workqueue: warn about flush_scheduled_work()
[linux-2.6.git] / kernel / workqueue.c
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
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.
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  */
43 struct 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  */
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         int rt;
66 #ifdef CONFIG_LOCKDEP
67         struct lockdep_map lockdep_map;
68 #endif
69 };
70
71 #ifdef CONFIG_DEBUG_OBJECTS_WORK
72
73 static struct debug_obj_descr work_debug_descr;
74
75 /*
76  * fixup_init is called when:
77  * - an active object is initialized
78  */
79 static int work_fixup_init(void *addr, enum debug_obj_state state)
80 {
81         struct work_struct *work = addr;
82
83         switch (state) {
84         case ODEBUG_STATE_ACTIVE:
85                 cancel_work_sync(work);
86                 debug_object_init(work, &work_debug_descr);
87                 return 1;
88         default:
89                 return 0;
90         }
91 }
92
93 /*
94  * fixup_activate is called when:
95  * - an active object is activated
96  * - an unknown object is activated (might be a statically initialized object)
97  */
98 static int work_fixup_activate(void *addr, enum debug_obj_state state)
99 {
100         struct work_struct *work = addr;
101
102         switch (state) {
103
104         case ODEBUG_STATE_NOTAVAILABLE:
105                 /*
106                  * This is not really a fixup. The work struct was
107                  * statically initialized. We just make sure that it
108                  * is tracked in the object tracker.
109                  */
110                 if (test_bit(WORK_STRUCT_STATIC, work_data_bits(work))) {
111                         debug_object_init(work, &work_debug_descr);
112                         debug_object_activate(work, &work_debug_descr);
113                         return 0;
114                 }
115                 WARN_ON_ONCE(1);
116                 return 0;
117
118         case ODEBUG_STATE_ACTIVE:
119                 WARN_ON(1);
120
121         default:
122                 return 0;
123         }
124 }
125
126 /*
127  * fixup_free is called when:
128  * - an active object is freed
129  */
130 static int work_fixup_free(void *addr, enum debug_obj_state state)
131 {
132         struct work_struct *work = addr;
133
134         switch (state) {
135         case ODEBUG_STATE_ACTIVE:
136                 cancel_work_sync(work);
137                 debug_object_free(work, &work_debug_descr);
138                 return 1;
139         default:
140                 return 0;
141         }
142 }
143
144 static struct debug_obj_descr work_debug_descr = {
145         .name           = "work_struct",
146         .fixup_init     = work_fixup_init,
147         .fixup_activate = work_fixup_activate,
148         .fixup_free     = work_fixup_free,
149 };
150
151 static inline void debug_work_activate(struct work_struct *work)
152 {
153         debug_object_activate(work, &work_debug_descr);
154 }
155
156 static inline void debug_work_deactivate(struct work_struct *work)
157 {
158         debug_object_deactivate(work, &work_debug_descr);
159 }
160
161 void __init_work(struct work_struct *work, int onstack)
162 {
163         if (onstack)
164                 debug_object_init_on_stack(work, &work_debug_descr);
165         else
166                 debug_object_init(work, &work_debug_descr);
167 }
168 EXPORT_SYMBOL_GPL(__init_work);
169
170 void destroy_work_on_stack(struct work_struct *work)
171 {
172         debug_object_free(work, &work_debug_descr);
173 }
174 EXPORT_SYMBOL_GPL(destroy_work_on_stack);
175
176 #else
177 static inline void debug_work_activate(struct work_struct *work) { }
178 static inline void debug_work_deactivate(struct work_struct *work) { }
179 #endif
180
181 /* Serializes the accesses to the list of workqueues. */
182 static DEFINE_SPINLOCK(workqueue_lock);
183 static LIST_HEAD(workqueues);
184
185 static int singlethread_cpu __read_mostly;
186 static const struct cpumask *cpu_singlethread_map __read_mostly;
187 /*
188  * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
189  * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
190  * which comes in between can't use for_each_online_cpu(). We could
191  * use cpu_possible_map, the cpumask below is more a documentation
192  * than optimization.
193  */
194 static cpumask_var_t cpu_populated_map __read_mostly;
195
196 /* If it's single threaded, it isn't in the list of workqueues. */
197 static inline int is_wq_single_threaded(struct workqueue_struct *wq)
198 {
199         return wq->singlethread;
200 }
201
202 static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)
203 {
204         return is_wq_single_threaded(wq)
205                 ? cpu_singlethread_map : cpu_populated_map;
206 }
207
208 static
209 struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
210 {
211         if (unlikely(is_wq_single_threaded(wq)))
212                 cpu = singlethread_cpu;
213         return per_cpu_ptr(wq->cpu_wq, cpu);
214 }
215
216 /*
217  * Set the workqueue on which a work item is to be run
218  * - Must *only* be called if the pending flag is set
219  */
220 static inline void set_wq_data(struct work_struct *work,
221                                 struct cpu_workqueue_struct *cwq)
222 {
223         unsigned long new;
224
225         BUG_ON(!work_pending(work));
226
227         new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);
228         new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
229         atomic_long_set(&work->data, new);
230 }
231
232 static inline
233 struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)
234 {
235         return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);
236 }
237
238 static void insert_work(struct cpu_workqueue_struct *cwq,
239                         struct work_struct *work, struct list_head *head)
240 {
241         trace_workqueue_insertion(cwq->thread, work);
242
243         set_wq_data(work, cwq);
244         /*
245          * Ensure that we get the right work->data if we see the
246          * result of list_add() below, see try_to_grab_pending().
247          */
248         smp_wmb();
249         list_add_tail(&work->entry, head);
250         wake_up(&cwq->more_work);
251 }
252
253 static void __queue_work(struct cpu_workqueue_struct *cwq,
254                          struct work_struct *work)
255 {
256         unsigned long flags;
257
258         debug_work_activate(work);
259         spin_lock_irqsave(&cwq->lock, flags);
260         insert_work(cwq, work, &cwq->worklist);
261         spin_unlock_irqrestore(&cwq->lock, flags);
262 }
263
264 /**
265  * queue_work - queue work on a workqueue
266  * @wq: workqueue to use
267  * @work: work to queue
268  *
269  * Returns 0 if @work was already on a queue, non-zero otherwise.
270  *
271  * We queue the work to the CPU on which it was submitted, but if the CPU dies
272  * it can be processed by another CPU.
273  */
274 int queue_work(struct workqueue_struct *wq, struct work_struct *work)
275 {
276         int ret;
277
278         ret = queue_work_on(get_cpu(), wq, work);
279         put_cpu();
280
281         return ret;
282 }
283 EXPORT_SYMBOL_GPL(queue_work);
284
285 /**
286  * queue_work_on - queue work on specific cpu
287  * @cpu: CPU number to execute work on
288  * @wq: workqueue to use
289  * @work: work to queue
290  *
291  * Returns 0 if @work was already on a queue, non-zero otherwise.
292  *
293  * We queue the work to a specific CPU, the caller must ensure it
294  * can't go away.
295  */
296 int
297 queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
298 {
299         int ret = 0;
300
301         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
302                 BUG_ON(!list_empty(&work->entry));
303                 __queue_work(wq_per_cpu(wq, cpu), work);
304                 ret = 1;
305         }
306         return ret;
307 }
308 EXPORT_SYMBOL_GPL(queue_work_on);
309
310 static void delayed_work_timer_fn(unsigned long __data)
311 {
312         struct delayed_work *dwork = (struct delayed_work *)__data;
313         struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
314         struct workqueue_struct *wq = cwq->wq;
315
316         __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);
317 }
318
319 /**
320  * queue_delayed_work - queue work on a workqueue after delay
321  * @wq: workqueue to use
322  * @dwork: delayable work to queue
323  * @delay: number of jiffies to wait before queueing
324  *
325  * Returns 0 if @work was already on a queue, non-zero otherwise.
326  */
327 int queue_delayed_work(struct workqueue_struct *wq,
328                         struct delayed_work *dwork, unsigned long delay)
329 {
330         if (delay == 0)
331                 return queue_work(wq, &dwork->work);
332
333         return queue_delayed_work_on(-1, wq, dwork, delay);
334 }
335 EXPORT_SYMBOL_GPL(queue_delayed_work);
336
337 /**
338  * queue_delayed_work_on - queue work on specific CPU after delay
339  * @cpu: CPU number to execute work on
340  * @wq: workqueue to use
341  * @dwork: work to queue
342  * @delay: number of jiffies to wait before queueing
343  *
344  * Returns 0 if @work was already on a queue, non-zero otherwise.
345  */
346 int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
347                         struct delayed_work *dwork, unsigned long delay)
348 {
349         int ret = 0;
350         struct timer_list *timer = &dwork->timer;
351         struct work_struct *work = &dwork->work;
352
353         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
354                 BUG_ON(timer_pending(timer));
355                 BUG_ON(!list_empty(&work->entry));
356
357                 timer_stats_timer_set_start_info(&dwork->timer);
358
359                 /* This stores cwq for the moment, for the timer_fn */
360                 set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));
361                 timer->expires = jiffies + delay;
362                 timer->data = (unsigned long)dwork;
363                 timer->function = delayed_work_timer_fn;
364
365                 if (unlikely(cpu >= 0))
366                         add_timer_on(timer, cpu);
367                 else
368                         add_timer(timer);
369                 ret = 1;
370         }
371         return ret;
372 }
373 EXPORT_SYMBOL_GPL(queue_delayed_work_on);
374
375 static void run_workqueue(struct cpu_workqueue_struct *cwq)
376 {
377         spin_lock_irq(&cwq->lock);
378         while (!list_empty(&cwq->worklist)) {
379                 struct work_struct *work = list_entry(cwq->worklist.next,
380                                                 struct work_struct, entry);
381                 work_func_t f = work->func;
382 #ifdef CONFIG_LOCKDEP
383                 /*
384                  * It is permissible to free the struct work_struct
385                  * from inside the function that is called from it,
386                  * this we need to take into account for lockdep too.
387                  * To avoid bogus "held lock freed" warnings as well
388                  * as problems when looking into work->lockdep_map,
389                  * make a copy and use that here.
390                  */
391                 struct lockdep_map lockdep_map = work->lockdep_map;
392 #endif
393                 trace_workqueue_execution(cwq->thread, work);
394                 debug_work_deactivate(work);
395                 cwq->current_work = work;
396                 list_del_init(cwq->worklist.next);
397                 spin_unlock_irq(&cwq->lock);
398
399                 BUG_ON(get_wq_data(work) != cwq);
400                 work_clear_pending(work);
401                 lock_map_acquire(&cwq->wq->lockdep_map);
402                 lock_map_acquire(&lockdep_map);
403                 f(work);
404                 lock_map_release(&lockdep_map);
405                 lock_map_release(&cwq->wq->lockdep_map);
406
407                 if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
408                         printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
409                                         "%s/0x%08x/%d\n",
410                                         current->comm, preempt_count(),
411                                         task_pid_nr(current));
412                         printk(KERN_ERR "    last function: ");
413                         print_symbol("%s\n", (unsigned long)f);
414                         debug_show_held_locks(current);
415                         dump_stack();
416                 }
417
418                 spin_lock_irq(&cwq->lock);
419                 cwq->current_work = NULL;
420         }
421         spin_unlock_irq(&cwq->lock);
422 }
423
424 static int worker_thread(void *__cwq)
425 {
426         struct cpu_workqueue_struct *cwq = __cwq;
427         DEFINE_WAIT(wait);
428
429         if (cwq->wq->freezeable)
430                 set_freezable();
431
432         for (;;) {
433                 prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);
434                 if (!freezing(current) &&
435                     !kthread_should_stop() &&
436                     list_empty(&cwq->worklist))
437                         schedule();
438                 finish_wait(&cwq->more_work, &wait);
439
440                 try_to_freeze();
441
442                 if (kthread_should_stop())
443                         break;
444
445                 run_workqueue(cwq);
446         }
447
448         return 0;
449 }
450
451 struct wq_barrier {
452         struct work_struct      work;
453         struct completion       done;
454 };
455
456 static void wq_barrier_func(struct work_struct *work)
457 {
458         struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
459         complete(&barr->done);
460 }
461
462 static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,
463                         struct wq_barrier *barr, struct list_head *head)
464 {
465         /*
466          * debugobject calls are safe here even with cwq->lock locked
467          * as we know for sure that this will not trigger any of the
468          * checks and call back into the fixup functions where we
469          * might deadlock.
470          */
471         INIT_WORK_ON_STACK(&barr->work, wq_barrier_func);
472         __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
473
474         init_completion(&barr->done);
475
476         debug_work_activate(&barr->work);
477         insert_work(cwq, &barr->work, head);
478 }
479
480 static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
481 {
482         int active = 0;
483         struct wq_barrier barr;
484
485         WARN_ON(cwq->thread == current);
486
487         spin_lock_irq(&cwq->lock);
488         if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
489                 insert_wq_barrier(cwq, &barr, &cwq->worklist);
490                 active = 1;
491         }
492         spin_unlock_irq(&cwq->lock);
493
494         if (active) {
495                 wait_for_completion(&barr.done);
496                 destroy_work_on_stack(&barr.work);
497         }
498
499         return active;
500 }
501
502 /**
503  * flush_workqueue - ensure that any scheduled work has run to completion.
504  * @wq: workqueue to flush
505  *
506  * Forces execution of the workqueue and blocks until its completion.
507  * This is typically used in driver shutdown handlers.
508  *
509  * We sleep until all works which were queued on entry have been handled,
510  * but we are not livelocked by new incoming ones.
511  *
512  * This function used to run the workqueues itself.  Now we just wait for the
513  * helper threads to do it.
514  */
515 void flush_workqueue(struct workqueue_struct *wq)
516 {
517         const struct cpumask *cpu_map = wq_cpu_map(wq);
518         int cpu;
519
520         might_sleep();
521         lock_map_acquire(&wq->lockdep_map);
522         lock_map_release(&wq->lockdep_map);
523         for_each_cpu(cpu, cpu_map)
524                 flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
525 }
526 EXPORT_SYMBOL_GPL(flush_workqueue);
527
528 /**
529  * flush_work - block until a work_struct's callback has terminated
530  * @work: the work which is to be flushed
531  *
532  * Returns false if @work has already terminated.
533  *
534  * It is expected that, prior to calling flush_work(), the caller has
535  * arranged for the work to not be requeued, otherwise it doesn't make
536  * sense to use this function.
537  */
538 int flush_work(struct work_struct *work)
539 {
540         struct cpu_workqueue_struct *cwq;
541         struct list_head *prev;
542         struct wq_barrier barr;
543
544         might_sleep();
545         cwq = get_wq_data(work);
546         if (!cwq)
547                 return 0;
548
549         lock_map_acquire(&cwq->wq->lockdep_map);
550         lock_map_release(&cwq->wq->lockdep_map);
551
552         prev = NULL;
553         spin_lock_irq(&cwq->lock);
554         if (!list_empty(&work->entry)) {
555                 /*
556                  * See the comment near try_to_grab_pending()->smp_rmb().
557                  * If it was re-queued under us we are not going to wait.
558                  */
559                 smp_rmb();
560                 if (unlikely(cwq != get_wq_data(work)))
561                         goto out;
562                 prev = &work->entry;
563         } else {
564                 if (cwq->current_work != work)
565                         goto out;
566                 prev = &cwq->worklist;
567         }
568         insert_wq_barrier(cwq, &barr, prev->next);
569 out:
570         spin_unlock_irq(&cwq->lock);
571         if (!prev)
572                 return 0;
573
574         wait_for_completion(&barr.done);
575         destroy_work_on_stack(&barr.work);
576         return 1;
577 }
578 EXPORT_SYMBOL_GPL(flush_work);
579
580 /*
581  * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
582  * so this work can't be re-armed in any way.
583  */
584 static int try_to_grab_pending(struct work_struct *work)
585 {
586         struct cpu_workqueue_struct *cwq;
587         int ret = -1;
588
589         if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))
590                 return 0;
591
592         /*
593          * The queueing is in progress, or it is already queued. Try to
594          * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
595          */
596
597         cwq = get_wq_data(work);
598         if (!cwq)
599                 return ret;
600
601         spin_lock_irq(&cwq->lock);
602         if (!list_empty(&work->entry)) {
603                 /*
604                  * This work is queued, but perhaps we locked the wrong cwq.
605                  * In that case we must see the new value after rmb(), see
606                  * insert_work()->wmb().
607                  */
608                 smp_rmb();
609                 if (cwq == get_wq_data(work)) {
610                         debug_work_deactivate(work);
611                         list_del_init(&work->entry);
612                         ret = 1;
613                 }
614         }
615         spin_unlock_irq(&cwq->lock);
616
617         return ret;
618 }
619
620 static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,
621                                 struct work_struct *work)
622 {
623         struct wq_barrier barr;
624         int running = 0;
625
626         spin_lock_irq(&cwq->lock);
627         if (unlikely(cwq->current_work == work)) {
628                 insert_wq_barrier(cwq, &barr, cwq->worklist.next);
629                 running = 1;
630         }
631         spin_unlock_irq(&cwq->lock);
632
633         if (unlikely(running)) {
634                 wait_for_completion(&barr.done);
635                 destroy_work_on_stack(&barr.work);
636         }
637 }
638
639 static void wait_on_work(struct work_struct *work)
640 {
641         struct cpu_workqueue_struct *cwq;
642         struct workqueue_struct *wq;
643         const struct cpumask *cpu_map;
644         int cpu;
645
646         might_sleep();
647
648         lock_map_acquire(&work->lockdep_map);
649         lock_map_release(&work->lockdep_map);
650
651         cwq = get_wq_data(work);
652         if (!cwq)
653                 return;
654
655         wq = cwq->wq;
656         cpu_map = wq_cpu_map(wq);
657
658         for_each_cpu(cpu, cpu_map)
659                 wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
660 }
661
662 static int __cancel_work_timer(struct work_struct *work,
663                                 struct timer_list* timer)
664 {
665         int ret;
666
667         do {
668                 ret = (timer && likely(del_timer(timer)));
669                 if (!ret)
670                         ret = try_to_grab_pending(work);
671                 wait_on_work(work);
672         } while (unlikely(ret < 0));
673
674         work_clear_pending(work);
675         return ret;
676 }
677
678 /**
679  * cancel_work_sync - block until a work_struct's callback has terminated
680  * @work: the work which is to be flushed
681  *
682  * Returns true if @work was pending.
683  *
684  * cancel_work_sync() will cancel the work if it is queued. If the work's
685  * callback appears to be running, cancel_work_sync() will block until it
686  * has completed.
687  *
688  * It is possible to use this function if the work re-queues itself. It can
689  * cancel the work even if it migrates to another workqueue, however in that
690  * case it only guarantees that work->func() has completed on the last queued
691  * workqueue.
692  *
693  * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
694  * pending, otherwise it goes into a busy-wait loop until the timer expires.
695  *
696  * The caller must ensure that workqueue_struct on which this work was last
697  * queued can't be destroyed before this function returns.
698  */
699 int cancel_work_sync(struct work_struct *work)
700 {
701         return __cancel_work_timer(work, NULL);
702 }
703 EXPORT_SYMBOL_GPL(cancel_work_sync);
704
705 /**
706  * cancel_delayed_work_sync - reliably kill off a delayed work.
707  * @dwork: the delayed work struct
708  *
709  * Returns true if @dwork was pending.
710  *
711  * It is possible to use this function if @dwork rearms itself via queue_work()
712  * or queue_delayed_work(). See also the comment for cancel_work_sync().
713  */
714 int cancel_delayed_work_sync(struct delayed_work *dwork)
715 {
716         return __cancel_work_timer(&dwork->work, &dwork->timer);
717 }
718 EXPORT_SYMBOL(cancel_delayed_work_sync);
719
720 static struct workqueue_struct *keventd_wq __read_mostly;
721
722 /**
723  * schedule_work - put work task in global workqueue
724  * @work: job to be done
725  *
726  * Returns zero if @work was already on the kernel-global workqueue and
727  * non-zero otherwise.
728  *
729  * This puts a job in the kernel-global workqueue if it was not already
730  * queued and leaves it in the same position on the kernel-global
731  * workqueue otherwise.
732  */
733 int schedule_work(struct work_struct *work)
734 {
735         return queue_work(keventd_wq, work);
736 }
737 EXPORT_SYMBOL(schedule_work);
738
739 /*
740  * schedule_work_on - put work task on a specific cpu
741  * @cpu: cpu to put the work task on
742  * @work: job to be done
743  *
744  * This puts a job on a specific cpu
745  */
746 int schedule_work_on(int cpu, struct work_struct *work)
747 {
748         return queue_work_on(cpu, keventd_wq, work);
749 }
750 EXPORT_SYMBOL(schedule_work_on);
751
752 /**
753  * schedule_delayed_work - put work task in global workqueue after delay
754  * @dwork: job to be done
755  * @delay: number of jiffies to wait or 0 for immediate execution
756  *
757  * After waiting for a given time this puts a job in the kernel-global
758  * workqueue.
759  */
760 int schedule_delayed_work(struct delayed_work *dwork,
761                                         unsigned long delay)
762 {
763         return queue_delayed_work(keventd_wq, dwork, delay);
764 }
765 EXPORT_SYMBOL(schedule_delayed_work);
766
767 /**
768  * flush_delayed_work - block until a dwork_struct's callback has terminated
769  * @dwork: the delayed work which is to be flushed
770  *
771  * Any timeout is cancelled, and any pending work is run immediately.
772  */
773 void flush_delayed_work(struct delayed_work *dwork)
774 {
775         if (del_timer_sync(&dwork->timer)) {
776                 struct cpu_workqueue_struct *cwq;
777                 cwq = wq_per_cpu(get_wq_data(&dwork->work)->wq, get_cpu());
778                 __queue_work(cwq, &dwork->work);
779                 put_cpu();
780         }
781         flush_work(&dwork->work);
782 }
783 EXPORT_SYMBOL(flush_delayed_work);
784
785 /**
786  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
787  * @cpu: cpu to use
788  * @dwork: job to be done
789  * @delay: number of jiffies to wait
790  *
791  * After waiting for a given time this puts a job in the kernel-global
792  * workqueue on the specified CPU.
793  */
794 int schedule_delayed_work_on(int cpu,
795                         struct delayed_work *dwork, unsigned long delay)
796 {
797         return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);
798 }
799 EXPORT_SYMBOL(schedule_delayed_work_on);
800
801 /**
802  * schedule_on_each_cpu - call a function on each online CPU from keventd
803  * @func: the function to call
804  *
805  * Returns zero on success.
806  * Returns -ve errno on failure.
807  *
808  * schedule_on_each_cpu() is very slow.
809  */
810 int schedule_on_each_cpu(work_func_t func)
811 {
812         int cpu;
813         int orig = -1;
814         struct work_struct *works;
815
816         works = alloc_percpu(struct work_struct);
817         if (!works)
818                 return -ENOMEM;
819
820         get_online_cpus();
821
822         /*
823          * When running in keventd don't schedule a work item on
824          * itself.  Can just call directly because the work queue is
825          * already bound.  This also is faster.
826          */
827         if (current_is_keventd())
828                 orig = raw_smp_processor_id();
829
830         for_each_online_cpu(cpu) {
831                 struct work_struct *work = per_cpu_ptr(works, cpu);
832
833                 INIT_WORK(work, func);
834                 if (cpu != orig)
835                         schedule_work_on(cpu, work);
836         }
837         if (orig >= 0)
838                 func(per_cpu_ptr(works, orig));
839
840         for_each_online_cpu(cpu)
841                 flush_work(per_cpu_ptr(works, cpu));
842
843         put_online_cpus();
844         free_percpu(works);
845         return 0;
846 }
847
848 /**
849  * flush_scheduled_work - ensure that any scheduled work has run to completion.
850  *
851  * Forces execution of the kernel-global workqueue and blocks until its
852  * completion.
853  *
854  * Think twice before calling this function!  It's very easy to get into
855  * trouble if you don't take great care.  Either of the following situations
856  * will lead to deadlock:
857  *
858  *      One of the work items currently on the workqueue needs to acquire
859  *      a lock held by your code or its caller.
860  *
861  *      Your code is running in the context of a work routine.
862  *
863  * They will be detected by lockdep when they occur, but the first might not
864  * occur very often.  It depends on what work items are on the workqueue and
865  * what locks they need, which you have no control over.
866  *
867  * In most situations flushing the entire workqueue is overkill; you merely
868  * need to know that a particular work item isn't queued and isn't running.
869  * In such cases you should use cancel_delayed_work_sync() or
870  * cancel_work_sync() instead.
871  */
872 void flush_scheduled_work(void)
873 {
874         flush_workqueue(keventd_wq);
875 }
876 EXPORT_SYMBOL(flush_scheduled_work);
877
878 /**
879  * execute_in_process_context - reliably execute the routine with user context
880  * @fn:         the function to execute
881  * @ew:         guaranteed storage for the execute work structure (must
882  *              be available when the work executes)
883  *
884  * Executes the function immediately if process context is available,
885  * otherwise schedules the function for delayed execution.
886  *
887  * Returns:     0 - function was executed
888  *              1 - function was scheduled for execution
889  */
890 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
891 {
892         if (!in_interrupt()) {
893                 fn(&ew->work);
894                 return 0;
895         }
896
897         INIT_WORK(&ew->work, fn);
898         schedule_work(&ew->work);
899
900         return 1;
901 }
902 EXPORT_SYMBOL_GPL(execute_in_process_context);
903
904 int keventd_up(void)
905 {
906         return keventd_wq != NULL;
907 }
908
909 int current_is_keventd(void)
910 {
911         struct cpu_workqueue_struct *cwq;
912         int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
913         int ret = 0;
914
915         BUG_ON(!keventd_wq);
916
917         cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
918         if (current == cwq->thread)
919                 ret = 1;
920
921         return ret;
922
923 }
924
925 static struct cpu_workqueue_struct *
926 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
927 {
928         struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
929
930         cwq->wq = wq;
931         spin_lock_init(&cwq->lock);
932         INIT_LIST_HEAD(&cwq->worklist);
933         init_waitqueue_head(&cwq->more_work);
934
935         return cwq;
936 }
937
938 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
939 {
940         struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
941         struct workqueue_struct *wq = cwq->wq;
942         const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";
943         struct task_struct *p;
944
945         p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
946         /*
947          * Nobody can add the work_struct to this cwq,
948          *      if (caller is __create_workqueue)
949          *              nobody should see this wq
950          *      else // caller is CPU_UP_PREPARE
951          *              cpu is not on cpu_online_map
952          * so we can abort safely.
953          */
954         if (IS_ERR(p))
955                 return PTR_ERR(p);
956         if (cwq->wq->rt)
957                 sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
958         cwq->thread = p;
959
960         trace_workqueue_creation(cwq->thread, cpu);
961
962         return 0;
963 }
964
965 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
966 {
967         struct task_struct *p = cwq->thread;
968
969         if (p != NULL) {
970                 if (cpu >= 0)
971                         kthread_bind(p, cpu);
972                 wake_up_process(p);
973         }
974 }
975
976 struct workqueue_struct *__create_workqueue_key(const char *name,
977                                                 int singlethread,
978                                                 int freezeable,
979                                                 int rt,
980                                                 struct lock_class_key *key,
981                                                 const char *lock_name)
982 {
983         struct workqueue_struct *wq;
984         struct cpu_workqueue_struct *cwq;
985         int err = 0, cpu;
986
987         wq = kzalloc(sizeof(*wq), GFP_KERNEL);
988         if (!wq)
989                 return NULL;
990
991         wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
992         if (!wq->cpu_wq) {
993                 kfree(wq);
994                 return NULL;
995         }
996
997         wq->name = name;
998         lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
999         wq->singlethread = singlethread;
1000         wq->freezeable = freezeable;
1001         wq->rt = rt;
1002         INIT_LIST_HEAD(&wq->list);
1003
1004         if (singlethread) {
1005                 cwq = init_cpu_workqueue(wq, singlethread_cpu);
1006                 err = create_workqueue_thread(cwq, singlethread_cpu);
1007                 start_workqueue_thread(cwq, -1);
1008         } else {
1009                 cpu_maps_update_begin();
1010                 /*
1011                  * We must place this wq on list even if the code below fails.
1012                  * cpu_down(cpu) can remove cpu from cpu_populated_map before
1013                  * destroy_workqueue() takes the lock, in that case we leak
1014                  * cwq[cpu]->thread.
1015                  */
1016                 spin_lock(&workqueue_lock);
1017                 list_add(&wq->list, &workqueues);
1018                 spin_unlock(&workqueue_lock);
1019                 /*
1020                  * We must initialize cwqs for each possible cpu even if we
1021                  * are going to call destroy_workqueue() finally. Otherwise
1022                  * cpu_up() can hit the uninitialized cwq once we drop the
1023                  * lock.
1024                  */
1025                 for_each_possible_cpu(cpu) {
1026                         cwq = init_cpu_workqueue(wq, cpu);
1027                         if (err || !cpu_online(cpu))
1028                                 continue;
1029                         err = create_workqueue_thread(cwq, cpu);
1030                         start_workqueue_thread(cwq, cpu);
1031                 }
1032                 cpu_maps_update_done();
1033         }
1034
1035         if (err) {
1036                 destroy_workqueue(wq);
1037                 wq = NULL;
1038         }
1039         return wq;
1040 }
1041 EXPORT_SYMBOL_GPL(__create_workqueue_key);
1042
1043 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
1044 {
1045         /*
1046          * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
1047          * cpu_add_remove_lock protects cwq->thread.
1048          */
1049         if (cwq->thread == NULL)
1050                 return;
1051
1052         lock_map_acquire(&cwq->wq->lockdep_map);
1053         lock_map_release(&cwq->wq->lockdep_map);
1054
1055         flush_cpu_workqueue(cwq);
1056         /*
1057          * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
1058          * a concurrent flush_workqueue() can insert a barrier after us.
1059          * However, in that case run_workqueue() won't return and check
1060          * kthread_should_stop() until it flushes all work_struct's.
1061          * When ->worklist becomes empty it is safe to exit because no
1062          * more work_structs can be queued on this cwq: flush_workqueue
1063          * checks list_empty(), and a "normal" queue_work() can't use
1064          * a dead CPU.
1065          */
1066         trace_workqueue_destruction(cwq->thread);
1067         kthread_stop(cwq->thread);
1068         cwq->thread = NULL;
1069 }
1070
1071 /**
1072  * destroy_workqueue - safely terminate a workqueue
1073  * @wq: target workqueue
1074  *
1075  * Safely destroy a workqueue. All work currently pending will be done first.
1076  */
1077 void destroy_workqueue(struct workqueue_struct *wq)
1078 {
1079         const struct cpumask *cpu_map = wq_cpu_map(wq);
1080         int cpu;
1081
1082         cpu_maps_update_begin();
1083         spin_lock(&workqueue_lock);
1084         list_del(&wq->list);
1085         spin_unlock(&workqueue_lock);
1086
1087         for_each_cpu(cpu, cpu_map)
1088                 cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
1089         cpu_maps_update_done();
1090
1091         free_percpu(wq->cpu_wq);
1092         kfree(wq);
1093 }
1094 EXPORT_SYMBOL_GPL(destroy_workqueue);
1095
1096 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
1097                                                 unsigned long action,
1098                                                 void *hcpu)
1099 {
1100         unsigned int cpu = (unsigned long)hcpu;
1101         struct cpu_workqueue_struct *cwq;
1102         struct workqueue_struct *wq;
1103         int ret = NOTIFY_OK;
1104
1105         action &= ~CPU_TASKS_FROZEN;
1106
1107         switch (action) {
1108         case CPU_UP_PREPARE:
1109                 cpumask_set_cpu(cpu, cpu_populated_map);
1110         }
1111 undo:
1112         list_for_each_entry(wq, &workqueues, list) {
1113                 cwq = per_cpu_ptr(wq->cpu_wq, cpu);
1114
1115                 switch (action) {
1116                 case CPU_UP_PREPARE:
1117                         if (!create_workqueue_thread(cwq, cpu))
1118                                 break;
1119                         printk(KERN_ERR "workqueue [%s] for %i failed\n",
1120                                 wq->name, cpu);
1121                         action = CPU_UP_CANCELED;
1122                         ret = NOTIFY_BAD;
1123                         goto undo;
1124
1125                 case CPU_ONLINE:
1126                         start_workqueue_thread(cwq, cpu);
1127                         break;
1128
1129                 case CPU_UP_CANCELED:
1130                         start_workqueue_thread(cwq, -1);
1131                 case CPU_POST_DEAD:
1132                         cleanup_workqueue_thread(cwq);
1133                         break;
1134                 }
1135         }
1136
1137         switch (action) {
1138         case CPU_UP_CANCELED:
1139         case CPU_POST_DEAD:
1140                 cpumask_clear_cpu(cpu, cpu_populated_map);
1141         }
1142
1143         return ret;
1144 }
1145
1146 #ifdef CONFIG_SMP
1147
1148 struct work_for_cpu {
1149         struct completion completion;
1150         long (*fn)(void *);
1151         void *arg;
1152         long ret;
1153 };
1154
1155 static int do_work_for_cpu(void *_wfc)
1156 {
1157         struct work_for_cpu *wfc = _wfc;
1158         wfc->ret = wfc->fn(wfc->arg);
1159         complete(&wfc->completion);
1160         return 0;
1161 }
1162
1163 /**
1164  * work_on_cpu - run a function in user context on a particular cpu
1165  * @cpu: the cpu to run on
1166  * @fn: the function to run
1167  * @arg: the function arg
1168  *
1169  * This will return the value @fn returns.
1170  * It is up to the caller to ensure that the cpu doesn't go offline.
1171  * The caller must not hold any locks which would prevent @fn from completing.
1172  */
1173 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
1174 {
1175         struct task_struct *sub_thread;
1176         struct work_for_cpu wfc = {
1177                 .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
1178                 .fn = fn,
1179                 .arg = arg,
1180         };
1181
1182         sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
1183         if (IS_ERR(sub_thread))
1184                 return PTR_ERR(sub_thread);
1185         kthread_bind(sub_thread, cpu);
1186         wake_up_process(sub_thread);
1187         wait_for_completion(&wfc.completion);
1188         return wfc.ret;
1189 }
1190 EXPORT_SYMBOL_GPL(work_on_cpu);
1191 #endif /* CONFIG_SMP */
1192
1193 void __init init_workqueues(void)
1194 {
1195         alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
1196
1197         cpumask_copy(cpu_populated_map, cpu_online_mask);
1198         singlethread_cpu = cpumask_first(cpu_possible_mask);
1199         cpu_singlethread_map = cpumask_of(singlethread_cpu);
1200         hotcpu_notifier(workqueue_cpu_callback, 0);
1201         keventd_wq = create_workqueue("events");
1202         BUG_ON(!keventd_wq);
1203 }