xref: /openbmc/linux/kernel/workqueue.c (revision b6dcefde)
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(keventd_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 void flush_scheduled_work(void)
849 {
850 	flush_workqueue(keventd_wq);
851 }
852 EXPORT_SYMBOL(flush_scheduled_work);
853 
854 /**
855  * execute_in_process_context - reliably execute the routine with user context
856  * @fn:		the function to execute
857  * @ew:		guaranteed storage for the execute work structure (must
858  *		be available when the work executes)
859  *
860  * Executes the function immediately if process context is available,
861  * otherwise schedules the function for delayed execution.
862  *
863  * Returns:	0 - function was executed
864  *		1 - function was scheduled for execution
865  */
866 int execute_in_process_context(work_func_t fn, struct execute_work *ew)
867 {
868 	if (!in_interrupt()) {
869 		fn(&ew->work);
870 		return 0;
871 	}
872 
873 	INIT_WORK(&ew->work, fn);
874 	schedule_work(&ew->work);
875 
876 	return 1;
877 }
878 EXPORT_SYMBOL_GPL(execute_in_process_context);
879 
880 int keventd_up(void)
881 {
882 	return keventd_wq != NULL;
883 }
884 
885 int current_is_keventd(void)
886 {
887 	struct cpu_workqueue_struct *cwq;
888 	int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */
889 	int ret = 0;
890 
891 	BUG_ON(!keventd_wq);
892 
893 	cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);
894 	if (current == cwq->thread)
895 		ret = 1;
896 
897 	return ret;
898 
899 }
900 
901 static struct cpu_workqueue_struct *
902 init_cpu_workqueue(struct workqueue_struct *wq, int cpu)
903 {
904 	struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);
905 
906 	cwq->wq = wq;
907 	spin_lock_init(&cwq->lock);
908 	INIT_LIST_HEAD(&cwq->worklist);
909 	init_waitqueue_head(&cwq->more_work);
910 
911 	return cwq;
912 }
913 
914 static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
915 {
916 	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
917 	struct workqueue_struct *wq = cwq->wq;
918 	const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";
919 	struct task_struct *p;
920 
921 	p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
922 	/*
923 	 * Nobody can add the work_struct to this cwq,
924 	 *	if (caller is __create_workqueue)
925 	 *		nobody should see this wq
926 	 *	else // caller is CPU_UP_PREPARE
927 	 *		cpu is not on cpu_online_map
928 	 * so we can abort safely.
929 	 */
930 	if (IS_ERR(p))
931 		return PTR_ERR(p);
932 	if (cwq->wq->rt)
933 		sched_setscheduler_nocheck(p, SCHED_FIFO, &param);
934 	cwq->thread = p;
935 
936 	trace_workqueue_creation(cwq->thread, cpu);
937 
938 	return 0;
939 }
940 
941 static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
942 {
943 	struct task_struct *p = cwq->thread;
944 
945 	if (p != NULL) {
946 		if (cpu >= 0)
947 			kthread_bind(p, cpu);
948 		wake_up_process(p);
949 	}
950 }
951 
952 struct workqueue_struct *__create_workqueue_key(const char *name,
953 						int singlethread,
954 						int freezeable,
955 						int rt,
956 						struct lock_class_key *key,
957 						const char *lock_name)
958 {
959 	struct workqueue_struct *wq;
960 	struct cpu_workqueue_struct *cwq;
961 	int err = 0, cpu;
962 
963 	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
964 	if (!wq)
965 		return NULL;
966 
967 	wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
968 	if (!wq->cpu_wq) {
969 		kfree(wq);
970 		return NULL;
971 	}
972 
973 	wq->name = name;
974 	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
975 	wq->singlethread = singlethread;
976 	wq->freezeable = freezeable;
977 	wq->rt = rt;
978 	INIT_LIST_HEAD(&wq->list);
979 
980 	if (singlethread) {
981 		cwq = init_cpu_workqueue(wq, singlethread_cpu);
982 		err = create_workqueue_thread(cwq, singlethread_cpu);
983 		start_workqueue_thread(cwq, -1);
984 	} else {
985 		cpu_maps_update_begin();
986 		/*
987 		 * We must place this wq on list even if the code below fails.
988 		 * cpu_down(cpu) can remove cpu from cpu_populated_map before
989 		 * destroy_workqueue() takes the lock, in that case we leak
990 		 * cwq[cpu]->thread.
991 		 */
992 		spin_lock(&workqueue_lock);
993 		list_add(&wq->list, &workqueues);
994 		spin_unlock(&workqueue_lock);
995 		/*
996 		 * We must initialize cwqs for each possible cpu even if we
997 		 * are going to call destroy_workqueue() finally. Otherwise
998 		 * cpu_up() can hit the uninitialized cwq once we drop the
999 		 * lock.
1000 		 */
1001 		for_each_possible_cpu(cpu) {
1002 			cwq = init_cpu_workqueue(wq, cpu);
1003 			if (err || !cpu_online(cpu))
1004 				continue;
1005 			err = create_workqueue_thread(cwq, cpu);
1006 			start_workqueue_thread(cwq, cpu);
1007 		}
1008 		cpu_maps_update_done();
1009 	}
1010 
1011 	if (err) {
1012 		destroy_workqueue(wq);
1013 		wq = NULL;
1014 	}
1015 	return wq;
1016 }
1017 EXPORT_SYMBOL_GPL(__create_workqueue_key);
1018 
1019 static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)
1020 {
1021 	/*
1022 	 * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
1023 	 * cpu_add_remove_lock protects cwq->thread.
1024 	 */
1025 	if (cwq->thread == NULL)
1026 		return;
1027 
1028 	lock_map_acquire(&cwq->wq->lockdep_map);
1029 	lock_map_release(&cwq->wq->lockdep_map);
1030 
1031 	flush_cpu_workqueue(cwq);
1032 	/*
1033 	 * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,
1034 	 * a concurrent flush_workqueue() can insert a barrier after us.
1035 	 * However, in that case run_workqueue() won't return and check
1036 	 * kthread_should_stop() until it flushes all work_struct's.
1037 	 * When ->worklist becomes empty it is safe to exit because no
1038 	 * more work_structs can be queued on this cwq: flush_workqueue
1039 	 * checks list_empty(), and a "normal" queue_work() can't use
1040 	 * a dead CPU.
1041 	 */
1042 	trace_workqueue_destruction(cwq->thread);
1043 	kthread_stop(cwq->thread);
1044 	cwq->thread = NULL;
1045 }
1046 
1047 /**
1048  * destroy_workqueue - safely terminate a workqueue
1049  * @wq: target workqueue
1050  *
1051  * Safely destroy a workqueue. All work currently pending will be done first.
1052  */
1053 void destroy_workqueue(struct workqueue_struct *wq)
1054 {
1055 	const struct cpumask *cpu_map = wq_cpu_map(wq);
1056 	int cpu;
1057 
1058 	cpu_maps_update_begin();
1059 	spin_lock(&workqueue_lock);
1060 	list_del(&wq->list);
1061 	spin_unlock(&workqueue_lock);
1062 
1063 	for_each_cpu(cpu, cpu_map)
1064 		cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));
1065  	cpu_maps_update_done();
1066 
1067 	free_percpu(wq->cpu_wq);
1068 	kfree(wq);
1069 }
1070 EXPORT_SYMBOL_GPL(destroy_workqueue);
1071 
1072 static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
1073 						unsigned long action,
1074 						void *hcpu)
1075 {
1076 	unsigned int cpu = (unsigned long)hcpu;
1077 	struct cpu_workqueue_struct *cwq;
1078 	struct workqueue_struct *wq;
1079 	int ret = NOTIFY_OK;
1080 
1081 	action &= ~CPU_TASKS_FROZEN;
1082 
1083 	switch (action) {
1084 	case CPU_UP_PREPARE:
1085 		cpumask_set_cpu(cpu, cpu_populated_map);
1086 	}
1087 undo:
1088 	list_for_each_entry(wq, &workqueues, list) {
1089 		cwq = per_cpu_ptr(wq->cpu_wq, cpu);
1090 
1091 		switch (action) {
1092 		case CPU_UP_PREPARE:
1093 			if (!create_workqueue_thread(cwq, cpu))
1094 				break;
1095 			printk(KERN_ERR "workqueue [%s] for %i failed\n",
1096 				wq->name, cpu);
1097 			action = CPU_UP_CANCELED;
1098 			ret = NOTIFY_BAD;
1099 			goto undo;
1100 
1101 		case CPU_ONLINE:
1102 			start_workqueue_thread(cwq, cpu);
1103 			break;
1104 
1105 		case CPU_UP_CANCELED:
1106 			start_workqueue_thread(cwq, -1);
1107 		case CPU_POST_DEAD:
1108 			cleanup_workqueue_thread(cwq);
1109 			break;
1110 		}
1111 	}
1112 
1113 	switch (action) {
1114 	case CPU_UP_CANCELED:
1115 	case CPU_POST_DEAD:
1116 		cpumask_clear_cpu(cpu, cpu_populated_map);
1117 	}
1118 
1119 	return ret;
1120 }
1121 
1122 #ifdef CONFIG_SMP
1123 
1124 struct work_for_cpu {
1125 	struct completion completion;
1126 	long (*fn)(void *);
1127 	void *arg;
1128 	long ret;
1129 };
1130 
1131 static int do_work_for_cpu(void *_wfc)
1132 {
1133 	struct work_for_cpu *wfc = _wfc;
1134 	wfc->ret = wfc->fn(wfc->arg);
1135 	complete(&wfc->completion);
1136 	return 0;
1137 }
1138 
1139 /**
1140  * work_on_cpu - run a function in user context on a particular cpu
1141  * @cpu: the cpu to run on
1142  * @fn: the function to run
1143  * @arg: the function arg
1144  *
1145  * This will return the value @fn returns.
1146  * It is up to the caller to ensure that the cpu doesn't go offline.
1147  * The caller must not hold any locks which would prevent @fn from completing.
1148  */
1149 long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
1150 {
1151 	struct task_struct *sub_thread;
1152 	struct work_for_cpu wfc = {
1153 		.completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
1154 		.fn = fn,
1155 		.arg = arg,
1156 	};
1157 
1158 	sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
1159 	if (IS_ERR(sub_thread))
1160 		return PTR_ERR(sub_thread);
1161 	kthread_bind(sub_thread, cpu);
1162 	wake_up_process(sub_thread);
1163 	wait_for_completion(&wfc.completion);
1164 	return wfc.ret;
1165 }
1166 EXPORT_SYMBOL_GPL(work_on_cpu);
1167 #endif /* CONFIG_SMP */
1168 
1169 void __init init_workqueues(void)
1170 {
1171 	alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
1172 
1173 	cpumask_copy(cpu_populated_map, cpu_online_mask);
1174 	singlethread_cpu = cpumask_first(cpu_possible_mask);
1175 	cpu_singlethread_map = cpumask_of(singlethread_cpu);
1176 	hotcpu_notifier(workqueue_cpu_callback, 0);
1177 	keventd_wq = create_workqueue("events");
1178 	BUG_ON(!keventd_wq);
1179 }
1180