Messages in this thread | | | Date | Thu, 26 Apr 2007 16:29:21 +0200 | From | Jarek Poplawski <> | Subject | Re: [PATCH] cancel_delayed_work: use del_timer() instead of del_timer_sync() |
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On Wed, Apr 25, 2007 at 04:52:14PM +0400, Oleg Nesterov wrote: > On 04/25, Jarek Poplawski wrote: > > > > On Wed, Apr 25, 2007 at 01:50:34AM +0400, Oleg Nesterov wrote: > > > 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(). > > > > I'm not sure what is the main aim of this patch. > > optimization > > > It seems this > > change cannot do any harm, but anyway it could change a few > > things, e.g. with current version of cancel_rearming_delayed_work > > some flush_workqueue could be done needlessly, before the work > > is queued from timer. > > I don't think so... Could you clarify?
With a code like:
if (!cancel_delayed_work(dwork)) flush_workqueue(wq); if cancel_ returns 0, and there is _queue_work in progress, flush_ will be done once, after this work is queued.
After the patch, and the same situation flush_ also runs one time, but maybe without the work in a queue.
So, if there is no more loops, there could be difference, and even if very unprobable, something could stop working after such change.
> > > It's not a big deal here, but if anybody > > did something like this without loop - it could matter. > > > > So, probably a lot of current code should be checked, before > > applying and I doubt the gain is worth of this. Maybe, for > > safety, make this with new name as an alternative and > > deprecate the current version? > > This change should not make any visible difference for the callers, > otherwise it is buggy.
IMHO, there is the same visible difference, as between del_timer and del_timer_sync.
Regards, Jarek P. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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