a valid mm struct for each one and
596 * then clears a corresponding bit in mm's cpumask. While this all sounds
597 * trivial, there are various non-obvious corner cases, which this function
598 * tries to solve in a safe manner.
599 *
600 * Also note that the function uses a somewhat relaxed locking scheme, so it may
601 * be called only for an already offlined CPU.
602 */
603void clear_tasks_mm_cpumask(int cpu)
604{
605 struct task_struct *p;
606
607 /*
608 * This function is called after the cpu is taken down and marked
609 * offline, so its not like new tasks will ever get this cpu set in
610 * their mm mask. -- Peter Zijlstra
611 * Thus, we may use rcu_read_lock() here, instead of grabbing
612 * full-fledged tasklist_lock.
613 */
614 WARN_ON(cpu_online(cpu));
615 rcu_read_lock();
616 for_each_process(p) {
617 struct task_struct *t;
618
619 /*
620 * Main thread might exit, but other threads may still have
621 * a valid mm. Find one.
622 */
623 t = find_lock_task_mm(p);
624 if (!t)
625 continue;
626 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
627 task_unlock(t);
628 }
629 rcu_read_unlock();
630}
631
632static inline void check_for_tasks(int dead_cpu)
633{
634 struct task_struct *g, *p;
635
636 read_lock(&tasklist_lock);
637 for_each_process_thread(g, p) {
638 if (!p->on_rq)
639 continue;
640 /*
641 * We do the check with unlocked task_rq(p)->lock.
642 * Order the reading to do not warn about a task,
643 * which was running on this cpu in the past, and
644 * it's just been woken on another cpu.
645 */
646 rmb();
647 if (task_cpu(p) != dead_cpu)
648 continue;
649
650 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
651 p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
652 }
653 read_unlock(&tasklist_lock);
654}
655
656static int notify_down_prepare(unsigned int cpu)
657{
658 int err, nr_calls = 0;
659
660 err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
661 if (err) {
662 nr_calls--;
663 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
664 pr_warn("%s: attempt to take down CPU %u failed\n",
665 __func__, cpu);
666 }
667 return err;
668}
669
670static int notify_dying(unsigned int cpu)
671{
672 cpu_notify(CPU_DYING, cpu);
673 return 0;
674}
675
676/* Take this CPU down. */
677static int take_cpu_down(void *_param)
678{
679 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
680 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
681 int err, cpu = smp_processor_id();
682
683 /* Ensure this CPU doesn't handle any more interrupts. */
684 err = __cpu_disable();
685 if (err < 0)
686 return err;
687
688 /* Invoke the former CPU_DYING callbacks */
689 for (; st->state > target; st->state--) {
690 struct cpuhp_step *step = cpuhp_ap_states + st->state;
691
692 cpuhp_invoke_callback(cpu, st->state, step->teardown);
693 }
694 /* Give up timekeeping duties */
695 tick_handover_do_timer();
696 /* Park the stopper thread */
697 stop_machine_park(cpu);
698 return 0;
699}
700
701static int takedown_cpu(unsigned int cpu)
702{
703 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
704 int err;
705
706 /*
707 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
708 * and RCU users of this state to go away such that all new such users
709 * will observe it.
710 *
711 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
712 * not imply sync_sched(), so wait for both.
713 *
714 * Do sync before park smpboot threads to take care the rcu boost case.
715 */
716 if (IS_ENABLED(CONFIG_PREEMPT))
717 synchronize_rcu_mult(call_rcu, call_rcu_sched);
718 else
719 synchronize_rcu();
720
721 /* Park the smpboot threads */
722 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
723 smpboot_park_threads(cpu);
724
725 /*
726 * Prevent irq alloc/free while the dying cpu reorganizes the
727 * interrupt affinities.
728 */
729 irq_lock_sparse();
730
731 /*
732 * So now all preempt/rcu users must observe !cpu_active().
733 */
734 err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
735 if (err) {
736 /* CPU refused to die */
737 irq_unlock_sparse();
738 /* Unpark the hotplug thread so we can rollback there */
739 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
740 return err;
741 }
742 BUG_ON(cpu_online(cpu));
743
744 /*
745 * The migration_call() CPU_DYING callback will have removed all
746 * runnable tasks from the cpu, there's only the idle task left now
747 * that the migration thread is done doing the stop_machine thing.
748 *
749 * Wait for the stop thread to go away.
750 */
751 wait_for_completion(&st->done);
752 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
753
754 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
755 irq_unlock_sparse();
756
757 hotplug_cpu__broadcast_tick_pull(cpu);
758 /* This actually kills the CPU. */
759 __cpu_die(cpu);
760
761 tick_cleanup_dead_cpu(cpu);
762 return 0;
763}
764
765static int notify_dead(unsigned int cpu)
766{
767 cpu_notify_nofail(CPU_DEAD, cpu);
768 check_for_tasks(cpu);
769 return 0;
770}
771
772static void cpuhp_complete_idle_dead(void *arg)
773{
774 struct cpuhp_cpu_state *st = arg;
775
776 complete(&st->done);
777}
778
779void cpuhp_report_idle_dead(void)
780{
781 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
782
783 BUG_ON(st->state != CPUHP_AP_OFFLINE);
784 rcu_report_dead(smp_processor_id());
785 st->state = CPUHP_AP_IDLE_DEAD;
786 /*
787 * We cannot call complete after rcu_report_dead() so we delegate it
788 * to an online cpu.
789 */
790 smp_call_function_single(cpumask_first(cpu_online_mask),
791 cpuhp_complete_idle_dead, st, 0);
792}
793
794#else
795#define notify_down_prepare NULL
796#define takedown_cpu NULL
797#define notify_dead NULL
798#define notify_dying NULL
799#endif
800
801#ifdef CONFIG_HOTPLUG_CPU
802
803/* Requires cpu_add_remove_lock to be held */
804static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
805 enum cpuhp_state target)
806{
807 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
808 int prev_state, ret = 0;
809 bool hasdied = false;
810
811 if (num_online_cpus() == 1)
812 return -EBUSY;
813
814 if (!cpu_present(cpu))
815 return -EINVAL;
816
817 cpu_hotplug_begin();
818
819 cpuhp_tasks_frozen = tasks_frozen;
820
821 prev_state = st->state;
822 st->target = target;
823 /*
824 * If the current CPU state is in the range of the AP hotplug thread,
825 * then we need to kick the thread.
826 */
827 if (st->state > CPUHP_TEARDOWN_CPU) {
828 ret = cpuhp_kick_ap_work(cpu);
829 /*
830 * The AP side has done the error rollback already. Just
831 * return the error code..
832 */
833 if (ret)
834 goto out;
835
836 /*
837 * We might have stopped still in the range of the AP hotplug
838 * thread. Nothing to do anymore.
839 */
840 if (st->state > CPUHP_TEARDOWN_CPU)
841 goto out;
842 }
843 /*
844 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
845 * to do the further cleanups.
846 */
847 ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);
848 if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
849 st->target = prev_state;
850 st->rollback = true;
851 cpuhp_kick_ap_work(cpu);
852 }
853
854 hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
855out:
856 cpu_hotplug_done();
857 /* This post dead nonsense must die */
858 if (!ret && hasdied)
859 cpu_notify_nofail(CPU_POST_DEAD, cpu);
860 return ret;
861}
862
863static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
864{
865 int err;
866
867 cpu_maps_update_begin();
868
869 if (cpu_hotplug_disabled) {
870 err = -EBUSY;
871 goto out;
872 }
873
874 err = _cpu_down(cpu, 0, target);
875
876out:
877 cpu_maps_update_done();
878 return err;
879}
880int cpu_down(unsigned int cpu)
881{
882 return do_cpu_down(cpu, CPUHP_OFFLINE);
883}
884EXPORT_SYMBOL(cpu_down);
885#endif /*CONFIG_HOTPLUG_CPU*/
886
887/**
888 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
889 * @cpu: cpu that just started
890 *
891 * This function calls the cpu_chain notifiers with CPU_STARTING.
892 * It must be called by the arch code on the new cpu, before the new cpu
893 * enables interrupts and before the "boot" cpu returns from __cpu_up().
894 */
895void notify_cpu_starting(unsigned int cpu)
896{
897 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
898 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
899
900 while (st->state < target) {
901 struct cpuhp_step *step;
902
903 st->state++;
904 step = cpuhp_ap_states + st->state;
905 cpuhp_invoke_callback(cpu, st->state, step->startup);
906 }
907}
908
909/*
910 * Called from the idle task. We need to set active here, so we can kick off
911 * the stopper thread and unpark the smpboot threads. If the target state is
912 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
913 * cpu further.
914 */
915void cpuhp_online_idle(enum cpuhp_state state)
916{
917 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
918 unsigned int cpu = smp_processor_id();
919
920 /* Happens for the boot cpu */
921 if (state != CPUHP_AP_ONLINE_IDLE)
922 return;
923
924 st->state = CPUHP_AP_ONLINE_IDLE;
925
926 /* The cpu is marked online, set it active now */
927 set_cpu_active(cpu, true);
928 /* Unpark the stopper thread and the hotplug thread of this cpu */
929 stop_machine_unpark(cpu);
930 kthread_unpark(st->thread);
931
932 /* Should we go further up ? */
933 if (st->target > CPUHP_AP_ONLINE_IDLE)
934 __cpuhp_kick_ap_work(st);
935 else
936 complete(&st->done);
937}
938
939/* Requires cpu_add_remove_lock to be held */
940static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
941{
942 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
943 struct task_struct *idle;
944 int ret = 0;
945
946 cpu_hotplug_begin();
947
948 if (!cpu_present(cpu)) {
949 ret = -EINVAL;
950 goto out;
951 }
952
953 /*
954 * The caller of do_cpu_up might have raced with another
955 * caller. Ignore it for now.
956 */
957 if (st->state >= target)
958 goto out;
959
960 if (st->state == CPUHP_OFFLINE) {
961 /* Let it fail before we try to bring the cpu up */
962 idle = idle_thread_get(cpu);
963 if (IS_ERR(idle)) {
964 ret = PTR_ERR(idle);
965 goto out;
966 }
967 }
968
969 cpuhp_tasks_frozen = tasks_frozen;
970
971 st->target = target;
972 /*
973 * If the current CPU state is in the range of the AP hotplug thread,
974 * then we need to kick the thread once more.
975 */
976 if (st->state > CPUHP_BRINGUP_CPU) {
977 ret = cpuhp_kick_ap_work(cpu);
978 /*
979 * The AP side has done the error rollback already. Just
980 * return the error code..
981 */
982 if (ret)
983 goto out;
984 }
985
986 /*
987 * Try to reach the target state. We max out on the BP at
988 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
989 * responsible for bringing it up to the target state.
990 */
991 target = min((int)target, CPUHP_BRINGUP_CPU);
992 ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
993out:
994 cpu_hotplug_done();
995 return ret;
996}
997
998static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
999{
1000 int err = 0;
1001
1002 if (!cpu_possible(cpu)) {
1003 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1004 cpu);
1005#if defined(CONFIG_IA64)
1006 pr_err("please check additional_cpus= boot parameter\n");
1007#endif
1008 return -EINVAL;
1009 }
1010
1011 err = try_online_node(cpu_to_node(cpu));
1012 if (err)
1013 return err;
1014
1015 cpu_maps_update_begin();
1016
1017 if (cpu_hotplug_disabled) {
1018 err = -EBUSY;
1019 goto out;
1020 }
1021
1022 err = _cpu_up(cpu, 0, target);
1023out:
1024 cpu_maps_update_done();
1025 return err;
1026}
1027
1028int cpu_up(unsigned int cpu)
1029{
1030 return do_cpu_up(cpu, CPUHP_ONLINE);
1031}
1032EXPORT_SYMBOL_GPL(cpu_up);
1033
1034#ifdef CONFIG_PM_SLEEP_SMP
1035static cpumask_var_t frozen_cpus;
1036
1037int disable_nonboot_cpus(void)
1038{
1039 int cpu, first_cpu, error = 0;
1040
1041 cpu_maps_update_begin();
1042 first_cpu = cpumask_first(cpu_online_mask);
1043 /*
1044 * We take down all of the non-boot CPUs in one shot to avoid races
1045 * with the userspace trying to use the CPU hotplug at the same time
1046 */
1047 cpumask_clear(frozen_cpus);
1048
1049 pr_info("Disabling non-boot CPUs ...\n");
1050 for_each_online_cpu(cpu) {
1051 if (cpu == first_cpu)
1052 continue;
1053 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1054 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1055 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1056 if (!error)
1057 cpumask_set_cpu(cpu, frozen_cpus);
1058 else {
1059 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1060 break;
1061 }
1062 }
1063
1064 if (!error)
1065 BUG_ON(num_online_cpus() > 1);
1066 else
1067 pr_err("Non-boot CPUs are not disabled\n");
1068
1069 /*
1070 * Make sure the CPUs won't be enabled by someone else. We need to do
1071 * this even in case of failure as all disable_nonboot_cpus() users are
1072 * supposed to do enable_nonboot_cpus() on the failure path.
1073 */
1074 cpu_hotplug_disabled++;
1075
1076 cpu_maps_update_done();
1077 return error;
1078}
1079
1080void __weak arch_enable_nonboot_cpus_begin(void)
1081{
1082}
1083
1084void __weak arch_enable_nonboot_cpus_end(void)
1085{
1086}
1087
1088void enable_nonboot_cpus(void)
1089{
1090 int cpu, error;
1091
1092 /* Allow everyone to use the CPU hotplug again */
1093 cpu_maps_update_begin();
1094 WARN_ON(--cpu_hotplug_disabled < 0);
1095 if (cpumask_empty(frozen_cpus))
1096 goto out;
1097
1098 pr_info("Enabling non-boot CPUs ...\n");
1099
1100 arch_enable_nonboot_cpus_begin();
1101
1102 for_each_cpu(cpu, frozen_cpus) {
1103 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1104 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1105 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1106 if (!error) {
1107 pr_info("CPU%d is up\n", cpu);
1108 continue;
1109 }
1110 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1111 }
1112
1113 arch_enable_nonboot_cpus_end();
1114
1115 cpumask_clear(frozen_cpus);
1116out:
1117 cpu_maps_update_done();
1118}
1119
1120static int __init alloc_frozen_cpus(void)
1121{
1122 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1123 return -ENOMEM;
1124 return 0;
1125}
1126core_initcall(alloc_frozen_cpus);
1127
1128/*
1129 * When callbacks for CPU hotplug notifications are being executed, we must
1130 * ensure that the state of the system with respect to the tasks being frozen
1131 * or not, as reported by the notification, remains unchanged *throughout the
1132 * duration* of the execution of the callbacks.
1133 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1134 *
1135 * This synchronization is implemented by mutually excluding regular CPU
1136 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1137 * Hibernate notifications.
1138 */
1139static int
1140cpu_hotplug_pm_callback(struct notifier_block *nb,
1141 unsigned long action, void *ptr)
1142{
1143 switch (action) {
1144
1145 case PM_SUSPEND_PREPARE:
1146 case PM_HIBERNATION_PREPARE:
1147 cpu_hotplug_disable();
1148 break;
1149
1150 case PM_POST_SUSPEND:
1151 case PM_POST_HIBERNATION:
1152 cpu_hotplug_enable();
1153 break;
1154
1155 default:
1156 return NOTIFY_DONE;
1157 }
1158
1159 return NOTIFY_OK;
1160}
1161
1162
1163static int __init cpu_hotplug_pm_sync_init(void)
1164{
1165 /*
1166 * cpu_hotplug_pm_callback has higher priority than x86
1167 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1168 * to disable cpu hotplug to avoid cpu hotplug race.
1169 */
1170 pm_notifier(cpu_hotplug_pm_callback, 0);
1171 return 0;
1172}
1173core_initcall(cpu_hotplug_pm_sync_init);
1174
1175#endif /* CONFIG_PM_SLEEP_SMP */
1176
1177#endif /* CONFIG_SMP */
1178
1179/* Boot processor state steps */
1180static struct cpuhp_step cpuhp_bp_states[] = {
1181 [CPUHP_OFFLINE] = {
1182 .name = "offline",
1183 .startup = NULL,
1184 .teardown = NULL,
1185 },
1186#ifdef CONFIG_SMP
1187 [CPUHP_CREATE_THREADS]= {
1188 .name = "threads:create",
1189 .startup = smpboot_create_threads,
1190 .teardown = NULL,
1191 .cant_stop = true,
1192 },
1193 /*
1194 * Preparatory and dead notifiers. Will be replaced once the notifiers
1195 * are converted to states.
1196 */
1197 [CPUHP_NOTIFY_PREPARE] = {
1198 .name = "notify:prepare",
1199 .startup = notify_prepare,
1200 .teardown = notify_dead,
1201 .skip_onerr = true,
1202 .cant_stop = true,
1203 },
1204 /* Kicks the plugged cpu into life */
1205 [CPUHP_BRINGUP_CPU] = {
1206 .name = "cpu:bringup",
1207 .startup = bringup_cpu,
1208 .teardown = NULL,
1209 .cant_stop = true,
1210 },
1211 /*
1212 * Handled on controll processor until the plugged processor manages
1213 * this itself.
1214 */
1215 [CPUHP_TEARDOWN_CPU] = {
1216 .name = "cpu:teardown",
1217 .startup = NULL,
1218 .teardown = takedown_cpu,
1219 .cant_stop = true,
1220 },
1221#endif
1222};
1223
1224/* Application processor state steps */
1225static struct cpuhp_step cpuhp_ap_states[] = {
1226#ifdef CONFIG_SMP
1227 /* Final state before CPU kills itself */
1228 [CPUHP_AP_IDLE_DEAD] = {
1229 .name = "idle:dead",
1230 },
1231 /*
1232 * Last state before CPU enters the idle loop to die. Transient state
1233 * for synchronization.
1234 */
1235 [CPUHP_AP_OFFLINE] = {
1236 .name = "ap:offline",
1237 .cant_stop = true,
1238 },
1239 /*
1240 * Low level startup/teardown notifiers. Run with interrupts
1241 * disabled. Will be removed once the notifiers are converted to
1242 * states.
1243 */
1244 [CPUHP_AP_NOTIFY_STARTING] = {
1245 .name = "notify:starting",
1246 .startup = notify_starting,
1247 .teardown = notify_dying,
1248 .skip_onerr = true,
1249 .cant_stop = true,
1250 },
1251 /* Entry state on starting. Interrupts enabled from here on. Transient
1252 * state for synchronsization */
1253 [CPUHP_AP_ONLINE] = {
1254 .name = "ap:online",
1255 },
1256 /* Handle smpboot threads park/unpark */
1257 [CPUHP_AP_SMPBOOT_THREADS] = {
1258 .name = "smpboot:threads",
1259 .startup = smpboot_unpark_threads,
1260 .teardown = NULL,
1261 },
1262 /*
1263 * Online/down_prepare notifiers. Will be removed once the notifiers
1264 * are converted to states.
1265 */
1266 [CPUHP_AP_NOTIFY_ONLINE] = {
1267 .name = "notify:online",
1268 .startup = notify_online,
1269 .teardown = notify_down_prepare,
1270 .skip_onerr = true,
1271 },
1272#endif
1273 /*
1274 * The dynamically registered state space is here
1275 */
1276
1277 /* CPU is fully up and running. */
1278 [CPUHP_ONLINE] = {
1279 .name = "online",
1280 .startup = NULL,
1281 .teardown = NULL,
1282 },
1283};
1284
1285/* Sanity check for callbacks */
1286static int cpuhp_cb_check(enum cpuhp_state state)
1287{
1288 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1289 return -EINVAL;
1290 return 0;
1291}
1292
1293static bool cpuhp_is_ap_state(enum cpuhp_state state)
1294{
1295 /*
1296 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
1297 * purposes as that state is handled explicitely in cpu_down.
1298 */
1299 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
1300}
1301
1302static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
1303{
1304 struct cpuhp_step *sp;
1305
1306 sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
1307 return sp + state;
1308}
1309
1310static void cpuhp_store_callbacks(enum cpuhp_state state,
1311 const char *name,
1312 int (*startup)(unsigned int cpu),
1313 int (*teardown)(unsigned int cpu))
1314{
1315 /* (Un)Install the callbacks for further cpu hotplug operations */
1316 struct cpuhp_step *sp;
1317
1318 mutex_lock(&cpuhp_state_mutex);
1319 sp = cpuhp_get_step(state);
1320 sp->startup = startup;
1321 sp->teardown = teardown;
1322 sp->name = name;
1323 mutex_unlock(&cpuhp_state_mutex);
1324}
1325
1326static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1327{
1328 return cpuhp_get_step(state)->teardown;
1329}
1330
1331/*
1332 * Call the startup/teardown function for a step either on the AP or
1333 * on the current CPU.
1334 */
1335static int cpuhp_issue_call(int cpu, enum cpuhp_state state,
1336 int (*cb)(unsigned int), bool bringup)
1337{
1338 int ret;
1339
1340 if (!cb)
1341 return 0;
1342 /*
1343 * The non AP bound callbacks can fail on bringup. On teardown
1344 * e.g. module removal we crash for now.
1345 */
1346#ifdef CONFIG_SMP
1347 if (cpuhp_is_ap_state(state))
1348 ret = cpuhp_invoke_ap_callback(cpu, state, cb);
1349 else
1350 ret = cpuhp_invoke_callback(cpu, state, cb);
1351#else
1352 ret = cpuhp_invoke_callback(cpu, state, cb);
1353#endif
1354 BUG_ON(ret && !bringup);
1355 return ret;
1356}
1357
1358/*
1359 * Called from __cpuhp_setup_state on a recoverable failure.
1360 *
1361 * Note: The teardown callbacks for rollback are not allowed to fail!
1362 */
1363static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1364 int (*teardown)(unsigned int cpu))
1365{
1366 int cpu;
1367
1368 if (!teardown)
1369 return;
1370
1371 /* Roll back the already executed steps on the other cpus */
1372 for_each_present_cpu(cpu) {
1373 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1374 int cpustate = st->state;
1375
1376 if (cpu >= failedcpu)
1377 break;
1378
1379 /* Did we invoke the startup call on that cpu ? */
1380 if (cpustate >= state)
1381 cpuhp_issue_call(cpu, state, teardown, false);
1382 }
1383}
1384
1385/*
1386 * Returns a free for dynamic slot assignment of the Online state. The states
1387 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1388 * by having no name assigned.
1389 */
1390static int cpuhp_reserve_state(enum cpuhp_state state)
1391{
1392 enum cpuhp_state i;
1393
1394 mutex_lock(&cpuhp_state_mutex);
1395 for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1396 if (cpuhp_ap_states[i].name)
1397 continue;
1398
1399 cpuhp_ap_states[i].name = "Reserved";
1400 mutex_unlock(&cpuhp_state_mutex);
1401 return i;
1402 }
1403 mutex_unlock(&cpuhp_state_mutex);
1404 WARN(1, "No more dynamic states available for CPU hotplug\n");
1405 return -ENOSPC;
1406}
1407
1408/**
1409 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1410 * @state: The state to setup
1411 * @invoke: If true, the startup function is invoked for cpus where
1412 * cpu state >= @state
1413 * @startup: startup callback function
1414 * @teardown: teardown callback function
1415 *
1416 * Returns 0 if successful, otherwise a proper error code
1417 */
1418int __cpuhp_setup_state(enum cpuhp_state state,
1419 const char *name, bool invoke,
1420 int (*startup)(unsigned int cpu),
1421 int (*teardown)(unsigned int cpu))
1422{
1423 int cpu, ret = 0;
1424 int dyn_state = 0;
1425
1426 if (cpuhp_cb_check(state) || !name)
1427 return -EINVAL;
1428
1429 get_online_cpus();
1430
1431 /* currently assignments for the ONLINE state are possible */
1432 if (state == CPUHP_AP_ONLINE_DYN) {
1433 dyn_state = 1;
1434 ret = cpuhp_reserve_state(state);
1435 if (ret < 0)
1436 goto out;
1437 state = ret;
1438 }
1439
1440 cpuhp_store_callbacks(state, name, startup, teardown);
1441
1442 if (!invoke || !startup)
1443 goto out;
1444
1445 /*
1446 * Try to call the startup callback for each present cpu
1447 * depending on the hotplug state of the cpu.
1448 */
1449 for_each_present_cpu(cpu) {
1450 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1451 int cpustate = st->state;
1452
1453 if (cpustate < state)
1454 continue;
1455
1456 ret = cpuhp_issue_call(cpu, state, startup, true);
1457 if (ret) {
1458 cpuhp_rollback_install(cpu, state, teardown);
1459 cpuhp_store_callbacks(state, NULL, NULL, NULL);
1460 goto out;
1461 }
1462 }
1463out:
1464 put_online_cpus();
1465 if (!ret && dyn_state)
1466 return state;
1467 return ret;
1468}
1469EXPORT_SYMBOL(__cpuhp_setup_state);
1470
1471/**
1472 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1473 * @state: The state to remove
1474 * @invoke: If true, the teardown function is invoked for cpus where
1475 * cpu state >= @state
1476 *
1477 * The teardown callback is currently not allowed to fail. Think
1478 * about module removal!
1479 */
1480void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1481{
1482 int (*teardown)(unsigned int cpu) = cpuhp_get_teardown_cb(state);
1483 int cpu;
1484
1485 BUG_ON(cpuhp_cb_check(state));
1486
1487 get_online_cpus();
1488
1489 if (!invoke || !teardown)
1490 goto remove;
1491
1492 /*
1493 * Call the teardown callback for each present cpu depending
1494 * on the hotplug state of the cpu. This function is not
1495 * allowed to fail currently!
1496 */
1497 for_each_present_cpu(cpu) {
1498 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1499 int cpustate = st->state;
1500
1501 if (cpustate >= state)
1502 cpuhp_issue_call(cpu, state, teardown, false);
1503 }
1504remove:
1505 cpuhp_store_callbacks(state, NULL, NULL, NULL);
1506 put_online_cpus();
1507}
1508EXPORT_SYMBOL(__cpuhp_remove_state);
1509
1510#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1511static ssize_t show_cpuhp_state(struct device *dev,
1512 struct device_attribute *attr, char *buf)
1513{
1514 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1515
1516 return sprintf(buf, "%d\n", st->state);
1517}
1518static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1519
1520static ssize_t write_cpuhp_target(struct device *dev,
1521 struct device_attribute *attr,
1522 const char *buf, size_t count)
1523{
1524 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1525 struct cpuhp_step *sp;
1526 int target, ret;
1527
1528 ret = kstrtoint(buf, 10, &target);
1529 if (ret)
1530 return ret;
1531
1532#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1533 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1534 return -EINVAL;
1535#else
1536 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1537 return -EINVAL;
1538#endif
1539
1540 ret = lock_device_hotplug_sysfs();
1541 if (ret)
1542 return ret;
1543
1544 mutex_lock(&cpuhp_state_mutex);
1545 sp = cpuhp_get_step(target);
1546 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1547 mutex_unlock(&cpuhp_state_mutex);
1548 if (ret)
1549 return ret;
1550
1551 if (st->state < target)
1552 ret = do_cpu_up(dev->id, target);
1553 else
1554 ret = do_cpu_down(dev->id, target);
1555
1556 unlock_device_hotplug();
1557 return ret ? ret : count;
1558}
1559
1560static ssize_t show_cpuhp_target(struct device *dev,
1561 struct device_attribute *attr, char *buf)
1562{
1563 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1564
1565 return sprintf(buf, "%d\n", st->target);
1566}
1567static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1568
1569static struct attribute *cpuhp_cpu_attrs[] = {
1570 &dev_attr_state.attr,
1571 &dev_attr_target.attr,
1572 NULL
1573};
1574
1575static struct attribute_group cpuhp_cpu_attr_group = {
1576 .attrs = cpuhp_cpu_attrs,
1577 .name = "hotplug",
1578 NULL
1579};
1580
1581static ssize_t show_cpuhp_states(struct device *dev,
1582 struct device_attribute *attr, char *buf)
1583{
1584 ssize_t cur, res = 0;
1585 int i;
1586
1587 mutex_lock(&cpuhp_state_mutex);
1588 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1589 struct cpuhp_step *sp = cpuhp_get_step(i);
1590
1591 if (sp->name) {
1592 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1593 buf += cur;
1594 res += cur;
1595 }
1596 }
1597 mutex_unlock(&cpuhp_state_mutex);
1598 return res;
1599}
1600static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1601
1602static struct attribute *cpuhp_cpu_root_attrs[] = {
1603 &dev_attr_states.attr,
1604 NULL
1605};
1606
1607static struct attribute_group cpuhp_cpu_root_attr_group = {
1608 .attrs = cpuhp_cpu_root_attrs,
1609 .name = "hotplug",
1610 NULL
1611};
1612
1613static int __init cpuhp_sysfs_init(void)
1614{
1615 int cpu, ret;
1616
1617 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1618 &cpuhp_cpu_root_attr_group);
1619 if (ret)
1620 return ret;
1621
1622 for_each_possible_cpu(cpu) {
1623 struct device *dev = get_cpu_device(cpu);
1624
1625 if (!dev)
1626 continue;
1627 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1628 if (ret)
1629 return ret;
1630 }
1631 return 0;
1632}
1633device_initcall(cpuhp_sysfs_init);
1634#endif
1635
1636/*
1637 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1638 * represents all NR_CPUS bits binary values of 1<<nr.
1639 *
1640 * It is used by cpumask_of() to get a constant address to a CPU
1641 * mask value that has a single bit set only.
1642 */
1643
1644/* cpu_bit_bitmap[0] is empty - so we can back into it */
1645#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
1646#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1647#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1648#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1649
1650const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1651
1652 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
1653 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
1654#if BITS_PER_LONG > 32
1655 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
1656 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
1657#endif
1658};
1659EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1660
1661const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1662EXPORT_SYMBOL(cpu_all_bits);
1663
1664#ifdef CONFIG_INIT_ALL_POSSIBLE
1665struct cpumask __cpu_possible_mask __read_mostly
1666 = {CPU_BITS_ALL};
1667#else
1668struct cpumask __cpu_possible_mask __read_mostly;
1669#endif
1670EXPORT_SYMBOL(__cpu_possible_mask);
1671
1672struct cpumask __cpu_online_mask __read_mostly;
1673EXPORT_SYMBOL(__cpu_online_mask);
1674
1675struct cpumask __cpu_present_mask __read_mostly;
1676EXPORT_SYMBOL(__cpu_present_mask);
1677
1678struct cpumask __cpu_active_mask __read_mostly;
1679EXPORT_SYMBOL(__cpu_active_mask);
1680
1681void init_cpu_present(const struct cpumask *src)
1682{
1683 cpumask_copy(&__cpu_present_mask, src);
1684}
1685
1686void init_cpu_possible(const struct cpumask *src)
1687{
1688 cpumask_copy(&__cpu_possible_mask, src);
1689}
1690
1691void init_cpu_online(const struct cpumask *src)
1692{
1693 cpumask_copy(&__cpu_online_mask, src);
1694}
1695
1696/*
1697 * Activate the first processor.
1698 */
1699void __init boot_cpu_init(void)
1700{
1701 int cpu = smp_processor_id();
1702
1703 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1704 set_cpu_online(cpu, true);
1705 set_cpu_active(cpu, true);
1706 set_cpu_present(cpu, true);
1707 set_cpu_possible(cpu, true);
1708}
1709
1710/*
1711 * Must be called _AFTER_ setting up the per_cpu areas
1712 */
1713void __init boot_cpu_state_init(void)
1714{
1715 per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1716}
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}