aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/workqueue.c
diff options
context:
space:
mode:
authorOleg Nesterov <oleg@tv-sign.ru>2008-07-25 04:47:49 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-25 13:53:40 -0400
commitdb700897224b5ebdf852f2d38920ce428940d059 (patch)
tree98f0052929e79b35393352addde70fa5e97b8dee /kernel/workqueue.c
parent1a4d9b0aa0d3c50314e57525a5e5ec2cfc48b4c8 (diff)
workqueues: implement flush_work()
Most of users of flush_workqueue() can be changed to use cancel_work_sync(), but sometimes we really need to wait for the completion and cancelling is not an option. schedule_on_each_cpu() is good example. Add the new helper, flush_work(work), which waits for the completion of the specific work_struct. More precisely, it "flushes" the result of of the last queue_work() which is visible to the caller. For example, this code queue_work(wq, work); /* WINDOW */ queue_work(wq, work); flush_work(work); doesn't necessary work "as expected". What can happen in the WINDOW above is - wq starts the execution of work->func() - the caller migrates to another CPU now, after the 2nd queue_work() this work is active on the previous CPU, and at the same time it is queued on another. In this case flush_work(work) may return before the first work->func() completes. It is trivial to add another helper int flush_work_sync(struct work_struct *work) { return flush_work(work) || wait_on_work(work); } which works "more correctly", but it has to iterate over all CPUs and thus it much slower than flush_work(). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Acked-by: Max Krasnyansky <maxk@qualcomm.com> Acked-by: Jarek Poplawski <jarkao2@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r--kernel/workqueue.c46
1 files changed, 46 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index d9a2d65cc63e..ee41cf857d55 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -423,6 +423,52 @@ void flush_workqueue(struct workqueue_struct *wq)
423} 423}
424EXPORT_SYMBOL_GPL(flush_workqueue); 424EXPORT_SYMBOL_GPL(flush_workqueue);
425 425
426/**
427 * flush_work - block until a work_struct's callback has terminated
428 * @work: the work which is to be flushed
429 *
430 * It is expected that, prior to calling flush_work(), the caller has
431 * arranged for the work to not be requeued, otherwise it doesn't make
432 * sense to use this function.
433 */
434int flush_work(struct work_struct *work)
435{
436 struct cpu_workqueue_struct *cwq;
437 struct list_head *prev;
438 struct wq_barrier barr;
439
440 might_sleep();
441 cwq = get_wq_data(work);
442 if (!cwq)
443 return 0;
444
445 prev = NULL;
446 spin_lock_irq(&cwq->lock);
447 if (!list_empty(&work->entry)) {
448 /*
449 * See the comment near try_to_grab_pending()->smp_rmb().
450 * If it was re-queued under us we are not going to wait.
451 */
452 smp_rmb();
453 if (unlikely(cwq != get_wq_data(work)))
454 goto out;
455 prev = &work->entry;
456 } else {
457 if (cwq->current_work != work)
458 goto out;
459 prev = &cwq->worklist;
460 }
461 insert_wq_barrier(cwq, &barr, prev->next);
462out:
463 spin_unlock_irq(&cwq->lock);
464 if (!prev)
465 return 0;
466
467 wait_for_completion(&barr.done);
468 return 1;
469}
470EXPORT_SYMBOL_GPL(flush_work);
471
426/* 472/*
427 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit, 473 * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,
428 * so this work can't be re-armed in any way. 474 * so this work can't be re-armed in any way.