linux-kernel - Re: [PATCH v3] workqueue: lock cwq access in drain

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Message-ID: <20110911033042.GN29319@htj.dyndns.org>
Date:	Sun, 11 Sep 2011 12:30:42 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Thomas Tuttle <ttuttle@...omium.org>
Cc:	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] workqueue: lock cwq access in drain_workqueue

Hello,

On Sat, Sep 10, 2011 at 11:26:41PM -0400, Thomas Tuttle wrote:
> Take cwq->gcwq->lock to avoid racing between drain_workqueue checking
> to make sure the workqueues are empty and cwq_dec_nr_in_flight
> decrementing and then incrementing nr_active when it activates a
> delayed work.
> 
> We discovered this when a corner case in one of our drivers resulted in
> us trying to destroy a workqueue in which the remaining work would
> always requeue itself again in the same workqueue.  We would hit this
> race condition and trip the BUG_ON on workqueue.c:3080.
> 
> Signed-off-by: Thomas Tuttle <ttuttle@...omium.org>

  Acked-by: Tejun Heo <tj@...nel.org>

Can you please also add "Cc: stable@...nel.org" and send it to Andrew
Morton <akpm@...ux-foundation.org>?

Thank you very much.

-- 
tejun
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