[WORKQUEUE]: cancel_delayed_work: use del_timer() instead of del_timer_sync()
authorOleg Nesterov <oleg@tv-sign.ru>
Thu, 26 Apr 2007 22:45:32 +0000 (15:45 -0700)
committerDavid S. Miller <davem@davemloft.net>
Thu, 26 Apr 2007 22:45:32 +0000 (15:45 -0700)
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 <oleg@tv-sign.ru>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
include/linux/workqueue.h

index 2a7b38d87018687d9b6e05083ea92b4f9c81f378..b8abfc74d038384092d1089337a51bf0aa6023ec 100644 (file)
@@ -191,14 +191,15 @@ int execute_in_process_context(work_func_t fn, struct execute_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_scheduled_work() 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_release(&work->work);
        return ret;