Root/
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/module.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 | |
45 | static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo) |
46 | { |
47 | memset(done, 0, sizeof(*done)); |
48 | atomic_set(&done->nr_todo, nr_todo); |
49 | init_completion(&done->completion); |
50 | } |
51 | |
52 | /* signal completion unless @done is NULL */ |
53 | static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed) |
54 | { |
55 | if (done) { |
56 | if (executed) |
57 | done->executed = true; |
58 | if (atomic_dec_and_test(&done->nr_todo)) |
59 | complete(&done->completion); |
60 | } |
61 | } |
62 | |
63 | /* queue @work to @stopper. if offline, @work is completed immediately */ |
64 | static void cpu_stop_queue_work(struct cpu_stopper *stopper, |
65 | struct cpu_stop_work *work) |
66 | { |
67 | unsigned long flags; |
68 | |
69 | spin_lock_irqsave(&stopper->lock, flags); |
70 | |
71 | if (stopper->enabled) { |
72 | list_add_tail(&work->list, &stopper->works); |
73 | wake_up_process(stopper->thread); |
74 | } else |
75 | cpu_stop_signal_done(work->done, false); |
76 | |
77 | spin_unlock_irqrestore(&stopper->lock, flags); |
78 | } |
79 | |
80 | /** |
81 | * stop_one_cpu - stop a cpu |
82 | * @cpu: cpu to stop |
83 | * @fn: function to execute |
84 | * @arg: argument to @fn |
85 | * |
86 | * Execute @fn(@arg) on @cpu. @fn is run in a process context with |
87 | * the highest priority preempting any task on the cpu and |
88 | * monopolizing it. This function returns after the execution is |
89 | * complete. |
90 | * |
91 | * This function doesn't guarantee @cpu stays online till @fn |
92 | * completes. If @cpu goes down in the middle, execution may happen |
93 | * partially or fully on different cpus. @fn should either be ready |
94 | * for that or the caller should ensure that @cpu stays online until |
95 | * this function completes. |
96 | * |
97 | * CONTEXT: |
98 | * Might sleep. |
99 | * |
100 | * RETURNS: |
101 | * -ENOENT if @fn(@arg) was not executed because @cpu was offline; |
102 | * otherwise, the return value of @fn. |
103 | */ |
104 | int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg) |
105 | { |
106 | struct cpu_stop_done done; |
107 | struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done }; |
108 | |
109 | cpu_stop_init_done(&done, 1); |
110 | cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), &work); |
111 | wait_for_completion(&done.completion); |
112 | return done.executed ? done.ret : -ENOENT; |
113 | } |
114 | |
115 | /** |
116 | * stop_one_cpu_nowait - stop a cpu but don't wait for completion |
117 | * @cpu: cpu to stop |
118 | * @fn: function to execute |
119 | * @arg: argument to @fn |
120 | * |
121 | * Similar to stop_one_cpu() but doesn't wait for completion. The |
122 | * caller is responsible for ensuring @work_buf is currently unused |
123 | * and will remain untouched until stopper starts executing @fn. |
124 | * |
125 | * CONTEXT: |
126 | * Don't care. |
127 | */ |
128 | void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg, |
129 | struct cpu_stop_work *work_buf) |
130 | { |
131 | *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, }; |
132 | cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), work_buf); |
133 | } |
134 | |
135 | /* static data for stop_cpus */ |
136 | static DEFINE_MUTEX(stop_cpus_mutex); |
137 | static DEFINE_PER_CPU(struct cpu_stop_work, stop_cpus_work); |
138 | |
139 | static void queue_stop_cpus_work(const struct cpumask *cpumask, |
140 | cpu_stop_fn_t fn, void *arg, |
141 | struct cpu_stop_done *done) |
142 | { |
143 | struct cpu_stop_work *work; |
144 | unsigned int cpu; |
145 | |
146 | /* initialize works and done */ |
147 | for_each_cpu(cpu, cpumask) { |
148 | work = &per_cpu(stop_cpus_work, cpu); |
149 | work->fn = fn; |
150 | work->arg = arg; |
151 | work->done = done; |
152 | } |
153 | |
154 | /* |
155 | * Disable preemption while queueing to avoid getting |
156 | * preempted by a stopper which might wait for other stoppers |
157 | * to enter @fn which can lead to deadlock. |
158 | */ |
159 | preempt_disable(); |
160 | for_each_cpu(cpu, cpumask) |
161 | cpu_stop_queue_work(&per_cpu(cpu_stopper, cpu), |
162 | &per_cpu(stop_cpus_work, cpu)); |
163 | preempt_enable(); |
164 | } |
165 | |
166 | static int __stop_cpus(const struct cpumask *cpumask, |
167 | cpu_stop_fn_t fn, void *arg) |
168 | { |
169 | struct cpu_stop_done done; |
170 | |
171 | cpu_stop_init_done(&done, cpumask_weight(cpumask)); |
172 | queue_stop_cpus_work(cpumask, fn, arg, &done); |
173 | wait_for_completion(&done.completion); |
174 | return done.executed ? done.ret : -ENOENT; |
175 | } |
176 | |
177 | /** |
178 | * stop_cpus - stop multiple cpus |
179 | * @cpumask: cpus to stop |
180 | * @fn: function to execute |
181 | * @arg: argument to @fn |
182 | * |
183 | * Execute @fn(@arg) on online cpus in @cpumask. On each target cpu, |
184 | * @fn is run in a process context with the highest priority |
185 | * preempting any task on the cpu and monopolizing it. This function |
186 | * returns after all executions are complete. |
187 | * |
188 | * This function doesn't guarantee the cpus in @cpumask stay online |
189 | * till @fn completes. If some cpus go down in the middle, execution |
190 | * on the cpu may happen partially or fully on different cpus. @fn |
191 | * should either be ready for that or the caller should ensure that |
192 | * the cpus stay online until this function completes. |
193 | * |
194 | * All stop_cpus() calls are serialized making it safe for @fn to wait |
195 | * for all cpus to start executing it. |
196 | * |
197 | * CONTEXT: |
198 | * Might sleep. |
199 | * |
200 | * RETURNS: |
201 | * -ENOENT if @fn(@arg) was not executed at all because all cpus in |
202 | * @cpumask were offline; otherwise, 0 if all executions of @fn |
203 | * returned 0, any non zero return value if any returned non zero. |
204 | */ |
205 | int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) |
206 | { |
207 | int ret; |
208 | |
209 | /* static works are used, process one request at a time */ |
210 | mutex_lock(&stop_cpus_mutex); |
211 | ret = __stop_cpus(cpumask, fn, arg); |
212 | mutex_unlock(&stop_cpus_mutex); |
213 | return ret; |
214 | } |
215 | |
216 | /** |
217 | * try_stop_cpus - try to stop multiple cpus |
218 | * @cpumask: cpus to stop |
219 | * @fn: function to execute |
220 | * @arg: argument to @fn |
221 | * |
222 | * Identical to stop_cpus() except that it fails with -EAGAIN if |
223 | * someone else is already using the facility. |
224 | * |
225 | * CONTEXT: |
226 | * Might sleep. |
227 | * |
228 | * RETURNS: |
229 | * -EAGAIN if someone else is already stopping cpus, -ENOENT if |
230 | * @fn(@arg) was not executed at all because all cpus in @cpumask were |
231 | * offline; otherwise, 0 if all executions of @fn returned 0, any non |
232 | * zero return value if any returned non zero. |
233 | */ |
234 | int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg) |
235 | { |
236 | int ret; |
237 | |
238 | /* static works are used, process one request at a time */ |
239 | if (!mutex_trylock(&stop_cpus_mutex)) |
240 | return -EAGAIN; |
241 | ret = __stop_cpus(cpumask, fn, arg); |
242 | mutex_unlock(&stop_cpus_mutex); |
243 | return ret; |
244 | } |
245 | |
246 | static int cpu_stopper_thread(void *data) |
247 | { |
248 | struct cpu_stopper *stopper = data; |
249 | struct cpu_stop_work *work; |
250 | int ret; |
251 | |
252 | repeat: |
253 | set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */ |
254 | |
255 | if (kthread_should_stop()) { |
256 | __set_current_state(TASK_RUNNING); |
257 | return 0; |
258 | } |
259 | |
260 | work = NULL; |
261 | spin_lock_irq(&stopper->lock); |
262 | if (!list_empty(&stopper->works)) { |
263 | work = list_first_entry(&stopper->works, |
264 | struct cpu_stop_work, list); |
265 | list_del_init(&work->list); |
266 | } |
267 | spin_unlock_irq(&stopper->lock); |
268 | |
269 | if (work) { |
270 | cpu_stop_fn_t fn = work->fn; |
271 | void *arg = work->arg; |
272 | struct cpu_stop_done *done = work->done; |
273 | char ksym_buf[KSYM_NAME_LEN] __maybe_unused; |
274 | |
275 | __set_current_state(TASK_RUNNING); |
276 | |
277 | /* cpu stop callbacks are not allowed to sleep */ |
278 | preempt_disable(); |
279 | |
280 | ret = fn(arg); |
281 | if (ret) |
282 | done->ret = ret; |
283 | |
284 | /* restore preemption and check it's still balanced */ |
285 | preempt_enable(); |
286 | WARN_ONCE(preempt_count(), |
287 | "cpu_stop: %s(%p) leaked preempt count\n", |
288 | kallsyms_lookup((unsigned long)fn, NULL, NULL, NULL, |
289 | ksym_buf), arg); |
290 | |
291 | cpu_stop_signal_done(done, true); |
292 | } else |
293 | schedule(); |
294 | |
295 | goto repeat; |
296 | } |
297 | |
298 | extern void sched_set_stop_task(int cpu, struct task_struct *stop); |
299 | |
300 | /* manage stopper for a cpu, mostly lifted from sched migration thread mgmt */ |
301 | static int __cpuinit cpu_stop_cpu_callback(struct notifier_block *nfb, |
302 | unsigned long action, void *hcpu) |
303 | { |
304 | unsigned int cpu = (unsigned long)hcpu; |
305 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
306 | struct task_struct *p; |
307 | |
308 | switch (action & ~CPU_TASKS_FROZEN) { |
309 | case CPU_UP_PREPARE: |
310 | BUG_ON(stopper->thread || stopper->enabled || |
311 | !list_empty(&stopper->works)); |
312 | p = kthread_create_on_node(cpu_stopper_thread, |
313 | stopper, |
314 | cpu_to_node(cpu), |
315 | "migration/%d", cpu); |
316 | if (IS_ERR(p)) |
317 | return notifier_from_errno(PTR_ERR(p)); |
318 | get_task_struct(p); |
319 | kthread_bind(p, cpu); |
320 | sched_set_stop_task(cpu, p); |
321 | stopper->thread = p; |
322 | break; |
323 | |
324 | case CPU_ONLINE: |
325 | /* strictly unnecessary, as first user will wake it */ |
326 | wake_up_process(stopper->thread); |
327 | /* mark enabled */ |
328 | spin_lock_irq(&stopper->lock); |
329 | stopper->enabled = true; |
330 | spin_unlock_irq(&stopper->lock); |
331 | break; |
332 | |
333 | #ifdef CONFIG_HOTPLUG_CPU |
334 | case CPU_UP_CANCELED: |
335 | case CPU_POST_DEAD: |
336 | { |
337 | struct cpu_stop_work *work; |
338 | |
339 | sched_set_stop_task(cpu, NULL); |
340 | /* kill the stopper */ |
341 | kthread_stop(stopper->thread); |
342 | /* drain remaining works */ |
343 | spin_lock_irq(&stopper->lock); |
344 | list_for_each_entry(work, &stopper->works, list) |
345 | cpu_stop_signal_done(work->done, false); |
346 | stopper->enabled = false; |
347 | spin_unlock_irq(&stopper->lock); |
348 | /* release the stopper */ |
349 | put_task_struct(stopper->thread); |
350 | stopper->thread = NULL; |
351 | break; |
352 | } |
353 | #endif |
354 | } |
355 | |
356 | return NOTIFY_OK; |
357 | } |
358 | |
359 | /* |
360 | * Give it a higher priority so that cpu stopper is available to other |
361 | * cpu notifiers. It currently shares the same priority as sched |
362 | * migration_notifier. |
363 | */ |
364 | static struct notifier_block __cpuinitdata cpu_stop_cpu_notifier = { |
365 | .notifier_call = cpu_stop_cpu_callback, |
366 | .priority = 10, |
367 | }; |
368 | |
369 | static int __init cpu_stop_init(void) |
370 | { |
371 | void *bcpu = (void *)(long)smp_processor_id(); |
372 | unsigned int cpu; |
373 | int err; |
374 | |
375 | for_each_possible_cpu(cpu) { |
376 | struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); |
377 | |
378 | spin_lock_init(&stopper->lock); |
379 | INIT_LIST_HEAD(&stopper->works); |
380 | } |
381 | |
382 | /* start one for the boot cpu */ |
383 | err = cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_UP_PREPARE, |
384 | bcpu); |
385 | BUG_ON(err != NOTIFY_OK); |
386 | cpu_stop_cpu_callback(&cpu_stop_cpu_notifier, CPU_ONLINE, bcpu); |
387 | register_cpu_notifier(&cpu_stop_cpu_notifier); |
388 | |
389 | return 0; |
390 | } |
391 | early_initcall(cpu_stop_init); |
392 | |
393 | #ifdef CONFIG_STOP_MACHINE |
394 | |
395 | /* This controls the threads on each CPU. */ |
396 | enum stopmachine_state { |
397 | /* Dummy starting state for thread. */ |
398 | STOPMACHINE_NONE, |
399 | /* Awaiting everyone to be scheduled. */ |
400 | STOPMACHINE_PREPARE, |
401 | /* Disable interrupts. */ |
402 | STOPMACHINE_DISABLE_IRQ, |
403 | /* Run the function */ |
404 | STOPMACHINE_RUN, |
405 | /* Exit */ |
406 | STOPMACHINE_EXIT, |
407 | }; |
408 | |
409 | struct stop_machine_data { |
410 | int (*fn)(void *); |
411 | void *data; |
412 | /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */ |
413 | unsigned int num_threads; |
414 | const struct cpumask *active_cpus; |
415 | |
416 | enum stopmachine_state state; |
417 | atomic_t thread_ack; |
418 | }; |
419 | |
420 | static void set_state(struct stop_machine_data *smdata, |
421 | enum stopmachine_state newstate) |
422 | { |
423 | /* Reset ack counter. */ |
424 | atomic_set(&smdata->thread_ack, smdata->num_threads); |
425 | smp_wmb(); |
426 | smdata->state = newstate; |
427 | } |
428 | |
429 | /* Last one to ack a state moves to the next state. */ |
430 | static void ack_state(struct stop_machine_data *smdata) |
431 | { |
432 | if (atomic_dec_and_test(&smdata->thread_ack)) |
433 | set_state(smdata, smdata->state + 1); |
434 | } |
435 | |
436 | /* This is the cpu_stop function which stops the CPU. */ |
437 | static int stop_machine_cpu_stop(void *data) |
438 | { |
439 | struct stop_machine_data *smdata = data; |
440 | enum stopmachine_state curstate = STOPMACHINE_NONE; |
441 | int cpu = smp_processor_id(), err = 0; |
442 | unsigned long flags; |
443 | bool is_active; |
444 | |
445 | /* |
446 | * When called from stop_machine_from_inactive_cpu(), irq might |
447 | * already be disabled. Save the state and restore it on exit. |
448 | */ |
449 | local_save_flags(flags); |
450 | |
451 | if (!smdata->active_cpus) |
452 | is_active = cpu == cpumask_first(cpu_online_mask); |
453 | else |
454 | is_active = cpumask_test_cpu(cpu, smdata->active_cpus); |
455 | |
456 | /* Simple state machine */ |
457 | do { |
458 | /* Chill out and ensure we re-read stopmachine_state. */ |
459 | cpu_relax(); |
460 | if (smdata->state != curstate) { |
461 | curstate = smdata->state; |
462 | switch (curstate) { |
463 | case STOPMACHINE_DISABLE_IRQ: |
464 | local_irq_disable(); |
465 | hard_irq_disable(); |
466 | break; |
467 | case STOPMACHINE_RUN: |
468 | if (is_active) |
469 | err = smdata->fn(smdata->data); |
470 | break; |
471 | default: |
472 | break; |
473 | } |
474 | ack_state(smdata); |
475 | } |
476 | } while (curstate != STOPMACHINE_EXIT); |
477 | |
478 | local_irq_restore(flags); |
479 | return err; |
480 | } |
481 | |
482 | int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) |
483 | { |
484 | struct stop_machine_data smdata = { .fn = fn, .data = data, |
485 | .num_threads = num_online_cpus(), |
486 | .active_cpus = cpus }; |
487 | |
488 | /* Set the initial state and stop all online cpus. */ |
489 | set_state(&smdata, STOPMACHINE_PREPARE); |
490 | return stop_cpus(cpu_online_mask, stop_machine_cpu_stop, &smdata); |
491 | } |
492 | |
493 | int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus) |
494 | { |
495 | int ret; |
496 | |
497 | /* No CPUs can come up or down during this. */ |
498 | get_online_cpus(); |
499 | ret = __stop_machine(fn, data, cpus); |
500 | put_online_cpus(); |
501 | return ret; |
502 | } |
503 | EXPORT_SYMBOL_GPL(stop_machine); |
504 | |
505 | /** |
506 | * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU |
507 | * @fn: the function to run |
508 | * @data: the data ptr for the @fn() |
509 | * @cpus: the cpus to run the @fn() on (NULL = any online cpu) |
510 | * |
511 | * This is identical to stop_machine() but can be called from a CPU which |
512 | * is not active. The local CPU is in the process of hotplug (so no other |
513 | * CPU hotplug can start) and not marked active and doesn't have enough |
514 | * context to sleep. |
515 | * |
516 | * This function provides stop_machine() functionality for such state by |
517 | * using busy-wait for synchronization and executing @fn directly for local |
518 | * CPU. |
519 | * |
520 | * CONTEXT: |
521 | * Local CPU is inactive. Temporarily stops all active CPUs. |
522 | * |
523 | * RETURNS: |
524 | * 0 if all executions of @fn returned 0, any non zero return value if any |
525 | * returned non zero. |
526 | */ |
527 | int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data, |
528 | const struct cpumask *cpus) |
529 | { |
530 | struct stop_machine_data smdata = { .fn = fn, .data = data, |
531 | .active_cpus = cpus }; |
532 | struct cpu_stop_done done; |
533 | int ret; |
534 | |
535 | /* Local CPU must be inactive and CPU hotplug in progress. */ |
536 | BUG_ON(cpu_active(raw_smp_processor_id())); |
537 | smdata.num_threads = num_active_cpus() + 1; /* +1 for local */ |
538 | |
539 | /* No proper task established and can't sleep - busy wait for lock. */ |
540 | while (!mutex_trylock(&stop_cpus_mutex)) |
541 | cpu_relax(); |
542 | |
543 | /* Schedule work on other CPUs and execute directly for local CPU */ |
544 | set_state(&smdata, STOPMACHINE_PREPARE); |
545 | cpu_stop_init_done(&done, num_active_cpus()); |
546 | queue_stop_cpus_work(cpu_active_mask, stop_machine_cpu_stop, &smdata, |
547 | &done); |
548 | ret = stop_machine_cpu_stop(&smdata); |
549 | |
550 | /* Busy wait for completion. */ |
551 | while (!completion_done(&done.completion)) |
552 | cpu_relax(); |
553 | |
554 | mutex_unlock(&stop_cpus_mutex); |
555 | return ret ?: done.ret; |
556 | } |
557 | |
558 | #endif /* CONFIG_STOP_MACHINE */ |
559 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9