linux-kernel - Re: [PATCH 5/7] workqueue: ensure the wq_worker

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Message-ID: <20120827200358.GA14812@dhcp-172-17-108-109.mtv.corp.google.com>
Date:	Mon, 27 Aug 2012 13:03:58 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Lai Jiangshan <laijs@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] workqueue: ensure the wq_worker_sleeping() see the
 right flags

Hello,

On Tue, Aug 28, 2012 at 01:58:25AM +0800, Lai Jiangshan wrote:
> The compiler may compile this code into TWO write/modify instructions.
> 		worker->flags &= ~WORKER_UNBOUND;
> 		worker->flags |= WORKER_REBIND;
> 
> so the other CPU may see the temporary of worker->flags which has
> not WORKER_UNBOUND nor WORKER_REBIND, it will wrongly do local wake up.
> 
> so we use one write/modify instruction explicitly instead.
> 
> This bug will not occur on idle workers, because they have another
> WORKER_NOT_RUNNING flags.

Yeap, I think this got broken while moving around when DISASSOCIATED
is cleared.  Can you please put this at the head of the series?

Thanks.

-- 
tejun
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