projects/linux·blob v4.6-rc2 · refs

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1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/proc_fs.h>
7#include <linux/smp.h>
8#include <linux/init.h>
9#include <linux/notifier.h>
10#include <linux/sched.h>
11#include <linux/unistd.h>
12#include <linux/cpu.h>
13#include <linux/oom.h>
14#include <linux/rcupdate.h>
15#include <linux/export.h>
16#include <linux/bug.h>
17#include <linux/kthread.h>
18#include <linux/stop_machine.h>
19#include <linux/mutex.h>
20#include <linux/gfp.h>
21#include <linux/suspend.h>
22#include <linux/lockdep.h>
23#include <linux/tick.h>
24#include <linux/irq.h>
25#include <linux/smpboot.h>
26
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 * @cb_stat: The state for a single callback (install/uninstall)
40 * @cb: Single callback function (install/uninstall)
41 * @result: Result of the operation
42 * @done: Signal completion to the issuer of the task
43 */
44struct cpuhp_cpu_state {
45 enum cpuhp_state state;
46 enum cpuhp_state target;
47#ifdef CONFIG_SMP
48 struct task_struct *thread;
49 bool should_run;
50 enum cpuhp_state cb_state;
51 int (*cb)(unsigned int cpu);
52 int result;
53 struct completion done;
54#endif
55};
56
57static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
58
59/**
60 * cpuhp_step - Hotplug state machine step
61 * @name: Name of the step
62 * @startup: Startup function of the step
63 * @teardown: Teardown function of the step
64 * @skip_onerr: Do not invoke the functions on error rollback
65 * Will go away once the notifiers are gone
66 * @cant_stop: Bringup/teardown can't be stopped at this step
67 */
68struct cpuhp_step {
69 const char *name;
70 int (*startup)(unsigned int cpu);
71 int (*teardown)(unsigned int cpu);
72 bool skip_onerr;
73 bool cant_stop;
74};
75
76static DEFINE_MUTEX(cpuhp_state_mutex);
77static struct cpuhp_step cpuhp_bp_states[];
78static struct cpuhp_step cpuhp_ap_states[];
79
80/**
81 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
82 * @cpu: The cpu for which the callback should be invoked
83 * @step: The step in the state machine
84 * @cb: The callback function to invoke
85 *
86 * Called from cpu hotplug and from the state register machinery
87 */
88static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step,
89 int (*cb)(unsigned int))
90{
91 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
92 int ret = 0;
93
94 if (cb) {
95 trace_cpuhp_enter(cpu, st->target, step, cb);
96 ret = cb(cpu);
97 trace_cpuhp_exit(cpu, st->state, step, ret);
98 }
99 return ret;
100}
101
102#ifdef CONFIG_SMP
103/* Serializes the updates to cpu_online_mask, cpu_present_mask */
104static DEFINE_MUTEX(cpu_add_remove_lock);
105bool cpuhp_tasks_frozen;
106EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
107
108/*
109 * The following two APIs (cpu_maps_update_begin/done) must be used when
110 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
111 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
112 * hotplug callback (un)registration performed using __register_cpu_notifier()
113 * or __unregister_cpu_notifier().
114 */
115void cpu_maps_update_begin(void)
116{
117 mutex_lock(&cpu_add_remove_lock);
118}
119EXPORT_SYMBOL(cpu_notifier_register_begin);
120
121void cpu_maps_update_done(void)
122{
123 mutex_unlock(&cpu_add_remove_lock);
124}
125EXPORT_SYMBOL(cpu_notifier_register_done);
126
127static RAW_NOTIFIER_HEAD(cpu_chain);
128
129/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
130 * Should always be manipulated under cpu_add_remove_lock
131 */
132static int cpu_hotplug_disabled;
133
134#ifdef CONFIG_HOTPLUG_CPU
135
136static struct {
137 struct task_struct *active_writer;
138 /* wait queue to wake up the active_writer */
139 wait_queue_head_t wq;
140 /* verifies that no writer will get active while readers are active */
141 struct mutex lock;
142 /*
143 * Also blocks the new readers during
144 * an ongoing cpu hotplug operation.
145 */
146 atomic_t refcount;
147
148#ifdef CONFIG_DEBUG_LOCK_ALLOC
149 struct lockdep_map dep_map;
150#endif
151} cpu_hotplug = {
152 .active_writer = NULL,
153 .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
154 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
155#ifdef CONFIG_DEBUG_LOCK_ALLOC
156 .dep_map = {.name = "cpu_hotplug.lock" },
157#endif
158};
159
160/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
161#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
162#define cpuhp_lock_acquire_tryread() \
163 lock_map_acquire_tryread(&cpu_hotplug.dep_map)
164#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
165#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
166
167
168void get_online_cpus(void)
169{
170 might_sleep();
171 if (cpu_hotplug.active_writer == current)
172 return;
173 cpuhp_lock_acquire_read();
174 mutex_lock(&cpu_hotplug.lock);
175 atomic_inc(&cpu_hotplug.refcount);
176 mutex_unlock(&cpu_hotplug.lock);
177}
178EXPORT_SYMBOL_GPL(get_online_cpus);
179
180void put_online_cpus(void)
181{
182 int refcount;
183
184 if (cpu_hotplug.active_writer == current)
185 return;
186
187 refcount = atomic_dec_return(&cpu_hotplug.refcount);
188 if (WARN_ON(refcount < 0)) /* try to fix things up */
189 atomic_inc(&cpu_hotplug.refcount);
190
191 if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
192 wake_up(&cpu_hotplug.wq);
193
194 cpuhp_lock_release();
195
196}
197EXPORT_SYMBOL_GPL(put_online_cpus);
198
199/*
200 * This ensures that the hotplug operation can begin only when the
201 * refcount goes to zero.
202 *
203 * Note that during a cpu-hotplug operation, the new readers, if any,
204 * will be blocked by the cpu_hotplug.lock
205 *
206 * Since cpu_hotplug_begin() is always called after invoking
207 * cpu_maps_update_begin(), we can be sure that only one writer is active.
208 *
209 * Note that theoretically, there is a possibility of a livelock:
210 * - Refcount goes to zero, last reader wakes up the sleeping
211 * writer.
212 * - Last reader unlocks the cpu_hotplug.lock.
213 * - A new reader arrives at this moment, bumps up the refcount.
214 * - The writer acquires the cpu_hotplug.lock finds the refcount
215 * non zero and goes to sleep again.
216 *
217 * However, this is very difficult to achieve in practice since
218 * get_online_cpus() not an api which is called all that often.
219 *
220 */
221void cpu_hotplug_begin(void)
222{
223 DEFINE_WAIT(wait);
224
225 cpu_hotplug.active_writer = current;
226 cpuhp_lock_acquire();
227
228 for (;;) {
229 mutex_lock(&cpu_hotplug.lock);
230 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
231 if (likely(!atomic_read(&cpu_hotplug.refcount)))
232 break;
233 mutex_unlock(&cpu_hotplug.lock);
234 schedule();
235 }
236 finish_wait(&cpu_hotplug.wq, &wait);
237}
238
239void cpu_hotplug_done(void)
240{
241 cpu_hotplug.active_writer = NULL;
242 mutex_unlock(&cpu_hotplug.lock);
243 cpuhp_lock_release();
244}
245
246/*
247 * Wait for currently running CPU hotplug operations to complete (if any) and
248 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
249 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
250 * hotplug path before performing hotplug operations. So acquiring that lock
251 * guarantees mutual exclusion from any currently running hotplug operations.
252 */
253void cpu_hotplug_disable(void)
254{
255 cpu_maps_update_begin();
256 cpu_hotplug_disabled++;
257 cpu_maps_update_done();
258}
259EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
260
261void cpu_hotplug_enable(void)
262{
263 cpu_maps_update_begin();
264 WARN_ON(--cpu_hotplug_disabled < 0);
265 cpu_maps_update_done();
266}
267EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
268#endif /* CONFIG_HOTPLUG_CPU */
269
270/* Need to know about CPUs going up/down? */
271int register_cpu_notifier(struct notifier_block *nb)
272{
273 int ret;
274 cpu_maps_update_begin();
275 ret = raw_notifier_chain_register(&cpu_chain, nb);
276 cpu_maps_update_done();
277 return ret;
278}
279
280int __register_cpu_notifier(struct notifier_block *nb)
281{
282 return raw_notifier_chain_register(&cpu_chain, nb);
283}
284
285static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
286 int *nr_calls)
287{
288 unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
289 void *hcpu = (void *)(long)cpu;
290
291 int ret;
292
293 ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
294 nr_calls);
295
296 return notifier_to_errno(ret);
297}
298
299static int cpu_notify(unsigned long val, unsigned int cpu)
300{
301 return __cpu_notify(val, cpu, -1, NULL);
302}
303
304/* Notifier wrappers for transitioning to state machine */
305static int notify_prepare(unsigned int cpu)
306{
307 int nr_calls = 0;
308 int ret;
309
310 ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
311 if (ret) {
312 nr_calls--;
313 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
314 __func__, cpu);
315 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
316 }
317 return ret;
318}
319
320static int notify_online(unsigned int cpu)
321{
322 cpu_notify(CPU_ONLINE, cpu);
323 return 0;
324}
325
326static int notify_starting(unsigned int cpu)
327{
328 cpu_notify(CPU_STARTING, cpu);
329 return 0;
330}
331
332static int bringup_wait_for_ap(unsigned int cpu)
333{
334 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
335
336 wait_for_completion(&st->done);
337 return st->result;
338}
339
340static int bringup_cpu(unsigned int cpu)
341{
342 struct task_struct *idle = idle_thread_get(cpu);
343 int ret;
344
345 /* Arch-specific enabling code. */
346 ret = __cpu_up(cpu, idle);
347 if (ret) {
348 cpu_notify(CPU_UP_CANCELED, cpu);
349 return ret;
350 }
351 ret = bringup_wait_for_ap(cpu);
352 BUG_ON(!cpu_online(cpu));
353 return ret;
354}
355
356/*
357 * Hotplug state machine related functions
358 */
359static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st,
360 struct cpuhp_step *steps)
361{
362 for (st->state++; st->state < st->target; st->state++) {
363 struct cpuhp_step *step = steps + st->state;
364
365 if (!step->skip_onerr)
366 cpuhp_invoke_callback(cpu, st->state, step->startup);
367 }
368}
369
370static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
371 struct cpuhp_step *steps, enum cpuhp_state target)
372{
373 enum cpuhp_state prev_state = st->state;
374 int ret = 0;
375
376 for (; st->state > target; st->state--) {
377 struct cpuhp_step *step = steps + st->state;
378
379 ret = cpuhp_invoke_callback(cpu, st->state, step->teardown);
380 if (ret) {
381 st->target = prev_state;
382 undo_cpu_down(cpu, st, steps);
383 break;
384 }
385 }
386 return ret;
387}
388
389static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st,
390 struct cpuhp_step *steps)
391{
392 for (st->state--; st->state > st->target; st->state--) {
393 struct cpuhp_step *step = steps + st->state;
394
395 if (!step->skip_onerr)
396 cpuhp_invoke_callback(cpu, st->state, step->teardown);
397 }
398}
399
400static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
401 struct cpuhp_step *steps, enum cpuhp_state target)
402{
403 enum cpuhp_state prev_state = st->state;
404 int ret = 0;
405
406 while (st->state < target) {
407 struct cpuhp_step *step;
408
409 st->state++;
410 step = steps + st->state;
411 ret = cpuhp_invoke_callback(cpu, st->state, step->startup);
412 if (ret) {
413 st->target = prev_state;
414 undo_cpu_up(cpu, st, steps);
415 break;
416 }
417 }
418 return ret;
419}
420
421/*
422 * The cpu hotplug threads manage the bringup and teardown of the cpus
423 */
424static void cpuhp_create(unsigned int cpu)
425{
426 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
427
428 init_completion(&st->done);
429}
430
431static int cpuhp_should_run(unsigned int cpu)
432{
433 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
434
435 return st->should_run;
436}
437
438/* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
439static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
440{
441 enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
442
443 return cpuhp_down_callbacks(cpu, st, cpuhp_ap_states, target);
444}
445
446/* Execute the online startup callbacks. Used to be CPU_ONLINE */
447static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
448{
449 return cpuhp_up_callbacks(cpu, st, cpuhp_ap_states, st->target);
450}
451
452/*
453 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
454 * callbacks when a state gets [un]installed at runtime.
455 */
456static void cpuhp_thread_fun(unsigned int cpu)
457{
458 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
459 int ret = 0;
460
461 /*
462 * Paired with the mb() in cpuhp_kick_ap_work and
463 * cpuhp_invoke_ap_callback, so the work set is consistent visible.
464 */
465 smp_mb();
466 if (!st->should_run)
467 return;
468
469 st->should_run = false;
470
471 /* Single callback invocation for [un]install ? */
472 if (st->cb) {
473 if (st->cb_state < CPUHP_AP_ONLINE) {
474 local_irq_disable();
475 ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
476 local_irq_enable();
477 } else {
478 ret = cpuhp_invoke_callback(cpu, st->cb_state, st->cb);
479 }
480 } else {
481 /* Cannot happen .... */
482 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
483
484 /* Regular hotplug work */
485 if (st->state < st->target)
486 ret = cpuhp_ap_online(cpu, st);
487 else if (st->state > st->target)
488 ret = cpuhp_ap_offline(cpu, st);
489 }
490 st->result = ret;
491 complete(&st->done);
492}
493
494/* Invoke a single callback on a remote cpu */
495static int cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state,
496 int (*cb)(unsigned int))
497{
498 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
499
500 if (!cpu_online(cpu))
501 return 0;
502
503 st->cb_state = state;
504 st->cb = cb;
505 /*
506 * Make sure the above stores are visible before should_run becomes
507 * true. Paired with the mb() above in cpuhp_thread_fun()
508 */
509 smp_mb();
510 st->should_run = true;
511 wake_up_process(st->thread);
512 wait_for_completion(&st->done);
513 return st->result;
514}
515
516/* Regular hotplug invocation of the AP hotplug thread */
517static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
518{
519 st->result = 0;
520 st->cb = NULL;
521 /*
522 * Make sure the above stores are visible before should_run becomes
523 * true. Paired with the mb() above in cpuhp_thread_fun()
524 */
525 smp_mb();
526 st->should_run = true;
527 wake_up_process(st->thread);
528}
529
530static int cpuhp_kick_ap_work(unsigned int cpu)
531{
532 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
533 enum cpuhp_state state = st->state;
534
535 trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
536 __cpuhp_kick_ap_work(st);
537 wait_for_completion(&st->done);
538 trace_cpuhp_exit(cpu, st->state, state, st->result);
539 return st->result;
540}
541
542static struct smp_hotplug_thread cpuhp_threads = {
543 .store = &cpuhp_state.thread,
544 .create = &cpuhp_create,
545 .thread_should_run = cpuhp_should_run,
546 .thread_fn = cpuhp_thread_fun,
547 .thread_comm = "cpuhp/%u",
548 .selfparking = true,
549};
550
551void __init cpuhp_threads_init(void)
552{
553 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
554 kthread_unpark(this_cpu_read(cpuhp_state.thread));
555}
556
557#ifdef CONFIG_HOTPLUG_CPU
558EXPORT_SYMBOL(register_cpu_notifier);
559EXPORT_SYMBOL(__register_cpu_notifier);
560void unregister_cpu_notifier(struct notifier_block *nb)
561{
562 cpu_maps_update_begin();
563 raw_notifier_chain_unregister(&cpu_chain, nb);
564 cpu_maps_update_done();
565}
566EXPORT_SYMBOL(unregister_cpu_notifier);
567
568void __unregister_cpu_notifier(struct notifier_block *nb)
569{
570 raw_notifier_chain_unregister(&cpu_chain, nb);
571}
572EXPORT_SYMBOL(__unregister_cpu_notifier);
573
574/**
575 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
576 * @cpu: a CPU id
577 *
578 * This function walks all processes, finds a valid mm struct for each one and
579 * then clears a corresponding bit in mm's cpumask. While this all sounds
580 * trivial, there are various non-obvious corner cases, which this function
581 * tries to solve in a safe manner.
582 *
583 * Also note that the function uses a somewhat relaxed locking scheme, so it may
584 * be called only for an already offlined CPU.
585 */
586void clear_tasks_mm_cpumask(int cpu)
587{
588 struct task_struct *p;
589
590 /*
591 * This function is called after the cpu is taken down and marked
592 * offline, so its not like new tasks will ever get this cpu set in
593 * their mm mask. -- Peter Zijlstra
594 * Thus, we may use rcu_read_lock() here, instead of grabbing
595 * full-fledged tasklist_lock.
596 */
597 WARN_ON(cpu_online(cpu));
598 rcu_read_lock();
599 for_each_process(p) {
600 struct task_struct *t;
601
602 /*
603 * Main thread might exit, but other threads may still have
604 * a valid mm. Find one.
605 */
606 t = find_lock_task_mm(p);
607 if (!t)
608 continue;
609 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
610 task_unlock(t);
611 }
612 rcu_read_unlock();
613}
614
615static inline void check_for_tasks(int dead_cpu)
616{
617 struct task_struct *g, *p;
618
619 read_lock(&tasklist_lock);
620 for_each_process_thread(g, p) {
621 if (!p->on_rq)
622 continue;
623 /*
624 * We do the check with unlocked task_rq(p)->lock.
625 * Order the reading to do not warn about a task,
626 * which was running on this cpu in the past, and
627 * it's just been woken on another cpu.
628 */
629 rmb();
630 if (task_cpu(p) != dead_cpu)
631 continue;
632
633 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
634 p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
635 }
636 read_unlock(&tasklist_lock);
637}
638
639static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
640{
641 BUG_ON(cpu_notify(val, cpu));
642}
643
644static int notify_down_prepare(unsigned int cpu)
645{
646 int err, nr_calls = 0;
647
648 err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
649 if (err) {
650 nr_calls--;
651 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
652 pr_warn("%s: attempt to take down CPU %u failed\n",
653 __func__, cpu);
654 }
655 return err;
656}
657
658static int notify_dying(unsigned int cpu)
659{
660 cpu_notify(CPU_DYING, cpu);
661 return 0;
662}
663
664/* Take this CPU down. */
665static int take_cpu_down(void *_param)
666{
667 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
668 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
669 int err, cpu = smp_processor_id();
670
671 /* Ensure this CPU doesn't handle any more interrupts. */
672 err = __cpu_disable();
673 if (err < 0)
674 return err;
675
676 /* Invoke the former CPU_DYING callbacks */
677 for (; st->state > target; st->state--) {
678 struct cpuhp_step *step = cpuhp_ap_states + st->state;
679
680 cpuhp_invoke_callback(cpu, st->state, step->teardown);
681 }
682 /* Give up timekeeping duties */
683 tick_handover_do_timer();
684 /* Park the stopper thread */
685 stop_machine_park(cpu);
686 return 0;
687}
688
689static int takedown_cpu(unsigned int cpu)
690{
691 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
692 int err;
693
694 /*
695 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
696 * and RCU users of this state to go away such that all new such users
697 * will observe it.
698 *
699 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
700 * not imply sync_sched(), so wait for both.
701 *
702 * Do sync before park smpboot threads to take care the rcu boost case.
703 */
704 if (IS_ENABLED(CONFIG_PREEMPT))
705 synchronize_rcu_mult(call_rcu, call_rcu_sched);
706 else
707 synchronize_rcu();
708
709 /* Park the smpboot threads */
710 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
711 smpboot_park_threads(cpu);
712
713 /*
714 * Prevent irq alloc/free while the dying cpu reorganizes the
715 * interrupt affinities.
716 */
717 irq_lock_sparse();
718
719 /*
720 * So now all preempt/rcu users must observe !cpu_active().
721 */
722 err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
723 if (err) {
724 /* CPU didn't die: tell everyone. Can't complain. */
725 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
726 irq_unlock_sparse();
727 return err;
728 }
729 BUG_ON(cpu_online(cpu));
730
731 /*
732 * The migration_call() CPU_DYING callback will have removed all
733 * runnable tasks from the cpu, there's only the idle task left now
734 * that the migration thread is done doing the stop_machine thing.
735 *
736 * Wait for the stop thread to go away.
737 */
738 wait_for_completion(&st->done);
739 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
740
741 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
742 irq_unlock_sparse();
743
744 hotplug_cpu__broadcast_tick_pull(cpu);
745 /* This actually kills the CPU. */
746 __cpu_die(cpu);
747
748 tick_cleanup_dead_cpu(cpu);
749 return 0;
750}
751
752static int notify_dead(unsigned int cpu)
753{
754 cpu_notify_nofail(CPU_DEAD, cpu);
755 check_for_tasks(cpu);
756 return 0;
757}
758
759static void cpuhp_complete_idle_dead(void *arg)
760{
761 struct cpuhp_cpu_state *st = arg;
762
763 complete(&st->done);
764}
765
766void cpuhp_report_idle_dead(void)
767{
768 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
769
770 BUG_ON(st->state != CPUHP_AP_OFFLINE);
771 rcu_report_dead(smp_processor_id());
772 st->state = CPUHP_AP_IDLE_DEAD;
773 /*
774 * We cannot call complete after rcu_report_dead() so we delegate it
775 * to an online cpu.
776 */
777 smp_call_function_single(cpumask_first(cpu_online_mask),
778 cpuhp_complete_idle_dead, st, 0);
779}
780
781#else
782#define notify_down_prepare NULL
783#define takedown_cpu NULL
784#define notify_dead NULL
785#define notify_dying NULL
786#endif
787
788#ifdef CONFIG_HOTPLUG_CPU
789
790/* Requires cpu_add_remove_lock to be held */
791static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
792 enum cpuhp_state target)
793{
794 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
795 int prev_state, ret = 0;
796 bool hasdied = false;
797
798 if (num_online_cpus() == 1)
799 return -EBUSY;
800
801 if (!cpu_present(cpu))
802 return -EINVAL;
803
804 cpu_hotplug_begin();
805
806 cpuhp_tasks_frozen = tasks_frozen;
807
808 prev_state = st->state;
809 st->target = target;
810 /*
811 * If the current CPU state is in the range of the AP hotplug thread,
812 * then we need to kick the thread.
813 */
814 if (st->state > CPUHP_TEARDOWN_CPU) {
815 ret = cpuhp_kick_ap_work(cpu);
816 /*
817 * The AP side has done the error rollback already. Just
818 * return the error code..
819 */
820 if (ret)
821 goto out;
822
823 /*
824 * We might have stopped still in the range of the AP hotplug
825 * thread. Nothing to do anymore.
826 */
827 if (st->state > CPUHP_TEARDOWN_CPU)
828 goto out;
829 }
830 /*
831 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
832 * to do the further cleanups.
833 */
834 ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);
835
836 hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
837out:
838 cpu_hotplug_done();
839 /* This post dead nonsense must die */
840 if (!ret && hasdied)
841 cpu_notify_nofail(CPU_POST_DEAD, cpu);
842 return ret;
843}
844
845static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
846{
847 int err;
848
849 cpu_maps_update_begin();
850
851 if (cpu_hotplug_disabled) {
852 err = -EBUSY;
853 goto out;
854 }
855
856 err = _cpu_down(cpu, 0, target);
857
858out:
859 cpu_maps_update_done();
860 return err;
861}
862int cpu_down(unsigned int cpu)
863{
864 return do_cpu_down(cpu, CPUHP_OFFLINE);
865}
866EXPORT_SYMBOL(cpu_down);
867#endif /*CONFIG_HOTPLUG_CPU*/
868
869/**
870 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
871 * @cpu: cpu that just started
872 *
873 * This function calls the cpu_chain notifiers with CPU_STARTING.
874 * It must be called by the arch code on the new cpu, before the new cpu
875 * enables interrupts and before the "boot" cpu returns from __cpu_up().
876 */
877void notify_cpu_starting(unsigned int cpu)
878{
879 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
880 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
881
882 while (st->state < target) {
883 struct cpuhp_step *step;
884
885 st->state++;
886 step = cpuhp_ap_states + st->state;
887 cpuhp_invoke_callback(cpu, st->state, step->startup);
888 }
889}
890
891/*
892 * Called from the idle task. We need to set active here, so we can kick off
893 * the stopper thread and unpark the smpboot threads. If the target state is
894 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
895 * cpu further.
896 */
897void cpuhp_online_idle(enum cpuhp_state state)
898{
899 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
900 unsigned int cpu = smp_processor_id();
901
902 /* Happens for the boot cpu */
903 if (state != CPUHP_AP_ONLINE_IDLE)
904 return;
905
906 st->state = CPUHP_AP_ONLINE_IDLE;
907
908 /* The cpu is marked online, set it active now */
909 set_cpu_active(cpu, true);
910 /* Unpark the stopper thread and the hotplug thread of this cpu */
911 stop_machine_unpark(cpu);
912 kthread_unpark(st->thread);
913
914 /* Should we go further up ? */
915 if (st->target > CPUHP_AP_ONLINE_IDLE)
916 __cpuhp_kick_ap_work(st);
917 else
918 complete(&st->done);
919}
920
921/* Requires cpu_add_remove_lock to be held */
922static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
923{
924 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
925 struct task_struct *idle;
926 int ret = 0;
927
928 cpu_hotplug_begin();
929
930 if (!cpu_present(cpu)) {
931 ret = -EINVAL;
932 goto out;
933 }
934
935 /*
936 * The caller of do_cpu_up might have raced with another
937 * caller. Ignore it for now.
938 */
939 if (st->state >= target)
940 goto out;
941
942 if (st->state == CPUHP_OFFLINE) {
943 /* Let it fail before we try to bring the cpu up */
944 idle = idle_thread_get(cpu);
945 if (IS_ERR(idle)) {
946 ret = PTR_ERR(idle);
947 goto out;
948 }
949 }
950
951 cpuhp_tasks_frozen = tasks_frozen;
952
953 st->target = target;
954 /*
955 * If the current CPU state is in the range of the AP hotplug thread,
956 * then we need to kick the thread once more.
957 */
958 if (st->state > CPUHP_BRINGUP_CPU) {
959 ret = cpuhp_kick_ap_work(cpu);
960 /*
961 * The AP side has done the error rollback already. Just
962 * return the error code..
963 */
964 if (ret)
965 goto out;
966 }
967
968 /*
969 * Try to reach the target state. We max out on the BP at
970 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
971 * responsible for bringing it up to the target state.
972 */
973 target = min((int)target, CPUHP_BRINGUP_CPU);
974 ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
975out:
976 cpu_hotplug_done();
977 return ret;
978}
979
980static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
981{
982 int err = 0;
983
984 if (!cpu_possible(cpu)) {
985 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
986 cpu);
987#if defined(CONFIG_IA64)
988 pr_err("please check additional_cpus= boot parameter\n");
989#endif
990 return -EINVAL;
991 }
992
993 err = try_online_node(cpu_to_node(cpu));
994 if (err)
995 return err;
996
997 cpu_maps_update_begin();
998
999 if (cpu_hotplug_disabled) {
1000 err = -EBUSY;
1001 goto out;
1002 }
1003
1004 err = _cpu_up(cpu, 0, target);
1005out:
1006 cpu_maps_update_done();
1007 return err;
1008}
1009
1010int cpu_up(unsigned int cpu)
1011{
1012 return do_cpu_up(cpu, CPUHP_ONLINE);
1013}
1014EXPORT_SYMBOL_GPL(cpu_up);
1015
1016#ifdef CONFIG_PM_SLEEP_SMP
1017static cpumask_var_t frozen_cpus;
1018
1019int disable_nonboot_cpus(void)
1020{
1021 int cpu, first_cpu, error = 0;
1022
1023 cpu_maps_update_begin();
1024 first_cpu = cpumask_first(cpu_online_mask);
1025 /*
1026 * We take down all of the non-boot CPUs in one shot to avoid races
1027 * with the userspace trying to use the CPU hotplug at the same time
1028 */
1029 cpumask_clear(frozen_cpus);
1030
1031 pr_info("Disabling non-boot CPUs ...\n");
1032 for_each_online_cpu(cpu) {
1033 if (cpu == first_cpu)
1034 continue;
1035 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1036 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1037 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1038 if (!error)
1039 cpumask_set_cpu(cpu, frozen_cpus);
1040 else {
1041 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1042 break;
1043 }
1044 }
1045
1046 if (!error)
1047 BUG_ON(num_online_cpus() > 1);
1048 else
1049 pr_err("Non-boot CPUs are not disabled\n");
1050
1051 /*
1052 * Make sure the CPUs won't be enabled by someone else. We need to do
1053 * this even in case of failure as all disable_nonboot_cpus() users are
1054 * supposed to do enable_nonboot_cpus() on the failure path.
1055 */
1056 cpu_hotplug_disabled++;
1057
1058 cpu_maps_update_done();
1059 return error;
1060}
1061
1062void __weak arch_enable_nonboot_cpus_begin(void)
1063{
1064}
1065
1066void __weak arch_enable_nonboot_cpus_end(void)
1067{
1068}
1069
1070void enable_nonboot_cpus(void)
1071{
1072 int cpu, error;
1073
1074 /* Allow everyone to use the CPU hotplug again */
1075 cpu_maps_update_begin();
1076 WARN_ON(--cpu_hotplug_disabled < 0);
1077 if (cpumask_empty(frozen_cpus))
1078 goto out;
1079
1080 pr_info("Enabling non-boot CPUs ...\n");
1081
1082 arch_enable_nonboot_cpus_begin();
1083
1084 for_each_cpu(cpu, frozen_cpus) {
1085 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1086 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1087 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1088 if (!error) {
1089 pr_info("CPU%d is up\n", cpu);
1090 continue;
1091 }
1092 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1093 }
1094
1095 arch_enable_nonboot_cpus_end();
1096
1097 cpumask_clear(frozen_cpus);
1098out:
1099 cpu_maps_update_done();
1100}
1101
1102static int __init alloc_frozen_cpus(void)
1103{
1104 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1105 return -ENOMEM;
1106 return 0;
1107}
1108core_initcall(alloc_frozen_cpus);
1109
1110/*
1111 * When callbacks for CPU hotplug notifications are being executed, we must
1112 * ensure that the state of the system with respect to the tasks being frozen
1113 * or not, as reported by the notification, remains unchanged *throughout the
1114 * duration* of the execution of the callbacks.
1115 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1116 *
1117 * This synchronization is implemented by mutually excluding regular CPU
1118 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1119 * Hibernate notifications.
1120 */
1121static int
1122cpu_hotplug_pm_callback(struct notifier_block *nb,
1123 unsigned long action, void *ptr)
1124{
1125 switch (action) {
1126
1127 case PM_SUSPEND_PREPARE:
1128 case PM_HIBERNATION_PREPARE:
1129 cpu_hotplug_disable();
1130 break;
1131
1132 case PM_POST_SUSPEND:
1133 case PM_POST_HIBERNATION:
1134 cpu_hotplug_enable();
1135 break;
1136
1137 default:
1138 return NOTIFY_DONE;
1139 }
1140
1141 return NOTIFY_OK;
1142}
1143
1144
1145static int __init cpu_hotplug_pm_sync_init(void)
1146{
1147 /*
1148 * cpu_hotplug_pm_callback has higher priority than x86
1149 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1150 * to disable cpu hotplug to avoid cpu hotplug race.
1151 */
1152 pm_notifier(cpu_hotplug_pm_callback, 0);
1153 return 0;
1154}
1155core_initcall(cpu_hotplug_pm_sync_init);
1156
1157#endif /* CONFIG_PM_SLEEP_SMP */
1158
1159#endif /* CONFIG_SMP */
1160
1161/* Boot processor state steps */
1162static struct cpuhp_step cpuhp_bp_states[] = {
1163 [CPUHP_OFFLINE] = {
1164 .name = "offline",
1165 .startup = NULL,
1166 .teardown = NULL,
1167 },
1168#ifdef CONFIG_SMP
1169 [CPUHP_CREATE_THREADS]= {
1170 .name = "threads:create",
1171 .startup = smpboot_create_threads,
1172 .teardown = NULL,
1173 .cant_stop = true,
1174 },
1175 /*
1176 * Preparatory and dead notifiers. Will be replaced once the notifiers
1177 * are converted to states.
1178 */
1179 [CPUHP_NOTIFY_PREPARE] = {
1180 .name = "notify:prepare",
1181 .startup = notify_prepare,
1182 .teardown = notify_dead,
1183 .skip_onerr = true,
1184 .cant_stop = true,
1185 },
1186 /* Kicks the plugged cpu into life */
1187 [CPUHP_BRINGUP_CPU] = {
1188 .name = "cpu:bringup",
1189 .startup = bringup_cpu,
1190 .teardown = NULL,
1191 .cant_stop = true,
1192 },
1193 /*
1194 * Handled on controll processor until the plugged processor manages
1195 * this itself.
1196 */
1197 [CPUHP_TEARDOWN_CPU] = {
1198 .name = "cpu:teardown",
1199 .startup = NULL,
1200 .teardown = takedown_cpu,
1201 .cant_stop = true,
1202 },
1203#endif
1204};
1205
1206/* Application processor state steps */
1207static struct cpuhp_step cpuhp_ap_states[] = {
1208#ifdef CONFIG_SMP
1209 /* Final state before CPU kills itself */
1210 [CPUHP_AP_IDLE_DEAD] = {
1211 .name = "idle:dead",
1212 },
1213 /*
1214 * Last state before CPU enters the idle loop to die. Transient state
1215 * for synchronization.
1216 */
1217 [CPUHP_AP_OFFLINE] = {
1218 .name = "ap:offline",
1219 .cant_stop = true,
1220 },
1221 /*
1222 * Low level startup/teardown notifiers. Run with interrupts
1223 * disabled. Will be removed once the notifiers are converted to
1224 * states.
1225 */
1226 [CPUHP_AP_NOTIFY_STARTING] = {
1227 .name = "notify:starting",
1228 .startup = notify_starting,
1229 .teardown = notify_dying,
1230 .skip_onerr = true,
1231 .cant_stop = true,
1232 },
1233 /* Entry state on starting. Interrupts enabled from here on. Transient
1234 * state for synchronsization */
1235 [CPUHP_AP_ONLINE] = {
1236 .name = "ap:online",
1237 },
1238 /* Handle smpboot threads park/unpark */
1239 [CPUHP_AP_SMPBOOT_THREADS] = {
1240 .name = "smpboot:threads",
1241 .startup = smpboot_unpark_threads,
1242 .teardown = NULL,
1243 },
1244 /*
1245 * Online/down_prepare notifiers. Will be removed once the notifiers
1246 * are converted to states.
1247 */
1248 [CPUHP_AP_NOTIFY_ONLINE] = {
1249 .name = "notify:online",
1250 .startup = notify_online,
1251 .teardown = notify_down_prepare,
1252 },
1253#endif
1254 /*
1255 * The dynamically registered state space is here
1256 */
1257
1258 /* CPU is fully up and running. */
1259 [CPUHP_ONLINE] = {
1260 .name = "online",
1261 .startup = NULL,
1262 .teardown = NULL,
1263 },
1264};
1265
1266/* Sanity check for callbacks */
1267static int cpuhp_cb_check(enum cpuhp_state state)
1268{
1269 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1270 return -EINVAL;
1271 return 0;
1272}
1273
1274static bool cpuhp_is_ap_state(enum cpuhp_state state)
1275{
1276 /*
1277 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
1278 * purposes as that state is handled explicitely in cpu_down.
1279 */
1280 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
1281}
1282
1283static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
1284{
1285 struct cpuhp_step *sp;
1286
1287 sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
1288 return sp + state;
1289}
1290
1291static void cpuhp_store_callbacks(enum cpuhp_state state,
1292 const char *name,
1293 int (*startup)(unsigned int cpu),
1294 int (*teardown)(unsigned int cpu))
1295{
1296 /* (Un)Install the callbacks for further cpu hotplug operations */
1297 struct cpuhp_step *sp;
1298
1299 mutex_lock(&cpuhp_state_mutex);
1300 sp = cpuhp_get_step(state);
1301 sp->startup = startup;
1302 sp->teardown = teardown;
1303 sp->name = name;
1304 mutex_unlock(&cpuhp_state_mutex);
1305}
1306
1307static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1308{
1309 return cpuhp_get_step(state)->teardown;
1310}
1311
1312/*
1313 * Call the startup/teardown function for a step either on the AP or
1314 * on the current CPU.
1315 */
1316static int cpuhp_issue_call(int cpu, enum cpuhp_state state,
1317 int (*cb)(unsigned int), bool bringup)
1318{
1319 int ret;
1320
1321 if (!cb)
1322 return 0;
1323 /*
1324 * The non AP bound callbacks can fail on bringup. On teardown
1325 * e.g. module removal we crash for now.
1326 */
1327#ifdef CONFIG_SMP
1328 if (cpuhp_is_ap_state(state))
1329 ret = cpuhp_invoke_ap_callback(cpu, state, cb);
1330 else
1331 ret = cpuhp_invoke_callback(cpu, state, cb);
1332#else
1333 ret = cpuhp_invoke_callback(cpu, state, cb);
1334#endif
1335 BUG_ON(ret && !bringup);
1336 return ret;
1337}
1338
1339/*
1340 * Called from __cpuhp_setup_state on a recoverable failure.
1341 *
1342 * Note: The teardown callbacks for rollback are not allowed to fail!
1343 */
1344static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1345 int (*teardown)(unsigned int cpu))
1346{
1347 int cpu;
1348
1349 if (!teardown)
1350 return;
1351
1352 /* Roll back the already executed steps on the other cpus */
1353 for_each_present_cpu(cpu) {
1354 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1355 int cpustate = st->state;
1356
1357 if (cpu >= failedcpu)
1358 break;
1359
1360 /* Did we invoke the startup call on that cpu ? */
1361 if (cpustate >= state)
1362 cpuhp_issue_call(cpu, state, teardown, false);
1363 }
1364}
1365
1366/*
1367 * Returns a free for dynamic slot assignment of the Online state. The states
1368 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1369 * by having no name assigned.
1370 */
1371static int cpuhp_reserve_state(enum cpuhp_state state)
1372{
1373 enum cpuhp_state i;
1374
1375 mutex_lock(&cpuhp_state_mutex);
1376 for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1377 if (cpuhp_ap_states[i].name)
1378 continue;
1379
1380 cpuhp_ap_states[i].name = "Reserved";
1381 mutex_unlock(&cpuhp_state_mutex);
1382 return i;
1383 }
1384 mutex_unlock(&cpuhp_state_mutex);
1385 WARN(1, "No more dynamic states available for CPU hotplug\n");
1386 return -ENOSPC;
1387}
1388
1389/**
1390 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1391 * @state: The state to setup
1392 * @invoke: If true, the startup function is invoked for cpus where
1393 * cpu state >= @state
1394 * @startup: startup callback function
1395 * @teardown: teardown callback function
1396 *
1397 * Returns 0 if successful, otherwise a proper error code
1398 */
1399int __cpuhp_setup_state(enum cpuhp_state state,
1400 const char *name, bool invoke,
1401 int (*startup)(unsigned int cpu),
1402 int (*teardown)(unsigned int cpu))
1403{
1404 int cpu, ret = 0;
1405 int dyn_state = 0;
1406
1407 if (cpuhp_cb_check(state) || !name)
1408 return -EINVAL;
1409
1410 get_online_cpus();
1411
1412 /* currently assignments for the ONLINE state are possible */
1413 if (state == CPUHP_AP_ONLINE_DYN) {
1414 dyn_state = 1;
1415 ret = cpuhp_reserve_state(state);
1416 if (ret < 0)
1417 goto out;
1418 state = ret;
1419 }
1420
1421 cpuhp_store_callbacks(state, name, startup, teardown);
1422
1423 if (!invoke || !startup)
1424 goto out;
1425
1426 /*
1427 * Try to call the startup callback for each present cpu
1428 * depending on the hotplug state of the cpu.
1429 */
1430 for_each_present_cpu(cpu) {
1431 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1432 int cpustate = st->state;
1433
1434 if (cpustate < state)
1435 continue;
1436
1437 ret = cpuhp_issue_call(cpu, state, startup, true);
1438 if (ret) {
1439 cpuhp_rollback_install(cpu, state, teardown);
1440 cpuhp_store_callbacks(state, NULL, NULL, NULL);
1441 goto out;
1442 }
1443 }
1444out:
1445 put_online_cpus();
1446 if (!ret && dyn_state)
1447 return state;
1448 return ret;
1449}
1450EXPORT_SYMBOL(__cpuhp_setup_state);
1451
1452/**
1453 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1454 * @state: The state to remove
1455 * @invoke: If true, the teardown function is invoked for cpus where
1456 * cpu state >= @state
1457 *
1458 * The teardown callback is currently not allowed to fail. Think
1459 * about module removal!
1460 */
1461void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1462{
1463 int (*teardown)(unsigned int cpu) = cpuhp_get_teardown_cb(state);
1464 int cpu;
1465
1466 BUG_ON(cpuhp_cb_check(state));
1467
1468 get_online_cpus();
1469
1470 if (!invoke || !teardown)
1471 goto remove;
1472
1473 /*
1474 * Call the teardown callback for each present cpu depending
1475 * on the hotplug state of the cpu. This function is not
1476 * allowed to fail currently!
1477 */
1478 for_each_present_cpu(cpu) {
1479 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1480 int cpustate = st->state;
1481
1482 if (cpustate >= state)
1483 cpuhp_issue_call(cpu, state, teardown, false);
1484 }
1485remove:
1486 cpuhp_store_callbacks(state, NULL, NULL, NULL);
1487 put_online_cpus();
1488}
1489EXPORT_SYMBOL(__cpuhp_remove_state);
1490
1491#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1492static ssize_t show_cpuhp_state(struct device *dev,
1493 struct device_attribute *attr, char *buf)
1494{
1495 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1496
1497 return sprintf(buf, "%d\n", st->state);
1498}
1499static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1500
1501static ssize_t write_cpuhp_target(struct device *dev,
1502 struct device_attribute *attr,
1503 const char *buf, size_t count)
1504{
1505 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1506 struct cpuhp_step *sp;
1507 int target, ret;
1508
1509 ret = kstrtoint(buf, 10, &target);
1510 if (ret)
1511 return ret;
1512
1513#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1514 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1515 return -EINVAL;
1516#else
1517 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1518 return -EINVAL;
1519#endif
1520
1521 ret = lock_device_hotplug_sysfs();
1522 if (ret)
1523 return ret;
1524
1525 mutex_lock(&cpuhp_state_mutex);
1526 sp = cpuhp_get_step(target);
1527 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1528 mutex_unlock(&cpuhp_state_mutex);
1529 if (ret)
1530 return ret;
1531
1532 if (st->state < target)
1533 ret = do_cpu_up(dev->id, target);
1534 else
1535 ret = do_cpu_down(dev->id, target);
1536
1537 unlock_device_hotplug();
1538 return ret ? ret : count;
1539}
1540
1541static ssize_t show_cpuhp_target(struct device *dev,
1542 struct device_attribute *attr, char *buf)
1543{
1544 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1545
1546 return sprintf(buf, "%d\n", st->target);
1547}
1548static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1549
1550static struct attribute *cpuhp_cpu_attrs[] = {
1551 &dev_attr_state.attr,
1552 &dev_attr_target.attr,
1553 NULL
1554};
1555
1556static struct attribute_group cpuhp_cpu_attr_group = {
1557 .attrs = cpuhp_cpu_attrs,
1558 .name = "hotplug",
1559 NULL
1560};
1561
1562static ssize_t show_cpuhp_states(struct device *dev,
1563 struct device_attribute *attr, char *buf)
1564{
1565 ssize_t cur, res = 0;
1566 int i;
1567
1568 mutex_lock(&cpuhp_state_mutex);
1569 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1570 struct cpuhp_step *sp = cpuhp_get_step(i);
1571
1572 if (sp->name) {
1573 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1574 buf += cur;
1575 res += cur;
1576 }
1577 }
1578 mutex_unlock(&cpuhp_state_mutex);
1579 return res;
1580}
1581static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1582
1583static struct attribute *cpuhp_cpu_root_attrs[] = {
1584 &dev_attr_states.attr,
1585 NULL
1586};
1587
1588static struct attribute_group cpuhp_cpu_root_attr_group = {
1589 .attrs = cpuhp_cpu_root_attrs,
1590 .name = "hotplug",
1591 NULL
1592};
1593
1594static int __init cpuhp_sysfs_init(void)
1595{
1596 int cpu, ret;
1597
1598 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1599 &cpuhp_cpu_root_attr_group);
1600 if (ret)
1601 return ret;
1602
1603 for_each_possible_cpu(cpu) {
1604 struct device *dev = get_cpu_device(cpu);
1605
1606 if (!dev)
1607 continue;
1608 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1609 if (ret)
1610 return ret;
1611 }
1612 return 0;
1613}
1614device_initcall(cpuhp_sysfs_init);
1615#endif
1616
1617/*
1618 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1619 * represents all NR_CPUS bits binary values of 1<<nr.
1620 *
1621 * It is used by cpumask_of() to get a constant address to a CPU
1622 * mask value that has a single bit set only.
1623 */
1624
1625/* cpu_bit_bitmap[0] is empty - so we can back into it */
1626#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
1627#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1628#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1629#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1630
1631const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1632
1633 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
1634 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
1635#if BITS_PER_LONG > 32
1636 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
1637 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
1638#endif
1639};
1640EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1641
1642const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1643EXPORT_SYMBOL(cpu_all_bits);
1644
1645#ifdef CONFIG_INIT_ALL_POSSIBLE
1646struct cpumask __cpu_possible_mask __read_mostly
1647 = {CPU_BITS_ALL};
1648#else
1649struct cpumask __cpu_possible_mask __read_mostly;
1650#endif
1651EXPORT_SYMBOL(__cpu_possible_mask);
1652
1653struct cpumask __cpu_online_mask __read_mostly;
1654EXPORT_SYMBOL(__cpu_online_mask);
1655
1656struct cpumask __cpu_present_mask __read_mostly;
1657EXPORT_SYMBOL(__cpu_present_mask);
1658
1659struct cpumask __cpu_active_mask __read_mostly;
1660EXPORT_SYMBOL(__cpu_active_mask);
1661
1662void init_cpu_present(const struct cpumask *src)
1663{
1664 cpumask_copy(&__cpu_present_mask, src);
1665}
1666
1667void init_cpu_possible(const struct cpumask *src)
1668{
1669 cpumask_copy(&__cpu_possible_mask, src);
1670}
1671
1672void init_cpu_online(const struct cpumask *src)
1673{
1674 cpumask_copy(&__cpu_online_mask, src);
1675}
1676
1677/*
1678 * Activate the first processor.
1679 */
1680void __init boot_cpu_init(void)
1681{
1682 int cpu = smp_processor_id();
1683
1684 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1685 set_cpu_online(cpu, true);
1686 set_cpu_active(cpu, true);
1687 set_cpu_present(cpu, true);
1688 set_cpu_possible(cpu, true);
1689}
1690
1691/*
1692 * Must be called _AFTER_ setting up the per_cpu areas
1693 */
1694void __init boot_cpu_state_init(void)
1695{
1696 per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1697}