projects/linux·blob v4.8-rc1 · 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 * @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 /*
521 * If we are up and running, use the hotplug thread. For early calls
522 * we invoke the thread function directly.
523 */
524 if (!st->thread)
525 return cpuhp_invoke_callback(cpu, state, cb);
526
527 st->cb_state = state;
528 st->cb = cb;
529 /*
530 * Make sure the above stores are visible before should_run becomes
531 * true. Paired with the mb() above in cpuhp_thread_fun()
532 */
533 smp_mb();
534 st->should_run = true;
535 wake_up_process(st->thread);
536 wait_for_completion(&st->done);
537 return st->result;
538}
539
540/* Regular hotplug invocation of the AP hotplug thread */
541static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
542{
543 st->result = 0;
544 st->cb = NULL;
545 /*
546 * Make sure the above stores are visible before should_run becomes
547 * true. Paired with the mb() above in cpuhp_thread_fun()
548 */
549 smp_mb();
550 st->should_run = true;
551 wake_up_process(st->thread);
552}
553
554static int cpuhp_kick_ap_work(unsigned int cpu)
555{
556 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
557 enum cpuhp_state state = st->state;
558
559 trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
560 __cpuhp_kick_ap_work(st);
561 wait_for_completion(&st->done);
562 trace_cpuhp_exit(cpu, st->state, state, st->result);
563 return st->result;
564}
565
566static struct smp_hotplug_thread cpuhp_threads = {
567 .store = &cpuhp_state.thread,
568 .create = &cpuhp_create,
569 .thread_should_run = cpuhp_should_run,
570 .thread_fn = cpuhp_thread_fun,
571 .thread_comm = "cpuhp/%u",
572 .selfparking = true,
573};
574
575void __init cpuhp_threads_init(void)
576{
577 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
578 kthread_unpark(this_cpu_read(cpuhp_state.thread));
579}
580
581#ifdef CONFIG_HOTPLUG_CPU
582EXPORT_SYMBOL(register_cpu_notifier);
583EXPORT_SYMBOL(__register_cpu_notifier);
584void unregister_cpu_notifier(struct notifier_block *nb)
585{
586 cpu_maps_update_begin();
587 raw_notifier_chain_unregister(&cpu_chain, nb);
588 cpu_maps_update_done();
589}
590EXPORT_SYMBOL(unregister_cpu_notifier);
591
592void __unregister_cpu_notifier(struct notifier_block *nb)
593{
594 raw_notifier_chain_unregister(&cpu_chain, nb);
595}
596EXPORT_SYMBOL(__unregister_cpu_notifier);
597
598/**
599 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
600 * @cpu: a CPU id
601 *
602 * This function walks all processes, finds a valid mm struct for each one and
603 * then clears a corresponding bit in mm's cpumask. While this all sounds
604 * trivial, there are various non-obvious corner cases, which this function
605 * tries to solve in a safe manner.
606 *
607 * Also note that the function uses a somewhat relaxed locking scheme, so it may
608 * be called only for an already offlined CPU.
609 */
610void clear_tasks_mm_cpumask(int cpu)
611{
612 struct task_struct *p;
613
614 /*
615 * This function is called after the cpu is taken down and marked
616 * offline, so its not like new tasks will ever get this cpu set in
617 * their mm mask. -- Peter Zijlstra
618 * Thus, we may use rcu_read_lock() here, instead of grabbing
619 * full-fledged tasklist_lock.
620 */
621 WARN_ON(cpu_online(cpu));
622 rcu_read_lock();
623 for_each_process(p) {
624 struct task_struct *t;
625
626 /*
627 * Main thread might exit, but other threads may still have
628 * a valid mm. Find one.
629 */
630 t = find_lock_task_mm(p);
631 if (!t)
632 continue;
633 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
634 task_unlock(t);
635 }
636 rcu_read_unlock();
637}
638
639static inline void check_for_tasks(int dead_cpu)
640{
641 struct task_struct *g, *p;
642
643 read_lock(&tasklist_lock);
644 for_each_process_thread(g, p) {
645 if (!p->on_rq)
646 continue;
647 /*
648 * We do the check with unlocked task_rq(p)->lock.
649 * Order the reading to do not warn about a task,
650 * which was running on this cpu in the past, and
651 * it's just been woken on another cpu.
652 */
653 rmb();
654 if (task_cpu(p) != dead_cpu)
655 continue;
656
657 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
658 p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
659 }
660 read_unlock(&tasklist_lock);
661}
662
663static int notify_down_prepare(unsigned int cpu)
664{
665 int err, nr_calls = 0;
666
667 err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
668 if (err) {
669 nr_calls--;
670 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
671 pr_warn("%s: attempt to take down CPU %u failed\n",
672 __func__, cpu);
673 }
674 return err;
675}
676
677static int notify_dying(unsigned int cpu)
678{
679 cpu_notify(CPU_DYING, cpu);
680 return 0;
681}
682
683/* Take this CPU down. */
684static int take_cpu_down(void *_param)
685{
686 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
687 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
688 int err, cpu = smp_processor_id();
689
690 /* Ensure this CPU doesn't handle any more interrupts. */
691 err = __cpu_disable();
692 if (err < 0)
693 return err;
694
695 /* Invoke the former CPU_DYING callbacks */
696 for (; st->state > target; st->state--) {
697 struct cpuhp_step *step = cpuhp_ap_states + st->state;
698
699 cpuhp_invoke_callback(cpu, st->state, step->teardown);
700 }
701 /* Give up timekeeping duties */
702 tick_handover_do_timer();
703 /* Park the stopper thread */
704 stop_machine_park(cpu);
705 return 0;
706}
707
708static int takedown_cpu(unsigned int cpu)
709{
710 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
711 int err;
712
713 /* Park the smpboot threads */
714 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
715 smpboot_park_threads(cpu);
716
717 /*
718 * Prevent irq alloc/free while the dying cpu reorganizes the
719 * interrupt affinities.
720 */
721 irq_lock_sparse();
722
723 /*
724 * So now all preempt/rcu users must observe !cpu_active().
725 */
726 err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
727 if (err) {
728 /* CPU refused to die */
729 irq_unlock_sparse();
730 /* Unpark the hotplug thread so we can rollback there */
731 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
732 return err;
733 }
734 BUG_ON(cpu_online(cpu));
735
736 /*
737 * The migration_call() CPU_DYING callback will have removed all
738 * runnable tasks from the cpu, there's only the idle task left now
739 * that the migration thread is done doing the stop_machine thing.
740 *
741 * Wait for the stop thread to go away.
742 */
743 wait_for_completion(&st->done);
744 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
745
746 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
747 irq_unlock_sparse();
748
749 hotplug_cpu__broadcast_tick_pull(cpu);
750 /* This actually kills the CPU. */
751 __cpu_die(cpu);
752
753 tick_cleanup_dead_cpu(cpu);
754 return 0;
755}
756
757static int notify_dead(unsigned int cpu)
758{
759 cpu_notify_nofail(CPU_DEAD, cpu);
760 check_for_tasks(cpu);
761 return 0;
762}
763
764static void cpuhp_complete_idle_dead(void *arg)
765{
766 struct cpuhp_cpu_state *st = arg;
767
768 complete(&st->done);
769}
770
771void cpuhp_report_idle_dead(void)
772{
773 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
774
775 BUG_ON(st->state != CPUHP_AP_OFFLINE);
776 rcu_report_dead(smp_processor_id());
777 st->state = CPUHP_AP_IDLE_DEAD;
778 /*
779 * We cannot call complete after rcu_report_dead() so we delegate it
780 * to an online cpu.
781 */
782 smp_call_function_single(cpumask_first(cpu_online_mask),
783 cpuhp_complete_idle_dead, st, 0);
784}
785
786#else
787#define notify_down_prepare NULL
788#define takedown_cpu NULL
789#define notify_dead NULL
790#define notify_dying NULL
791#endif
792
793#ifdef CONFIG_HOTPLUG_CPU
794
795/* Requires cpu_add_remove_lock to be held */
796static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
797 enum cpuhp_state target)
798{
799 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
800 int prev_state, ret = 0;
801 bool hasdied = false;
802
803 if (num_online_cpus() == 1)
804 return -EBUSY;
805
806 if (!cpu_present(cpu))
807 return -EINVAL;
808
809 cpu_hotplug_begin();
810
811 cpuhp_tasks_frozen = tasks_frozen;
812
813 prev_state = st->state;
814 st->target = target;
815 /*
816 * If the current CPU state is in the range of the AP hotplug thread,
817 * then we need to kick the thread.
818 */
819 if (st->state > CPUHP_TEARDOWN_CPU) {
820 ret = cpuhp_kick_ap_work(cpu);
821 /*
822 * The AP side has done the error rollback already. Just
823 * return the error code..
824 */
825 if (ret)
826 goto out;
827
828 /*
829 * We might have stopped still in the range of the AP hotplug
830 * thread. Nothing to do anymore.
831 */
832 if (st->state > CPUHP_TEARDOWN_CPU)
833 goto out;
834 }
835 /*
836 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
837 * to do the further cleanups.
838 */
839 ret = cpuhp_down_callbacks(cpu, st, cpuhp_bp_states, target);
840 if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
841 st->target = prev_state;
842 st->rollback = true;
843 cpuhp_kick_ap_work(cpu);
844 }
845
846 hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
847out:
848 cpu_hotplug_done();
849 /* This post dead nonsense must die */
850 if (!ret && hasdied)
851 cpu_notify_nofail(CPU_POST_DEAD, cpu);
852 return ret;
853}
854
855static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
856{
857 int err;
858
859 cpu_maps_update_begin();
860
861 if (cpu_hotplug_disabled) {
862 err = -EBUSY;
863 goto out;
864 }
865
866 err = _cpu_down(cpu, 0, target);
867
868out:
869 cpu_maps_update_done();
870 return err;
871}
872int cpu_down(unsigned int cpu)
873{
874 return do_cpu_down(cpu, CPUHP_OFFLINE);
875}
876EXPORT_SYMBOL(cpu_down);
877#endif /*CONFIG_HOTPLUG_CPU*/
878
879/**
880 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
881 * @cpu: cpu that just started
882 *
883 * This function calls the cpu_chain notifiers with CPU_STARTING.
884 * It must be called by the arch code on the new cpu, before the new cpu
885 * enables interrupts and before the "boot" cpu returns from __cpu_up().
886 */
887void notify_cpu_starting(unsigned int cpu)
888{
889 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
890 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
891
892 while (st->state < target) {
893 struct cpuhp_step *step;
894
895 st->state++;
896 step = cpuhp_ap_states + st->state;
897 cpuhp_invoke_callback(cpu, st->state, step->startup);
898 }
899}
900
901/*
902 * Called from the idle task. We need to set active here, so we can kick off
903 * the stopper thread and unpark the smpboot threads. If the target state is
904 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
905 * cpu further.
906 */
907void cpuhp_online_idle(enum cpuhp_state state)
908{
909 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
910 unsigned int cpu = smp_processor_id();
911
912 /* Happens for the boot cpu */
913 if (state != CPUHP_AP_ONLINE_IDLE)
914 return;
915
916 st->state = CPUHP_AP_ONLINE_IDLE;
917
918 /* Unpark the stopper thread and the hotplug thread of this cpu */
919 stop_machine_unpark(cpu);
920 kthread_unpark(st->thread);
921
922 /* Should we go further up ? */
923 if (st->target > CPUHP_AP_ONLINE_IDLE)
924 __cpuhp_kick_ap_work(st);
925 else
926 complete(&st->done);
927}
928
929/* Requires cpu_add_remove_lock to be held */
930static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
931{
932 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
933 struct task_struct *idle;
934 int ret = 0;
935
936 cpu_hotplug_begin();
937
938 if (!cpu_present(cpu)) {
939 ret = -EINVAL;
940 goto out;
941 }
942
943 /*
944 * The caller of do_cpu_up might have raced with another
945 * caller. Ignore it for now.
946 */
947 if (st->state >= target)
948 goto out;
949
950 if (st->state == CPUHP_OFFLINE) {
951 /* Let it fail before we try to bring the cpu up */
952 idle = idle_thread_get(cpu);
953 if (IS_ERR(idle)) {
954 ret = PTR_ERR(idle);
955 goto out;
956 }
957 }
958
959 cpuhp_tasks_frozen = tasks_frozen;
960
961 st->target = target;
962 /*
963 * If the current CPU state is in the range of the AP hotplug thread,
964 * then we need to kick the thread once more.
965 */
966 if (st->state > CPUHP_BRINGUP_CPU) {
967 ret = cpuhp_kick_ap_work(cpu);
968 /*
969 * The AP side has done the error rollback already. Just
970 * return the error code..
971 */
972 if (ret)
973 goto out;
974 }
975
976 /*
977 * Try to reach the target state. We max out on the BP at
978 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
979 * responsible for bringing it up to the target state.
980 */
981 target = min((int)target, CPUHP_BRINGUP_CPU);
982 ret = cpuhp_up_callbacks(cpu, st, cpuhp_bp_states, target);
983out:
984 cpu_hotplug_done();
985 return ret;
986}
987
988static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
989{
990 int err = 0;
991
992 if (!cpu_possible(cpu)) {
993 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
994 cpu);
995#if defined(CONFIG_IA64)
996 pr_err("please check additional_cpus= boot parameter\n");
997#endif
998 return -EINVAL;
999 }
1000
1001 err = try_online_node(cpu_to_node(cpu));
1002 if (err)
1003 return err;
1004
1005 cpu_maps_update_begin();
1006
1007 if (cpu_hotplug_disabled) {
1008 err = -EBUSY;
1009 goto out;
1010 }
1011
1012 err = _cpu_up(cpu, 0, target);
1013out:
1014 cpu_maps_update_done();
1015 return err;
1016}
1017
1018int cpu_up(unsigned int cpu)
1019{
1020 return do_cpu_up(cpu, CPUHP_ONLINE);
1021}
1022EXPORT_SYMBOL_GPL(cpu_up);
1023
1024#ifdef CONFIG_PM_SLEEP_SMP
1025static cpumask_var_t frozen_cpus;
1026
1027int disable_nonboot_cpus(void)
1028{
1029 int cpu, first_cpu, error = 0;
1030
1031 cpu_maps_update_begin();
1032 first_cpu = cpumask_first(cpu_online_mask);
1033 /*
1034 * We take down all of the non-boot CPUs in one shot to avoid races
1035 * with the userspace trying to use the CPU hotplug at the same time
1036 */
1037 cpumask_clear(frozen_cpus);
1038
1039 pr_info("Disabling non-boot CPUs ...\n");
1040 for_each_online_cpu(cpu) {
1041 if (cpu == first_cpu)
1042 continue;
1043 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1044 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1045 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1046 if (!error)
1047 cpumask_set_cpu(cpu, frozen_cpus);
1048 else {
1049 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1050 break;
1051 }
1052 }
1053
1054 if (!error)
1055 BUG_ON(num_online_cpus() > 1);
1056 else
1057 pr_err("Non-boot CPUs are not disabled\n");
1058
1059 /*
1060 * Make sure the CPUs won't be enabled by someone else. We need to do
1061 * this even in case of failure as all disable_nonboot_cpus() users are
1062 * supposed to do enable_nonboot_cpus() on the failure path.
1063 */
1064 cpu_hotplug_disabled++;
1065
1066 cpu_maps_update_done();
1067 return error;
1068}
1069
1070void __weak arch_enable_nonboot_cpus_begin(void)
1071{
1072}
1073
1074void __weak arch_enable_nonboot_cpus_end(void)
1075{
1076}
1077
1078void enable_nonboot_cpus(void)
1079{
1080 int cpu, error;
1081
1082 /* Allow everyone to use the CPU hotplug again */
1083 cpu_maps_update_begin();
1084 WARN_ON(--cpu_hotplug_disabled < 0);
1085 if (cpumask_empty(frozen_cpus))
1086 goto out;
1087
1088 pr_info("Enabling non-boot CPUs ...\n");
1089
1090 arch_enable_nonboot_cpus_begin();
1091
1092 for_each_cpu(cpu, frozen_cpus) {
1093 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1094 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1095 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1096 if (!error) {
1097 pr_info("CPU%d is up\n", cpu);
1098 continue;
1099 }
1100 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1101 }
1102
1103 arch_enable_nonboot_cpus_end();
1104
1105 cpumask_clear(frozen_cpus);
1106out:
1107 cpu_maps_update_done();
1108}
1109
1110static int __init alloc_frozen_cpus(void)
1111{
1112 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1113 return -ENOMEM;
1114 return 0;
1115}
1116core_initcall(alloc_frozen_cpus);
1117
1118/*
1119 * When callbacks for CPU hotplug notifications are being executed, we must
1120 * ensure that the state of the system with respect to the tasks being frozen
1121 * or not, as reported by the notification, remains unchanged *throughout the
1122 * duration* of the execution of the callbacks.
1123 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1124 *
1125 * This synchronization is implemented by mutually excluding regular CPU
1126 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1127 * Hibernate notifications.
1128 */
1129static int
1130cpu_hotplug_pm_callback(struct notifier_block *nb,
1131 unsigned long action, void *ptr)
1132{
1133 switch (action) {
1134
1135 case PM_SUSPEND_PREPARE:
1136 case PM_HIBERNATION_PREPARE:
1137 cpu_hotplug_disable();
1138 break;
1139
1140 case PM_POST_SUSPEND:
1141 case PM_POST_HIBERNATION:
1142 cpu_hotplug_enable();
1143 break;
1144
1145 default:
1146 return NOTIFY_DONE;
1147 }
1148
1149 return NOTIFY_OK;
1150}
1151
1152
1153static int __init cpu_hotplug_pm_sync_init(void)
1154{
1155 /*
1156 * cpu_hotplug_pm_callback has higher priority than x86
1157 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1158 * to disable cpu hotplug to avoid cpu hotplug race.
1159 */
1160 pm_notifier(cpu_hotplug_pm_callback, 0);
1161 return 0;
1162}
1163core_initcall(cpu_hotplug_pm_sync_init);
1164
1165#endif /* CONFIG_PM_SLEEP_SMP */
1166
1167#endif /* CONFIG_SMP */
1168
1169/* Boot processor state steps */
1170static struct cpuhp_step cpuhp_bp_states[] = {
1171 [CPUHP_OFFLINE] = {
1172 .name = "offline",
1173 .startup = NULL,
1174 .teardown = NULL,
1175 },
1176#ifdef CONFIG_SMP
1177 [CPUHP_CREATE_THREADS]= {
1178 .name = "threads:create",
1179 .startup = smpboot_create_threads,
1180 .teardown = NULL,
1181 .cant_stop = true,
1182 },
1183 [CPUHP_PERF_PREPARE] = {
1184 .name = "perf prepare",
1185 .startup = perf_event_init_cpu,
1186 .teardown = perf_event_exit_cpu,
1187 },
1188 [CPUHP_WORKQUEUE_PREP] = {
1189 .name = "workqueue prepare",
1190 .startup = workqueue_prepare_cpu,
1191 .teardown = NULL,
1192 },
1193 [CPUHP_HRTIMERS_PREPARE] = {
1194 .name = "hrtimers prepare",
1195 .startup = hrtimers_prepare_cpu,
1196 .teardown = hrtimers_dead_cpu,
1197 },
1198 [CPUHP_SMPCFD_PREPARE] = {
1199 .name = "SMPCFD prepare",
1200 .startup = smpcfd_prepare_cpu,
1201 .teardown = smpcfd_dead_cpu,
1202 },
1203 [CPUHP_RCUTREE_PREP] = {
1204 .name = "RCU-tree prepare",
1205 .startup = rcutree_prepare_cpu,
1206 .teardown = rcutree_dead_cpu,
1207 },
1208 /*
1209 * Preparatory and dead notifiers. Will be replaced once the notifiers
1210 * are converted to states.
1211 */
1212 [CPUHP_NOTIFY_PREPARE] = {
1213 .name = "notify:prepare",
1214 .startup = notify_prepare,
1215 .teardown = notify_dead,
1216 .skip_onerr = true,
1217 .cant_stop = true,
1218 },
1219 /*
1220 * On the tear-down path, timers_dead_cpu() must be invoked
1221 * before blk_mq_queue_reinit_notify() from notify_dead(),
1222 * otherwise a RCU stall occurs.
1223 */
1224 [CPUHP_TIMERS_DEAD] = {
1225 .name = "timers dead",
1226 .startup = NULL,
1227 .teardown = timers_dead_cpu,
1228 },
1229 /* Kicks the plugged cpu into life */
1230 [CPUHP_BRINGUP_CPU] = {
1231 .name = "cpu:bringup",
1232 .startup = bringup_cpu,
1233 .teardown = NULL,
1234 .cant_stop = true,
1235 },
1236 [CPUHP_AP_SMPCFD_DYING] = {
1237 .startup = NULL,
1238 .teardown = smpcfd_dying_cpu,
1239 },
1240 /*
1241 * Handled on controll processor until the plugged processor manages
1242 * this itself.
1243 */
1244 [CPUHP_TEARDOWN_CPU] = {
1245 .name = "cpu:teardown",
1246 .startup = NULL,
1247 .teardown = takedown_cpu,
1248 .cant_stop = true,
1249 },
1250#else
1251 [CPUHP_BRINGUP_CPU] = { },
1252#endif
1253};
1254
1255/* Application processor state steps */
1256static struct cpuhp_step cpuhp_ap_states[] = {
1257#ifdef CONFIG_SMP
1258 /* Final state before CPU kills itself */
1259 [CPUHP_AP_IDLE_DEAD] = {
1260 .name = "idle:dead",
1261 },
1262 /*
1263 * Last state before CPU enters the idle loop to die. Transient state
1264 * for synchronization.
1265 */
1266 [CPUHP_AP_OFFLINE] = {
1267 .name = "ap:offline",
1268 .cant_stop = true,
1269 },
1270 /* First state is scheduler control. Interrupts are disabled */
1271 [CPUHP_AP_SCHED_STARTING] = {
1272 .name = "sched:starting",
1273 .startup = sched_cpu_starting,
1274 .teardown = sched_cpu_dying,
1275 },
1276 [CPUHP_AP_RCUTREE_DYING] = {
1277 .startup = NULL,
1278 .teardown = rcutree_dying_cpu,
1279 },
1280 /*
1281 * Low level startup/teardown notifiers. Run with interrupts
1282 * disabled. Will be removed once the notifiers are converted to
1283 * states.
1284 */
1285 [CPUHP_AP_NOTIFY_STARTING] = {
1286 .name = "notify:starting",
1287 .startup = notify_starting,
1288 .teardown = notify_dying,
1289 .skip_onerr = true,
1290 .cant_stop = true,
1291 },
1292 /* Entry state on starting. Interrupts enabled from here on. Transient
1293 * state for synchronsization */
1294 [CPUHP_AP_ONLINE] = {
1295 .name = "ap:online",
1296 },
1297 /* Handle smpboot threads park/unpark */
1298 [CPUHP_AP_SMPBOOT_THREADS] = {
1299 .name = "smpboot:threads",
1300 .startup = smpboot_unpark_threads,
1301 .teardown = NULL,
1302 },
1303 [CPUHP_AP_PERF_ONLINE] = {
1304 .name = "perf online",
1305 .startup = perf_event_init_cpu,
1306 .teardown = perf_event_exit_cpu,
1307 },
1308 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1309 .name = "workqueue online",
1310 .startup = workqueue_online_cpu,
1311 .teardown = workqueue_offline_cpu,
1312 },
1313 [CPUHP_AP_RCUTREE_ONLINE] = {
1314 .name = "RCU-tree online",
1315 .startup = rcutree_online_cpu,
1316 .teardown = rcutree_offline_cpu,
1317 },
1318
1319 /*
1320 * Online/down_prepare notifiers. Will be removed once the notifiers
1321 * are converted to states.
1322 */
1323 [CPUHP_AP_NOTIFY_ONLINE] = {
1324 .name = "notify:online",
1325 .startup = notify_online,
1326 .teardown = notify_down_prepare,
1327 .skip_onerr = true,
1328 },
1329#endif
1330 /*
1331 * The dynamically registered state space is here
1332 */
1333
1334#ifdef CONFIG_SMP
1335 /* Last state is scheduler control setting the cpu active */
1336 [CPUHP_AP_ACTIVE] = {
1337 .name = "sched:active",
1338 .startup = sched_cpu_activate,
1339 .teardown = sched_cpu_deactivate,
1340 },
1341#endif
1342
1343 /* CPU is fully up and running. */
1344 [CPUHP_ONLINE] = {
1345 .name = "online",
1346 .startup = NULL,
1347 .teardown = NULL,
1348 },
1349};
1350
1351/* Sanity check for callbacks */
1352static int cpuhp_cb_check(enum cpuhp_state state)
1353{
1354 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1355 return -EINVAL;
1356 return 0;
1357}
1358
1359static bool cpuhp_is_ap_state(enum cpuhp_state state)
1360{
1361 /*
1362 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
1363 * purposes as that state is handled explicitely in cpu_down.
1364 */
1365 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
1366}
1367
1368static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
1369{
1370 struct cpuhp_step *sp;
1371
1372 sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
1373 return sp + state;
1374}
1375
1376static void cpuhp_store_callbacks(enum cpuhp_state state,
1377 const char *name,
1378 int (*startup)(unsigned int cpu),
1379 int (*teardown)(unsigned int cpu))
1380{
1381 /* (Un)Install the callbacks for further cpu hotplug operations */
1382 struct cpuhp_step *sp;
1383
1384 mutex_lock(&cpuhp_state_mutex);
1385 sp = cpuhp_get_step(state);
1386 sp->startup = startup;
1387 sp->teardown = teardown;
1388 sp->name = name;
1389 mutex_unlock(&cpuhp_state_mutex);
1390}
1391
1392static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1393{
1394 return cpuhp_get_step(state)->teardown;
1395}
1396
1397/*
1398 * Call the startup/teardown function for a step either on the AP or
1399 * on the current CPU.
1400 */
1401static int cpuhp_issue_call(int cpu, enum cpuhp_state state,
1402 int (*cb)(unsigned int), bool bringup)
1403{
1404 int ret;
1405
1406 if (!cb)
1407 return 0;
1408 /*
1409 * The non AP bound callbacks can fail on bringup. On teardown
1410 * e.g. module removal we crash for now.
1411 */
1412#ifdef CONFIG_SMP
1413 if (cpuhp_is_ap_state(state))
1414 ret = cpuhp_invoke_ap_callback(cpu, state, cb);
1415 else
1416 ret = cpuhp_invoke_callback(cpu, state, cb);
1417#else
1418 ret = cpuhp_invoke_callback(cpu, state, cb);
1419#endif
1420 BUG_ON(ret && !bringup);
1421 return ret;
1422}
1423
1424/*
1425 * Called from __cpuhp_setup_state on a recoverable failure.
1426 *
1427 * Note: The teardown callbacks for rollback are not allowed to fail!
1428 */
1429static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1430 int (*teardown)(unsigned int cpu))
1431{
1432 int cpu;
1433
1434 if (!teardown)
1435 return;
1436
1437 /* Roll back the already executed steps on the other cpus */
1438 for_each_present_cpu(cpu) {
1439 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1440 int cpustate = st->state;
1441
1442 if (cpu >= failedcpu)
1443 break;
1444
1445 /* Did we invoke the startup call on that cpu ? */
1446 if (cpustate >= state)
1447 cpuhp_issue_call(cpu, state, teardown, false);
1448 }
1449}
1450
1451/*
1452 * Returns a free for dynamic slot assignment of the Online state. The states
1453 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1454 * by having no name assigned.
1455 */
1456static int cpuhp_reserve_state(enum cpuhp_state state)
1457{
1458 enum cpuhp_state i;
1459
1460 mutex_lock(&cpuhp_state_mutex);
1461 for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1462 if (cpuhp_ap_states[i].name)
1463 continue;
1464
1465 cpuhp_ap_states[i].name = "Reserved";
1466 mutex_unlock(&cpuhp_state_mutex);
1467 return i;
1468 }
1469 mutex_unlock(&cpuhp_state_mutex);
1470 WARN(1, "No more dynamic states available for CPU hotplug\n");
1471 return -ENOSPC;
1472}
1473
1474/**
1475 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1476 * @state: The state to setup
1477 * @invoke: If true, the startup function is invoked for cpus where
1478 * cpu state >= @state
1479 * @startup: startup callback function
1480 * @teardown: teardown callback function
1481 *
1482 * Returns 0 if successful, otherwise a proper error code
1483 */
1484int __cpuhp_setup_state(enum cpuhp_state state,
1485 const char *name, bool invoke,
1486 int (*startup)(unsigned int cpu),
1487 int (*teardown)(unsigned int cpu))
1488{
1489 int cpu, ret = 0;
1490 int dyn_state = 0;
1491
1492 if (cpuhp_cb_check(state) || !name)
1493 return -EINVAL;
1494
1495 get_online_cpus();
1496
1497 /* currently assignments for the ONLINE state are possible */
1498 if (state == CPUHP_AP_ONLINE_DYN) {
1499 dyn_state = 1;
1500 ret = cpuhp_reserve_state(state);
1501 if (ret < 0)
1502 goto out;
1503 state = ret;
1504 }
1505
1506 cpuhp_store_callbacks(state, name, startup, teardown);
1507
1508 if (!invoke || !startup)
1509 goto out;
1510
1511 /*
1512 * Try to call the startup callback for each present cpu
1513 * depending on the hotplug state of the cpu.
1514 */
1515 for_each_present_cpu(cpu) {
1516 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1517 int cpustate = st->state;
1518
1519 if (cpustate < state)
1520 continue;
1521
1522 ret = cpuhp_issue_call(cpu, state, startup, true);
1523 if (ret) {
1524 cpuhp_rollback_install(cpu, state, teardown);
1525 cpuhp_store_callbacks(state, NULL, NULL, NULL);
1526 goto out;
1527 }
1528 }
1529out:
1530 put_online_cpus();
1531 if (!ret && dyn_state)
1532 return state;
1533 return ret;
1534}
1535EXPORT_SYMBOL(__cpuhp_setup_state);
1536
1537/**
1538 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1539 * @state: The state to remove
1540 * @invoke: If true, the teardown function is invoked for cpus where
1541 * cpu state >= @state
1542 *
1543 * The teardown callback is currently not allowed to fail. Think
1544 * about module removal!
1545 */
1546void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1547{
1548 int (*teardown)(unsigned int cpu) = cpuhp_get_teardown_cb(state);
1549 int cpu;
1550
1551 BUG_ON(cpuhp_cb_check(state));
1552
1553 get_online_cpus();
1554
1555 if (!invoke || !teardown)
1556 goto remove;
1557
1558 /*
1559 * Call the teardown callback for each present cpu depending
1560 * on the hotplug state of the cpu. This function is not
1561 * allowed to fail currently!
1562 */
1563 for_each_present_cpu(cpu) {
1564 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1565 int cpustate = st->state;
1566
1567 if (cpustate >= state)
1568 cpuhp_issue_call(cpu, state, teardown, false);
1569 }
1570remove:
1571 cpuhp_store_callbacks(state, NULL, NULL, NULL);
1572 put_online_cpus();
1573}
1574EXPORT_SYMBOL(__cpuhp_remove_state);
1575
1576#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1577static ssize_t show_cpuhp_state(struct device *dev,
1578 struct device_attribute *attr, char *buf)
1579{
1580 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1581
1582 return sprintf(buf, "%d\n", st->state);
1583}
1584static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1585
1586static ssize_t write_cpuhp_target(struct device *dev,
1587 struct device_attribute *attr,
1588 const char *buf, size_t count)
1589{
1590 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1591 struct cpuhp_step *sp;
1592 int target, ret;
1593
1594 ret = kstrtoint(buf, 10, &target);
1595 if (ret)
1596 return ret;
1597
1598#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1599 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1600 return -EINVAL;
1601#else
1602 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1603 return -EINVAL;
1604#endif
1605
1606 ret = lock_device_hotplug_sysfs();
1607 if (ret)
1608 return ret;
1609
1610 mutex_lock(&cpuhp_state_mutex);
1611 sp = cpuhp_get_step(target);
1612 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1613 mutex_unlock(&cpuhp_state_mutex);
1614 if (ret)
1615 return ret;
1616
1617 if (st->state < target)
1618 ret = do_cpu_up(dev->id, target);
1619 else
1620 ret = do_cpu_down(dev->id, target);
1621
1622 unlock_device_hotplug();
1623 return ret ? ret : count;
1624}
1625
1626static ssize_t show_cpuhp_target(struct device *dev,
1627 struct device_attribute *attr, char *buf)
1628{
1629 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1630
1631 return sprintf(buf, "%d\n", st->target);
1632}
1633static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1634
1635static struct attribute *cpuhp_cpu_attrs[] = {
1636 &dev_attr_state.attr,
1637 &dev_attr_target.attr,
1638 NULL
1639};
1640
1641static struct attribute_group cpuhp_cpu_attr_group = {
1642 .attrs = cpuhp_cpu_attrs,
1643 .name = "hotplug",
1644 NULL
1645};
1646
1647static ssize_t show_cpuhp_states(struct device *dev,
1648 struct device_attribute *attr, char *buf)
1649{
1650 ssize_t cur, res = 0;
1651 int i;
1652
1653 mutex_lock(&cpuhp_state_mutex);
1654 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1655 struct cpuhp_step *sp = cpuhp_get_step(i);
1656
1657 if (sp->name) {
1658 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1659 buf += cur;
1660 res += cur;
1661 }
1662 }
1663 mutex_unlock(&cpuhp_state_mutex);
1664 return res;
1665}
1666static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1667
1668static struct attribute *cpuhp_cpu_root_attrs[] = {
1669 &dev_attr_states.attr,
1670 NULL
1671};
1672
1673static struct attribute_group cpuhp_cpu_root_attr_group = {
1674 .attrs = cpuhp_cpu_root_attrs,
1675 .name = "hotplug",
1676 NULL
1677};
1678
1679static int __init cpuhp_sysfs_init(void)
1680{
1681 int cpu, ret;
1682
1683 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1684 &cpuhp_cpu_root_attr_group);
1685 if (ret)
1686 return ret;
1687
1688 for_each_possible_cpu(cpu) {
1689 struct device *dev = get_cpu_device(cpu);
1690
1691 if (!dev)
1692 continue;
1693 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1694 if (ret)
1695 return ret;
1696 }
1697 return 0;
1698}
1699device_initcall(cpuhp_sysfs_init);
1700#endif
1701
1702/*
1703 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1704 * represents all NR_CPUS bits binary values of 1<<nr.
1705 *
1706 * It is used by cpumask_of() to get a constant address to a CPU
1707 * mask value that has a single bit set only.
1708 */
1709
1710/* cpu_bit_bitmap[0] is empty - so we can back into it */
1711#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
1712#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1713#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1714#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1715
1716const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1717
1718 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
1719 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
1720#if BITS_PER_LONG > 32
1721 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
1722 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
1723#endif
1724};
1725EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1726
1727const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1728EXPORT_SYMBOL(cpu_all_bits);
1729
1730#ifdef CONFIG_INIT_ALL_POSSIBLE
1731struct cpumask __cpu_possible_mask __read_mostly
1732 = {CPU_BITS_ALL};
1733#else
1734struct cpumask __cpu_possible_mask __read_mostly;
1735#endif
1736EXPORT_SYMBOL(__cpu_possible_mask);
1737
1738struct cpumask __cpu_online_mask __read_mostly;
1739EXPORT_SYMBOL(__cpu_online_mask);
1740
1741struct cpumask __cpu_present_mask __read_mostly;
1742EXPORT_SYMBOL(__cpu_present_mask);
1743
1744struct cpumask __cpu_active_mask __read_mostly;
1745EXPORT_SYMBOL(__cpu_active_mask);
1746
1747void init_cpu_present(const struct cpumask *src)
1748{
1749 cpumask_copy(&__cpu_present_mask, src);
1750}
1751
1752void init_cpu_possible(const struct cpumask *src)
1753{
1754 cpumask_copy(&__cpu_possible_mask, src);
1755}
1756
1757void init_cpu_online(const struct cpumask *src)
1758{
1759 cpumask_copy(&__cpu_online_mask, src);
1760}
1761
1762/*
1763 * Activate the first processor.
1764 */
1765void __init boot_cpu_init(void)
1766{
1767 int cpu = smp_processor_id();
1768
1769 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1770 set_cpu_online(cpu, true);
1771 set_cpu_active(cpu, true);
1772 set_cpu_present(cpu, true);
1773 set_cpu_possible(cpu, true);
1774}
1775
1776/*
1777 * Must be called _AFTER_ setting up the per_cpu areas
1778 */
1779void __init boot_cpu_state_init(void)
1780{
1781 per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1782}