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1 /* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6 #include <linux/proc_fs.h>
7 #include <linux/smp.h>
8 #include <linux/init.h>
9 #include <linux/notifier.h>
10 #include <linux/sched.h>
11 #include <linux/unistd.h>
12 #include <linux/cpu.h>
13 #include <linux/oom.h>
14 #include <linux/rcupdate.h>
15 #include <linux/export.h>
16 #include <linux/bug.h>
17 #include <linux/kthread.h>
18 #include <linux/stop_machine.h>
19 #include <linux/mutex.h>
20 #include <linux/gfp.h>
21 #include <linux/suspend.h>
22 #include <linux/lockdep.h>
23 #include <linux/tick.h>
24 #include <linux/irq.h>
25 #include <linux/smpboot.h>
26 #include <linux/relay.h>
27 #include <linux/slab.h>
28
29 #include <trace/events/power.h>
30 #define CREATE_TRACE_POINTS
31 #include <trace/events/cpuhp.h>
32
33 #include "smpboot.h"
34
35 /**
36 * cpuhp_cpu_state - Per cpu hotplug state storage
37 * @state: The current cpu state
38 * @target: The target state
39 * @thread: Pointer to the hotplug thread
40 * @should_run: Thread should execute
41 * @rollback: Perform a rollback
42 * @single: Single callback invocation
43 * @bringup: Single callback bringup or teardown selector
44 * @cb_state: The state for a single callback (install/uninstall)
45 * @result: Result of the operation
46 * @done: Signal completion to the issuer of the task
47 */
48 struct cpuhp_cpu_state {
49 enum cpuhp_state state;
50 enum cpuhp_state target;
51 #ifdef CONFIG_SMP
52 struct task_struct *thread;
53 bool should_run;
54 bool rollback;
55 bool single;
56 bool bringup;
57 struct hlist_node *node;
58 enum cpuhp_state cb_state;
59 int result;
60 struct completion done;
61 #endif
62 };
63
64 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
65
66 /**
67 * cpuhp_step - Hotplug state machine step
68 * @name: Name of the step
69 * @startup: Startup function of the step
70 * @teardown: Teardown function of the step
71 * @skip_onerr: Do not invoke the functions on error rollback
72 * Will go away once the notifiers are gone
73 * @cant_stop: Bringup/teardown can't be stopped at this step
74 */
75 struct cpuhp_step {
76 const char *name;
77 union {
78 int (*single)(unsigned int cpu);
79 int (*multi)(unsigned int cpu,
80 struct hlist_node *node);
81 } startup;
82 union {
83 int (*single)(unsigned int cpu);
84 int (*multi)(unsigned int cpu,
85 struct hlist_node *node);
86 } teardown;
87 struct hlist_head list;
88 bool skip_onerr;
89 bool cant_stop;
90 bool multi_instance;
91 };
92
93 static DEFINE_MUTEX(cpuhp_state_mutex);
94 static struct cpuhp_step cpuhp_bp_states[];
95 static struct cpuhp_step cpuhp_ap_states[];
96
97 static bool cpuhp_is_ap_state(enum cpuhp_state state)
98 {
99 /*
100 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
101 * purposes as that state is handled explicitly in cpu_down.
102 */
103 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
104 }
105
106 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
107 {
108 struct cpuhp_step *sp;
109
110 sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
111 return sp + state;
112 }
113
114 /**
115 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
116 * @cpu: The cpu for which the callback should be invoked
117 * @step: The step in the state machine
118 * @bringup: True if the bringup callback should be invoked
119 *
120 * Called from cpu hotplug and from the state register machinery.
121 */
122 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
123 bool bringup, struct hlist_node *node)
124 {
125 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
126 struct cpuhp_step *step = cpuhp_get_step(state);
127 int (*cbm)(unsigned int cpu, struct hlist_node *node);
128 int (*cb)(unsigned int cpu);
129 int ret, cnt;
130
131 if (!step->multi_instance) {
132 cb = bringup ? step->startup.single : step->teardown.single;
133 if (!cb)
134 return 0;
135 trace_cpuhp_enter(cpu, st->target, state, cb);
136 ret = cb(cpu);
137 trace_cpuhp_exit(cpu, st->state, state, ret);
138 return ret;
139 }
140 cbm = bringup ? step->startup.multi : step->teardown.multi;
141 if (!cbm)
142 return 0;
143
144 /* Single invocation for instance add/remove */
145 if (node) {
146 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
147 ret = cbm(cpu, node);
148 trace_cpuhp_exit(cpu, st->state, state, ret);
149 return ret;
150 }
151
152 /* State transition. Invoke on all instances */
153 cnt = 0;
154 hlist_for_each(node, &step->list) {
155 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
156 ret = cbm(cpu, node);
157 trace_cpuhp_exit(cpu, st->state, state, ret);
158 if (ret)
159 goto err;
160 cnt++;
161 }
162 return 0;
163 err:
164 /* Rollback the instances if one failed */
165 cbm = !bringup ? step->startup.multi : step->teardown.multi;
166 if (!cbm)
167 return ret;
168
169 hlist_for_each(node, &step->list) {
170 if (!cnt--)
171 break;
172 cbm(cpu, node);
173 }
174 return ret;
175 }
176
177 #ifdef CONFIG_SMP
178 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
179 static DEFINE_MUTEX(cpu_add_remove_lock);
180 bool cpuhp_tasks_frozen;
181 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
182
183 /*
184 * The following two APIs (cpu_maps_update_begin/done) must be used when
185 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
186 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
187 * hotplug callback (un)registration performed using __register_cpu_notifier()
188 * or __unregister_cpu_notifier().
189 */
190 void cpu_maps_update_begin(void)
191 {
192 mutex_lock(&cpu_add_remove_lock);
193 }
194 EXPORT_SYMBOL(cpu_notifier_register_begin);
195
196 void cpu_maps_update_done(void)
197 {
198 mutex_unlock(&cpu_add_remove_lock);
199 }
200 EXPORT_SYMBOL(cpu_notifier_register_done);
201
202 static RAW_NOTIFIER_HEAD(cpu_chain);
203
204 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
205 * Should always be manipulated under cpu_add_remove_lock
206 */
207 static int cpu_hotplug_disabled;
208
209 #ifdef CONFIG_HOTPLUG_CPU
210
211 static struct {
212 struct task_struct *active_writer;
213 /* wait queue to wake up the active_writer */
214 wait_queue_head_t wq;
215 /* verifies that no writer will get active while readers are active */
216 struct mutex lock;
217 /*
218 * Also blocks the new readers during
219 * an ongoing cpu hotplug operation.
220 */
221 atomic_t refcount;
222
223 #ifdef CONFIG_DEBUG_LOCK_ALLOC
224 struct lockdep_map dep_map;
225 #endif
226 } cpu_hotplug = {
227 .active_writer = NULL,
228 .wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
229 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
230 #ifdef CONFIG_DEBUG_LOCK_ALLOC
231 .dep_map = {.name = "cpu_hotplug.lock" },
232 #endif
233 };
234
235 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
236 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
237 #define cpuhp_lock_acquire_tryread() \
238 lock_map_acquire_tryread(&cpu_hotplug.dep_map)
239 #define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
240 #define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
241
242
243 void get_online_cpus(void)
244 {
245 might_sleep();
246 if (cpu_hotplug.active_writer == current)
247 return;
248 cpuhp_lock_acquire_read();
249 mutex_lock(&cpu_hotplug.lock);
250 atomic_inc(&cpu_hotplug.refcount);
251 mutex_unlock(&cpu_hotplug.lock);
252 }
253 EXPORT_SYMBOL_GPL(get_online_cpus);
254
255 void put_online_cpus(void)
256 {
257 int refcount;
258
259 if (cpu_hotplug.active_writer == current)
260 return;
261
262 refcount = atomic_dec_return(&cpu_hotplug.refcount);
263 if (WARN_ON(refcount < 0)) /* try to fix things up */
264 atomic_inc(&cpu_hotplug.refcount);
265
266 if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
267 wake_up(&cpu_hotplug.wq);
268
269 cpuhp_lock_release();
270
271 }
272 EXPORT_SYMBOL_GPL(put_online_cpus);
273
274 /*
275 * This ensures that the hotplug operation can begin only when the
276 * refcount goes to zero.
277 *
278 * Note that during a cpu-hotplug operation, the new readers, if any,
279 * will be blocked by the cpu_hotplug.lock
280 *
281 * Since cpu_hotplug_begin() is always called after invoking
282 * cpu_maps_update_begin(), we can be sure that only one writer is active.
283 *
284 * Note that theoretically, there is a possibility of a livelock:
285 * - Refcount goes to zero, last reader wakes up the sleeping
286 * writer.
287 * - Last reader unlocks the cpu_hotplug.lock.
288 * - A new reader arrives at this moment, bumps up the refcount.
289 * - The writer acquires the cpu_hotplug.lock finds the refcount
290 * non zero and goes to sleep again.
291 *
292 * However, this is very difficult to achieve in practice since
293 * get_online_cpus() not an api which is called all that often.
294 *
295 */
296 void cpu_hotplug_begin(void)
297 {
298 DEFINE_WAIT(wait);
299
300 cpu_hotplug.active_writer = current;
301 cpuhp_lock_acquire();
302
303 for (;;) {
304 mutex_lock(&cpu_hotplug.lock);
305 prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
306 if (likely(!atomic_read(&cpu_hotplug.refcount)))
307 break;
308 mutex_unlock(&cpu_hotplug.lock);
309 schedule();
310 }
311 finish_wait(&cpu_hotplug.wq, &wait);
312 }
313
314 void cpu_hotplug_done(void)
315 {
316 cpu_hotplug.active_writer = NULL;
317 mutex_unlock(&cpu_hotplug.lock);
318 cpuhp_lock_release();
319 }
320
321 /*
322 * Wait for currently running CPU hotplug operations to complete (if any) and
323 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
324 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
325 * hotplug path before performing hotplug operations. So acquiring that lock
326 * guarantees mutual exclusion from any currently running hotplug operations.
327 */
328 void cpu_hotplug_disable(void)
329 {
330 cpu_maps_update_begin();
331 cpu_hotplug_disabled++;
332 cpu_maps_update_done();
333 }
334 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
335
336 static void __cpu_hotplug_enable(void)
337 {
338 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
339 return;
340 cpu_hotplug_disabled--;
341 }
342
343 void cpu_hotplug_enable(void)
344 {
345 cpu_maps_update_begin();
346 __cpu_hotplug_enable();
347 cpu_maps_update_done();
348 }
349 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
350 #endif /* CONFIG_HOTPLUG_CPU */
351
352 /* Need to know about CPUs going up/down? */
353 int register_cpu_notifier(struct notifier_block *nb)
354 {
355 int ret;
356 cpu_maps_update_begin();
357 ret = raw_notifier_chain_register(&cpu_chain, nb);
358 cpu_maps_update_done();
359 return ret;
360 }
361
362 int __register_cpu_notifier(struct notifier_block *nb)
363 {
364 return raw_notifier_chain_register(&cpu_chain, nb);
365 }
366
367 static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
368 int *nr_calls)
369 {
370 unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
371 void *hcpu = (void *)(long)cpu;
372
373 int ret;
374
375 ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
376 nr_calls);
377
378 return notifier_to_errno(ret);
379 }
380
381 static int cpu_notify(unsigned long val, unsigned int cpu)
382 {
383 return __cpu_notify(val, cpu, -1, NULL);
384 }
385
386 static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
387 {
388 BUG_ON(cpu_notify(val, cpu));
389 }
390
391 /* Notifier wrappers for transitioning to state machine */
392 static int notify_prepare(unsigned int cpu)
393 {
394 int nr_calls = 0;
395 int ret;
396
397 ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
398 if (ret) {
399 nr_calls--;
400 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
401 __func__, cpu);
402 __cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
403 }
404 return ret;
405 }
406
407 static int notify_online(unsigned int cpu)
408 {
409 cpu_notify(CPU_ONLINE, cpu);
410 return 0;
411 }
412
413 static int bringup_wait_for_ap(unsigned int cpu)
414 {
415 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
416
417 wait_for_completion(&st->done);
418 return st->result;
419 }
420
421 static int bringup_cpu(unsigned int cpu)
422 {
423 struct task_struct *idle = idle_thread_get(cpu);
424 int ret;
425
426 /*
427 * Some architectures have to walk the irq descriptors to
428 * setup the vector space for the cpu which comes online.
429 * Prevent irq alloc/free across the bringup.
430 */
431 irq_lock_sparse();
432
433 /* Arch-specific enabling code. */
434 ret = __cpu_up(cpu, idle);
435 irq_unlock_sparse();
436 if (ret) {
437 cpu_notify(CPU_UP_CANCELED, cpu);
438 return ret;
439 }
440 ret = bringup_wait_for_ap(cpu);
441 BUG_ON(!cpu_online(cpu));
442 return ret;
443 }
444
445 /*
446 * Hotplug state machine related functions
447 */
448 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
449 {
450 for (st->state++; st->state < st->target; st->state++) {
451 struct cpuhp_step *step = cpuhp_get_step(st->state);
452
453 if (!step->skip_onerr)
454 cpuhp_invoke_callback(cpu, st->state, true, NULL);
455 }
456 }
457
458 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
459 enum cpuhp_state target)
460 {
461 enum cpuhp_state prev_state = st->state;
462 int ret = 0;
463
464 for (; st->state > target; st->state--) {
465 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL);
466 if (ret) {
467 st->target = prev_state;
468 undo_cpu_down(cpu, st);
469 break;
470 }
471 }
472 return ret;
473 }
474
475 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
476 {
477 for (st->state--; st->state > st->target; st->state--) {
478 struct cpuhp_step *step = cpuhp_get_step(st->state);
479
480 if (!step->skip_onerr)
481 cpuhp_invoke_callback(cpu, st->state, false, NULL);
482 }
483 }
484
485 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
486 enum cpuhp_state target)
487 {
488 enum cpuhp_state prev_state = st->state;
489 int ret = 0;
490
491 while (st->state < target) {
492 st->state++;
493 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL);
494 if (ret) {
495 st->target = prev_state;
496 undo_cpu_up(cpu, st);
497 break;
498 }
499 }
500 return ret;
501 }
502
503 /*
504 * The cpu hotplug threads manage the bringup and teardown of the cpus
505 */
506 static void cpuhp_create(unsigned int cpu)
507 {
508 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
509
510 init_completion(&st->done);
511 }
512
513 static int cpuhp_should_run(unsigned int cpu)
514 {
515 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
516
517 return st->should_run;
518 }
519
520 /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
521 static int cpuhp_ap_offline(unsigned int cpu, struct cpuhp_cpu_state *st)
522 {
523 enum cpuhp_state target = max((int)st->target, CPUHP_TEARDOWN_CPU);
524
525 return cpuhp_down_callbacks(cpu, st, target);
526 }
527
528 /* Execute the online startup callbacks. Used to be CPU_ONLINE */
529 static int cpuhp_ap_online(unsigned int cpu, struct cpuhp_cpu_state *st)
530 {
531 return cpuhp_up_callbacks(cpu, st, st->target);
532 }
533
534 /*
535 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
536 * callbacks when a state gets [un]installed at runtime.
537 */
538 static void cpuhp_thread_fun(unsigned int cpu)
539 {
540 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
541 int ret = 0;
542
543 /*
544 * Paired with the mb() in cpuhp_kick_ap_work and
545 * cpuhp_invoke_ap_callback, so the work set is consistent visible.
546 */
547 smp_mb();
548 if (!st->should_run)
549 return;
550
551 st->should_run = false;
552
553 /* Single callback invocation for [un]install ? */
554 if (st->single) {
555 if (st->cb_state < CPUHP_AP_ONLINE) {
556 local_irq_disable();
557 ret = cpuhp_invoke_callback(cpu, st->cb_state,
558 st->bringup, st->node);
559 local_irq_enable();
560 } else {
561 ret = cpuhp_invoke_callback(cpu, st->cb_state,
562 st->bringup, st->node);
563 }
564 } else if (st->rollback) {
565 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
566
567 undo_cpu_down(cpu, st);
568 /*
569 * This is a momentary workaround to keep the notifier users
570 * happy. Will go away once we got rid of the notifiers.
571 */
572 cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
573 st->rollback = false;
574 } else {
575 /* Cannot happen .... */
576 BUG_ON(st->state < CPUHP_AP_ONLINE_IDLE);
577
578 /* Regular hotplug work */
579 if (st->state < st->target)
580 ret = cpuhp_ap_online(cpu, st);
581 else if (st->state > st->target)
582 ret = cpuhp_ap_offline(cpu, st);
583 }
584 st->result = ret;
585 complete(&st->done);
586 }
587
588 /* Invoke a single callback on a remote cpu */
589 static int
590 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
591 struct hlist_node *node)
592 {
593 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
594
595 if (!cpu_online(cpu))
596 return 0;
597
598 /*
599 * If we are up and running, use the hotplug thread. For early calls
600 * we invoke the thread function directly.
601 */
602 if (!st->thread)
603 return cpuhp_invoke_callback(cpu, state, bringup, node);
604
605 st->cb_state = state;
606 st->single = true;
607 st->bringup = bringup;
608 st->node = node;
609
610 /*
611 * Make sure the above stores are visible before should_run becomes
612 * true. Paired with the mb() above in cpuhp_thread_fun()
613 */
614 smp_mb();
615 st->should_run = true;
616 wake_up_process(st->thread);
617 wait_for_completion(&st->done);
618 return st->result;
619 }
620
621 /* Regular hotplug invocation of the AP hotplug thread */
622 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state *st)
623 {
624 st->result = 0;
625 st->single = false;
626 /*
627 * Make sure the above stores are visible before should_run becomes
628 * true. Paired with the mb() above in cpuhp_thread_fun()
629 */
630 smp_mb();
631 st->should_run = true;
632 wake_up_process(st->thread);
633 }
634
635 static int cpuhp_kick_ap_work(unsigned int cpu)
636 {
637 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
638 enum cpuhp_state state = st->state;
639
640 trace_cpuhp_enter(cpu, st->target, state, cpuhp_kick_ap_work);
641 __cpuhp_kick_ap_work(st);
642 wait_for_completion(&st->done);
643 trace_cpuhp_exit(cpu, st->state, state, st->result);
644 return st->result;
645 }
646
647 static struct smp_hotplug_thread cpuhp_threads = {
648 .store = &cpuhp_state.thread,
649 .create = &cpuhp_create,
650 .thread_should_run = cpuhp_should_run,
651 .thread_fn = cpuhp_thread_fun,
652 .thread_comm = "cpuhp/%u",
653 .selfparking = true,
654 };
655
656 void __init cpuhp_threads_init(void)
657 {
658 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
659 kthread_unpark(this_cpu_read(cpuhp_state.thread));
660 }
661
662 #ifdef CONFIG_HOTPLUG_CPU
663 EXPORT_SYMBOL(register_cpu_notifier);
664 EXPORT_SYMBOL(__register_cpu_notifier);
665 void unregister_cpu_notifier(struct notifier_block *nb)
666 {
667 cpu_maps_update_begin();
668 raw_notifier_chain_unregister(&cpu_chain, nb);
669 cpu_maps_update_done();
670 }
671 EXPORT_SYMBOL(unregister_cpu_notifier);
672
673 void __unregister_cpu_notifier(struct notifier_block *nb)
674 {
675 raw_notifier_chain_unregister(&cpu_chain, nb);
676 }
677 EXPORT_SYMBOL(__unregister_cpu_notifier);
678
679 /**
680 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
681 * @cpu: a CPU id
682 *
683 * This function walks all processes, finds a valid mm struct for each one and
684 * then clears a corresponding bit in mm's cpumask. While this all sounds
685 * trivial, there are various non-obvious corner cases, which this function
686 * tries to solve in a safe manner.
687 *
688 * Also note that the function uses a somewhat relaxed locking scheme, so it may
689 * be called only for an already offlined CPU.
690 */
691 void clear_tasks_mm_cpumask(int cpu)
692 {
693 struct task_struct *p;
694
695 /*
696 * This function is called after the cpu is taken down and marked
697 * offline, so its not like new tasks will ever get this cpu set in
698 * their mm mask. -- Peter Zijlstra
699 * Thus, we may use rcu_read_lock() here, instead of grabbing
700 * full-fledged tasklist_lock.
701 */
702 WARN_ON(cpu_online(cpu));
703 rcu_read_lock();
704 for_each_process(p) {
705 struct task_struct *t;
706
707 /*
708 * Main thread might exit, but other threads may still have
709 * a valid mm. Find one.
710 */
711 t = find_lock_task_mm(p);
712 if (!t)
713 continue;
714 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
715 task_unlock(t);
716 }
717 rcu_read_unlock();
718 }
719
720 static inline void check_for_tasks(int dead_cpu)
721 {
722 struct task_struct *g, *p;
723
724 read_lock(&tasklist_lock);
725 for_each_process_thread(g, p) {
726 if (!p->on_rq)
727 continue;
728 /*
729 * We do the check with unlocked task_rq(p)->lock.
730 * Order the reading to do not warn about a task,
731 * which was running on this cpu in the past, and
732 * it's just been woken on another cpu.
733 */
734 rmb();
735 if (task_cpu(p) != dead_cpu)
736 continue;
737
738 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
739 p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
740 }
741 read_unlock(&tasklist_lock);
742 }
743
744 static int notify_down_prepare(unsigned int cpu)
745 {
746 int err, nr_calls = 0;
747
748 err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
749 if (err) {
750 nr_calls--;
751 __cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
752 pr_warn("%s: attempt to take down CPU %u failed\n",
753 __func__, cpu);
754 }
755 return err;
756 }
757
758 /* Take this CPU down. */
759 static int take_cpu_down(void *_param)
760 {
761 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
762 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
763 int err, cpu = smp_processor_id();
764
765 /* Ensure this CPU doesn't handle any more interrupts. */
766 err = __cpu_disable();
767 if (err < 0)
768 return err;
769
770 /*
771 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
772 * do this step again.
773 */
774 WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
775 st->state--;
776 /* Invoke the former CPU_DYING callbacks */
777 for (; st->state > target; st->state--)
778 cpuhp_invoke_callback(cpu, st->state, false, NULL);
779
780 /* Give up timekeeping duties */
781 tick_handover_do_timer();
782 /* Park the stopper thread */
783 stop_machine_park(cpu);
784 return 0;
785 }
786
787 static int takedown_cpu(unsigned int cpu)
788 {
789 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
790 int err;
791
792 /* Park the smpboot threads */
793 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
794 smpboot_park_threads(cpu);
795
796 /*
797 * Prevent irq alloc/free while the dying cpu reorganizes the
798 * interrupt affinities.
799 */
800 irq_lock_sparse();
801
802 /*
803 * So now all preempt/rcu users must observe !cpu_active().
804 */
805 err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
806 if (err) {
807 /* CPU refused to die */
808 irq_unlock_sparse();
809 /* Unpark the hotplug thread so we can rollback there */
810 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
811 return err;
812 }
813 BUG_ON(cpu_online(cpu));
814
815 /*
816 * The CPUHP_AP_SCHED_MIGRATE_DYING callback will have removed all
817 * runnable tasks from the cpu, there's only the idle task left now
818 * that the migration thread is done doing the stop_machine thing.
819 *
820 * Wait for the stop thread to go away.
821 */
822 wait_for_completion(&st->done);
823 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
824
825 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
826 irq_unlock_sparse();
827
828 hotplug_cpu__broadcast_tick_pull(cpu);
829 /* This actually kills the CPU. */
830 __cpu_die(cpu);
831
832 tick_cleanup_dead_cpu(cpu);
833 return 0;
834 }
835
836 static int notify_dead(unsigned int cpu)
837 {
838 cpu_notify_nofail(CPU_DEAD, cpu);
839 check_for_tasks(cpu);
840 return 0;
841 }
842
843 static void cpuhp_complete_idle_dead(void *arg)
844 {
845 struct cpuhp_cpu_state *st = arg;
846
847 complete(&st->done);
848 }
849
850 void cpuhp_report_idle_dead(void)
851 {
852 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
853
854 BUG_ON(st->state != CPUHP_AP_OFFLINE);
855 rcu_report_dead(smp_processor_id());
856 st->state = CPUHP_AP_IDLE_DEAD;
857 /*
858 * We cannot call complete after rcu_report_dead() so we delegate it
859 * to an online cpu.
860 */
861 smp_call_function_single(cpumask_first(cpu_online_mask),
862 cpuhp_complete_idle_dead, st, 0);
863 }
864
865 #else
866 #define notify_down_prepare NULL
867 #define takedown_cpu NULL
868 #define notify_dead NULL
869 #endif
870
871 #ifdef CONFIG_HOTPLUG_CPU
872
873 /* Requires cpu_add_remove_lock to be held */
874 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
875 enum cpuhp_state target)
876 {
877 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
878 int prev_state, ret = 0;
879 bool hasdied = false;
880
881 if (num_online_cpus() == 1)
882 return -EBUSY;
883
884 if (!cpu_present(cpu))
885 return -EINVAL;
886
887 cpu_hotplug_begin();
888
889 cpuhp_tasks_frozen = tasks_frozen;
890
891 prev_state = st->state;
892 st->target = target;
893 /*
894 * If the current CPU state is in the range of the AP hotplug thread,
895 * then we need to kick the thread.
896 */
897 if (st->state > CPUHP_TEARDOWN_CPU) {
898 ret = cpuhp_kick_ap_work(cpu);
899 /*
900 * The AP side has done the error rollback already. Just
901 * return the error code..
902 */
903 if (ret)
904 goto out;
905
906 /*
907 * We might have stopped still in the range of the AP hotplug
908 * thread. Nothing to do anymore.
909 */
910 if (st->state > CPUHP_TEARDOWN_CPU)
911 goto out;
912 }
913 /*
914 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
915 * to do the further cleanups.
916 */
917 ret = cpuhp_down_callbacks(cpu, st, target);
918 if (ret && st->state > CPUHP_TEARDOWN_CPU && st->state < prev_state) {
919 st->target = prev_state;
920 st->rollback = true;
921 cpuhp_kick_ap_work(cpu);
922 }
923
924 hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
925 out:
926 cpu_hotplug_done();
927 /* This post dead nonsense must die */
928 if (!ret && hasdied)
929 cpu_notify_nofail(CPU_POST_DEAD, cpu);
930 return ret;
931 }
932
933 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
934 {
935 int err;
936
937 cpu_maps_update_begin();
938
939 if (cpu_hotplug_disabled) {
940 err = -EBUSY;
941 goto out;
942 }
943
944 err = _cpu_down(cpu, 0, target);
945
946 out:
947 cpu_maps_update_done();
948 return err;
949 }
950 int cpu_down(unsigned int cpu)
951 {
952 return do_cpu_down(cpu, CPUHP_OFFLINE);
953 }
954 EXPORT_SYMBOL(cpu_down);
955 #endif /*CONFIG_HOTPLUG_CPU*/
956
957 /**
958 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
959 * @cpu: cpu that just started
960 *
961 * It must be called by the arch code on the new cpu, before the new cpu
962 * enables interrupts and before the "boot" cpu returns from __cpu_up().
963 */
964 void notify_cpu_starting(unsigned int cpu)
965 {
966 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
967 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
968
969 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
970 while (st->state < target) {
971 st->state++;
972 cpuhp_invoke_callback(cpu, st->state, true, NULL);
973 }
974 }
975
976 /*
977 * Called from the idle task. We need to set active here, so we can kick off
978 * the stopper thread and unpark the smpboot threads. If the target state is
979 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
980 * cpu further.
981 */
982 void cpuhp_online_idle(enum cpuhp_state state)
983 {
984 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
985 unsigned int cpu = smp_processor_id();
986
987 /* Happens for the boot cpu */
988 if (state != CPUHP_AP_ONLINE_IDLE)
989 return;
990
991 st->state = CPUHP_AP_ONLINE_IDLE;
992
993 /* Unpark the stopper thread and the hotplug thread of this cpu */
994 stop_machine_unpark(cpu);
995 kthread_unpark(st->thread);
996
997 /* Should we go further up ? */
998 if (st->target > CPUHP_AP_ONLINE_IDLE)
999 __cpuhp_kick_ap_work(st);
1000 else
1001 complete(&st->done);
1002 }
1003
1004 /* Requires cpu_add_remove_lock to be held */
1005 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1006 {
1007 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1008 struct task_struct *idle;
1009 int ret = 0;
1010
1011 cpu_hotplug_begin();
1012
1013 if (!cpu_present(cpu)) {
1014 ret = -EINVAL;
1015 goto out;
1016 }
1017
1018 /*
1019 * The caller of do_cpu_up might have raced with another
1020 * caller. Ignore it for now.
1021 */
1022 if (st->state >= target)
1023 goto out;
1024
1025 if (st->state == CPUHP_OFFLINE) {
1026 /* Let it fail before we try to bring the cpu up */
1027 idle = idle_thread_get(cpu);
1028 if (IS_ERR(idle)) {
1029 ret = PTR_ERR(idle);
1030 goto out;
1031 }
1032 }
1033
1034 cpuhp_tasks_frozen = tasks_frozen;
1035
1036 st->target = target;
1037 /*
1038 * If the current CPU state is in the range of the AP hotplug thread,
1039 * then we need to kick the thread once more.
1040 */
1041 if (st->state > CPUHP_BRINGUP_CPU) {
1042 ret = cpuhp_kick_ap_work(cpu);
1043 /*
1044 * The AP side has done the error rollback already. Just
1045 * return the error code..
1046 */
1047 if (ret)
1048 goto out;
1049 }
1050
1051 /*
1052 * Try to reach the target state. We max out on the BP at
1053 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1054 * responsible for bringing it up to the target state.
1055 */
1056 target = min((int)target, CPUHP_BRINGUP_CPU);
1057 ret = cpuhp_up_callbacks(cpu, st, target);
1058 out:
1059 cpu_hotplug_done();
1060 return ret;
1061 }
1062
1063 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1064 {
1065 int err = 0;
1066
1067 if (!cpu_possible(cpu)) {
1068 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1069 cpu);
1070 #if defined(CONFIG_IA64)
1071 pr_err("please check additional_cpus= boot parameter\n");
1072 #endif
1073 return -EINVAL;
1074 }
1075
1076 err = try_online_node(cpu_to_node(cpu));
1077 if (err)
1078 return err;
1079
1080 cpu_maps_update_begin();
1081
1082 if (cpu_hotplug_disabled) {
1083 err = -EBUSY;
1084 goto out;
1085 }
1086
1087 err = _cpu_up(cpu, 0, target);
1088 out:
1089 cpu_maps_update_done();
1090 return err;
1091 }
1092
1093 int cpu_up(unsigned int cpu)
1094 {
1095 return do_cpu_up(cpu, CPUHP_ONLINE);
1096 }
1097 EXPORT_SYMBOL_GPL(cpu_up);
1098
1099 #ifdef CONFIG_PM_SLEEP_SMP
1100 static cpumask_var_t frozen_cpus;
1101
1102 int freeze_secondary_cpus(int primary)
1103 {
1104 int cpu, error = 0;
1105
1106 cpu_maps_update_begin();
1107 if (!cpu_online(primary))
1108 primary = cpumask_first(cpu_online_mask);
1109 /*
1110 * We take down all of the non-boot CPUs in one shot to avoid races
1111 * with the userspace trying to use the CPU hotplug at the same time
1112 */
1113 cpumask_clear(frozen_cpus);
1114
1115 pr_info("Disabling non-boot CPUs ...\n");
1116 for_each_online_cpu(cpu) {
1117 if (cpu == primary)
1118 continue;
1119 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1120 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1121 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1122 if (!error)
1123 cpumask_set_cpu(cpu, frozen_cpus);
1124 else {
1125 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1126 break;
1127 }
1128 }
1129
1130 if (!error)
1131 BUG_ON(num_online_cpus() > 1);
1132 else
1133 pr_err("Non-boot CPUs are not disabled\n");
1134
1135 /*
1136 * Make sure the CPUs won't be enabled by someone else. We need to do
1137 * this even in case of failure as all disable_nonboot_cpus() users are
1138 * supposed to do enable_nonboot_cpus() on the failure path.
1139 */
1140 cpu_hotplug_disabled++;
1141
1142 cpu_maps_update_done();
1143 return error;
1144 }
1145
1146 void __weak arch_enable_nonboot_cpus_begin(void)
1147 {
1148 }
1149
1150 void __weak arch_enable_nonboot_cpus_end(void)
1151 {
1152 }
1153
1154 void enable_nonboot_cpus(void)
1155 {
1156 int cpu, error;
1157
1158 /* Allow everyone to use the CPU hotplug again */
1159 cpu_maps_update_begin();
1160 __cpu_hotplug_enable();
1161 if (cpumask_empty(frozen_cpus))
1162 goto out;
1163
1164 pr_info("Enabling non-boot CPUs ...\n");
1165
1166 arch_enable_nonboot_cpus_begin();
1167
1168 for_each_cpu(cpu, frozen_cpus) {
1169 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1170 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1171 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1172 if (!error) {
1173 pr_info("CPU%d is up\n", cpu);
1174 continue;
1175 }
1176 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1177 }
1178
1179 arch_enable_nonboot_cpus_end();
1180
1181 cpumask_clear(frozen_cpus);
1182 out:
1183 cpu_maps_update_done();
1184 }
1185
1186 static int __init alloc_frozen_cpus(void)
1187 {
1188 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1189 return -ENOMEM;
1190 return 0;
1191 }
1192 core_initcall(alloc_frozen_cpus);
1193
1194 /*
1195 * When callbacks for CPU hotplug notifications are being executed, we must
1196 * ensure that the state of the system with respect to the tasks being frozen
1197 * or not, as reported by the notification, remains unchanged *throughout the
1198 * duration* of the execution of the callbacks.
1199 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1200 *
1201 * This synchronization is implemented by mutually excluding regular CPU
1202 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1203 * Hibernate notifications.
1204 */
1205 static int
1206 cpu_hotplug_pm_callback(struct notifier_block *nb,
1207 unsigned long action, void *ptr)
1208 {
1209 switch (action) {
1210
1211 case PM_SUSPEND_PREPARE:
1212 case PM_HIBERNATION_PREPARE:
1213 cpu_hotplug_disable();
1214 break;
1215
1216 case PM_POST_SUSPEND:
1217 case PM_POST_HIBERNATION:
1218 cpu_hotplug_enable();
1219 break;
1220
1221 default:
1222 return NOTIFY_DONE;
1223 }
1224
1225 return NOTIFY_OK;
1226 }
1227
1228
1229 static int __init cpu_hotplug_pm_sync_init(void)
1230 {
1231 /*
1232 * cpu_hotplug_pm_callback has higher priority than x86
1233 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1234 * to disable cpu hotplug to avoid cpu hotplug race.
1235 */
1236 pm_notifier(cpu_hotplug_pm_callback, 0);
1237 return 0;
1238 }
1239 core_initcall(cpu_hotplug_pm_sync_init);
1240
1241 #endif /* CONFIG_PM_SLEEP_SMP */
1242
1243 #endif /* CONFIG_SMP */
1244
1245 /* Boot processor state steps */
1246 static struct cpuhp_step cpuhp_bp_states[] = {
1247 [CPUHP_OFFLINE] = {
1248 .name = "offline",
1249 .startup.single = NULL,
1250 .teardown.single = NULL,
1251 },
1252 #ifdef CONFIG_SMP
1253 [CPUHP_CREATE_THREADS]= {
1254 .name = "threads:prepare",
1255 .startup.single = smpboot_create_threads,
1256 .teardown.single = NULL,
1257 .cant_stop = true,
1258 },
1259 [CPUHP_PERF_PREPARE] = {
1260 .name = "perf:prepare",
1261 .startup.single = perf_event_init_cpu,
1262 .teardown.single = perf_event_exit_cpu,
1263 },
1264 [CPUHP_WORKQUEUE_PREP] = {
1265 .name = "workqueue:prepare",
1266 .startup.single = workqueue_prepare_cpu,
1267 .teardown.single = NULL,
1268 },
1269 [CPUHP_HRTIMERS_PREPARE] = {
1270 .name = "hrtimers:prepare",
1271 .startup.single = hrtimers_prepare_cpu,
1272 .teardown.single = hrtimers_dead_cpu,
1273 },
1274 [CPUHP_SMPCFD_PREPARE] = {
1275 .name = "smpcfd:prepare",
1276 .startup.single = smpcfd_prepare_cpu,
1277 .teardown.single = smpcfd_dead_cpu,
1278 },
1279 [CPUHP_RELAY_PREPARE] = {
1280 .name = "relay:prepare",
1281 .startup.single = relay_prepare_cpu,
1282 .teardown.single = NULL,
1283 },
1284 [CPUHP_SLAB_PREPARE] = {
1285 .name = "slab:prepare",
1286 .startup.single = slab_prepare_cpu,
1287 .teardown.single = slab_dead_cpu,
1288 },
1289 [CPUHP_RCUTREE_PREP] = {
1290 .name = "RCU/tree:prepare",
1291 .startup.single = rcutree_prepare_cpu,
1292 .teardown.single = rcutree_dead_cpu,
1293 },
1294 /*
1295 * Preparatory and dead notifiers. Will be replaced once the notifiers
1296 * are converted to states.
1297 */
1298 [CPUHP_NOTIFY_PREPARE] = {
1299 .name = "notify:prepare",
1300 .startup.single = notify_prepare,
1301 .teardown.single = notify_dead,
1302 .skip_onerr = true,
1303 .cant_stop = true,
1304 },
1305 /*
1306 * On the tear-down path, timers_dead_cpu() must be invoked
1307 * before blk_mq_queue_reinit_notify() from notify_dead(),
1308 * otherwise a RCU stall occurs.
1309 */
1310 [CPUHP_TIMERS_DEAD] = {
1311 .name = "timers:dead",
1312 .startup.single = NULL,
1313 .teardown.single = timers_dead_cpu,
1314 },
1315 /* Kicks the plugged cpu into life */
1316 [CPUHP_BRINGUP_CPU] = {
1317 .name = "cpu:bringup",
1318 .startup.single = bringup_cpu,
1319 .teardown.single = NULL,
1320 .cant_stop = true,
1321 },
1322 [CPUHP_AP_SMPCFD_DYING] = {
1323 .name = "smpcfd:dying",
1324 .startup.single = NULL,
1325 .teardown.single = smpcfd_dying_cpu,
1326 },
1327 /*
1328 * Handled on controll processor until the plugged processor manages
1329 * this itself.
1330 */
1331 [CPUHP_TEARDOWN_CPU] = {
1332 .name = "cpu:teardown",
1333 .startup.single = NULL,
1334 .teardown.single = takedown_cpu,
1335 .cant_stop = true,
1336 },
1337 #else
1338 [CPUHP_BRINGUP_CPU] = { },
1339 #endif
1340 };
1341
1342 /* Application processor state steps */
1343 static struct cpuhp_step cpuhp_ap_states[] = {
1344 #ifdef CONFIG_SMP
1345 /* Final state before CPU kills itself */
1346 [CPUHP_AP_IDLE_DEAD] = {
1347 .name = "idle:dead",
1348 },
1349 /*
1350 * Last state before CPU enters the idle loop to die. Transient state
1351 * for synchronization.
1352 */
1353 [CPUHP_AP_OFFLINE] = {
1354 .name = "ap:offline",
1355 .cant_stop = true,
1356 },
1357 /* First state is scheduler control. Interrupts are disabled */
1358 [CPUHP_AP_SCHED_STARTING] = {
1359 .name = "sched:starting",
1360 .startup.single = sched_cpu_starting,
1361 .teardown.single = sched_cpu_dying,
1362 },
1363 [CPUHP_AP_RCUTREE_DYING] = {
1364 .name = "RCU/tree:dying",
1365 .startup.single = NULL,
1366 .teardown.single = rcutree_dying_cpu,
1367 },
1368 /* Entry state on starting. Interrupts enabled from here on. Transient
1369 * state for synchronsization */
1370 [CPUHP_AP_ONLINE] = {
1371 .name = "ap:online",
1372 },
1373 /* Handle smpboot threads park/unpark */
1374 [CPUHP_AP_SMPBOOT_THREADS] = {
1375 .name = "smpboot/threads:online",
1376 .startup.single = smpboot_unpark_threads,
1377 .teardown.single = NULL,
1378 },
1379 [CPUHP_AP_PERF_ONLINE] = {
1380 .name = "perf:online",
1381 .startup.single = perf_event_init_cpu,
1382 .teardown.single = perf_event_exit_cpu,
1383 },
1384 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1385 .name = "workqueue:online",
1386 .startup.single = workqueue_online_cpu,
1387 .teardown.single = workqueue_offline_cpu,
1388 },
1389 [CPUHP_AP_RCUTREE_ONLINE] = {
1390 .name = "RCU/tree:online",
1391 .startup.single = rcutree_online_cpu,
1392 .teardown.single = rcutree_offline_cpu,
1393 },
1394
1395 /*
1396 * Online/down_prepare notifiers. Will be removed once the notifiers
1397 * are converted to states.
1398 */
1399 [CPUHP_AP_NOTIFY_ONLINE] = {
1400 .name = "notify:online",
1401 .startup.single = notify_online,
1402 .teardown.single = notify_down_prepare,
1403 .skip_onerr = true,
1404 },
1405 #endif
1406 /*
1407 * The dynamically registered state space is here
1408 */
1409
1410 #ifdef CONFIG_SMP
1411 /* Last state is scheduler control setting the cpu active */
1412 [CPUHP_AP_ACTIVE] = {
1413 .name = "sched:active",
1414 .startup.single = sched_cpu_activate,
1415 .teardown.single = sched_cpu_deactivate,
1416 },
1417 #endif
1418
1419 /* CPU is fully up and running. */
1420 [CPUHP_ONLINE] = {
1421 .name = "online",
1422 .startup.single = NULL,
1423 .teardown.single = NULL,
1424 },
1425 };
1426
1427 /* Sanity check for callbacks */
1428 static int cpuhp_cb_check(enum cpuhp_state state)
1429 {
1430 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1431 return -EINVAL;
1432 return 0;
1433 }
1434
1435 static void cpuhp_store_callbacks(enum cpuhp_state state,
1436 const char *name,
1437 int (*startup)(unsigned int cpu),
1438 int (*teardown)(unsigned int cpu),
1439 bool multi_instance)
1440 {
1441 /* (Un)Install the callbacks for further cpu hotplug operations */
1442 struct cpuhp_step *sp;
1443
1444 mutex_lock(&cpuhp_state_mutex);
1445 sp = cpuhp_get_step(state);
1446 sp->startup.single = startup;
1447 sp->teardown.single = teardown;
1448 sp->name = name;
1449 sp->multi_instance = multi_instance;
1450 INIT_HLIST_HEAD(&sp->list);
1451 mutex_unlock(&cpuhp_state_mutex);
1452 }
1453
1454 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1455 {
1456 return cpuhp_get_step(state)->teardown.single;
1457 }
1458
1459 /*
1460 * Call the startup/teardown function for a step either on the AP or
1461 * on the current CPU.
1462 */
1463 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1464 struct hlist_node *node)
1465 {
1466 struct cpuhp_step *sp = cpuhp_get_step(state);
1467 int ret;
1468
1469 if ((bringup && !sp->startup.single) ||
1470 (!bringup && !sp->teardown.single))
1471 return 0;
1472 /*
1473 * The non AP bound callbacks can fail on bringup. On teardown
1474 * e.g. module removal we crash for now.
1475 */
1476 #ifdef CONFIG_SMP
1477 if (cpuhp_is_ap_state(state))
1478 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1479 else
1480 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1481 #else
1482 ret = cpuhp_invoke_callback(cpu, state, bringup, node);
1483 #endif
1484 BUG_ON(ret && !bringup);
1485 return ret;
1486 }
1487
1488 /*
1489 * Called from __cpuhp_setup_state on a recoverable failure.
1490 *
1491 * Note: The teardown callbacks for rollback are not allowed to fail!
1492 */
1493 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1494 struct hlist_node *node)
1495 {
1496 int cpu;
1497
1498 /* Roll back the already executed steps on the other cpus */
1499 for_each_present_cpu(cpu) {
1500 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1501 int cpustate = st->state;
1502
1503 if (cpu >= failedcpu)
1504 break;
1505
1506 /* Did we invoke the startup call on that cpu ? */
1507 if (cpustate >= state)
1508 cpuhp_issue_call(cpu, state, false, node);
1509 }
1510 }
1511
1512 /*
1513 * Returns a free for dynamic slot assignment of the Online state. The states
1514 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1515 * by having no name assigned.
1516 */
1517 static int cpuhp_reserve_state(enum cpuhp_state state)
1518 {
1519 enum cpuhp_state i;
1520
1521 mutex_lock(&cpuhp_state_mutex);
1522 for (i = CPUHP_AP_ONLINE_DYN; i <= CPUHP_AP_ONLINE_DYN_END; i++) {
1523 if (cpuhp_ap_states[i].name)
1524 continue;
1525
1526 cpuhp_ap_states[i].name = "Reserved";
1527 mutex_unlock(&cpuhp_state_mutex);
1528 return i;
1529 }
1530 mutex_unlock(&cpuhp_state_mutex);
1531 WARN(1, "No more dynamic states available for CPU hotplug\n");
1532 return -ENOSPC;
1533 }
1534
1535 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1536 bool invoke)
1537 {
1538 struct cpuhp_step *sp;
1539 int cpu;
1540 int ret;
1541
1542 sp = cpuhp_get_step(state);
1543 if (sp->multi_instance == false)
1544 return -EINVAL;
1545
1546 get_online_cpus();
1547
1548 if (!invoke || !sp->startup.multi)
1549 goto add_node;
1550
1551 /*
1552 * Try to call the startup callback for each present cpu
1553 * depending on the hotplug state of the cpu.
1554 */
1555 for_each_present_cpu(cpu) {
1556 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1557 int cpustate = st->state;
1558
1559 if (cpustate < state)
1560 continue;
1561
1562 ret = cpuhp_issue_call(cpu, state, true, node);
1563 if (ret) {
1564 if (sp->teardown.multi)
1565 cpuhp_rollback_install(cpu, state, node);
1566 goto err;
1567 }
1568 }
1569 add_node:
1570 ret = 0;
1571 mutex_lock(&cpuhp_state_mutex);
1572 hlist_add_head(node, &sp->list);
1573 mutex_unlock(&cpuhp_state_mutex);
1574
1575 err:
1576 put_online_cpus();
1577 return ret;
1578 }
1579 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1580
1581 /**
1582 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1583 * @state: The state to setup
1584 * @invoke: If true, the startup function is invoked for cpus where
1585 * cpu state >= @state
1586 * @startup: startup callback function
1587 * @teardown: teardown callback function
1588 *
1589 * Returns 0 if successful, otherwise a proper error code
1590 */
1591 int __cpuhp_setup_state(enum cpuhp_state state,
1592 const char *name, bool invoke,
1593 int (*startup)(unsigned int cpu),
1594 int (*teardown)(unsigned int cpu),
1595 bool multi_instance)
1596 {
1597 int cpu, ret = 0;
1598 int dyn_state = 0;
1599
1600 if (cpuhp_cb_check(state) || !name)
1601 return -EINVAL;
1602
1603 get_online_cpus();
1604
1605 /* currently assignments for the ONLINE state are possible */
1606 if (state == CPUHP_AP_ONLINE_DYN) {
1607 dyn_state = 1;
1608 ret = cpuhp_reserve_state(state);
1609 if (ret < 0)
1610 goto out;
1611 state = ret;
1612 }
1613
1614 cpuhp_store_callbacks(state, name, startup, teardown, multi_instance);
1615
1616 if (!invoke || !startup)
1617 goto out;
1618
1619 /*
1620 * Try to call the startup callback for each present cpu
1621 * depending on the hotplug state of the cpu.
1622 */
1623 for_each_present_cpu(cpu) {
1624 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1625 int cpustate = st->state;
1626
1627 if (cpustate < state)
1628 continue;
1629
1630 ret = cpuhp_issue_call(cpu, state, true, NULL);
1631 if (ret) {
1632 if (teardown)
1633 cpuhp_rollback_install(cpu, state, NULL);
1634 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1635 goto out;
1636 }
1637 }
1638 out:
1639 put_online_cpus();
1640 if (!ret && dyn_state)
1641 return state;
1642 return ret;
1643 }
1644 EXPORT_SYMBOL(__cpuhp_setup_state);
1645
1646 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1647 struct hlist_node *node, bool invoke)
1648 {
1649 struct cpuhp_step *sp = cpuhp_get_step(state);
1650 int cpu;
1651
1652 BUG_ON(cpuhp_cb_check(state));
1653
1654 if (!sp->multi_instance)
1655 return -EINVAL;
1656
1657 get_online_cpus();
1658 if (!invoke || !cpuhp_get_teardown_cb(state))
1659 goto remove;
1660 /*
1661 * Call the teardown callback for each present cpu depending
1662 * on the hotplug state of the cpu. This function is not
1663 * allowed to fail currently!
1664 */
1665 for_each_present_cpu(cpu) {
1666 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1667 int cpustate = st->state;
1668
1669 if (cpustate >= state)
1670 cpuhp_issue_call(cpu, state, false, node);
1671 }
1672
1673 remove:
1674 mutex_lock(&cpuhp_state_mutex);
1675 hlist_del(node);
1676 mutex_unlock(&cpuhp_state_mutex);
1677 put_online_cpus();
1678
1679 return 0;
1680 }
1681 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1682 /**
1683 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1684 * @state: The state to remove
1685 * @invoke: If true, the teardown function is invoked for cpus where
1686 * cpu state >= @state
1687 *
1688 * The teardown callback is currently not allowed to fail. Think
1689 * about module removal!
1690 */
1691 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1692 {
1693 struct cpuhp_step *sp = cpuhp_get_step(state);
1694 int cpu;
1695
1696 BUG_ON(cpuhp_cb_check(state));
1697
1698 get_online_cpus();
1699
1700 if (sp->multi_instance) {
1701 WARN(!hlist_empty(&sp->list),
1702 "Error: Removing state %d which has instances left.\n",
1703 state);
1704 goto remove;
1705 }
1706
1707 if (!invoke || !cpuhp_get_teardown_cb(state))
1708 goto remove;
1709
1710 /*
1711 * Call the teardown callback for each present cpu depending
1712 * on the hotplug state of the cpu. This function is not
1713 * allowed to fail currently!
1714 */
1715 for_each_present_cpu(cpu) {
1716 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1717 int cpustate = st->state;
1718
1719 if (cpustate >= state)
1720 cpuhp_issue_call(cpu, state, false, NULL);
1721 }
1722 remove:
1723 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1724 put_online_cpus();
1725 }
1726 EXPORT_SYMBOL(__cpuhp_remove_state);
1727
1728 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1729 static ssize_t show_cpuhp_state(struct device *dev,
1730 struct device_attribute *attr, char *buf)
1731 {
1732 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1733
1734 return sprintf(buf, "%d\n", st->state);
1735 }
1736 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1737
1738 static ssize_t write_cpuhp_target(struct device *dev,
1739 struct device_attribute *attr,
1740 const char *buf, size_t count)
1741 {
1742 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1743 struct cpuhp_step *sp;
1744 int target, ret;
1745
1746 ret = kstrtoint(buf, 10, &target);
1747 if (ret)
1748 return ret;
1749
1750 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1751 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1752 return -EINVAL;
1753 #else
1754 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1755 return -EINVAL;
1756 #endif
1757
1758 ret = lock_device_hotplug_sysfs();
1759 if (ret)
1760 return ret;
1761
1762 mutex_lock(&cpuhp_state_mutex);
1763 sp = cpuhp_get_step(target);
1764 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1765 mutex_unlock(&cpuhp_state_mutex);
1766 if (ret)
1767 return ret;
1768
1769 if (st->state < target)
1770 ret = do_cpu_up(dev->id, target);
1771 else
1772 ret = do_cpu_down(dev->id, target);
1773
1774 unlock_device_hotplug();
1775 return ret ? ret : count;
1776 }
1777
1778 static ssize_t show_cpuhp_target(struct device *dev,
1779 struct device_attribute *attr, char *buf)
1780 {
1781 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1782
1783 return sprintf(buf, "%d\n", st->target);
1784 }
1785 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1786
1787 static struct attribute *cpuhp_cpu_attrs[] = {
1788 &dev_attr_state.attr,
1789 &dev_attr_target.attr,
1790 NULL
1791 };
1792
1793 static struct attribute_group cpuhp_cpu_attr_group = {
1794 .attrs = cpuhp_cpu_attrs,
1795 .name = "hotplug",
1796 NULL
1797 };
1798
1799 static ssize_t show_cpuhp_states(struct device *dev,
1800 struct device_attribute *attr, char *buf)
1801 {
1802 ssize_t cur, res = 0;
1803 int i;
1804
1805 mutex_lock(&cpuhp_state_mutex);
1806 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1807 struct cpuhp_step *sp = cpuhp_get_step(i);
1808
1809 if (sp->name) {
1810 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1811 buf += cur;
1812 res += cur;
1813 }
1814 }
1815 mutex_unlock(&cpuhp_state_mutex);
1816 return res;
1817 }
1818 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1819
1820 static struct attribute *cpuhp_cpu_root_attrs[] = {
1821 &dev_attr_states.attr,
1822 NULL
1823 };
1824
1825 static struct attribute_group cpuhp_cpu_root_attr_group = {
1826 .attrs = cpuhp_cpu_root_attrs,
1827 .name = "hotplug",
1828 NULL
1829 };
1830
1831 static int __init cpuhp_sysfs_init(void)
1832 {
1833 int cpu, ret;
1834
1835 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
1836 &cpuhp_cpu_root_attr_group);
1837 if (ret)
1838 return ret;
1839
1840 for_each_possible_cpu(cpu) {
1841 struct device *dev = get_cpu_device(cpu);
1842
1843 if (!dev)
1844 continue;
1845 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
1846 if (ret)
1847 return ret;
1848 }
1849 return 0;
1850 }
1851 device_initcall(cpuhp_sysfs_init);
1852 #endif
1853
1854 /*
1855 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1856 * represents all NR_CPUS bits binary values of 1<<nr.
1857 *
1858 * It is used by cpumask_of() to get a constant address to a CPU
1859 * mask value that has a single bit set only.
1860 */
1861
1862 /* cpu_bit_bitmap[0] is empty - so we can back into it */
1863 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
1864 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1865 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1866 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1867
1868 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
1869
1870 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
1871 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
1872 #if BITS_PER_LONG > 32
1873 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
1874 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
1875 #endif
1876 };
1877 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
1878
1879 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
1880 EXPORT_SYMBOL(cpu_all_bits);
1881
1882 #ifdef CONFIG_INIT_ALL_POSSIBLE
1883 struct cpumask __cpu_possible_mask __read_mostly
1884 = {CPU_BITS_ALL};
1885 #else
1886 struct cpumask __cpu_possible_mask __read_mostly;
1887 #endif
1888 EXPORT_SYMBOL(__cpu_possible_mask);
1889
1890 struct cpumask __cpu_online_mask __read_mostly;
1891 EXPORT_SYMBOL(__cpu_online_mask);
1892
1893 struct cpumask __cpu_present_mask __read_mostly;
1894 EXPORT_SYMBOL(__cpu_present_mask);
1895
1896 struct cpumask __cpu_active_mask __read_mostly;
1897 EXPORT_SYMBOL(__cpu_active_mask);
1898
1899 void init_cpu_present(const struct cpumask *src)
1900 {
1901 cpumask_copy(&__cpu_present_mask, src);
1902 }
1903
1904 void init_cpu_possible(const struct cpumask *src)
1905 {
1906 cpumask_copy(&__cpu_possible_mask, src);
1907 }
1908
1909 void init_cpu_online(const struct cpumask *src)
1910 {
1911 cpumask_copy(&__cpu_online_mask, src);
1912 }
1913
1914 /*
1915 * Activate the first processor.
1916 */
1917 void __init boot_cpu_init(void)
1918 {
1919 int cpu = smp_processor_id();
1920
1921 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1922 set_cpu_online(cpu, true);
1923 set_cpu_active(cpu, true);
1924 set_cpu_present(cpu, true);
1925 set_cpu_possible(cpu, true);
1926 }
1927
1928 /*
1929 * Must be called _AFTER_ setting up the per_cpu areas
1930 */
1931 void __init boot_cpu_state_init(void)
1932 {
1933 per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
1934 }