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 * Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>.
17 */
18
19 #include <linux/module.h>
20 #include <linux/kernel.h>
21 #include <linux/sched.h>
22 #include <linux/init.h>
23 #include <linux/signal.h>
24 #include <linux/completion.h>
25 #include <linux/workqueue.h>
26 #include <linux/slab.h>
27 #include <linux/cpu.h>
28 #include <linux/notifier.h>
29 #include <linux/kthread.h>
30 #include <linux/hardirq.h>
31 #include <linux/mempolicy.h>
32 #include <linux/freezer.h>
33 #include <linux/kallsyms.h>
34 #include <linux/debug_locks.h>
35 #include <linux/lockdep.h>
36
37 /*
38 * The per-CPU workqueue (if single thread, we always use the first
39 * possible cpu).
40 */
41 struct cpu_workqueue_struct {
42
43 spinlock_t lock;
44
45 struct list_head worklist;
46 wait_queue_head_t more_work;
47 struct work_struct *current_work;
48
49 struct workqueue_struct *wq;
50 struct task_struct *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;
61 struct list_head list;
62 const char *name;
63 int singlethread;
64 int freezeable; /* Freeze threads during suspend */
65 #ifdef CONFIG_LOCKDEP
66 struct lockdep_map lockdep_map;
67 #endif
68 };
69
70 /* Serializes the accesses to the list of workqueues. */
71 static DEFINE_SPINLOCK(workqueue_lock);
72 static LIST_HEAD(workqueues);
73
74 static int singlethread_cpu __read_mostly;
75 static cpumask_t cpu_singlethread_map __read_mostly;
76 /*
77 * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
78 * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
79 * which comes in between can't use for_each_online_cpu(). We could
80 * use cpu_possible_map, the cpumask below is more a documentation
81 * than optimization.
82 */
83 static cpumask_t cpu_populated_map __read_mostly;
84
85 /* If it's single threaded, it isn't in the list of workqueues. */
86 static inline int is_single_threaded(struct workqueue_struct *wq)
87 {
88 return wq->singlethread;
89 }
90
91 static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
92 {
93 return is_single_threaded(wq)
94 ? &cpu_singlethread_map : &cpu_populated_map;
95 }
96
97 static
98 struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
99 {
100 if (unlikely(is_single_threaded(wq)))
101 cpu = singlethread_cpu;
102 return per_cpu_ptr(wq->cpu_wq, cpu);
103 }
104
105 /*
106 * Set the workqueue on which a work item is to be run
107 * - Must *only* be called if the pending flag is set
108 */
109 static inline void set_wq_data(struct work_struct *work,
110 struct cpu_workqueue_struct *cwq)
111 {
112 unsigned long new;
113
114 BUG_ON(!work_pending(work));
115
116 new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
117 new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
118 atomic_long_set(&work->data, new);
119 }
120
121 static inline
122 struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
123 {
124 return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
125 }
126
127 static void insert_work(struct cpu_workqueue_struct *cwq,
128 struct work_struct *work, int tail)
129 {
130 set_wq_data(work, cwq);
131 /*
132 * Ensure that we get the right work->data if we see the
133 * result of list_add() below, see try_to_grab_pending().
134 */
135 smp_wmb();
136 if (tail)
137 list_add_tail(&work->entry, &cwq->worklist);
138 else
139 list_add(&work->entry, &cwq->worklist);
140 wake_up(&cwq->more_work);
141 }
142
143 /* Preempt must be disabled. */
144 static void __queue_work(struct cpu_workqueue_struct *cwq,
145 struct work_struct *work)
146 {
147 unsigned long flags;
148
149 spin_lock_irqsave(&cwq->lock, flags);
150 insert_work(cwq, work, 1);
151 spin_unlock_irqrestore(&cwq->lock, flags);
152 }
153
154 /**
155 * queue_work - queue work on a workqueue
156 * @wq: workqueue to use
157 * @work: work to queue
158 *
159 * Returns 0 if @work was already on a queue, non-zero otherwise.
160 *
161 * We queue the work to the CPU it was submitted, but there is no
162 * guarantee that it will be processed by that CPU.
163 */
164 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
165 {
166 int ret = 0;
167
168 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
169 BUG_ON(!list_empty(&work->entry));
170 __queue_work(wq_per_cpu(wq, get_cpu()), work);
171 put_cpu();
172 ret = 1;
173 }
174 return ret;
175 }
176 EXPORT_SYMBOL_GPL(queue_work);
177
178 static void delayed_work_timer_fn(unsigned long __data)
179 {
180 struct delayed_work *dwork = (struct delayed_work *)__data;
181 struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
182 struct workqueue_struct *wq = cwq->wq;
183
184 __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
185 }
186
187 /**
188 * queue_delayed_work - queue work on a workqueue after delay
189 * @wq: workqueue to use
190 * @dwork: delayable work to queue
191 * @delay: number of jiffies to wait before queueing
192 *
193 * Returns 0 if @work was already on a queue, non-zero otherwise.
194 */
195 int queue_delayed_work(struct workqueue_struct *wq,
196 struct delayed_work *dwork, unsigned long delay)
197 {
198 timer_stats_timer_set_start_info(&dwork->timer);
199 if (delay == 0)
200 return queue_work(wq, &dwork->work);
201
202 return queue_delayed_work_on(-1, wq, dwork, delay);
203 }
204 EXPORT_SYMBOL_GPL(queue_delayed_work);
205
206 /**
207 * queue_delayed_work_on - queue work on specific CPU after delay
208 * @cpu: CPU number to execute work on
209 * @wq: workqueue to use
210 * @dwork: work to queue
211 * @delay: number of jiffies to wait before queueing
212 *
213 * Returns 0 if @work was already on a queue, non-zero otherwise.
214 */
215 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
216 struct delayed_work *dwork, unsigned long delay)
217 {
218 int ret = 0;
219 struct timer_list *timer = &dwork->timer;
220 struct work_struct *work = &dwork->work;
221
222 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
223 BUG_ON(timer_pending(timer));
224 BUG_ON(!list_empty(&work->entry));
225
226 /* This stores cwq for the moment, for the timer_fn */
227 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
228 timer->expires = jiffies + delay;
229 timer->data = (unsigned long)dwork;
230 timer->function = delayed_work_timer_fn;
231
232 if (unlikely(cpu >= 0))
233 add_timer_on(timer, cpu);
234 else
235 add_timer(timer);
236 ret = 1;
237 }
238 return ret;
239 }
240 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
241
242 static void run_workqueue(struct cpu_workqueue_struct *cwq)
243 {
244 spin_lock_irq(&cwq->lock);
245 cwq->run_depth++;
246 if (cwq->run_depth > 3) {
247 /* morton gets to eat his hat */
248 printk("%s: recursion depth exceeded: %d\n",
249 __FUNCTION__, cwq->run_depth);
250 dump_stack();
251 }
252 while (!list_empty(&cwq->worklist)) {
253 struct work_struct *work = list_entry(cwq->worklist.next,
254 struct work_struct, entry);
255 work_func_t f = work->func;
256 #ifdef CONFIG_LOCKDEP
257 /*
258 * It is permissible to free the struct work_struct
259 * from inside the function that is called from it,
260 * this we need to take into account for lockdep too.
261 * To avoid bogus "held lock freed" warnings as well
262 * as problems when looking into work->lockdep_map,
263 * make a copy and use that here.
264 */
265 struct lockdep_map lockdep_map = work->lockdep_map;
266 #endif
267
268 cwq->current_work = work;
269 list_del_init(cwq->worklist.next);
270 spin_unlock_irq(&cwq->lock);
271
272 BUG_ON(get_wq_data(work) != cwq);
273 work_clear_pending(work);
274 lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
275 lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_);
276 f(work);
277 lock_release(&lockdep_map, 1, _THIS_IP_);
278 lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
279
280 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
281 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
282 "%s/0x%08x/%d\n",
283 current->comm, preempt_count(),
284 task_pid_nr(current));
285 printk(KERN_ERR " last function: ");
286 print_symbol("%s\n", (unsigned long)f);
287 debug_show_held_locks(current);
288 dump_stack();
289 }
290
291 spin_lock_irq(&cwq->lock);
292 cwq->current_work = NULL;
293 }
294 cwq->run_depth--;
295 spin_unlock_irq(&cwq->lock);
296 }
297
298 static int worker_thread(void *__cwq)
299 {
300 struct cpu_workqueue_struct *cwq = __cwq;
301 DEFINE_WAIT(wait);
302
303 if (cwq->wq->freezeable)
304 set_freezable();
305
306 set_user_nice(current, -5);
307
308 for (;;) {
309 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
310 if (!freezing(current) &&
311 !kthread_should_stop() &&
312 list_empty(&cwq->worklist))
313 schedule();
314 finish_wait(&cwq->more_work, &wait);
315
316 try_to_freeze();
317
318 if (kthread_should_stop())
319 break;
320
321 run_workqueue(cwq);
322 }
323
324 return 0;
325 }
326
327 struct wq_barrier {
328 struct work_struct work;
329 struct completion done;
330 };
331
332 static void wq_barrier_func(struct work_struct *work)
333 {
334 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
335 complete(&barr->done);
336 }
337
338 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
339 struct wq_barrier *barr, int tail)
340 {
341 INIT_WORK(&barr->work, wq_barrier_func);
342 __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
343
344 init_completion(&barr->done);
345
346 insert_work(cwq, &barr->work, tail);
347 }
348
349 static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
350 {
351 int active;
352
353 if (cwq->thread == current) {
354 /*
355 * Probably keventd trying to flush its own queue. So simply run
356 * it by hand rather than deadlocking.
357 */
358 run_workqueue(cwq);
359 active = 1;
360 } else {
361 struct wq_barrier barr;
362
363 active = 0;
364 spin_lock_irq(&cwq->lock);
365 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
366 insert_wq_barrier(cwq, &barr, 1);
367 active = 1;
368 }
369 spin_unlock_irq(&cwq->lock);
370
371 if (active)
372 wait_for_completion(&barr.done);
373 }
374
375 return active;
376 }
377
378 /**
379 * flush_workqueue - ensure that any scheduled work has run to completion.
380 * @wq: workqueue to flush
381 *
382 * Forces execution of the workqueue and blocks until its completion.
383 * This is typically used in driver shutdown handlers.
384 *
385 * We sleep until all works which were queued on entry have been handled,
386 * but we are not livelocked by new incoming ones.
387 *
388 * This function used to run the workqueues itself. Now we just wait for the
389 * helper threads to do it.
390 */
391 void flush_workqueue(struct workqueue_struct *wq)
392 {
393 const cpumask_t *cpu_map = wq_cpu_map(wq);
394 int cpu;
395
396 might_sleep();
397 lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
398 lock_release(&wq->lockdep_map, 1, _THIS_IP_);
399 for_each_cpu_mask(cpu, *cpu_map)
400 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
401 }
402 EXPORT_SYMBOL_GPL(flush_workqueue);
403
404 /*
405 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
406 * so this work can't be re-armed in any way.
407 */
408 static int try_to_grab_pending(struct work_struct *work)
409 {
410 struct cpu_workqueue_struct *cwq;
411 int ret = -1;
412
413 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
414 return 0;
415
416 /*
417 * The queueing is in progress, or it is already queued. Try to
418 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
419 */
420
421 cwq = get_wq_data(work);
422 if (!cwq)
423 return ret;
424
425 spin_lock_irq(&cwq->lock);
426 if (!list_empty(&work->entry)) {
427 /*
428 * This work is queued, but perhaps we locked the wrong cwq.
429 * In that case we must see the new value after rmb(), see
430 * insert_work()->wmb().
431 */
432 smp_rmb();
433 if (cwq == get_wq_data(work)) {
434 list_del_init(&work->entry);
435 ret = 1;
436 }
437 }
438 spin_unlock_irq(&cwq->lock);
439
440 return ret;
441 }
442
443 static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
444 struct work_struct *work)
445 {
446 struct wq_barrier barr;
447 int running = 0;
448
449 spin_lock_irq(&cwq->lock);
450 if (unlikely(cwq->current_work == work)) {
451 insert_wq_barrier(cwq, &barr, 0);
452 running = 1;
453 }
454 spin_unlock_irq(&cwq->lock);
455
456 if (unlikely(running))
457 wait_for_completion(&barr.done);
458 }
459
460 static void wait_on_work(struct work_struct *work)
461 {
462 struct cpu_workqueue_struct *cwq;
463 struct workqueue_struct *wq;
464 const cpumask_t *cpu_map;
465 int cpu;
466
467 might_sleep();
468
469 lock_acquire(&work->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
470 lock_release(&work->lockdep_map, 1, _THIS_IP_);
471
472 cwq = get_wq_data(work);
473 if (!cwq)
474 return;
475
476 wq = cwq->wq;
477 cpu_map = wq_cpu_map(wq);
478
479 for_each_cpu_mask(cpu, *cpu_map)
480 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
481 }
482
483 static int __cancel_work_timer(struct work_struct *work,
484 struct timer_list* timer)
485 {
486 int ret;
487
488 do {
489 ret = (timer && likely(del_timer(timer)));
490 if (!ret)
491 ret = try_to_grab_pending(work);
492 wait_on_work(work);
493 } while (unlikely(ret < 0));
494
495 work_clear_pending(work);
496 return ret;
497 }
498
499 /**
500 * cancel_work_sync - block until a work_struct's callback has terminated
501 * @work: the work which is to be flushed
502 *
503 * Returns true if @work was pending.
504 *
505 * cancel_work_sync() will cancel the work if it is queued. If the work's
506 * callback appears to be running, cancel_work_sync() will block until it
507 * has completed.
508 *
509 * It is possible to use this function if the work re-queues itself. It can
510 * cancel the work even if it migrates to another workqueue, however in that
511 * case it only guarantees that work->func() has completed on the last queued
512 * workqueue.
513 *
514 * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
515 * pending, otherwise it goes into a busy-wait loop until the timer expires.
516 *
517 * The caller must ensure that workqueue_struct on which this work was last
518 * queued can't be destroyed before this function returns.
519 */
520 int cancel_work_sync(struct work_struct *work)
521 {
522 return __cancel_work_timer(work, NULL);
523 }
524 EXPORT_SYMBOL_GPL(cancel_work_sync);
525
526 /**
527 * cancel_delayed_work_sync - reliably kill off a delayed work.
528 * @dwork: the delayed work struct
529 *
530 * Returns true if @dwork was pending.
531 *
532 * It is possible to use this function if @dwork rearms itself via queue_work()
533 * or queue_delayed_work(). See also the comment for cancel_work_sync().
534 */
535 int cancel_delayed_work_sync(struct delayed_work *dwork)
536 {
537 return __cancel_work_timer(&dwork->work, &dwork->timer);
538 }
539 EXPORT_SYMBOL(cancel_delayed_work_sync);
540
541 static struct workqueue_struct *keventd_wq __read_mostly;
542
543 /**
544 * schedule_work - put work task in global workqueue
545 * @work: job to be done
546 *
547 * This puts a job in the kernel-global workqueue.
548 */
549 int schedule_work(struct work_struct *work)
550 {
551 return queue_work(keventd_wq, work);
552 }
553 EXPORT_SYMBOL(schedule_work);
554
555 /**
556 * schedule_delayed_work - put work task in global workqueue after delay
557 * @dwork: job to be done
558 * @delay: number of jiffies to wait or 0 for immediate execution
559 *
560 * After waiting for a given time this puts a job in the kernel-global
561 * workqueue.
562 */
563 int schedule_delayed_work(struct delayed_work *dwork,
564 unsigned long delay)
565 {
566 timer_stats_timer_set_start_info(&dwork->timer);
567 return queue_delayed_work(keventd_wq, dwork, delay);
568 }
569 EXPORT_SYMBOL(schedule_delayed_work);
570
571 /**
572 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
573 * @cpu: cpu to use
574 * @dwork: job to be done
575 * @delay: number of jiffies to wait
576 *
577 * After waiting for a given time this puts a job in the kernel-global
578 * workqueue on the specified CPU.
579 */
580 int schedule_delayed_work_on(int cpu,
581 struct delayed_work *dwork, unsigned long delay)
582 {
583 return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
584 }
585 EXPORT_SYMBOL(schedule_delayed_work_on);
586
587 /**
588 * schedule_on_each_cpu - call a function on each online CPU from keventd
589 * @func: the function to call
590 *
591 * Returns zero on success.
592 * Returns -ve errno on failure.
593 *
594 * schedule_on_each_cpu() is very slow.
595 */
596 int schedule_on_each_cpu(work_func_t func)
597 {
598 int cpu;
599 struct work_struct *works;
600
601 works = alloc_percpu(struct work_struct);
602 if (!works)
603 return -ENOMEM;
604
605 get_online_cpus();
606 for_each_online_cpu(cpu) {
607 struct work_struct *work = per_cpu_ptr(works, cpu);
608
609 INIT_WORK(work, func);
610 set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
611 __queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu), work);
612 }
613 flush_workqueue(keventd_wq);
614 put_online_cpus();
615 free_percpu(works);
616 return 0;
617 }
618
619 void flush_scheduled_work(void)
620 {
621 flush_workqueue(keventd_wq);
622 }
623 EXPORT_SYMBOL(flush_scheduled_work);
624
625 /**
626 * execute_in_process_context - reliably execute the routine with user context
627 * @fn: the function to execute
628 * @ew: guaranteed storage for the execute work structure (must
629 * be available when the work executes)
630 *
631 * Executes the function immediately if process context is available,
632 * otherwise schedules the function for delayed execution.
633 *
634 * Returns: 0 - function was executed
635 * 1 - function was scheduled for execution
636 */
637 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
638 {
639 if (!in_interrupt()) {
640 fn(&ew->work);
641 return 0;
642 }
643
644 INIT_WORK(&ew->work, fn);
645 schedule_work(&ew->work);
646
647 return 1;
648 }
649 EXPORT_SYMBOL_GPL(execute_in_process_context);
650
651 int keventd_up(void)
652 {
653 return keventd_wq != NULL;
654 }
655
656 int current_is_keventd(void)
657 {
658 struct cpu_workqueue_struct *cwq;
659 int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
660 int ret = 0;
661
662 BUG_ON(!keventd_wq);
663
664 cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
665 if (current == cwq->thread)
666 ret = 1;
667
668 return ret;
669
670 }
671
672 static struct cpu_workqueue_struct *
673 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
674 {
675 struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
676
677 cwq->wq = wq;
678 spin_lock_init(&cwq->lock);
679 INIT_LIST_HEAD(&cwq->worklist);
680 init_waitqueue_head(&cwq->more_work);
681
682 return cwq;
683 }
684
685 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
686 {
687 struct workqueue_struct *wq = cwq->wq;
688 const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d";
689 struct task_struct *p;
690
691 p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
692 /*
693 * Nobody can add the work_struct to this cwq,
694 * if (caller is __create_workqueue)
695 * nobody should see this wq
696 * else // caller is CPU_UP_PREPARE
697 * cpu is not on cpu_online_map
698 * so we can abort safely.
699 */
700 if (IS_ERR(p))
701 return PTR_ERR(p);
702
703 cwq->thread = p;
704
705 return 0;
706 }
707
708 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
709 {
710 struct task_struct *p = cwq->thread;
711
712 if (p != NULL) {
713 if (cpu >= 0)
714 kthread_bind(p, cpu);
715 wake_up_process(p);
716 }
717 }
718
719 struct workqueue_struct *__create_workqueue_key(const char *name,
720 int singlethread,
721 int freezeable,
722 struct lock_class_key *key,
723 const char *lock_name)
724 {
725 struct workqueue_struct *wq;
726 struct cpu_workqueue_struct *cwq;
727 int err = 0, cpu;
728
729 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
730 if (!wq)
731 return NULL;
732
733 wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
734 if (!wq->cpu_wq) {
735 kfree(wq);
736 return NULL;
737 }
738
739 wq->name = name;
740 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
741 wq->singlethread = singlethread;
742 wq->freezeable = freezeable;
743 INIT_LIST_HEAD(&wq->list);
744
745 if (singlethread) {
746 cwq = init_cpu_workqueue(wq, singlethread_cpu);
747 err = create_workqueue_thread(cwq, singlethread_cpu);
748 start_workqueue_thread(cwq, -1);
749 } else {
750 get_online_cpus();
751 spin_lock(&workqueue_lock);
752 list_add(&wq->list, &workqueues);
753 spin_unlock(&workqueue_lock);
754
755 for_each_possible_cpu(cpu) {
756 cwq = init_cpu_workqueue(wq, cpu);
757 if (err || !cpu_online(cpu))
758 continue;
759 err = create_workqueue_thread(cwq, cpu);
760 start_workqueue_thread(cwq, cpu);
761 }
762 put_online_cpus();
763 }
764
765 if (err) {
766 destroy_workqueue(wq);
767 wq = NULL;
768 }
769 return wq;
770 }
771 EXPORT_SYMBOL_GPL(__create_workqueue_key);
772
773 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
774 {
775 /*
776 * Our caller is either destroy_workqueue() or CPU_DEAD,
777 * get_online_cpus() protects cwq->thread.
778 */
779 if (cwq->thread == NULL)
780 return;
781
782 lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_);
783 lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_);
784
785 flush_cpu_workqueue(cwq);
786 /*
787 * If the caller is CPU_DEAD and cwq->worklist was not empty,
788 * a concurrent flush_workqueue() can insert a barrier after us.
789 * However, in that case run_workqueue() won't return and check
790 * kthread_should_stop() until it flushes all work_struct's.
791 * When ->worklist becomes empty it is safe to exit because no
792 * more work_structs can be queued on this cwq: flush_workqueue
793 * checks list_empty(), and a "normal" queue_work() can't use
794 * a dead CPU.
795 */
796 kthread_stop(cwq->thread);
797 cwq->thread = NULL;
798 }
799
800 /**
801 * destroy_workqueue - safely terminate a workqueue
802 * @wq: target workqueue
803 *
804 * Safely destroy a workqueue. All work currently pending will be done first.
805 */
806 void destroy_workqueue(struct workqueue_struct *wq)
807 {
808 const cpumask_t *cpu_map = wq_cpu_map(wq);
809 struct cpu_workqueue_struct *cwq;
810 int cpu;
811
812 get_online_cpus();
813 spin_lock(&workqueue_lock);
814 list_del(&wq->list);
815 spin_unlock(&workqueue_lock);
816 put_online_cpus();
817
818 for_each_cpu_mask(cpu, *cpu_map) {
819 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
820 cleanup_workqueue_thread(cwq, cpu);
821 }
822
823 free_percpu(wq->cpu_wq);
824 kfree(wq);
825 }
826 EXPORT_SYMBOL_GPL(destroy_workqueue);
827
828 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
829 unsigned long action,
830 void *hcpu)
831 {
832 unsigned int cpu = (unsigned long)hcpu;
833 struct cpu_workqueue_struct *cwq;
834 struct workqueue_struct *wq;
835
836 action &= ~CPU_TASKS_FROZEN;
837
838 switch (action) {
839
840 case CPU_UP_PREPARE:
841 cpu_set(cpu, cpu_populated_map);
842 }
843
844 list_for_each_entry(wq, &workqueues, list) {
845 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
846
847 switch (action) {
848 case CPU_UP_PREPARE:
849 if (!create_workqueue_thread(cwq, cpu))
850 break;
851 printk(KERN_ERR "workqueue [%s] for %i failed\n",
852 wq->name, cpu);
853 return NOTIFY_BAD;
854
855 case CPU_ONLINE:
856 start_workqueue_thread(cwq, cpu);
857 break;
858
859 case CPU_UP_CANCELED:
860 start_workqueue_thread(cwq, -1);
861 case CPU_DEAD:
862 cleanup_workqueue_thread(cwq, cpu);
863 break;
864 }
865 }
866
867 return NOTIFY_OK;
868 }
869
870 void __init init_workqueues(void)
871 {
872 cpu_populated_map = cpu_online_map;
873 singlethread_cpu = first_cpu(cpu_possible_map);
874 cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
875 hotcpu_notifier(workqueue_cpu_callback, 0);
876 keventd_wq = create_workqueue("events");
877 BUG_ON(!keventd_wq);
878 }
879
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