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Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 12 years 9 months ago. By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing | |
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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. |
10 | */ |
11 | #include <linux/completion.h> |
12 | #include <linux/cpu.h> |
13 | #include <linux/init.h> |
14 | #include <linux/kthread.h> |
15 | #include <linux/export.h> |
16 | #include <linux/percpu.h> |
17 | #include <linux/sched.h> |
18 | #include <linux/stop_machine.h> |
19 | #include <linux/interrupt.h> |
20 | #include <linux/kallsyms.h> |
21 | |
22 | #include <linux/atomic.h> |
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; |
38 | bool enabled; /* is this stopper enabled? */ |
39 | struct list_head works; /* list of pending works */ |
40 | struct task_struct *thread; /* stopper thread */ |
41 | }; |
42 | |
43 | static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper); |
44 | static bool stop_machine_initialized = false; |
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 */ |
65 | static void cpu_stop_queue_work(struct cpu_stopper *stopper, |
66 | struct cpu_stop_work *work) |
67 | { |
68 | unsigned long flags; |
69 | |
70 | spin_lock_irqsave(&stopper->lock, flags); |
71 | |
72 | if (stopper->enabled) { |
73 | list_add_tail(&work->list, &stopper->works); |
74 | wake_up_process(stopper->thread); |
75 | } else |
76 | cpu_stop_signal_done(work->done, false); |
77 | |
78 | spin_unlock_irqrestore(&stopper->lock, flags); |
79 | } |
80 | |
81 | /** |
82 | * stop_one_cpu - stop a cpu |
83 | * @cpu: cpu to stop |
84 | * @fn: function to execute |
85 | * @arg: argument to @fn |
86 | * |
87 | * Execute @fn(@arg) on @cpu. @fn is run in a process context with |
88 | * the highest priority preempting any task on the cpu and |
89 | * monopolizing it. This function returns after the execution is |
90 | * complete. |
91 | * |
92 | * This function doesn't guarantee @cpu stays online till @fn |
93 | * completes. If @cpu goes down in the middle, execution may happen |
94 | * partially or fully on different cpus. @fn should either be ready |
95 | * for that or the caller should ensure that @cpu stays online until |
96 | * this function completes. |
97 | * |
98 | * CONTEXT: |
99 | * Might sleep. |
100 | * |
101 | * RETURNS: |
102 | * -ENOENT if @fn(@arg) was not executed because @cpu was offline; |
103 | * otherwise, the return value of @fn. |
104 | */ |
105 | int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) |
106 | { |
107 | struct cpu_stop_done done; |
108 | struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done }; |
109 | |
110 | cpu_stop_init_done(&done, 1); |
111 | cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), &work); |
112 | wait_for_completion(&done.completion); |
113 | return done.executed ? done.ret : -ENOENT; |
114 | } |
115 | |
116 | /** |
117 | * stop_one_cpu_nowait - stop a cpu but don't wait for completion |
118 | * @cpu: cpu to stop |
119 | * @fn: function to execute |
120 | * @arg: argument to @fn |
121 | * |
122 | * Similar to stop_one_cpu() but doesn't wait for completion. The |
123 | * caller is responsible for ensuring @work_buf is currently unused |
124 | * and will remain untouched until stopper starts executing @fn. |
125 | * |
126 | * CONTEXT: |
127 | * Don't care. |
128 | */ |
129 | void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, |
130 | struct cpu_stop_work *work_buf) |
131 | { |
132 | *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, }; |
133 | cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf); |
134 | } |
135 | |
136 | /* static data for stop_cpus */ |
137 | static DEFINE_MUTEX(stop_cpus_mutex); |
138 | static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work); |
139 | |
140 | static void queue_stop_cpus_work(const struct cpumask *cpumask, |
141 | cpu_stop_fn_t fn, void *arg, |
142 | struct cpu_stop_done *done) |
143 | { |
144 | struct cpu_stop_work *work; |
145 | unsigned int cpu; |
146 | |
147 | /* initialize works and done */ |
148 | for_each_cpu(cpu, cpumask) { |
149 | work = &per_cpu(stop_cpus_work, cpu); |
150 | work->fn = fn; |
151 | work->arg = arg; |
152 | work->done = done; |
153 | } |
154 | |
155 | /* |
156 | * Disable preemption while queueing to avoid getting |
157 | * preempted by a stopper which might wait for other stoppers |
158 | * to enter @fn which can lead to deadlock. |
159 | */ |
160 | preempt_disable(); |
161 | for_each_cpu(cpu, cpumask) |
162 | cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), |
163 | &per_cpu(stop_cpus_work, cpu)); |
164 | preempt_enable(); |
165 | } |
166 | |
167 | static int __stop_cpus(const struct cpumask *cpumask, |
168 | cpu_stop_fn_t fn, void *arg) |
169 | { |
170 | struct cpu_stop_done done; |
171 | |
172 | cpu_stop_init_done(&done, cpumask_weight(cpumask)); |
173 | queue_stop_cpus_work(cpumask, fn, arg, &done); |
174 | wait_for_completion(&done.completion); |
175 | return done.executed ? done.ret : -ENOENT; |
176 | } |
177 | |
178 | /** |
179 | * stop_cpus - stop multiple cpus |
180 | * @cpumask: cpus to stop |
181 | * @fn: function to execute |
182 | * @arg: argument to @fn |
183 | * |
184 | * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu, |
185 | * @fn is run in a process context with the highest priority |
186 | * preempting any task on the cpu and monopolizing it. This function |
187 | * returns after all executions are complete. |
188 | * |
189 | * This function doesn't guarantee the cpus in @cpumask stay online |
190 | * till @fn completes. If some cpus go down in the middle, execution |
191 | * on the cpu may happen partially or fully on different cpus. @fn |
192 | * should either be ready for that or the caller should ensure that |
193 | * the cpus stay online until this function completes. |
194 | * |
195 | * All stop_cpus() calls are serialized making it safe for @fn to wait |
196 | * for all cpus to start executing it. |
197 | * |
198 | * CONTEXT: |
199 | * Might sleep. |
200 | * |
201 | * RETURNS: |
202 | * -ENOENT if @fn(@arg) was not executed at all because all cpus in |
203 | * @cpumask were offline; otherwise, 0 if all executions of @fn |
204 | * returned 0, any non zero return value if any returned non zero. |
205 | */ |
206 | int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) |
207 | { |
208 | int ret; |
209 | |
210 | /* static works are used, process one request at a time */ |
211 | mutex_lock(&stop_cpus_mutex); |
212 | ret = __stop_cpus(cpumask, fn, arg); |
213 | mutex_unlock(&stop_cpus_mutex); |
214 | return ret; |
215 | } |
216 | |
217 | /** |
218 | * try_stop_cpus - try to stop multiple cpus |
219 | * @cpumask: cpus to stop |
220 | * @fn: function to execute |
221 | * @arg: argument to @fn |
222 | * |
223 | * Identical to stop_cpus() except that it fails with -EAGAIN if |
224 | * someone else is already using the facility. |
225 | * |
226 | * CONTEXT: |
227 | * Might sleep. |
228 | * |
229 | * RETURNS: |
230 | * -EAGAIN if someone else is already stopping cpus, -ENOENT if |
231 | * @fn(@arg) was not executed at all because all cpus in @cpumask were |
232 | * offline; otherwise, 0 if all executions of @fn returned 0, any non |
233 | * zero return value if any returned non zero. |
234 | */ |
235 | int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) |
236 | { |
237 | int ret; |
238 | |
239 | /* static works are used, process one request at a time */ |
240 | if (!mutex_trylock(&stop_cpus_mutex)) |
241 | return -EAGAIN; |
242 | ret = __stop_cpus(cpumask, fn, arg); |
243 | mutex_unlock(&stop_cpus_mutex); |
244 | return ret; |
245 | } |
246 | |
247 | static int cpu_stopper_thread(void *data) |
248 | { |
249 | struct cpu_stopper *stopper = data; |
250 | struct cpu_stop_work *work; |
251 | int ret; |
252 | |
253 | repeat: |
254 | set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ |
255 | |
256 | if (kthread_should_stop()) { |
257 | __set_current_state(TASK_RUNNING); |
258 | return 0; |
259 | } |
260 | |
261 | work = NULL; |
262 | spin_lock_irq(&stopper->lock); |
263 | if (!list_empty(&stopper->works)) { |
264 | work = list_first_entry(&stopper->works, |
265 | struct cpu_stop_work, list); |
266 | list_del_init(&work->list); |
267 | } |
268 | spin_unlock_irq(&stopper->lock); |
269 | |
270 | if (work) { |
271 | cpu_stop_fn_t fn = work->fn; |
272 | void *arg = work->arg; |
273 | struct cpu_stop_done *done = work->done; |
274 | char ksym_buf[KSYM_NAME_LEN] __maybe_unused; |
275 | |
276 | __set_current_state(TASK_RUNNING); |
277 | |
278 | /* cpu stop callbacks are not allowed to sleep */ |
279 | preempt_disable(); |
280 | |
281 | ret = fn(arg); |
282 | if (ret) |
283 | done->ret = ret; |
284 | |
285 | /* restore preemption and check it's still balanced */ |
286 | preempt_enable(); |
287 | WARN_ONCE(preempt_count(), |
288 | "cpu_stop: %s(%p) leaked preempt count\n", |
289 | kallsyms_lookup((unsigned long)fn, NULL, NULL, NULL, |
290 | ksym_buf), arg); |
291 | |
292 | cpu_stop_signal_done(done, true); |
293 | } else |
294 | schedule(); |
295 | |
296 | goto repeat; |
297 | } |
298 | |
299 | extern void sched_set_stop_task(int cpu, struct task_struct *stop); |
300 | |
301 | /* manage stopper for a cpu, mostly lifted from sched migration thread mgmt */ |
302 | static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, |
303 | unsigned long action, void *hcpu) |
304 | { |
305 | unsigned int cpu = (unsigned long)hcpu; |
306 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
307 | struct task_struct *p; |
308 | |
309 | switch (action & ~CPU_TASKS_FROZEN) { |
310 | case CPU_UP_PREPARE: |
311 | BUG_ON(stopper->thread || stopper->enabled || |
312 | !list_empty(&stopper->works)); |
313 | p = kthread_create_on_node(cpu_stopper_thread, |
314 | stopper, |
315 | cpu_to_node(cpu), |
316 | "migration/%d", cpu); |
317 | if (IS_ERR(p)) |
318 | return notifier_from_errno(PTR_ERR(p)); |
319 | get_task_struct(p); |
320 | kthread_bind(p, cpu); |
321 | sched_set_stop_task(cpu, p); |
322 | stopper->thread = p; |
323 | break; |
324 | |
325 | case CPU_ONLINE: |
326 | /* strictly unnecessary, as first user will wake it */ |
327 | wake_up_process(stopper->thread); |
328 | /* mark enabled */ |
329 | spin_lock_irq(&stopper->lock); |
330 | stopper->enabled = true; |
331 | spin_unlock_irq(&stopper->lock); |
332 | break; |
333 | |
334 | #ifdef CONFIG_HOTPLUG_CPU |
335 | case CPU_UP_CANCELED: |
336 | case CPU_POST_DEAD: |
337 | { |
338 | struct cpu_stop_work *work; |
339 | |
340 | sched_set_stop_task(cpu, NULL); |
341 | /* kill the stopper */ |
342 | kthread_stop(stopper->thread); |
343 | /* drain remaining works */ |
344 | spin_lock_irq(&stopper->lock); |
345 | list_for_each_entry(work, &stopper->works, list) |
346 | cpu_stop_signal_done(work->done, false); |
347 | stopper->enabled = false; |
348 | spin_unlock_irq(&stopper->lock); |
349 | /* release the stopper */ |
350 | put_task_struct(stopper->thread); |
351 | stopper->thread = NULL; |
352 | break; |
353 | } |
354 | #endif |
355 | } |
356 | |
357 | return NOTIFY_OK; |
358 | } |
359 | |
360 | /* |
361 | * Give it a higher priority so that cpu stopper is available to other |
362 | * cpu notifiers. It currently shares the same priority as sched |
363 | * migration_notifier. |
364 | */ |
365 | static struct notifier_block __cpuinitdata cpu_stop_cpu_notifier = { |
366 | .notifier_call = cpu_stop_cpu_callback, |
367 | .priority = 10, |
368 | }; |
369 | |
370 | static int __init cpu_stop_init(void) |
371 | { |
372 | void *bcpu = (void *)(long)smp_processor_id(); |
373 | unsigned int cpu; |
374 | int err; |
375 | |
376 | for_each_possible_cpu(cpu) { |
377 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
378 | |
379 | spin_lock_init(&stopper->lock); |
380 | INIT_LIST_HEAD(&stopper->works); |
381 | } |
382 | |
383 | /* start one for the boot cpu */ |
384 | err = cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_UP_PREPARE, |
385 | bcpu); |
386 | BUG_ON(err != NOTIFY_OK); |
387 | cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); |
388 | register_cpu_notifier(&cpu_stop_cpu_notifier); |
389 | |
390 | stop_machine_initialized = true; |
391 | |
392 | return 0; |
393 | } |
394 | early_initcall(cpu_stop_init); |
395 | |
396 | #ifdef CONFIG_STOP_MACHINE |
397 | |
398 | /* This controls the threads on each CPU. */ |
399 | enum stopmachine_state { |
400 | /* Dummy starting state for thread. */ |
401 | STOPMACHINE_NONE, |
402 | /* Awaiting everyone to be scheduled. */ |
403 | STOPMACHINE_PREPARE, |
404 | /* Disable interrupts. */ |
405 | STOPMACHINE_DISABLE_IRQ, |
406 | /* Run the function */ |
407 | STOPMACHINE_RUN, |
408 | /* Exit */ |
409 | STOPMACHINE_EXIT, |
410 | }; |
411 | |
412 | struct stop_machine_data { |
413 | int (*fn)(void *); |
414 | void *data; |
415 | /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ |
416 | unsigned int num_threads; |
417 | const struct cpumask *active_cpus; |
418 | |
419 | enum stopmachine_state state; |
420 | atomic_t thread_ack; |
421 | }; |
422 | |
423 | static void set_state(struct stop_machine_data *smdata, |
424 | enum stopmachine_state newstate) |
425 | { |
426 | /* Reset ack counter. */ |
427 | atomic_set(&smdata->thread_ack, smdata->num_threads); |
428 | smp_wmb(); |
429 | smdata->state = newstate; |
430 | } |
431 | |
432 | /* Last one to ack a state moves to the next state. */ |
433 | static void ack_state(struct stop_machine_data *smdata) |
434 | { |
435 | if (atomic_dec_and_test(&smdata->thread_ack)) |
436 | set_state(smdata, smdata->state + 1); |
437 | } |
438 | |
439 | /* This is the cpu_stop function which stops the CPU. */ |
440 | static int stop_machine_cpu_stop(void *data) |
441 | { |
442 | struct stop_machine_data *smdata = data; |
443 | enum stopmachine_state curstate = STOPMACHINE_NONE; |
444 | int cpu = smp_processor_id(), err = 0; |
445 | unsigned long flags; |
446 | bool is_active; |
447 | |
448 | /* |
449 | * When called from stop_machine_from_inactive_cpu(), irq might |
450 | * already be disabled. Save the state and restore it on exit. |
451 | */ |
452 | local_save_flags(flags); |
453 | |
454 | if (!smdata->active_cpus) |
455 | is_active = cpu == cpumask_first(cpu_online_mask); |
456 | else |
457 | is_active = cpumask_test_cpu(cpu, smdata->active_cpus); |
458 | |
459 | /* Simple state machine */ |
460 | do { |
461 | /* Chill out and ensure we re-read stopmachine_state. */ |
462 | cpu_relax(); |
463 | if (smdata->state != curstate) { |
464 | curstate = smdata->state; |
465 | switch (curstate) { |
466 | case STOPMACHINE_DISABLE_IRQ: |
467 | local_irq_disable(); |
468 | hard_irq_disable(); |
469 | break; |
470 | case STOPMACHINE_RUN: |
471 | if (is_active) |
472 | err = smdata->fn(smdata->data); |
473 | break; |
474 | default: |
475 | break; |
476 | } |
477 | ack_state(smdata); |
478 | } |
479 | } while (curstate != STOPMACHINE_EXIT); |
480 | |
481 | local_irq_restore(flags); |
482 | return err; |
483 | } |
484 | |
485 | int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) |
486 | { |
487 | struct stop_machine_data smdata = { .fn = fn, .data = data, |
488 | .num_threads = num_online_cpus(), |
489 | .active_cpus = cpus }; |
490 | |
491 | if (!stop_machine_initialized) { |
492 | /* |
493 | * Handle the case where stop_machine() is called |
494 | * early in boot before stop_machine() has been |
495 | * initialized. |
496 | */ |
497 | unsigned long flags; |
498 | int ret; |
499 | |
500 | WARN_ON_ONCE(smdata.num_threads != 1); |
501 | |
502 | local_irq_save(flags); |
503 | hard_irq_disable(); |
504 | ret = (*fn)(data); |
505 | local_irq_restore(flags); |
506 | |
507 | return ret; |
508 | } |
509 | |
510 | /* Set the initial state and stop all online cpus. */ |
511 | set_state(&smdata, STOPMACHINE_PREPARE); |
512 | return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata); |
513 | } |
514 | |
515 | int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) |
516 | { |
517 | int ret; |
518 | |
519 | /* No CPUs can come up or down during this. */ |
520 | get_online_cpus(); |
521 | ret = __stop_machine(fn, data, cpus); |
522 | put_online_cpus(); |
523 | return ret; |
524 | } |
525 | EXPORT_SYMBOL_GPL(stop_machine); |
526 | |
527 | /** |
528 | * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU |
529 | * @fn: the function to run |
530 | * @data: the data ptr for the @fn() |
531 | * @cpus: the cpus to run the @fn() on (NULL = any online cpu) |
532 | * |
533 | * This is identical to stop_machine() but can be called from a CPU which |
534 | * is not active. The local CPU is in the process of hotplug (so no other |
535 | * CPU hotplug can start) and not marked active and doesn't have enough |
536 | * context to sleep. |
537 | * |
538 | * This function provides stop_machine() functionality for such state by |
539 | * using busy-wait for synchronization and executing @fn directly for local |
540 | * CPU. |
541 | * |
542 | * CONTEXT: |
543 | * Local CPU is inactive. Temporarily stops all active CPUs. |
544 | * |
545 | * RETURNS: |
546 | * 0 if all executions of @fn returned 0, any non zero return value if any |
547 | * returned non zero. |
548 | */ |
549 | int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data, |
550 | const struct cpumask *cpus) |
551 | { |
552 | struct stop_machine_data smdata = { .fn = fn, .data = data, |
553 | .active_cpus = cpus }; |
554 | struct cpu_stop_done done; |
555 | int ret; |
556 | |
557 | /* Local CPU must be inactive and CPU hotplug in progress. */ |
558 | BUG_ON(cpu_active(raw_smp_processor_id())); |
559 | smdata.num_threads = num_active_cpus() + 1; /* +1 for local */ |
560 | |
561 | /* No proper task established and can't sleep - busy wait for lock. */ |
562 | while (!mutex_trylock(&stop_cpus_mutex)) |
563 | cpu_relax(); |
564 | |
565 | /* Schedule work on other CPUs and execute directly for local CPU */ |
566 | set_state(&smdata, STOPMACHINE_PREPARE); |
567 | cpu_stop_init_done(&done, num_active_cpus()); |
568 | queue_stop_cpus_work(cpu_active_mask, stop_machine_cpu_stop, &smdata, |
569 | &done); |
570 | ret = stop_machine_cpu_stop(&smdata); |
571 | |
572 | /* Busy wait for completion. */ |
573 | while (!completion_done(&done.completion)) |
574 | cpu_relax(); |
575 | |
576 | mutex_unlock(&stop_cpus_mutex); |
577 | return ret ?: done.ret; |
578 | } |
579 | |
580 | #endif /* CONFIG_STOP_MACHINE */ |
581 |
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