del_timer_sync() buys nothing for cancel_delayed_work(), but it is less efficient since it locks the timer unconditionally, and may wait for the completion of the delayed_work_timer_fn().
cancel_delayed_work() == 0 means: before this patch: work->func may still be running or queued after this patch: work->func may still be running or queued, or delayed_work_timer_fn->__queue_work() in progress. The latter doesn't differ from the caller's POV, delayed_work_timer_fn() is called with _PENDING bit set. cancel_delayed_work() == 1 with this patch adds a new possibility: delayed_work->work was cancelled, but delayed_work_timer_fn is still running (this is only possible for the re-arming works on single-threaded workqueue). In this case the timer was re-started by work->func(), nobody else can do this. This in turn means that delayed_work_timer_fn has already passed __queue_work() (and wont't touch delayed_work) because nobody else can queue delayed_work->work. Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]> --- OLD/include/linux/workqueue.h~2_CDW 2007-04-05 12:20:35.000000000 +0400 +++ OLD/include/linux/workqueue.h 2007-04-25 01:48:24.000000000 +0400 @@ -152,14 +152,15 @@ extern void cancel_work_sync(struct work /* * Kill off a pending schedule_delayed_work(). Note that the work callback - * function may still be running on return from cancel_delayed_work(). Run - * flush_workqueue() or cancel_work_sync() to wait on it. + * function may still be running on return from cancel_delayed_work(), unless + * it returns 1 and the work doesn't re-arm itself. Run flush_workqueue() or + * cancel_work_sync() to wait on it. */ static inline int cancel_delayed_work(struct delayed_work *work) { int ret; - ret = del_timer_sync(&work->timer); + ret = del_timer(&work->timer); if (ret) work_clear_pending(&work->work); return ret; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/