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1da177e4 LT |
1 | /* |
2 | * linux/kernel/workqueue.c | |
3 | * | |
4 | * Generic mechanism for defining kernel helper threads for running | |
5 | * arbitrary tasks in process context. | |
6 | * | |
7 | * Started by Ingo Molnar, Copyright (C) 2002 | |
8 | * | |
9 | * Derived from the taskqueue/keventd code by: | |
10 | * | |
11 | * David Woodhouse <dwmw2@infradead.org> | |
12 | * Andrew Morton <andrewm@uow.edu.au> | |
13 | * Kai Petzke <wpp@marie.physik.tu-berlin.de> | |
14 | * Theodore Ts'o <tytso@mit.edu> | |
15 | */ | |
16 | ||
17 | #include <linux/module.h> | |
18 | #include <linux/kernel.h> | |
19 | #include <linux/sched.h> | |
20 | #include <linux/init.h> | |
21 | #include <linux/signal.h> | |
22 | #include <linux/completion.h> | |
23 | #include <linux/workqueue.h> | |
24 | #include <linux/slab.h> | |
25 | #include <linux/cpu.h> | |
26 | #include <linux/notifier.h> | |
27 | #include <linux/kthread.h> | |
28 | ||
29 | /* | |
30 | * The per-CPU workqueue (if single thread, we always use cpu 0's). | |
31 | * | |
32 | * The sequence counters are for flush_scheduled_work(). It wants to wait | |
33 | * until until all currently-scheduled works are completed, but it doesn't | |
34 | * want to be livelocked by new, incoming ones. So it waits until | |
35 | * remove_sequence is >= the insert_sequence which pertained when | |
36 | * flush_scheduled_work() was called. | |
37 | */ | |
38 | struct cpu_workqueue_struct { | |
39 | ||
40 | spinlock_t lock; | |
41 | ||
42 | long remove_sequence; /* Least-recently added (next to run) */ | |
43 | long insert_sequence; /* Next to add */ | |
44 | ||
45 | struct list_head worklist; | |
46 | wait_queue_head_t more_work; | |
47 | wait_queue_head_t work_done; | |
48 | ||
49 | struct workqueue_struct *wq; | |
50 | task_t *thread; | |
51 | ||
52 | int run_depth; /* Detect run_workqueue() recursion depth */ | |
53 | } ____cacheline_aligned; | |
54 | ||
55 | /* | |
56 | * The externally visible workqueue abstraction is an array of | |
57 | * per-CPU workqueues: | |
58 | */ | |
59 | struct workqueue_struct { | |
60 | struct cpu_workqueue_struct cpu_wq[NR_CPUS]; | |
61 | const char *name; | |
62 | struct list_head list; /* Empty if single thread */ | |
63 | }; | |
64 | ||
65 | /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove | |
66 | threads to each one as cpus come/go. */ | |
67 | static DEFINE_SPINLOCK(workqueue_lock); | |
68 | static LIST_HEAD(workqueues); | |
69 | ||
70 | /* If it's single threaded, it isn't in the list of workqueues. */ | |
71 | static inline int is_single_threaded(struct workqueue_struct *wq) | |
72 | { | |
73 | return list_empty(&wq->list); | |
74 | } | |
75 | ||
76 | /* Preempt must be disabled. */ | |
77 | static void __queue_work(struct cpu_workqueue_struct *cwq, | |
78 | struct work_struct *work) | |
79 | { | |
80 | unsigned long flags; | |
81 | ||
82 | spin_lock_irqsave(&cwq->lock, flags); | |
83 | work->wq_data = cwq; | |
84 | list_add_tail(&work->entry, &cwq->worklist); | |
85 | cwq->insert_sequence++; | |
86 | wake_up(&cwq->more_work); | |
87 | spin_unlock_irqrestore(&cwq->lock, flags); | |
88 | } | |
89 | ||
90 | /* | |
91 | * Queue work on a workqueue. Return non-zero if it was successfully | |
92 | * added. | |
93 | * | |
94 | * We queue the work to the CPU it was submitted, but there is no | |
95 | * guarantee that it will be processed by that CPU. | |
96 | */ | |
97 | int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work) | |
98 | { | |
99 | int ret = 0, cpu = get_cpu(); | |
100 | ||
101 | if (!test_and_set_bit(0, &work->pending)) { | |
102 | if (unlikely(is_single_threaded(wq))) | |
103 | cpu = 0; | |
104 | BUG_ON(!list_empty(&work->entry)); | |
105 | __queue_work(wq->cpu_wq + cpu, work); | |
106 | ret = 1; | |
107 | } | |
108 | put_cpu(); | |
109 | return ret; | |
110 | } | |
111 | ||
112 | static void delayed_work_timer_fn(unsigned long __data) | |
113 | { | |
114 | struct work_struct *work = (struct work_struct *)__data; | |
115 | struct workqueue_struct *wq = work->wq_data; | |
116 | int cpu = smp_processor_id(); | |
117 | ||
118 | if (unlikely(is_single_threaded(wq))) | |
119 | cpu = 0; | |
120 | ||
121 | __queue_work(wq->cpu_wq + cpu, work); | |
122 | } | |
123 | ||
124 | int fastcall queue_delayed_work(struct workqueue_struct *wq, | |
125 | struct work_struct *work, unsigned long delay) | |
126 | { | |
127 | int ret = 0; | |
128 | struct timer_list *timer = &work->timer; | |
129 | ||
130 | if (!test_and_set_bit(0, &work->pending)) { | |
131 | BUG_ON(timer_pending(timer)); | |
132 | BUG_ON(!list_empty(&work->entry)); | |
133 | ||
134 | /* This stores wq for the moment, for the timer_fn */ | |
135 | work->wq_data = wq; | |
136 | timer->expires = jiffies + delay; | |
137 | timer->data = (unsigned long)work; | |
138 | timer->function = delayed_work_timer_fn; | |
139 | add_timer(timer); | |
140 | ret = 1; | |
141 | } | |
142 | return ret; | |
143 | } | |
144 | ||
145 | static inline void run_workqueue(struct cpu_workqueue_struct *cwq) | |
146 | { | |
147 | unsigned long flags; | |
148 | ||
149 | /* | |
150 | * Keep taking off work from the queue until | |
151 | * done. | |
152 | */ | |
153 | spin_lock_irqsave(&cwq->lock, flags); | |
154 | cwq->run_depth++; | |
155 | if (cwq->run_depth > 3) { | |
156 | /* morton gets to eat his hat */ | |
157 | printk("%s: recursion depth exceeded: %d\n", | |
158 | __FUNCTION__, cwq->run_depth); | |
159 | dump_stack(); | |
160 | } | |
161 | while (!list_empty(&cwq->worklist)) { | |
162 | struct work_struct *work = list_entry(cwq->worklist.next, | |
163 | struct work_struct, entry); | |
164 | void (*f) (void *) = work->func; | |
165 | void *data = work->data; | |
166 | ||
167 | list_del_init(cwq->worklist.next); | |
168 | spin_unlock_irqrestore(&cwq->lock, flags); | |
169 | ||
170 | BUG_ON(work->wq_data != cwq); | |
171 | clear_bit(0, &work->pending); | |
172 | f(data); | |
173 | ||
174 | spin_lock_irqsave(&cwq->lock, flags); | |
175 | cwq->remove_sequence++; | |
176 | wake_up(&cwq->work_done); | |
177 | } | |
178 | cwq->run_depth--; | |
179 | spin_unlock_irqrestore(&cwq->lock, flags); | |
180 | } | |
181 | ||
182 | static int worker_thread(void *__cwq) | |
183 | { | |
184 | struct cpu_workqueue_struct *cwq = __cwq; | |
185 | DECLARE_WAITQUEUE(wait, current); | |
186 | struct k_sigaction sa; | |
187 | sigset_t blocked; | |
188 | ||
189 | current->flags |= PF_NOFREEZE; | |
190 | ||
191 | set_user_nice(current, -5); | |
192 | ||
193 | /* Block and flush all signals */ | |
194 | sigfillset(&blocked); | |
195 | sigprocmask(SIG_BLOCK, &blocked, NULL); | |
196 | flush_signals(current); | |
197 | ||
198 | /* SIG_IGN makes children autoreap: see do_notify_parent(). */ | |
199 | sa.sa.sa_handler = SIG_IGN; | |
200 | sa.sa.sa_flags = 0; | |
201 | siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD)); | |
202 | do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0); | |
203 | ||
204 | set_current_state(TASK_INTERRUPTIBLE); | |
205 | while (!kthread_should_stop()) { | |
206 | add_wait_queue(&cwq->more_work, &wait); | |
207 | if (list_empty(&cwq->worklist)) | |
208 | schedule(); | |
209 | else | |
210 | __set_current_state(TASK_RUNNING); | |
211 | remove_wait_queue(&cwq->more_work, &wait); | |
212 | ||
213 | if (!list_empty(&cwq->worklist)) | |
214 | run_workqueue(cwq); | |
215 | set_current_state(TASK_INTERRUPTIBLE); | |
216 | } | |
217 | __set_current_state(TASK_RUNNING); | |
218 | return 0; | |
219 | } | |
220 | ||
221 | static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) | |
222 | { | |
223 | if (cwq->thread == current) { | |
224 | /* | |
225 | * Probably keventd trying to flush its own queue. So simply run | |
226 | * it by hand rather than deadlocking. | |
227 | */ | |
228 | run_workqueue(cwq); | |
229 | } else { | |
230 | DEFINE_WAIT(wait); | |
231 | long sequence_needed; | |
232 | ||
233 | spin_lock_irq(&cwq->lock); | |
234 | sequence_needed = cwq->insert_sequence; | |
235 | ||
236 | while (sequence_needed - cwq->remove_sequence > 0) { | |
237 | prepare_to_wait(&cwq->work_done, &wait, | |
238 | TASK_UNINTERRUPTIBLE); | |
239 | spin_unlock_irq(&cwq->lock); | |
240 | schedule(); | |
241 | spin_lock_irq(&cwq->lock); | |
242 | } | |
243 | finish_wait(&cwq->work_done, &wait); | |
244 | spin_unlock_irq(&cwq->lock); | |
245 | } | |
246 | } | |
247 | ||
248 | /* | |
249 | * flush_workqueue - ensure that any scheduled work has run to completion. | |
250 | * | |
251 | * Forces execution of the workqueue and blocks until its completion. | |
252 | * This is typically used in driver shutdown handlers. | |
253 | * | |
254 | * This function will sample each workqueue's current insert_sequence number and | |
255 | * will sleep until the head sequence is greater than or equal to that. This | |
256 | * means that we sleep until all works which were queued on entry have been | |
257 | * handled, but we are not livelocked by new incoming ones. | |
258 | * | |
259 | * This function used to run the workqueues itself. Now we just wait for the | |
260 | * helper threads to do it. | |
261 | */ | |
262 | void fastcall flush_workqueue(struct workqueue_struct *wq) | |
263 | { | |
264 | might_sleep(); | |
265 | ||
266 | if (is_single_threaded(wq)) { | |
267 | /* Always use cpu 0's area. */ | |
268 | flush_cpu_workqueue(wq->cpu_wq + 0); | |
269 | } else { | |
270 | int cpu; | |
271 | ||
272 | lock_cpu_hotplug(); | |
273 | for_each_online_cpu(cpu) | |
274 | flush_cpu_workqueue(wq->cpu_wq + cpu); | |
275 | unlock_cpu_hotplug(); | |
276 | } | |
277 | } | |
278 | ||
279 | static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq, | |
280 | int cpu) | |
281 | { | |
282 | struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu; | |
283 | struct task_struct *p; | |
284 | ||
285 | spin_lock_init(&cwq->lock); | |
286 | cwq->wq = wq; | |
287 | cwq->thread = NULL; | |
288 | cwq->insert_sequence = 0; | |
289 | cwq->remove_sequence = 0; | |
290 | INIT_LIST_HEAD(&cwq->worklist); | |
291 | init_waitqueue_head(&cwq->more_work); | |
292 | init_waitqueue_head(&cwq->work_done); | |
293 | ||
294 | if (is_single_threaded(wq)) | |
295 | p = kthread_create(worker_thread, cwq, "%s", wq->name); | |
296 | else | |
297 | p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu); | |
298 | if (IS_ERR(p)) | |
299 | return NULL; | |
300 | cwq->thread = p; | |
301 | return p; | |
302 | } | |
303 | ||
304 | struct workqueue_struct *__create_workqueue(const char *name, | |
305 | int singlethread) | |
306 | { | |
307 | int cpu, destroy = 0; | |
308 | struct workqueue_struct *wq; | |
309 | struct task_struct *p; | |
310 | ||
1da177e4 LT |
311 | wq = kmalloc(sizeof(*wq), GFP_KERNEL); |
312 | if (!wq) | |
313 | return NULL; | |
314 | memset(wq, 0, sizeof(*wq)); | |
315 | ||
316 | wq->name = name; | |
317 | /* We don't need the distraction of CPUs appearing and vanishing. */ | |
318 | lock_cpu_hotplug(); | |
319 | if (singlethread) { | |
320 | INIT_LIST_HEAD(&wq->list); | |
321 | p = create_workqueue_thread(wq, 0); | |
322 | if (!p) | |
323 | destroy = 1; | |
324 | else | |
325 | wake_up_process(p); | |
326 | } else { | |
327 | spin_lock(&workqueue_lock); | |
328 | list_add(&wq->list, &workqueues); | |
329 | spin_unlock(&workqueue_lock); | |
330 | for_each_online_cpu(cpu) { | |
331 | p = create_workqueue_thread(wq, cpu); | |
332 | if (p) { | |
333 | kthread_bind(p, cpu); | |
334 | wake_up_process(p); | |
335 | } else | |
336 | destroy = 1; | |
337 | } | |
338 | } | |
339 | unlock_cpu_hotplug(); | |
340 | ||
341 | /* | |
342 | * Was there any error during startup? If yes then clean up: | |
343 | */ | |
344 | if (destroy) { | |
345 | destroy_workqueue(wq); | |
346 | wq = NULL; | |
347 | } | |
348 | return wq; | |
349 | } | |
350 | ||
351 | static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu) | |
352 | { | |
353 | struct cpu_workqueue_struct *cwq; | |
354 | unsigned long flags; | |
355 | struct task_struct *p; | |
356 | ||
357 | cwq = wq->cpu_wq + cpu; | |
358 | spin_lock_irqsave(&cwq->lock, flags); | |
359 | p = cwq->thread; | |
360 | cwq->thread = NULL; | |
361 | spin_unlock_irqrestore(&cwq->lock, flags); | |
362 | if (p) | |
363 | kthread_stop(p); | |
364 | } | |
365 | ||
366 | void destroy_workqueue(struct workqueue_struct *wq) | |
367 | { | |
368 | int cpu; | |
369 | ||
370 | flush_workqueue(wq); | |
371 | ||
372 | /* We don't need the distraction of CPUs appearing and vanishing. */ | |
373 | lock_cpu_hotplug(); | |
374 | if (is_single_threaded(wq)) | |
375 | cleanup_workqueue_thread(wq, 0); | |
376 | else { | |
377 | for_each_online_cpu(cpu) | |
378 | cleanup_workqueue_thread(wq, cpu); | |
379 | spin_lock(&workqueue_lock); | |
380 | list_del(&wq->list); | |
381 | spin_unlock(&workqueue_lock); | |
382 | } | |
383 | unlock_cpu_hotplug(); | |
384 | kfree(wq); | |
385 | } | |
386 | ||
387 | static struct workqueue_struct *keventd_wq; | |
388 | ||
389 | int fastcall schedule_work(struct work_struct *work) | |
390 | { | |
391 | return queue_work(keventd_wq, work); | |
392 | } | |
393 | ||
394 | int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay) | |
395 | { | |
396 | return queue_delayed_work(keventd_wq, work, delay); | |
397 | } | |
398 | ||
399 | int schedule_delayed_work_on(int cpu, | |
400 | struct work_struct *work, unsigned long delay) | |
401 | { | |
402 | int ret = 0; | |
403 | struct timer_list *timer = &work->timer; | |
404 | ||
405 | if (!test_and_set_bit(0, &work->pending)) { | |
406 | BUG_ON(timer_pending(timer)); | |
407 | BUG_ON(!list_empty(&work->entry)); | |
408 | /* This stores keventd_wq for the moment, for the timer_fn */ | |
409 | work->wq_data = keventd_wq; | |
410 | timer->expires = jiffies + delay; | |
411 | timer->data = (unsigned long)work; | |
412 | timer->function = delayed_work_timer_fn; | |
413 | add_timer_on(timer, cpu); | |
414 | ret = 1; | |
415 | } | |
416 | return ret; | |
417 | } | |
418 | ||
419 | void flush_scheduled_work(void) | |
420 | { | |
421 | flush_workqueue(keventd_wq); | |
422 | } | |
423 | ||
424 | /** | |
425 | * cancel_rearming_delayed_workqueue - reliably kill off a delayed | |
426 | * work whose handler rearms the delayed work. | |
427 | * @wq: the controlling workqueue structure | |
428 | * @work: the delayed work struct | |
429 | */ | |
81ddef77 JB |
430 | void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq, |
431 | struct work_struct *work) | |
1da177e4 LT |
432 | { |
433 | while (!cancel_delayed_work(work)) | |
434 | flush_workqueue(wq); | |
435 | } | |
81ddef77 | 436 | EXPORT_SYMBOL(cancel_rearming_delayed_workqueue); |
1da177e4 LT |
437 | |
438 | /** | |
439 | * cancel_rearming_delayed_work - reliably kill off a delayed keventd | |
440 | * work whose handler rearms the delayed work. | |
441 | * @work: the delayed work struct | |
442 | */ | |
443 | void cancel_rearming_delayed_work(struct work_struct *work) | |
444 | { | |
445 | cancel_rearming_delayed_workqueue(keventd_wq, work); | |
446 | } | |
447 | EXPORT_SYMBOL(cancel_rearming_delayed_work); | |
448 | ||
449 | int keventd_up(void) | |
450 | { | |
451 | return keventd_wq != NULL; | |
452 | } | |
453 | ||
454 | int current_is_keventd(void) | |
455 | { | |
456 | struct cpu_workqueue_struct *cwq; | |
457 | int cpu = smp_processor_id(); /* preempt-safe: keventd is per-cpu */ | |
458 | int ret = 0; | |
459 | ||
460 | BUG_ON(!keventd_wq); | |
461 | ||
462 | cwq = keventd_wq->cpu_wq + cpu; | |
463 | if (current == cwq->thread) | |
464 | ret = 1; | |
465 | ||
466 | return ret; | |
467 | ||
468 | } | |
469 | ||
470 | #ifdef CONFIG_HOTPLUG_CPU | |
471 | /* Take the work from this (downed) CPU. */ | |
472 | static void take_over_work(struct workqueue_struct *wq, unsigned int cpu) | |
473 | { | |
474 | struct cpu_workqueue_struct *cwq = wq->cpu_wq + cpu; | |
475 | LIST_HEAD(list); | |
476 | struct work_struct *work; | |
477 | ||
478 | spin_lock_irq(&cwq->lock); | |
479 | list_splice_init(&cwq->worklist, &list); | |
480 | ||
481 | while (!list_empty(&list)) { | |
482 | printk("Taking work for %s\n", wq->name); | |
483 | work = list_entry(list.next,struct work_struct,entry); | |
484 | list_del(&work->entry); | |
485 | __queue_work(wq->cpu_wq + smp_processor_id(), work); | |
486 | } | |
487 | spin_unlock_irq(&cwq->lock); | |
488 | } | |
489 | ||
490 | /* We're holding the cpucontrol mutex here */ | |
491 | static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, | |
492 | unsigned long action, | |
493 | void *hcpu) | |
494 | { | |
495 | unsigned int hotcpu = (unsigned long)hcpu; | |
496 | struct workqueue_struct *wq; | |
497 | ||
498 | switch (action) { | |
499 | case CPU_UP_PREPARE: | |
500 | /* Create a new workqueue thread for it. */ | |
501 | list_for_each_entry(wq, &workqueues, list) { | |
230649da | 502 | if (!create_workqueue_thread(wq, hotcpu)) { |
1da177e4 LT |
503 | printk("workqueue for %i failed\n", hotcpu); |
504 | return NOTIFY_BAD; | |
505 | } | |
506 | } | |
507 | break; | |
508 | ||
509 | case CPU_ONLINE: | |
510 | /* Kick off worker threads. */ | |
511 | list_for_each_entry(wq, &workqueues, list) { | |
512 | kthread_bind(wq->cpu_wq[hotcpu].thread, hotcpu); | |
513 | wake_up_process(wq->cpu_wq[hotcpu].thread); | |
514 | } | |
515 | break; | |
516 | ||
517 | case CPU_UP_CANCELED: | |
518 | list_for_each_entry(wq, &workqueues, list) { | |
519 | /* Unbind so it can run. */ | |
520 | kthread_bind(wq->cpu_wq[hotcpu].thread, | |
521 | smp_processor_id()); | |
522 | cleanup_workqueue_thread(wq, hotcpu); | |
523 | } | |
524 | break; | |
525 | ||
526 | case CPU_DEAD: | |
527 | list_for_each_entry(wq, &workqueues, list) | |
528 | cleanup_workqueue_thread(wq, hotcpu); | |
529 | list_for_each_entry(wq, &workqueues, list) | |
530 | take_over_work(wq, hotcpu); | |
531 | break; | |
532 | } | |
533 | ||
534 | return NOTIFY_OK; | |
535 | } | |
536 | #endif | |
537 | ||
538 | void init_workqueues(void) | |
539 | { | |
540 | hotcpu_notifier(workqueue_cpu_callback, 0); | |
541 | keventd_wq = create_workqueue("events"); | |
542 | BUG_ON(!keventd_wq); | |
543 | } | |
544 | ||
545 | EXPORT_SYMBOL_GPL(__create_workqueue); | |
546 | EXPORT_SYMBOL_GPL(queue_work); | |
547 | EXPORT_SYMBOL_GPL(queue_delayed_work); | |
548 | EXPORT_SYMBOL_GPL(flush_workqueue); | |
549 | EXPORT_SYMBOL_GPL(destroy_workqueue); | |
550 | ||
551 | EXPORT_SYMBOL(schedule_work); | |
552 | EXPORT_SYMBOL(schedule_delayed_work); | |
553 | EXPORT_SYMBOL(schedule_delayed_work_on); | |
554 | EXPORT_SYMBOL(flush_scheduled_work); |