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.
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