linux-kernel - Re: [PATCH] cancel_delayed_work: use del_timer() instead of del_timer

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Message-ID: <20070425125214.GB94@tv-sign.ru>
Date:	Wed, 25 Apr 2007 16:52:14 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Jarek Poplawski <jarkao2@...pl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	David Miller <davem@...emloft.net>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cancel_delayed_work: use del_timer() instead of del_timer_sync()

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?

>                       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.

Oleg.

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