Commit | Line | Data |
---|---|---|
1142d810 TH |
1 | /* |
2 | * kernel/stop_machine.c | |
3 | * | |
4 | * Copyright (C) 2008, 2005 IBM Corporation. | |
5 | * Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au | |
6 | * Copyright (C) 2010 SUSE Linux Products GmbH | |
7 | * Copyright (C) 2010 Tejun Heo <tj@kernel.org> | |
8 | * | |
9 | * This file is released under the GPLv2 and any later version. | |
e5582ca2 | 10 | */ |
1142d810 | 11 | #include <linux/completion.h> |
1da177e4 | 12 | #include <linux/cpu.h> |
1142d810 | 13 | #include <linux/init.h> |
ee527cd3 | 14 | #include <linux/kthread.h> |
9984de1a | 15 | #include <linux/export.h> |
1142d810 | 16 | #include <linux/percpu.h> |
ee527cd3 PB |
17 | #include <linux/sched.h> |
18 | #include <linux/stop_machine.h> | |
a12bb444 | 19 | #include <linux/interrupt.h> |
1142d810 | 20 | #include <linux/kallsyms.h> |
14e568e7 | 21 | #include <linux/smpboot.h> |
60063497 | 22 | #include <linux/atomic.h> |
1142d810 TH |
23 | |
24 | /* | |
25 | * Structure to determine completion condition and record errors. May | |
26 | * be shared by works on different cpus. | |
27 | */ | |
28 | struct cpu_stop_done { | |
29 | atomic_t nr_todo; /* nr left to execute */ | |
30 | bool executed; /* actually executed? */ | |
31 | int ret; /* collected return value */ | |
32 | struct completion completion; /* fired if nr_todo reaches 0 */ | |
33 | }; | |
34 | ||
35 | /* the actual stopper, one per every possible cpu, enabled on online cpus */ | |
36 | struct cpu_stopper { | |
37 | spinlock_t lock; | |
878ae127 | 38 | bool enabled; /* is this stopper enabled? */ |
1142d810 | 39 | struct list_head works; /* list of pending works */ |
1142d810 TH |
40 | }; |
41 | ||
42 | static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); | |
860a0ffa | 43 | static DEFINE_PER_CPU(struct task_struct *, cpu_stopper_task); |
f445027e | 44 | static bool stop_machine_initialized = false; |
1142d810 TH |
45 | |
46 | static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) | |
47 | { | |
48 | memset(done, 0, sizeof(*done)); | |
49 | atomic_set(&done->nr_todo, nr_todo); | |
50 | init_completion(&done->completion); | |
51 | } | |
52 | ||
53 | /* signal completion unless @done is NULL */ | |
54 | static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed) | |
55 | { | |
56 | if (done) { | |
57 | if (executed) | |
58 | done->executed = true; | |
59 | if (atomic_dec_and_test(&done->nr_todo)) | |
60 | complete(&done->completion); | |
61 | } | |
62 | } | |
63 | ||
64 | /* queue @work to @stopper. if offline, @work is completed immediately */ | |
860a0ffa | 65 | static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) |
1142d810 | 66 | { |
860a0ffa TG |
67 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
68 | struct task_struct *p = per_cpu(cpu_stopper_task, cpu); | |
69 | ||
1142d810 TH |
70 | unsigned long flags; |
71 | ||
72 | spin_lock_irqsave(&stopper->lock, flags); | |
73 | ||
74 | if (stopper->enabled) { | |
75 | list_add_tail(&work->list, &stopper->works); | |
860a0ffa | 76 | wake_up_process(p); |
1142d810 TH |
77 | } else |
78 | cpu_stop_signal_done(work->done, false); | |
79 | ||
80 | spin_unlock_irqrestore(&stopper->lock, flags); | |
81 | } | |
82 | ||
83 | /** | |
84 | * stop_one_cpu - stop a cpu | |
85 | * @cpu: cpu to stop | |
86 | * @fn: function to execute | |
87 | * @arg: argument to @fn | |
88 | * | |
89 | * Execute @fn(@arg) on @cpu. @fn is run in a process context with | |
90 | * the highest priority preempting any task on the cpu and | |
91 | * monopolizing it. This function returns after the execution is | |
92 | * complete. | |
93 | * | |
94 | * This function doesn't guarantee @cpu stays online till @fn | |
95 | * completes. If @cpu goes down in the middle, execution may happen | |
96 | * partially or fully on different cpus. @fn should either be ready | |
97 | * for that or the caller should ensure that @cpu stays online until | |
98 | * this function completes. | |
99 | * | |
100 | * CONTEXT: | |
101 | * Might sleep. | |
102 | * | |
103 | * RETURNS: | |
104 | * -ENOENT if @fn(@arg) was not executed because @cpu was offline; | |
105 | * otherwise, the return value of @fn. | |
106 | */ | |
107 | int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) | |
108 | { | |
109 | struct cpu_stop_done done; | |
110 | struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done }; | |
111 | ||
112 | cpu_stop_init_done(&done, 1); | |
860a0ffa | 113 | cpu_stop_queue_work(cpu, &work); |
1142d810 TH |
114 | wait_for_completion(&done.completion); |
115 | return done.executed ? done.ret : -ENOENT; | |
116 | } | |
117 | ||
1be0bd77 PZ |
118 | /* This controls the threads on each CPU. */ |
119 | enum multi_stop_state { | |
120 | /* Dummy starting state for thread. */ | |
121 | MULTI_STOP_NONE, | |
122 | /* Awaiting everyone to be scheduled. */ | |
123 | MULTI_STOP_PREPARE, | |
124 | /* Disable interrupts. */ | |
125 | MULTI_STOP_DISABLE_IRQ, | |
126 | /* Run the function */ | |
127 | MULTI_STOP_RUN, | |
128 | /* Exit */ | |
129 | MULTI_STOP_EXIT, | |
130 | }; | |
131 | ||
132 | struct multi_stop_data { | |
133 | int (*fn)(void *); | |
134 | void *data; | |
135 | /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ | |
136 | unsigned int num_threads; | |
137 | const struct cpumask *active_cpus; | |
138 | ||
139 | enum multi_stop_state state; | |
140 | atomic_t thread_ack; | |
141 | }; | |
142 | ||
143 | static void set_state(struct multi_stop_data *msdata, | |
144 | enum multi_stop_state newstate) | |
145 | { | |
146 | /* Reset ack counter. */ | |
147 | atomic_set(&msdata->thread_ack, msdata->num_threads); | |
148 | smp_wmb(); | |
149 | msdata->state = newstate; | |
150 | } | |
151 | ||
152 | /* Last one to ack a state moves to the next state. */ | |
153 | static void ack_state(struct multi_stop_data *msdata) | |
154 | { | |
155 | if (atomic_dec_and_test(&msdata->thread_ack)) | |
156 | set_state(msdata, msdata->state + 1); | |
157 | } | |
158 | ||
159 | /* This is the cpu_stop function which stops the CPU. */ | |
160 | static int multi_cpu_stop(void *data) | |
161 | { | |
162 | struct multi_stop_data *msdata = data; | |
163 | enum multi_stop_state curstate = MULTI_STOP_NONE; | |
164 | int cpu = smp_processor_id(), err = 0; | |
165 | unsigned long flags; | |
166 | bool is_active; | |
167 | ||
168 | /* | |
169 | * When called from stop_machine_from_inactive_cpu(), irq might | |
170 | * already be disabled. Save the state and restore it on exit. | |
171 | */ | |
172 | local_save_flags(flags); | |
173 | ||
174 | if (!msdata->active_cpus) | |
175 | is_active = cpu == cpumask_first(cpu_online_mask); | |
176 | else | |
177 | is_active = cpumask_test_cpu(cpu, msdata->active_cpus); | |
178 | ||
179 | /* Simple state machine */ | |
180 | do { | |
181 | /* Chill out and ensure we re-read multi_stop_state. */ | |
182 | cpu_relax(); | |
183 | if (msdata->state != curstate) { | |
184 | curstate = msdata->state; | |
185 | switch (curstate) { | |
186 | case MULTI_STOP_DISABLE_IRQ: | |
187 | local_irq_disable(); | |
188 | hard_irq_disable(); | |
189 | break; | |
190 | case MULTI_STOP_RUN: | |
191 | if (is_active) | |
192 | err = msdata->fn(msdata->data); | |
193 | break; | |
194 | default: | |
195 | break; | |
196 | } | |
197 | ack_state(msdata); | |
198 | } | |
199 | } while (curstate != MULTI_STOP_EXIT); | |
200 | ||
201 | local_irq_restore(flags); | |
202 | return err; | |
203 | } | |
204 | ||
205 | struct irq_cpu_stop_queue_work_info { | |
206 | int cpu1; | |
207 | int cpu2; | |
208 | struct cpu_stop_work *work1; | |
209 | struct cpu_stop_work *work2; | |
210 | }; | |
211 | ||
212 | /* | |
213 | * This function is always run with irqs and preemption disabled. | |
214 | * This guarantees that both work1 and work2 get queued, before | |
215 | * our local migrate thread gets the chance to preempt us. | |
216 | */ | |
217 | static void irq_cpu_stop_queue_work(void *arg) | |
218 | { | |
219 | struct irq_cpu_stop_queue_work_info *info = arg; | |
220 | cpu_stop_queue_work(info->cpu1, info->work1); | |
221 | cpu_stop_queue_work(info->cpu2, info->work2); | |
222 | } | |
223 | ||
224 | /** | |
225 | * stop_two_cpus - stops two cpus | |
226 | * @cpu1: the cpu to stop | |
227 | * @cpu2: the other cpu to stop | |
228 | * @fn: function to execute | |
229 | * @arg: argument to @fn | |
230 | * | |
231 | * Stops both the current and specified CPU and runs @fn on one of them. | |
232 | * | |
233 | * returns when both are completed. | |
234 | */ | |
235 | int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg) | |
236 | { | |
237 | int call_cpu; | |
238 | struct cpu_stop_done done; | |
239 | struct cpu_stop_work work1, work2; | |
240 | struct irq_cpu_stop_queue_work_info call_args; | |
241 | struct multi_stop_data msdata = { | |
242 | .fn = fn, | |
243 | .data = arg, | |
244 | .num_threads = 2, | |
245 | .active_cpus = cpumask_of(cpu1), | |
246 | }; | |
247 | ||
248 | work1 = work2 = (struct cpu_stop_work){ | |
249 | .fn = multi_cpu_stop, | |
250 | .arg = &msdata, | |
251 | .done = &done | |
252 | }; | |
253 | ||
254 | call_args = (struct irq_cpu_stop_queue_work_info){ | |
255 | .cpu1 = cpu1, | |
256 | .cpu2 = cpu2, | |
257 | .work1 = &work1, | |
258 | .work2 = &work2, | |
259 | }; | |
260 | ||
261 | cpu_stop_init_done(&done, 2); | |
262 | set_state(&msdata, MULTI_STOP_PREPARE); | |
263 | ||
264 | /* | |
265 | * Queuing needs to be done by the lowest numbered CPU, to ensure | |
266 | * that works are always queued in the same order on every CPU. | |
267 | * This prevents deadlocks. | |
268 | */ | |
269 | call_cpu = min(cpu1, cpu2); | |
270 | ||
271 | smp_call_function_single(call_cpu, &irq_cpu_stop_queue_work, | |
272 | &call_args, 0); | |
273 | ||
274 | wait_for_completion(&done.completion); | |
275 | return done.executed ? done.ret : -ENOENT; | |
276 | } | |
277 | ||
1142d810 TH |
278 | /** |
279 | * stop_one_cpu_nowait - stop a cpu but don't wait for completion | |
280 | * @cpu: cpu to stop | |
281 | * @fn: function to execute | |
282 | * @arg: argument to @fn | |
283 | * | |
284 | * Similar to stop_one_cpu() but doesn't wait for completion. The | |
285 | * caller is responsible for ensuring @work_buf is currently unused | |
286 | * and will remain untouched until stopper starts executing @fn. | |
287 | * | |
288 | * CONTEXT: | |
289 | * Don't care. | |
290 | */ | |
291 | void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, | |
292 | struct cpu_stop_work *work_buf) | |
293 | { | |
294 | *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, }; | |
860a0ffa | 295 | cpu_stop_queue_work(cpu, work_buf); |
1142d810 TH |
296 | } |
297 | ||
298 | /* static data for stop_cpus */ | |
192d8857 | 299 | static DEFINE_MUTEX(stop_cpus_mutex); |
1142d810 TH |
300 | static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work); |
301 | ||
fd7355ba TH |
302 | static void queue_stop_cpus_work(const struct cpumask *cpumask, |
303 | cpu_stop_fn_t fn, void *arg, | |
304 | struct cpu_stop_done *done) | |
1142d810 TH |
305 | { |
306 | struct cpu_stop_work *work; | |
1142d810 TH |
307 | unsigned int cpu; |
308 | ||
309 | /* initialize works and done */ | |
310 | for_each_cpu(cpu, cpumask) { | |
311 | work = &per_cpu(stop_cpus_work, cpu); | |
312 | work->fn = fn; | |
313 | work->arg = arg; | |
fd7355ba | 314 | work->done = done; |
1142d810 | 315 | } |
1142d810 TH |
316 | |
317 | /* | |
318 | * Disable preemption while queueing to avoid getting | |
319 | * preempted by a stopper which might wait for other stoppers | |
320 | * to enter @fn which can lead to deadlock. | |
321 | */ | |
322 | preempt_disable(); | |
323 | for_each_cpu(cpu, cpumask) | |
860a0ffa | 324 | cpu_stop_queue_work(cpu, &per_cpu(stop_cpus_work, cpu)); |
1142d810 | 325 | preempt_enable(); |
fd7355ba | 326 | } |
1142d810 | 327 | |
fd7355ba TH |
328 | static int __stop_cpus(const struct cpumask *cpumask, |
329 | cpu_stop_fn_t fn, void *arg) | |
330 | { | |
331 | struct cpu_stop_done done; | |
332 | ||
333 | cpu_stop_init_done(&done, cpumask_weight(cpumask)); | |
334 | queue_stop_cpus_work(cpumask, fn, arg, &done); | |
1142d810 TH |
335 | wait_for_completion(&done.completion); |
336 | return done.executed ? done.ret : -ENOENT; | |
337 | } | |
338 | ||
339 | /** | |
340 | * stop_cpus - stop multiple cpus | |
341 | * @cpumask: cpus to stop | |
342 | * @fn: function to execute | |
343 | * @arg: argument to @fn | |
344 | * | |
345 | * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu, | |
346 | * @fn is run in a process context with the highest priority | |
347 | * preempting any task on the cpu and monopolizing it. This function | |
348 | * returns after all executions are complete. | |
349 | * | |
350 | * This function doesn't guarantee the cpus in @cpumask stay online | |
351 | * till @fn completes. If some cpus go down in the middle, execution | |
352 | * on the cpu may happen partially or fully on different cpus. @fn | |
353 | * should either be ready for that or the caller should ensure that | |
354 | * the cpus stay online until this function completes. | |
355 | * | |
356 | * All stop_cpus() calls are serialized making it safe for @fn to wait | |
357 | * for all cpus to start executing it. | |
358 | * | |
359 | * CONTEXT: | |
360 | * Might sleep. | |
361 | * | |
362 | * RETURNS: | |
363 | * -ENOENT if @fn(@arg) was not executed at all because all cpus in | |
364 | * @cpumask were offline; otherwise, 0 if all executions of @fn | |
365 | * returned 0, any non zero return value if any returned non zero. | |
366 | */ | |
367 | int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) | |
368 | { | |
369 | int ret; | |
370 | ||
371 | /* static works are used, process one request at a time */ | |
372 | mutex_lock(&stop_cpus_mutex); | |
373 | ret = __stop_cpus(cpumask, fn, arg); | |
374 | mutex_unlock(&stop_cpus_mutex); | |
375 | return ret; | |
376 | } | |
377 | ||
378 | /** | |
379 | * try_stop_cpus - try to stop multiple cpus | |
380 | * @cpumask: cpus to stop | |
381 | * @fn: function to execute | |
382 | * @arg: argument to @fn | |
383 | * | |
384 | * Identical to stop_cpus() except that it fails with -EAGAIN if | |
385 | * someone else is already using the facility. | |
386 | * | |
387 | * CONTEXT: | |
388 | * Might sleep. | |
389 | * | |
390 | * RETURNS: | |
391 | * -EAGAIN if someone else is already stopping cpus, -ENOENT if | |
392 | * @fn(@arg) was not executed at all because all cpus in @cpumask were | |
393 | * offline; otherwise, 0 if all executions of @fn returned 0, any non | |
394 | * zero return value if any returned non zero. | |
395 | */ | |
396 | int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) | |
397 | { | |
398 | int ret; | |
399 | ||
400 | /* static works are used, process one request at a time */ | |
401 | if (!mutex_trylock(&stop_cpus_mutex)) | |
402 | return -EAGAIN; | |
403 | ret = __stop_cpus(cpumask, fn, arg); | |
404 | mutex_unlock(&stop_cpus_mutex); | |
405 | return ret; | |
406 | } | |
407 | ||
14e568e7 TG |
408 | static int cpu_stop_should_run(unsigned int cpu) |
409 | { | |
410 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); | |
411 | unsigned long flags; | |
412 | int run; | |
413 | ||
414 | spin_lock_irqsave(&stopper->lock, flags); | |
415 | run = !list_empty(&stopper->works); | |
416 | spin_unlock_irqrestore(&stopper->lock, flags); | |
417 | return run; | |
418 | } | |
419 | ||
420 | static void cpu_stopper_thread(unsigned int cpu) | |
1142d810 | 421 | { |
14e568e7 | 422 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
1142d810 TH |
423 | struct cpu_stop_work *work; |
424 | int ret; | |
425 | ||
426 | repeat: | |
1142d810 TH |
427 | work = NULL; |
428 | spin_lock_irq(&stopper->lock); | |
429 | if (!list_empty(&stopper->works)) { | |
430 | work = list_first_entry(&stopper->works, | |
431 | struct cpu_stop_work, list); | |
432 | list_del_init(&work->list); | |
433 | } | |
434 | spin_unlock_irq(&stopper->lock); | |
435 | ||
436 | if (work) { | |
437 | cpu_stop_fn_t fn = work->fn; | |
438 | void *arg = work->arg; | |
439 | struct cpu_stop_done *done = work->done; | |
ca51c5a7 | 440 | char ksym_buf[KSYM_NAME_LEN] __maybe_unused; |
1142d810 | 441 | |
1142d810 TH |
442 | /* cpu stop callbacks are not allowed to sleep */ |
443 | preempt_disable(); | |
444 | ||
445 | ret = fn(arg); | |
446 | if (ret) | |
447 | done->ret = ret; | |
448 | ||
449 | /* restore preemption and check it's still balanced */ | |
450 | preempt_enable(); | |
451 | WARN_ONCE(preempt_count(), | |
452 | "cpu_stop: %s(%p) leaked preempt count\n", | |
453 | kallsyms_lookup((unsigned long)fn, NULL, NULL, NULL, | |
454 | ksym_buf), arg); | |
455 | ||
456 | cpu_stop_signal_done(done, true); | |
14e568e7 TG |
457 | goto repeat; |
458 | } | |
1142d810 TH |
459 | } |
460 | ||
34f971f6 PZ |
461 | extern void sched_set_stop_task(int cpu, struct task_struct *stop); |
462 | ||
14e568e7 TG |
463 | static void cpu_stop_create(unsigned int cpu) |
464 | { | |
465 | sched_set_stop_task(cpu, per_cpu(cpu_stopper_task, cpu)); | |
466 | } | |
467 | ||
468 | static void cpu_stop_park(unsigned int cpu) | |
1142d810 | 469 | { |
1142d810 | 470 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
14e568e7 TG |
471 | struct cpu_stop_work *work; |
472 | unsigned long flags; | |
1142d810 | 473 | |
14e568e7 TG |
474 | /* drain remaining works */ |
475 | spin_lock_irqsave(&stopper->lock, flags); | |
476 | list_for_each_entry(work, &stopper->works, list) | |
477 | cpu_stop_signal_done(work->done, false); | |
478 | stopper->enabled = false; | |
479 | spin_unlock_irqrestore(&stopper->lock, flags); | |
480 | } | |
1142d810 | 481 | |
14e568e7 TG |
482 | static void cpu_stop_unpark(unsigned int cpu) |
483 | { | |
484 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); | |
485 | ||
486 | spin_lock_irq(&stopper->lock); | |
487 | stopper->enabled = true; | |
488 | spin_unlock_irq(&stopper->lock); | |
1142d810 TH |
489 | } |
490 | ||
14e568e7 TG |
491 | static struct smp_hotplug_thread cpu_stop_threads = { |
492 | .store = &cpu_stopper_task, | |
493 | .thread_should_run = cpu_stop_should_run, | |
494 | .thread_fn = cpu_stopper_thread, | |
495 | .thread_comm = "migration/%u", | |
496 | .create = cpu_stop_create, | |
497 | .setup = cpu_stop_unpark, | |
498 | .park = cpu_stop_park, | |
46c498c2 | 499 | .pre_unpark = cpu_stop_unpark, |
14e568e7 | 500 | .selfparking = true, |
1142d810 TH |
501 | }; |
502 | ||
503 | static int __init cpu_stop_init(void) | |
504 | { | |
1142d810 | 505 | unsigned int cpu; |
1142d810 TH |
506 | |
507 | for_each_possible_cpu(cpu) { | |
508 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); | |
509 | ||
510 | spin_lock_init(&stopper->lock); | |
511 | INIT_LIST_HEAD(&stopper->works); | |
512 | } | |
513 | ||
14e568e7 | 514 | BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads)); |
f445027e | 515 | stop_machine_initialized = true; |
1142d810 TH |
516 | return 0; |
517 | } | |
518 | early_initcall(cpu_stop_init); | |
1da177e4 | 519 | |
bbf1bb3e TH |
520 | #ifdef CONFIG_STOP_MACHINE |
521 | ||
41c7bb95 | 522 | int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) |
1da177e4 | 523 | { |
1be0bd77 PZ |
524 | struct multi_stop_data msdata = { |
525 | .fn = fn, | |
526 | .data = data, | |
527 | .num_threads = num_online_cpus(), | |
528 | .active_cpus = cpus, | |
529 | }; | |
3fc1f1e2 | 530 | |
f445027e JF |
531 | if (!stop_machine_initialized) { |
532 | /* | |
533 | * Handle the case where stop_machine() is called | |
534 | * early in boot before stop_machine() has been | |
535 | * initialized. | |
536 | */ | |
537 | unsigned long flags; | |
538 | int ret; | |
539 | ||
1be0bd77 | 540 | WARN_ON_ONCE(msdata.num_threads != 1); |
f445027e JF |
541 | |
542 | local_irq_save(flags); | |
543 | hard_irq_disable(); | |
544 | ret = (*fn)(data); | |
545 | local_irq_restore(flags); | |
546 | ||
547 | return ret; | |
548 | } | |
549 | ||
3fc1f1e2 | 550 | /* Set the initial state and stop all online cpus. */ |
1be0bd77 PZ |
551 | set_state(&msdata, MULTI_STOP_PREPARE); |
552 | return stop_cpus(cpu_online_mask, multi_cpu_stop, &msdata); | |
1da177e4 LT |
553 | } |
554 | ||
41c7bb95 | 555 | int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) |
1da177e4 | 556 | { |
1da177e4 LT |
557 | int ret; |
558 | ||
559 | /* No CPUs can come up or down during this. */ | |
86ef5c9a | 560 | get_online_cpus(); |
eeec4fad | 561 | ret = __stop_machine(fn, data, cpus); |
86ef5c9a | 562 | put_online_cpus(); |
1da177e4 LT |
563 | return ret; |
564 | } | |
eeec4fad | 565 | EXPORT_SYMBOL_GPL(stop_machine); |
bbf1bb3e | 566 | |
f740e6cd TH |
567 | /** |
568 | * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU | |
569 | * @fn: the function to run | |
570 | * @data: the data ptr for the @fn() | |
571 | * @cpus: the cpus to run the @fn() on (NULL = any online cpu) | |
572 | * | |
573 | * This is identical to stop_machine() but can be called from a CPU which | |
574 | * is not active. The local CPU is in the process of hotplug (so no other | |
575 | * CPU hotplug can start) and not marked active and doesn't have enough | |
576 | * context to sleep. | |
577 | * | |
578 | * This function provides stop_machine() functionality for such state by | |
579 | * using busy-wait for synchronization and executing @fn directly for local | |
580 | * CPU. | |
581 | * | |
582 | * CONTEXT: | |
583 | * Local CPU is inactive. Temporarily stops all active CPUs. | |
584 | * | |
585 | * RETURNS: | |
586 | * 0 if all executions of @fn returned 0, any non zero return value if any | |
587 | * returned non zero. | |
588 | */ | |
589 | int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data, | |
590 | const struct cpumask *cpus) | |
591 | { | |
1be0bd77 | 592 | struct multi_stop_data msdata = { .fn = fn, .data = data, |
f740e6cd TH |
593 | .active_cpus = cpus }; |
594 | struct cpu_stop_done done; | |
595 | int ret; | |
596 | ||
597 | /* Local CPU must be inactive and CPU hotplug in progress. */ | |
598 | BUG_ON(cpu_active(raw_smp_processor_id())); | |
1be0bd77 | 599 | msdata.num_threads = num_active_cpus() + 1; /* +1 for local */ |
f740e6cd TH |
600 | |
601 | /* No proper task established and can't sleep - busy wait for lock. */ | |
602 | while (!mutex_trylock(&stop_cpus_mutex)) | |
603 | cpu_relax(); | |
604 | ||
605 | /* Schedule work on other CPUs and execute directly for local CPU */ | |
1be0bd77 | 606 | set_state(&msdata, MULTI_STOP_PREPARE); |
f740e6cd | 607 | cpu_stop_init_done(&done, num_active_cpus()); |
1be0bd77 | 608 | queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata, |
f740e6cd | 609 | &done); |
1be0bd77 | 610 | ret = multi_cpu_stop(&msdata); |
f740e6cd TH |
611 | |
612 | /* Busy wait for completion. */ | |
613 | while (!completion_done(&done.completion)) | |
614 | cpu_relax(); | |
615 | ||
616 | mutex_unlock(&stop_cpus_mutex); | |
617 | return ret ?: done.ret; | |
618 | } | |
619 | ||
bbf1bb3e | 620 | #endif /* CONFIG_STOP_MACHINE */ |