linux-kernel - Re: [PATCH 2.6.32-rc6] workqueue: fix race condition in schedule_on_each

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Message-ID: <20091113093341.GB26185@elte.hu>
Date:	Fri, 13 Nov 2009 10:33:41 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2.6.32-rc6] workqueue: fix race condition in
 schedule_on_each_cpu()


* Tejun Heo <tj@...nel.org> wrote:

> Commit 65a64464349883891e21e74af16c05d6e1eeb4e9 which allows
> schedule_on_each_cpu() to be called from keventd added a race
> condition.  schedule_on_each_cpu() may race with cpu hotplug and end
> up executing the function twice on a cpu.
> 
> Fix it by moving direct execution into the section protected with
> get/put_online_cpus().  While at it, update code such that direct
> execution is done after works have been scheduled for all other cpus
> and drop unnecessary cpu != orig test from flush loop.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> ---
> Andi, Oleg, this patch tested fine on my machine but it would be great
> if you guys can ack it.  Ingo, upon ack, can you please route this
> patch?
> 
> Thanks.

Andrew's doing workqueue patches - i've Cc:-ed him.

Looks good to me. Btw., 65a644643 should have been done via -mm, or at 
least it should have gathered proper Acks from interested parties before 
pushing the change upstream.

	Ingo
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