Commit | Line | Data |
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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> |
7053ea1a | 23 | #include <linux/lglock.h> |
1142d810 TH |
24 | |
25 | /* | |
26 | * Structure to determine completion condition and record errors. May | |
27 | * be shared by works on different cpus. | |
28 | */ | |
29 | struct cpu_stop_done { | |
30 | atomic_t nr_todo; /* nr left to execute */ | |
31 | bool executed; /* actually executed? */ | |
32 | int ret; /* collected return value */ | |
33 | struct completion completion; /* fired if nr_todo reaches 0 */ | |
34 | }; | |
35 | ||
36 | /* the actual stopper, one per every possible cpu, enabled on online cpus */ | |
37 | struct cpu_stopper { | |
02cb7aa9 ON |
38 | struct task_struct *thread; |
39 | ||
1142d810 | 40 | spinlock_t lock; |
878ae127 | 41 | bool enabled; /* is this stopper enabled? */ |
1142d810 | 42 | struct list_head works; /* list of pending works */ |
02cb7aa9 ON |
43 | |
44 | struct cpu_stop_work stop_work; /* for stop_cpus */ | |
1142d810 TH |
45 | }; |
46 | ||
47 | static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); | |
f445027e | 48 | static bool stop_machine_initialized = false; |
1142d810 | 49 | |
7053ea1a RR |
50 | /* |
51 | * Avoids a race between stop_two_cpus and global stop_cpus, where | |
52 | * the stoppers could get queued up in reverse order, leading to | |
53 | * system deadlock. Using an lglock means stop_two_cpus remains | |
54 | * relatively cheap. | |
55 | */ | |
56 | DEFINE_STATIC_LGLOCK(stop_cpus_lock); | |
57 | ||
1142d810 TH |
58 | static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) |
59 | { | |
60 | memset(done, 0, sizeof(*done)); | |
61 | atomic_set(&done->nr_todo, nr_todo); | |
62 | init_completion(&done->completion); | |
63 | } | |
64 | ||
65 | /* signal completion unless @done is NULL */ | |
66 | static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed) | |
67 | { | |
68 | if (done) { | |
69 | if (executed) | |
70 | done->executed = true; | |
71 | if (atomic_dec_and_test(&done->nr_todo)) | |
72 | complete(&done->completion); | |
73 | } | |
74 | } | |
75 | ||
76 | /* queue @work to @stopper. if offline, @work is completed immediately */ | |
860a0ffa | 77 | static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) |
1142d810 | 78 | { |
860a0ffa | 79 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
860a0ffa | 80 | |
1142d810 TH |
81 | unsigned long flags; |
82 | ||
83 | spin_lock_irqsave(&stopper->lock, flags); | |
84 | ||
85 | if (stopper->enabled) { | |
86 | list_add_tail(&work->list, &stopper->works); | |
02cb7aa9 | 87 | wake_up_process(stopper->thread); |
1142d810 TH |
88 | } else |
89 | cpu_stop_signal_done(work->done, false); | |
90 | ||
91 | spin_unlock_irqrestore(&stopper->lock, flags); | |
92 | } | |
93 | ||
94 | /** | |
95 | * stop_one_cpu - stop a cpu | |
96 | * @cpu: cpu to stop | |
97 | * @fn: function to execute | |
98 | * @arg: argument to @fn | |
99 | * | |
100 | * Execute @fn(@arg) on @cpu. @fn is run in a process context with | |
101 | * the highest priority preempting any task on the cpu and | |
102 | * monopolizing it. This function returns after the execution is | |
103 | * complete. | |
104 | * | |
105 | * This function doesn't guarantee @cpu stays online till @fn | |
106 | * completes. If @cpu goes down in the middle, execution may happen | |
107 | * partially or fully on different cpus. @fn should either be ready | |
108 | * for that or the caller should ensure that @cpu stays online until | |
109 | * this function completes. | |
110 | * | |
111 | * CONTEXT: | |
112 | * Might sleep. | |
113 | * | |
114 | * RETURNS: | |
115 | * -ENOENT if @fn(@arg) was not executed because @cpu was offline; | |
116 | * otherwise, the return value of @fn. | |
117 | */ | |
118 | int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) | |
119 | { | |
120 | struct cpu_stop_done done; | |
121 | struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done }; | |
122 | ||
123 | cpu_stop_init_done(&done, 1); | |
860a0ffa | 124 | cpu_stop_queue_work(cpu, &work); |
1142d810 TH |
125 | wait_for_completion(&done.completion); |
126 | return done.executed ? done.ret : -ENOENT; | |
127 | } | |
128 | ||
1be0bd77 PZ |
129 | /* This controls the threads on each CPU. */ |
130 | enum multi_stop_state { | |
131 | /* Dummy starting state for thread. */ | |
132 | MULTI_STOP_NONE, | |
133 | /* Awaiting everyone to be scheduled. */ | |
134 | MULTI_STOP_PREPARE, | |
135 | /* Disable interrupts. */ | |
136 | MULTI_STOP_DISABLE_IRQ, | |
137 | /* Run the function */ | |
138 | MULTI_STOP_RUN, | |
139 | /* Exit */ | |
140 | MULTI_STOP_EXIT, | |
141 | }; | |
142 | ||
143 | struct multi_stop_data { | |
9a301f22 | 144 | cpu_stop_fn_t fn; |
1be0bd77 PZ |
145 | void *data; |
146 | /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ | |
147 | unsigned int num_threads; | |
148 | const struct cpumask *active_cpus; | |
149 | ||
150 | enum multi_stop_state state; | |
151 | atomic_t thread_ack; | |
152 | }; | |
153 | ||
154 | static void set_state(struct multi_stop_data *msdata, | |
155 | enum multi_stop_state newstate) | |
156 | { | |
157 | /* Reset ack counter. */ | |
158 | atomic_set(&msdata->thread_ack, msdata->num_threads); | |
159 | smp_wmb(); | |
160 | msdata->state = newstate; | |
161 | } | |
162 | ||
163 | /* Last one to ack a state moves to the next state. */ | |
164 | static void ack_state(struct multi_stop_data *msdata) | |
165 | { | |
166 | if (atomic_dec_and_test(&msdata->thread_ack)) | |
167 | set_state(msdata, msdata->state + 1); | |
168 | } | |
169 | ||
170 | /* This is the cpu_stop function which stops the CPU. */ | |
171 | static int multi_cpu_stop(void *data) | |
172 | { | |
173 | struct multi_stop_data *msdata = data; | |
174 | enum multi_stop_state curstate = MULTI_STOP_NONE; | |
175 | int cpu = smp_processor_id(), err = 0; | |
176 | unsigned long flags; | |
177 | bool is_active; | |
178 | ||
179 | /* | |
180 | * When called from stop_machine_from_inactive_cpu(), irq might | |
181 | * already be disabled. Save the state and restore it on exit. | |
182 | */ | |
183 | local_save_flags(flags); | |
184 | ||
185 | if (!msdata->active_cpus) | |
186 | is_active = cpu == cpumask_first(cpu_online_mask); | |
187 | else | |
188 | is_active = cpumask_test_cpu(cpu, msdata->active_cpus); | |
189 | ||
190 | /* Simple state machine */ | |
191 | do { | |
192 | /* Chill out and ensure we re-read multi_stop_state. */ | |
193 | cpu_relax(); | |
194 | if (msdata->state != curstate) { | |
195 | curstate = msdata->state; | |
196 | switch (curstate) { | |
197 | case MULTI_STOP_DISABLE_IRQ: | |
198 | local_irq_disable(); | |
199 | hard_irq_disable(); | |
200 | break; | |
201 | case MULTI_STOP_RUN: | |
202 | if (is_active) | |
203 | err = msdata->fn(msdata->data); | |
204 | break; | |
205 | default: | |
206 | break; | |
207 | } | |
208 | ack_state(msdata); | |
209 | } | |
210 | } while (curstate != MULTI_STOP_EXIT); | |
211 | ||
212 | local_irq_restore(flags); | |
213 | return err; | |
214 | } | |
215 | ||
1be0bd77 PZ |
216 | /** |
217 | * stop_two_cpus - stops two cpus | |
218 | * @cpu1: the cpu to stop | |
219 | * @cpu2: the other cpu to stop | |
220 | * @fn: function to execute | |
221 | * @arg: argument to @fn | |
222 | * | |
223 | * Stops both the current and specified CPU and runs @fn on one of them. | |
224 | * | |
225 | * returns when both are completed. | |
226 | */ | |
227 | int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg) | |
228 | { | |
1be0bd77 PZ |
229 | struct cpu_stop_done done; |
230 | struct cpu_stop_work work1, work2; | |
6acce3ef PZ |
231 | struct multi_stop_data msdata; |
232 | ||
233 | preempt_disable(); | |
234 | msdata = (struct multi_stop_data){ | |
1be0bd77 PZ |
235 | .fn = fn, |
236 | .data = arg, | |
237 | .num_threads = 2, | |
238 | .active_cpus = cpumask_of(cpu1), | |
239 | }; | |
240 | ||
241 | work1 = work2 = (struct cpu_stop_work){ | |
242 | .fn = multi_cpu_stop, | |
243 | .arg = &msdata, | |
244 | .done = &done | |
245 | }; | |
246 | ||
1be0bd77 PZ |
247 | cpu_stop_init_done(&done, 2); |
248 | set_state(&msdata, MULTI_STOP_PREPARE); | |
249 | ||
6acce3ef PZ |
250 | /* |
251 | * If we observe both CPUs active we know _cpu_down() cannot yet have | |
252 | * queued its stop_machine works and therefore ours will get executed | |
253 | * first. Or its not either one of our CPUs that's getting unplugged, | |
254 | * in which case we don't care. | |
255 | * | |
256 | * This relies on the stopper workqueues to be FIFO. | |
257 | */ | |
258 | if (!cpu_active(cpu1) || !cpu_active(cpu2)) { | |
259 | preempt_enable(); | |
260 | return -ENOENT; | |
261 | } | |
262 | ||
b17718d0 PZ |
263 | lg_double_lock(&stop_cpus_lock, cpu1, cpu2); |
264 | cpu_stop_queue_work(cpu1, &work1); | |
265 | cpu_stop_queue_work(cpu2, &work2); | |
266 | lg_double_unlock(&stop_cpus_lock, cpu1, cpu2); | |
267 | ||
6acce3ef | 268 | preempt_enable(); |
1be0bd77 PZ |
269 | |
270 | wait_for_completion(&done.completion); | |
6acce3ef | 271 | |
1be0bd77 PZ |
272 | return done.executed ? done.ret : -ENOENT; |
273 | } | |
274 | ||
1142d810 TH |
275 | /** |
276 | * stop_one_cpu_nowait - stop a cpu but don't wait for completion | |
277 | * @cpu: cpu to stop | |
278 | * @fn: function to execute | |
279 | * @arg: argument to @fn | |
cf250040 | 280 | * @work_buf: pointer to cpu_stop_work structure |
1142d810 TH |
281 | * |
282 | * Similar to stop_one_cpu() but doesn't wait for completion. The | |
283 | * caller is responsible for ensuring @work_buf is currently unused | |
284 | * and will remain untouched until stopper starts executing @fn. | |
285 | * | |
286 | * CONTEXT: | |
287 | * Don't care. | |
288 | */ | |
289 | void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, | |
290 | struct cpu_stop_work *work_buf) | |
291 | { | |
292 | *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, }; | |
860a0ffa | 293 | cpu_stop_queue_work(cpu, work_buf); |
1142d810 TH |
294 | } |
295 | ||
296 | /* static data for stop_cpus */ | |
192d8857 | 297 | static DEFINE_MUTEX(stop_cpus_mutex); |
1142d810 | 298 | |
fd7355ba TH |
299 | static void queue_stop_cpus_work(const struct cpumask *cpumask, |
300 | cpu_stop_fn_t fn, void *arg, | |
301 | struct cpu_stop_done *done) | |
1142d810 TH |
302 | { |
303 | struct cpu_stop_work *work; | |
1142d810 TH |
304 | unsigned int cpu; |
305 | ||
1142d810 TH |
306 | /* |
307 | * Disable preemption while queueing to avoid getting | |
308 | * preempted by a stopper which might wait for other stoppers | |
309 | * to enter @fn which can lead to deadlock. | |
310 | */ | |
7053ea1a | 311 | lg_global_lock(&stop_cpus_lock); |
b377c2a0 ON |
312 | for_each_cpu(cpu, cpumask) { |
313 | work = &per_cpu(cpu_stopper.stop_work, cpu); | |
314 | work->fn = fn; | |
315 | work->arg = arg; | |
316 | work->done = done; | |
317 | cpu_stop_queue_work(cpu, work); | |
318 | } | |
7053ea1a | 319 | lg_global_unlock(&stop_cpus_lock); |
fd7355ba | 320 | } |
1142d810 | 321 | |
fd7355ba TH |
322 | static int __stop_cpus(const struct cpumask *cpumask, |
323 | cpu_stop_fn_t fn, void *arg) | |
324 | { | |
325 | struct cpu_stop_done done; | |
326 | ||
327 | cpu_stop_init_done(&done, cpumask_weight(cpumask)); | |
328 | queue_stop_cpus_work(cpumask, fn, arg, &done); | |
1142d810 TH |
329 | wait_for_completion(&done.completion); |
330 | return done.executed ? done.ret : -ENOENT; | |
331 | } | |
332 | ||
333 | /** | |
334 | * stop_cpus - stop multiple cpus | |
335 | * @cpumask: cpus to stop | |
336 | * @fn: function to execute | |
337 | * @arg: argument to @fn | |
338 | * | |
339 | * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu, | |
340 | * @fn is run in a process context with the highest priority | |
341 | * preempting any task on the cpu and monopolizing it. This function | |
342 | * returns after all executions are complete. | |
343 | * | |
344 | * This function doesn't guarantee the cpus in @cpumask stay online | |
345 | * till @fn completes. If some cpus go down in the middle, execution | |
346 | * on the cpu may happen partially or fully on different cpus. @fn | |
347 | * should either be ready for that or the caller should ensure that | |
348 | * the cpus stay online until this function completes. | |
349 | * | |
350 | * All stop_cpus() calls are serialized making it safe for @fn to wait | |
351 | * for all cpus to start executing it. | |
352 | * | |
353 | * CONTEXT: | |
354 | * Might sleep. | |
355 | * | |
356 | * RETURNS: | |
357 | * -ENOENT if @fn(@arg) was not executed at all because all cpus in | |
358 | * @cpumask were offline; otherwise, 0 if all executions of @fn | |
359 | * returned 0, any non zero return value if any returned non zero. | |
360 | */ | |
361 | int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) | |
362 | { | |
363 | int ret; | |
364 | ||
365 | /* static works are used, process one request at a time */ | |
366 | mutex_lock(&stop_cpus_mutex); | |
367 | ret = __stop_cpus(cpumask, fn, arg); | |
368 | mutex_unlock(&stop_cpus_mutex); | |
369 | return ret; | |
370 | } | |
371 | ||
372 | /** | |
373 | * try_stop_cpus - try to stop multiple cpus | |
374 | * @cpumask: cpus to stop | |
375 | * @fn: function to execute | |
376 | * @arg: argument to @fn | |
377 | * | |
378 | * Identical to stop_cpus() except that it fails with -EAGAIN if | |
379 | * someone else is already using the facility. | |
380 | * | |
381 | * CONTEXT: | |
382 | * Might sleep. | |
383 | * | |
384 | * RETURNS: | |
385 | * -EAGAIN if someone else is already stopping cpus, -ENOENT if | |
386 | * @fn(@arg) was not executed at all because all cpus in @cpumask were | |
387 | * offline; otherwise, 0 if all executions of @fn returned 0, any non | |
388 | * zero return value if any returned non zero. | |
389 | */ | |
390 | int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) | |
391 | { | |
392 | int ret; | |
393 | ||
394 | /* static works are used, process one request at a time */ | |
395 | if (!mutex_trylock(&stop_cpus_mutex)) | |
396 | return -EAGAIN; | |
397 | ret = __stop_cpus(cpumask, fn, arg); | |
398 | mutex_unlock(&stop_cpus_mutex); | |
399 | return ret; | |
400 | } | |
401 | ||
14e568e7 TG |
402 | static int cpu_stop_should_run(unsigned int cpu) |
403 | { | |
404 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); | |
405 | unsigned long flags; | |
406 | int run; | |
407 | ||
408 | spin_lock_irqsave(&stopper->lock, flags); | |
409 | run = !list_empty(&stopper->works); | |
410 | spin_unlock_irqrestore(&stopper->lock, flags); | |
411 | return run; | |
412 | } | |
413 | ||
414 | static void cpu_stopper_thread(unsigned int cpu) | |
1142d810 | 415 | { |
14e568e7 | 416 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
1142d810 TH |
417 | struct cpu_stop_work *work; |
418 | int ret; | |
419 | ||
420 | repeat: | |
1142d810 TH |
421 | work = NULL; |
422 | spin_lock_irq(&stopper->lock); | |
423 | if (!list_empty(&stopper->works)) { | |
424 | work = list_first_entry(&stopper->works, | |
425 | struct cpu_stop_work, list); | |
426 | list_del_init(&work->list); | |
427 | } | |
428 | spin_unlock_irq(&stopper->lock); | |
429 | ||
430 | if (work) { | |
431 | cpu_stop_fn_t fn = work->fn; | |
432 | void *arg = work->arg; | |
433 | struct cpu_stop_done *done = work->done; | |
ca51c5a7 | 434 | char ksym_buf[KSYM_NAME_LEN] __maybe_unused; |
1142d810 | 435 | |
1142d810 TH |
436 | /* cpu stop callbacks are not allowed to sleep */ |
437 | preempt_disable(); | |
438 | ||
439 | ret = fn(arg); | |
440 | if (ret) | |
441 | done->ret = ret; | |
442 | ||
443 | /* restore preemption and check it's still balanced */ | |
444 | preempt_enable(); | |
445 | WARN_ONCE(preempt_count(), | |
446 | "cpu_stop: %s(%p) leaked preempt count\n", | |
447 | kallsyms_lookup((unsigned long)fn, NULL, NULL, NULL, | |
448 | ksym_buf), arg); | |
449 | ||
450 | cpu_stop_signal_done(done, true); | |
14e568e7 TG |
451 | goto repeat; |
452 | } | |
1142d810 TH |
453 | } |
454 | ||
34f971f6 PZ |
455 | extern void sched_set_stop_task(int cpu, struct task_struct *stop); |
456 | ||
14e568e7 TG |
457 | static void cpu_stop_create(unsigned int cpu) |
458 | { | |
02cb7aa9 | 459 | sched_set_stop_task(cpu, per_cpu(cpu_stopper.thread, cpu)); |
14e568e7 TG |
460 | } |
461 | ||
462 | static void cpu_stop_park(unsigned int cpu) | |
1142d810 | 463 | { |
1142d810 | 464 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
d308b9f1 | 465 | struct cpu_stop_work *work, *tmp; |
14e568e7 | 466 | unsigned long flags; |
1142d810 | 467 | |
14e568e7 TG |
468 | /* drain remaining works */ |
469 | spin_lock_irqsave(&stopper->lock, flags); | |
d308b9f1 ON |
470 | list_for_each_entry_safe(work, tmp, &stopper->works, list) { |
471 | list_del_init(&work->list); | |
14e568e7 | 472 | cpu_stop_signal_done(work->done, false); |
d308b9f1 | 473 | } |
14e568e7 TG |
474 | stopper->enabled = false; |
475 | spin_unlock_irqrestore(&stopper->lock, flags); | |
476 | } | |
1142d810 | 477 | |
14e568e7 TG |
478 | static void cpu_stop_unpark(unsigned int cpu) |
479 | { | |
480 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); | |
481 | ||
482 | spin_lock_irq(&stopper->lock); | |
483 | stopper->enabled = true; | |
484 | spin_unlock_irq(&stopper->lock); | |
1142d810 TH |
485 | } |
486 | ||
14e568e7 | 487 | static struct smp_hotplug_thread cpu_stop_threads = { |
02cb7aa9 | 488 | .store = &cpu_stopper.thread, |
14e568e7 TG |
489 | .thread_should_run = cpu_stop_should_run, |
490 | .thread_fn = cpu_stopper_thread, | |
491 | .thread_comm = "migration/%u", | |
492 | .create = cpu_stop_create, | |
493 | .setup = cpu_stop_unpark, | |
494 | .park = cpu_stop_park, | |
46c498c2 | 495 | .pre_unpark = cpu_stop_unpark, |
14e568e7 | 496 | .selfparking = true, |
1142d810 TH |
497 | }; |
498 | ||
499 | static int __init cpu_stop_init(void) | |
500 | { | |
1142d810 | 501 | unsigned int cpu; |
1142d810 TH |
502 | |
503 | for_each_possible_cpu(cpu) { | |
504 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); | |
505 | ||
506 | spin_lock_init(&stopper->lock); | |
507 | INIT_LIST_HEAD(&stopper->works); | |
508 | } | |
509 | ||
14e568e7 | 510 | BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads)); |
f445027e | 511 | stop_machine_initialized = true; |
1142d810 TH |
512 | return 0; |
513 | } | |
514 | early_initcall(cpu_stop_init); | |
1da177e4 | 515 | |
bbf1bb3e TH |
516 | #ifdef CONFIG_STOP_MACHINE |
517 | ||
9a301f22 | 518 | static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus) |
1da177e4 | 519 | { |
1be0bd77 PZ |
520 | struct multi_stop_data msdata = { |
521 | .fn = fn, | |
522 | .data = data, | |
523 | .num_threads = num_online_cpus(), | |
524 | .active_cpus = cpus, | |
525 | }; | |
3fc1f1e2 | 526 | |
f445027e JF |
527 | if (!stop_machine_initialized) { |
528 | /* | |
529 | * Handle the case where stop_machine() is called | |
530 | * early in boot before stop_machine() has been | |
531 | * initialized. | |
532 | */ | |
533 | unsigned long flags; | |
534 | int ret; | |
535 | ||
1be0bd77 | 536 | WARN_ON_ONCE(msdata.num_threads != 1); |
f445027e JF |
537 | |
538 | local_irq_save(flags); | |
539 | hard_irq_disable(); | |
540 | ret = (*fn)(data); | |
541 | local_irq_restore(flags); | |
542 | ||
543 | return ret; | |
544 | } | |
545 | ||
3fc1f1e2 | 546 | /* Set the initial state and stop all online cpus. */ |
1be0bd77 PZ |
547 | set_state(&msdata, MULTI_STOP_PREPARE); |
548 | return stop_cpus(cpu_online_mask, multi_cpu_stop, &msdata); | |
1da177e4 LT |
549 | } |
550 | ||
9a301f22 | 551 | int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus) |
1da177e4 | 552 | { |
1da177e4 LT |
553 | int ret; |
554 | ||
555 | /* No CPUs can come up or down during this. */ | |
86ef5c9a | 556 | get_online_cpus(); |
eeec4fad | 557 | ret = __stop_machine(fn, data, cpus); |
86ef5c9a | 558 | put_online_cpus(); |
1da177e4 LT |
559 | return ret; |
560 | } | |
eeec4fad | 561 | EXPORT_SYMBOL_GPL(stop_machine); |
bbf1bb3e | 562 | |
f740e6cd TH |
563 | /** |
564 | * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU | |
565 | * @fn: the function to run | |
566 | * @data: the data ptr for the @fn() | |
567 | * @cpus: the cpus to run the @fn() on (NULL = any online cpu) | |
568 | * | |
569 | * This is identical to stop_machine() but can be called from a CPU which | |
570 | * is not active. The local CPU is in the process of hotplug (so no other | |
571 | * CPU hotplug can start) and not marked active and doesn't have enough | |
572 | * context to sleep. | |
573 | * | |
574 | * This function provides stop_machine() functionality for such state by | |
575 | * using busy-wait for synchronization and executing @fn directly for local | |
576 | * CPU. | |
577 | * | |
578 | * CONTEXT: | |
579 | * Local CPU is inactive. Temporarily stops all active CPUs. | |
580 | * | |
581 | * RETURNS: | |
582 | * 0 if all executions of @fn returned 0, any non zero return value if any | |
583 | * returned non zero. | |
584 | */ | |
9a301f22 | 585 | int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, |
f740e6cd TH |
586 | const struct cpumask *cpus) |
587 | { | |
1be0bd77 | 588 | struct multi_stop_data msdata = { .fn = fn, .data = data, |
f740e6cd TH |
589 | .active_cpus = cpus }; |
590 | struct cpu_stop_done done; | |
591 | int ret; | |
592 | ||
593 | /* Local CPU must be inactive and CPU hotplug in progress. */ | |
594 | BUG_ON(cpu_active(raw_smp_processor_id())); | |
1be0bd77 | 595 | msdata.num_threads = num_active_cpus() + 1; /* +1 for local */ |
f740e6cd TH |
596 | |
597 | /* No proper task established and can't sleep - busy wait for lock. */ | |
598 | while (!mutex_trylock(&stop_cpus_mutex)) | |
599 | cpu_relax(); | |
600 | ||
601 | /* Schedule work on other CPUs and execute directly for local CPU */ | |
1be0bd77 | 602 | set_state(&msdata, MULTI_STOP_PREPARE); |
f740e6cd | 603 | cpu_stop_init_done(&done, num_active_cpus()); |
1be0bd77 | 604 | queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata, |
f740e6cd | 605 | &done); |
1be0bd77 | 606 | ret = multi_cpu_stop(&msdata); |
f740e6cd TH |
607 | |
608 | /* Busy wait for completion. */ | |
609 | while (!completion_done(&done.completion)) | |
610 | cpu_relax(); | |
611 | ||
612 | mutex_unlock(&stop_cpus_mutex); | |
613 | return ret ?: done.ret; | |
614 | } | |
615 | ||
bbf1bb3e | 616 | #endif /* CONFIG_STOP_MACHINE */ |