projects/linux·blob v2.6.31-rc1 · refs

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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 <[email protected]>
12 * Andrew Morton
13 * Kai Petzke <[email protected]>
14 * Theodore Ts'o <[email protected]>
15 *
16 * Made to use alloc_percpu by Christoph Lameter.
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#define CREATE_TRACE_POINTS
37#include <trace/events/workqueue.h>
38
39/*
40 * The per-CPU workqueue (if single thread, we always use the first
41 * possible cpu).
42 */
43struct cpu_workqueue_struct {
44
45 spinlock_t lock;
46
47 struct list_head worklist;
48 wait_queue_head_t more_work;
49 struct work_struct *current_work;
50
51 struct workqueue_struct *wq;
52 struct task_struct *thread;
53} ____cacheline_aligned;
54
55/*
56 * The externally visible workqueue abstraction is an array of
57 * per-CPU workqueues:
58 */
59struct 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 int rt;
66#ifdef CONFIG_LOCKDEP
67 struct lockdep_map lockdep_map;
68#endif
69};
70
71/* Serializes the accesses to the list of workqueues. */
72static DEFINE_SPINLOCK(workqueue_lock);
73static LIST_HEAD(workqueues);
74
75static int singlethread_cpu __read_mostly;
76static const struct cpumask *cpu_singlethread_map __read_mostly;
77/*
78 * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
79 * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
80 * which comes in between can't use for_each_online_cpu(). We could
81 * use cpu_possible_map, the cpumask below is more a documentation
82 * than optimization.
83 */
84static cpumask_var_t cpu_populated_map __read_mostly;
85
86/* If it's single threaded, it isn't in the list of workqueues. */
87static inline int is_wq_single_threaded(struct workqueue_struct *wq)
88{
89 return wq->singlethread;
90}
91
92static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)
93{
94 return is_wq_single_threaded(wq)
95 ? cpu_singlethread_map : cpu_populated_map;
96}
97
98static
99struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
100{
101 if (unlikely(is_wq_single_threaded(wq)))
102 cpu = singlethread_cpu;
103 return per_cpu_ptr(wq->cpu_wq, cpu);
104}
105
106/*
107 * Set the workqueue on which a work item is to be run
108 * - Must *only* be called if the pending flag is set
109 */
110static inline void set_wq_data(struct work_struct *work,
111 struct cpu_workqueue_struct *cwq)
112{
113 unsigned long new;
114
115 BUG_ON(!work_pending(work));
116
117 new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
118 new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
119 atomic_long_set(&work->data, new);
120}
121
122static inline
123struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
124{
125 return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
126}
127
128static void insert_work(struct cpu_workqueue_struct *cwq,
129 struct work_struct *work, struct list_head *head)
130{
131 trace_workqueue_insertion(cwq->thread, work);
132
133 set_wq_data(work, cwq);
134 /*
135 * Ensure that we get the right work->data if we see the
136 * result of list_add() below, see try_to_grab_pending().
137 */
138 smp_wmb();
139 list_add_tail(&work->entry, head);
140 wake_up(&cwq->more_work);
141}
142
143static void __queue_work(struct cpu_workqueue_struct *cwq,
144 struct work_struct *work)
145{
146 unsigned long flags;
147
148 spin_lock_irqsave(&cwq->lock, flags);
149 insert_work(cwq, work, &cwq->worklist);
150 spin_unlock_irqrestore(&cwq->lock, flags);
151}
152
153/**
154 * queue_work - queue work on a workqueue
155 * @wq: workqueue to use
156 * @work: work to queue
157 *
158 * Returns 0 if @work was already on a queue, non-zero otherwise.
159 *
160 * We queue the work to the CPU on which it was submitted, but if the CPU dies
161 * it can be processed by another CPU.
162 */
163int queue_work(struct workqueue_struct *wq, struct work_struct *work)
164{
165 int ret;
166
167 ret = queue_work_on(get_cpu(), wq, work);
168 put_cpu();
169
170 return ret;
171}
172EXPORT_SYMBOL_GPL(queue_work);
173
174/**
175 * queue_work_on - queue work on specific cpu
176 * @cpu: CPU number to execute work on
177 * @wq: workqueue to use
178 * @work: work to queue
179 *
180 * Returns 0 if @work was already on a queue, non-zero otherwise.
181 *
182 * We queue the work to a specific CPU, the caller must ensure it
183 * can't go away.
184 */
185int
186queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
187{
188 int ret = 0;
189
190 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
191 BUG_ON(!list_empty(&work->entry));
192 __queue_work(wq_per_cpu(wq, cpu), work);
193 ret = 1;
194 }
195 return ret;
196}
197EXPORT_SYMBOL_GPL(queue_work_on);
198
199static void delayed_work_timer_fn(unsigned long __data)
200{
201 struct delayed_work *dwork = (struct delayed_work *)__data;
202 struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
203 struct workqueue_struct *wq = cwq->wq;
204
205 __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
206}
207
208/**
209 * queue_delayed_work - queue work on a workqueue after delay
210 * @wq: workqueue to use
211 * @dwork: delayable work to queue
212 * @delay: number of jiffies to wait before queueing
213 *
214 * Returns 0 if @work was already on a queue, non-zero otherwise.
215 */
216int queue_delayed_work(struct workqueue_struct *wq,
217 struct delayed_work *dwork, unsigned long delay)
218{
219 if (delay == 0)
220 return queue_work(wq, &dwork->work);
221
222 return queue_delayed_work_on(-1, wq, dwork, delay);
223}
224EXPORT_SYMBOL_GPL(queue_delayed_work);
225
226/**
227 * queue_delayed_work_on - queue work on specific CPU after delay
228 * @cpu: CPU number to execute work on
229 * @wq: workqueue to use
230 * @dwork: work to queue
231 * @delay: number of jiffies to wait before queueing
232 *
233 * Returns 0 if @work was already on a queue, non-zero otherwise.
234 */
235int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
236 struct delayed_work *dwork, unsigned long delay)
237{
238 int ret = 0;
239 struct timer_list *timer = &dwork->timer;
240 struct work_struct *work = &dwork->work;
241
242 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
243 BUG_ON(timer_pending(timer));
244 BUG_ON(!list_empty(&work->entry));
245
246 timer_stats_timer_set_start_info(&dwork->timer);
247
248 /* This stores cwq for the moment, for the timer_fn */
249 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
250 timer->expires = jiffies + delay;
251 timer->data = (unsigned long)dwork;
252 timer->function = delayed_work_timer_fn;
253
254 if (unlikely(cpu >= 0))
255 add_timer_on(timer, cpu);
256 else
257 add_timer(timer);
258 ret = 1;
259 }
260 return ret;
261}
262EXPORT_SYMBOL_GPL(queue_delayed_work_on);
263
264static void run_workqueue(struct cpu_workqueue_struct *cwq)
265{
266 spin_lock_irq(&cwq->lock);
267 while (!list_empty(&cwq->worklist)) {
268 struct work_struct *work = list_entry(cwq->worklist.next,
269 struct work_struct, entry);
270 work_func_t f = work->func;
271#ifdef CONFIG_LOCKDEP
272 /*
273 * It is permissible to free the struct work_struct
274 * from inside the function that is called from it,
275 * this we need to take into account for lockdep too.
276 * To avoid bogus "held lock freed" warnings as well
277 * as problems when looking into work->lockdep_map,
278 * make a copy and use that here.
279 */
280 struct lockdep_map lockdep_map = work->lockdep_map;
281#endif
282 trace_workqueue_execution(cwq->thread, work);
283 cwq->current_work = work;
284 list_del_init(cwq->worklist.next);
285 spin_unlock_irq(&cwq->lock);
286
287 BUG_ON(get_wq_data(work) != cwq);
288 work_clear_pending(work);
289 lock_map_acquire(&cwq->wq->lockdep_map);
290 lock_map_acquire(&lockdep_map);
291 f(work);
292 lock_map_release(&lockdep_map);
293 lock_map_release(&cwq->wq->lockdep_map);
294
295 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
296 printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
297 "%s/0x%08x/%d\n",
298 current->comm, preempt_count(),
299 task_pid_nr(current));
300 printk(KERN_ERR " last function: ");
301 print_symbol("%s\n", (unsigned long)f);
302 debug_show_held_locks(current);
303 dump_stack();
304 }
305
306 spin_lock_irq(&cwq->lock);
307 cwq->current_work = NULL;
308 }
309 spin_unlock_irq(&cwq->lock);
310}
311
312static int worker_thread(void *__cwq)
313{
314 struct cpu_workqueue_struct *cwq = __cwq;
315 DEFINE_WAIT(wait);
316
317 if (cwq->wq->freezeable)
318 set_freezable();
319
320 set_user_nice(current, -5);
321
322 for (;;) {
323 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
324 if (!freezing(current) &&
325 !kthread_should_stop() &&
326 list_empty(&cwq->worklist))
327 schedule();
328 finish_wait(&cwq->more_work, &wait);
329
330 try_to_freeze();
331
332 if (kthread_should_stop())
333 break;
334
335 run_workqueue(cwq);
336 }
337
338 return 0;
339}
340
341struct wq_barrier {
342 struct work_struct work;
343 struct completion done;
344};
345
346static void wq_barrier_func(struct work_struct *work)
347{
348 struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
349 complete(&barr->done);
350}
351
352static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
353 struct wq_barrier *barr, struct list_head *head)
354{
355 INIT_WORK(&barr->work, wq_barrier_func);
356 __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
357
358 init_completion(&barr->done);
359
360 insert_work(cwq, &barr->work, head);
361}
362
363static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
364{
365 int active = 0;
366 struct wq_barrier barr;
367
368 WARN_ON(cwq->thread == current);
369
370 spin_lock_irq(&cwq->lock);
371 if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
372 insert_wq_barrier(cwq, &barr, &cwq->worklist);
373 active = 1;
374 }
375 spin_unlock_irq(&cwq->lock);
376
377 if (active)
378 wait_for_completion(&barr.done);
379
380 return active;
381}
382
383/**
384 * flush_workqueue - ensure that any scheduled work has run to completion.
385 * @wq: workqueue to flush
386 *
387 * Forces execution of the workqueue and blocks until its completion.
388 * This is typically used in driver shutdown handlers.
389 *
390 * We sleep until all works which were queued on entry have been handled,
391 * but we are not livelocked by new incoming ones.
392 *
393 * This function used to run the workqueues itself. Now we just wait for the
394 * helper threads to do it.
395 */
396void flush_workqueue(struct workqueue_struct *wq)
397{
398 const struct cpumask *cpu_map = wq_cpu_map(wq);
399 int cpu;
400
401 might_sleep();
402 lock_map_acquire(&wq->lockdep_map);
403 lock_map_release(&wq->lockdep_map);
404 for_each_cpu(cpu, cpu_map)
405 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
406}
407EXPORT_SYMBOL_GPL(flush_workqueue);
408
409/**
410 * flush_work - block until a work_struct's callback has terminated
411 * @work: the work which is to be flushed
412 *
413 * Returns false if @work has already terminated.
414 *
415 * It is expected that, prior to calling flush_work(), the caller has
416 * arranged for the work to not be requeued, otherwise it doesn't make
417 * sense to use this function.
418 */
419int flush_work(struct work_struct *work)
420{
421 struct cpu_workqueue_struct *cwq;
422 struct list_head *prev;
423 struct wq_barrier barr;
424
425 might_sleep();
426 cwq = get_wq_data(work);
427 if (!cwq)
428 return 0;
429
430 lock_map_acquire(&cwq->wq->lockdep_map);
431 lock_map_release(&cwq->wq->lockdep_map);
432
433 prev = NULL;
434 spin_lock_irq(&cwq->lock);
435 if (!list_empty(&work->entry)) {
436 /*
437 * See the comment near try_to_grab_pending()->smp_rmb().
438 * If it was re-queued under us we are not going to wait.
439 */
440 smp_rmb();
441 if (unlikely(cwq != get_wq_data(work)))
442 goto out;
443 prev = &work->entry;
444 } else {
445 if (cwq->current_work != work)
446 goto out;
447 prev = &cwq->worklist;
448 }
449 insert_wq_barrier(cwq, &barr, prev->next);
450out:
451 spin_unlock_irq(&cwq->lock);
452 if (!prev)
453 return 0;
454
455 wait_for_completion(&barr.done);
456 return 1;
457}
458EXPORT_SYMBOL_GPL(flush_work);
459
460/*
461 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
462 * so this work can't be re-armed in any way.
463 */
464static int try_to_grab_pending(struct work_struct *work)
465{
466 struct cpu_workqueue_struct *cwq;
467 int ret = -1;
468
469 if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
470 return 0;
471
472 /*
473 * The queueing is in progress, or it is already queued. Try to
474 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
475 */
476
477 cwq = get_wq_data(work);
478 if (!cwq)
479 return ret;
480
481 spin_lock_irq(&cwq->lock);
482 if (!list_empty(&work->entry)) {
483 /*
484 * This work is queued, but perhaps we locked the wrong cwq.
485 * In that case we must see the new value after rmb(), see
486 * insert_work()->wmb().
487 */
488 smp_rmb();
489 if (cwq == get_wq_data(work)) {
490 list_del_init(&work->entry);
491 ret = 1;
492 }
493 }
494 spin_unlock_irq(&cwq->lock);
495
496 return ret;
497}
498
499static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
500 struct work_struct *work)
501{
502 struct wq_barrier barr;
503 int running = 0;
504
505 spin_lock_irq(&cwq->lock);
506 if (unlikely(cwq->current_work == work)) {
507 insert_wq_barrier(cwq, &barr, cwq->worklist.next);
508 running = 1;
509 }
510 spin_unlock_irq(&cwq->lock);
511
512 if (unlikely(running))
513 wait_for_completion(&barr.done);
514}
515
516static void wait_on_work(struct work_struct *work)
517{
518 struct cpu_workqueue_struct *cwq;
519 struct workqueue_struct *wq;
520 const struct cpumask *cpu_map;
521 int cpu;
522
523 might_sleep();
524
525 lock_map_acquire(&work->lockdep_map);
526 lock_map_release(&work->lockdep_map);
527
528 cwq = get_wq_data(work);
529 if (!cwq)
530 return;
531
532 wq = cwq->wq;
533 cpu_map = wq_cpu_map(wq);
534
535 for_each_cpu(cpu, cpu_map)
536 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
537}
538
539static int __cancel_work_timer(struct work_struct *work,
540 struct timer_list* timer)
541{
542 int ret;
543
544 do {
545 ret = (timer && likely(del_timer(timer)));
546 if (!ret)
547 ret = try_to_grab_pending(work);
548 wait_on_work(work);
549 } while (unlikely(ret < 0));
550
551 work_clear_pending(work);
552 return ret;
553}
554
555/**
556 * cancel_work_sync - block until a work_struct's callback has terminated
557 * @work: the work which is to be flushed
558 *
559 * Returns true if @work was pending.
560 *
561 * cancel_work_sync() will cancel the work if it is queued. If the work's
562 * callback appears to be running, cancel_work_sync() will block until it
563 * has completed.
564 *
565 * It is possible to use this function if the work re-queues itself. It can
566 * cancel the work even if it migrates to another workqueue, however in that
567 * case it only guarantees that work->func() has completed on the last queued
568 * workqueue.
569 *
570 * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
571 * pending, otherwise it goes into a busy-wait loop until the timer expires.
572 *
573 * The caller must ensure that workqueue_struct on which this work was last
574 * queued can't be destroyed before this function returns.
575 */
576int cancel_work_sync(struct work_struct *work)
577{
578 return __cancel_work_timer(work, NULL);
579}
580EXPORT_SYMBOL_GPL(cancel_work_sync);
581
582/**
583 * cancel_delayed_work_sync - reliably kill off a delayed work.
584 * @dwork: the delayed work struct
585 *
586 * Returns true if @dwork was pending.
587 *
588 * It is possible to use this function if @dwork rearms itself via queue_work()
589 * or queue_delayed_work(). See also the comment for cancel_work_sync().
590 */
591int cancel_delayed_work_sync(struct delayed_work *dwork)
592{
593 return __cancel_work_timer(&dwork->work, &dwork->timer);
594}
595EXPORT_SYMBOL(cancel_delayed_work_sync);
596
597static struct workqueue_struct *keventd_wq __read_mostly;
598
599/**
600 * schedule_work - put work task in global workqueue
601 * @work: job to be done
602 *
603 * This puts a job in the kernel-global workqueue.
604 */
605int schedule_work(struct work_struct *work)
606{
607 return queue_work(keventd_wq, work);
608}
609EXPORT_SYMBOL(schedule_work);
610
611/*
612 * schedule_work_on - put work task on a specific cpu
613 * @cpu: cpu to put the work task on
614 * @work: job to be done
615 *
616 * This puts a job on a specific cpu
617 */
618int schedule_work_on(int cpu, struct work_struct *work)
619{
620 return queue_work_on(cpu, keventd_wq, work);
621}
622EXPORT_SYMBOL(schedule_work_on);
623
624/**
625 * schedule_delayed_work - put work task in global workqueue after delay
626 * @dwork: job to be done
627 * @delay: number of jiffies to wait or 0 for immediate execution
628 *
629 * After waiting for a given time this puts a job in the kernel-global
630 * workqueue.
631 */
632int schedule_delayed_work(struct delayed_work *dwork,
633 unsigned long delay)
634{
635 return queue_delayed_work(keventd_wq, dwork, delay);
636}
637EXPORT_SYMBOL(schedule_delayed_work);
638
639/**
640 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
641 * @cpu: cpu to use
642 * @dwork: job to be done
643 * @delay: number of jiffies to wait
644 *
645 * After waiting for a given time this puts a job in the kernel-global
646 * workqueue on the specified CPU.
647 */
648int schedule_delayed_work_on(int cpu,
649 struct delayed_work *dwork, unsigned long delay)
650{
651 return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
652}
653EXPORT_SYMBOL(schedule_delayed_work_on);
654
655/**
656 * schedule_on_each_cpu - call a function on each online CPU from keventd
657 * @func: the function to call
658 *
659 * Returns zero on success.
660 * Returns -ve errno on failure.
661 *
662 * schedule_on_each_cpu() is very slow.
663 */
664int schedule_on_each_cpu(work_func_t func)
665{
666 int cpu;
667 struct work_struct *works;
668
669 works = alloc_percpu(struct work_struct);
670 if (!works)
671 return -ENOMEM;
672
673 get_online_cpus();
674 for_each_online_cpu(cpu) {
675 struct work_struct *work = per_cpu_ptr(works, cpu);
676
677 INIT_WORK(work, func);
678 schedule_work_on(cpu, work);
679 }
680 for_each_online_cpu(cpu)
681 flush_work(per_cpu_ptr(works, cpu));
682 put_online_cpus();
683 free_percpu(works);
684 return 0;
685}
686
687void flush_scheduled_work(void)
688{
689 flush_workqueue(keventd_wq);
690}
691EXPORT_SYMBOL(flush_scheduled_work);
692
693/**
694 * execute_in_process_context - reliably execute the routine with user context
695 * @fn: the function to execute
696 * @ew: guaranteed storage for the execute work structure (must
697 * be available when the work executes)
698 *
699 * Executes the function immediately if process context is available,
700 * otherwise schedules the function for delayed execution.
701 *
702 * Returns: 0 - function was executed
703 * 1 - function was scheduled for execution
704 */
705int execute_in_process_context(work_func_t fn, struct execute_work *ew)
706{
707 if (!in_interrupt()) {
708 fn(&ew->work);
709 return 0;
710 }
711
712 INIT_WORK(&ew->work, fn);
713 schedule_work(&ew->work);
714
715 return 1;
716}
717EXPORT_SYMBOL_GPL(execute_in_process_context);
718
719int keventd_up(void)
720{
721 return keventd_wq != NULL;
722}
723
724int current_is_keventd(void)
725{
726 struct cpu_workqueue_struct *cwq;
727 int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
728 int ret = 0;
729
730 BUG_ON(!keventd_wq);
731
732 cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
733 if (current == cwq->thread)
734 ret = 1;
735
736 return ret;
737
738}
739
740static struct cpu_workqueue_struct *
741init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
742{
743 struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
744
745 cwq->wq = wq;
746 spin_lock_init(&cwq->lock);
747 INIT_LIST_HEAD(&cwq->worklist);
748 init_waitqueue_head(&cwq->more_work);
749
750 return cwq;
751}
752
753static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
754{
755 struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
756 struct workqueue_struct *wq = cwq->wq;
757 const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";
758 struct task_struct *p;
759
760 p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
761 /*
762 * Nobody can add the work_struct to this cwq,
763 * if (caller is __create_workqueue)
764 * nobody should see this wq
765 * else // caller is CPU_UP_PREPARE
766 * cpu is not on cpu_online_map
767 * so we can abort safely.
768 */
769 if (IS_ERR(p))
770 return PTR_ERR(p);
771 if (cwq->wq->rt)
772 sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
773 cwq->thread = p;
774
775 trace_workqueue_creation(cwq->thread, cpu);
776
777 return 0;
778}
779
780static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
781{
782 struct task_struct *p = cwq->thread;
783
784 if (p != NULL) {
785 if (cpu >= 0)
786 kthread_bind(p, cpu);
787 wake_up_process(p);
788 }
789}
790
791struct workqueue_struct *__create_workqueue_key(const char *name,
792 int singlethread,
793 int freezeable,
794 int rt,
795 struct lock_class_key *key,
796 const char *lock_name)
797{
798 struct workqueue_struct *wq;
799 struct cpu_workqueue_struct *cwq;
800 int err = 0, cpu;
801
802 wq = kzalloc(sizeof(*wq), GFP_KERNEL);
803 if (!wq)
804 return NULL;
805
806 wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
807 if (!wq->cpu_wq) {
808 kfree(wq);
809 return NULL;
810 }
811
812 wq->name = name;
813 lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
814 wq->singlethread = singlethread;
815 wq->freezeable = freezeable;
816 wq->rt = rt;
817 INIT_LIST_HEAD(&wq->list);
818
819 if (singlethread) {
820 cwq = init_cpu_workqueue(wq, singlethread_cpu);
821 err = create_workqueue_thread(cwq, singlethread_cpu);
822 start_workqueue_thread(cwq, -1);
823 } else {
824 cpu_maps_update_begin();
825 /*
826 * We must place this wq on list even if the code below fails.
827 * cpu_down(cpu) can remove cpu from cpu_populated_map before
828 * destroy_workqueue() takes the lock, in that case we leak
829 * cwq[cpu]->thread.
830 */
831 spin_lock(&workqueue_lock);
832 list_add(&wq->list, &workqueues);
833 spin_unlock(&workqueue_lock);
834 /*
835 * We must initialize cwqs for each possible cpu even if we
836 * are going to call destroy_workqueue() finally. Otherwise
837 * cpu_up() can hit the uninitialized cwq once we drop the
838 * lock.
839 */
840 for_each_possible_cpu(cpu) {
841 cwq = init_cpu_workqueue(wq, cpu);
842 if (err || !cpu_online(cpu))
843 continue;
844 err = create_workqueue_thread(cwq, cpu);
845 start_workqueue_thread(cwq, cpu);
846 }
847 cpu_maps_update_done();
848 }
849
850 if (err) {
851 destroy_workqueue(wq);
852 wq = NULL;
853 }
854 return wq;
855}
856EXPORT_SYMBOL_GPL(__create_workqueue_key);
857
858static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
859{
860 /*
861 * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
862 * cpu_add_remove_lock protects cwq->thread.
863 */
864 if (cwq->thread == NULL)
865 return;
866
867 lock_map_acquire(&cwq->wq->lockdep_map);
868 lock_map_release(&cwq->wq->lockdep_map);
869
870 flush_cpu_workqueue(cwq);
871 /*
872 * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
873 * a concurrent flush_workqueue() can insert a barrier after us.
874 * However, in that case run_workqueue() won't return and check
875 * kthread_should_stop() until it flushes all work_struct's.
876 * When ->worklist becomes empty it is safe to exit because no
877 * more work_structs can be queued on this cwq: flush_workqueue
878 * checks list_empty(), and a "normal" queue_work() can't use
879 * a dead CPU.
880 */
881 trace_workqueue_destruction(cwq->thread);
882 kthread_stop(cwq->thread);
883 cwq->thread = NULL;
884}
885
886/**
887 * destroy_workqueue - safely terminate a workqueue
888 * @wq: target workqueue
889 *
890 * Safely destroy a workqueue. All work currently pending will be done first.
891 */
892void destroy_workqueue(struct workqueue_struct *wq)
893{
894 const struct cpumask *cpu_map = wq_cpu_map(wq);
895 int cpu;
896
897 cpu_maps_update_begin();
898 spin_lock(&workqueue_lock);
899 list_del(&wq->list);
900 spin_unlock(&workqueue_lock);
901
902 for_each_cpu(cpu, cpu_map)
903 cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
904 cpu_maps_update_done();
905
906 free_percpu(wq->cpu_wq);
907 kfree(wq);
908}
909EXPORT_SYMBOL_GPL(destroy_workqueue);
910
911static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
912 unsigned long action,
913 void *hcpu)
914{
915 unsigned int cpu = (unsigned long)hcpu;
916 struct cpu_workqueue_struct *cwq;
917 struct workqueue_struct *wq;
918 int ret = NOTIFY_OK;
919
920 action &= ~CPU_TASKS_FROZEN;
921
922 switch (action) {
923 case CPU_UP_PREPARE:
924 cpumask_set_cpu(cpu, cpu_populated_map);
925 }
926undo:
927 list_for_each_entry(wq, &workqueues, list) {
928 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
929
930 switch (action) {
931 case CPU_UP_PREPARE:
932 if (!create_workqueue_thread(cwq, cpu))
933 break;
934 printk(KERN_ERR "workqueue [%s] for %i failed\n",
935 wq->name, cpu);
936 action = CPU_UP_CANCELED;
937 ret = NOTIFY_BAD;
938 goto undo;
939
940 case CPU_ONLINE:
941 start_workqueue_thread(cwq, cpu);
942 break;
943
944 case CPU_UP_CANCELED:
945 start_workqueue_thread(cwq, -1);
946 case CPU_POST_DEAD:
947 cleanup_workqueue_thread(cwq);
948 break;
949 }
950 }
951
952 switch (action) {
953 case CPU_UP_CANCELED:
954 case CPU_POST_DEAD:
955 cpumask_clear_cpu(cpu, cpu_populated_map);
956 }
957
958 return ret;
959}
960
961#ifdef CONFIG_SMP
962
963struct work_for_cpu {
964 struct completion completion;
965 long (*fn)(void *);
966 void *arg;
967 long ret;
968};
969
970static int do_work_for_cpu(void *_wfc)
971{
972 struct work_for_cpu *wfc = _wfc;
973 wfc->ret = wfc->fn(wfc->arg);
974 complete(&wfc->completion);
975 return 0;
976}
977
978/**
979 * work_on_cpu - run a function in user context on a particular cpu
980 * @cpu: the cpu to run on
981 * @fn: the function to run
982 * @arg: the function arg
983 *
984 * This will return the value @fn returns.
985 * It is up to the caller to ensure that the cpu doesn't go offline.
986 * The caller must not hold any locks which would prevent @fn from completing.
987 */
988long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
989{
990 struct task_struct *sub_thread;
991 struct work_for_cpu wfc = {
992 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
993 .fn = fn,
994 .arg = arg,
995 };
996
997 sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
998 if (IS_ERR(sub_thread))
999 return PTR_ERR(sub_thread);
1000 kthread_bind(sub_thread, cpu);
1001 wake_up_process(sub_thread);
1002 wait_for_completion(&wfc.completion);
1003 return wfc.ret;
1004}
1005EXPORT_SYMBOL_GPL(work_on_cpu);
1006#endif /* CONFIG_SMP */
1007
1008void __init init_workqueues(void)
1009{
1010 alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
1011
1012 cpumask_copy(cpu_populated_map, cpu_online_mask);
1013 singlethread_cpu = cpumask_first(cpu_possible_mask);
1014 cpu_singlethread_map = cpumask_of(singlethread_cpu);
1015 hotcpu_notifier(workqueue_cpu_callback, 0);
1016 keventd_wq = create_workqueue("events");
1017 BUG_ON(!keventd_wq);
1018}