Date: Mon, 14 May 2007 01:25:48 +0400
From: Oleg Nesterov <oleg@tv-sign.ru>
To: Tejun Heo <htejun@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, David Chinner <dgc@sgi.com>,
       David Howells <dhowells@redhat.com>, Gautham Shenoy <ego@in.ibm.com>,
       Jarek Poplawski <jarkao2@o2.pl>, Ingo Molnar <mingo@elte.hu>,
       Srivatsa Vaddagiri <vatsa@in.ibm.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] make cancel_rearming_delayed_work() reliable
Message-ID: <20070513212548.GA3185@tv-sign.ru>
References: <20070503204226.GA212@tv-sign.ru> <464475EB.3000408@gmail.com> <20070511134714.GA191@tv-sign.ru> <46448965.7070500@gmail.com> <20070511145345.GA240@tv-sign.ru> <4645559D.4050602@gmail.com> <20070513192753.GA3014@tv-sign.ru> <46477239.9030007@gmail.com>
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Hi Tejun,

Sorry, I can't give a "complete" reply today (will do tomorrow),
just one note right now...

On 05/13, Tejun Heo wrote:
> 
> Oleg Nesterov wrote:
> >> * try_to_grab_pending() checks VALID && pointers equal after grabbing
> >> cwq->lock.
> > 
> > We don't even need to check the pointers. VALID bit is always changed
> > under cwq->lock. So, if we see VALID under cwq->lock, we have a right
> > pointer.
> 
> But there are multiple cwq->lock's.  VALID can be set with one of other
> cwq->lock's locked.

Oops. Thanks for correcting me. _This_ was a reson for a stupid barrier!

Oleg.

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