linux-kernel - Re: [PATCH 1/3] fix the racy usage of ->signal in account_group_xxx/run_posix_cpu

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Message-ID: <20081117155009.GA12081@elte.hu>
Date:	Mon, 17 Nov 2008 16:50:09 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Roland McGrath <roland@...hat.com>,
	Doug Chapman <doug.chapman@...com>,
	Frank Mayhar <fmayhar@...gle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] fix the racy usage of ->signal in
	account_group_xxx/run_posix_cpu_timers


* Oleg Nesterov <oleg@...hat.com> wrote:

> Another stupid patch for 2.6.28 until we find the good fix.
> 
> Contrary to ad474caca3e2a0550b7ce0706527ad5ab389a4d4 changelog, 
> other acct_group_xxx() helpers can be called after exit_notify() by 
> timer tick. Thanks to Roland for pointing out this. Somehow I missed 
> this simple fact when I read the original patch, and I am afraid I 
> confused Frank during the discussion. Sorry.
> 
> Fortunately, these helpers work with current, we can check 
> ->exit_state to ensure that ->signal can't go away under us.
> 
> Also, add the comment and compiler barrier to 
> account_group_exec_runtime(), to make sure we load ->signal only 
> once.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

applied to tip/sched/urgent, thanks Oleg.

	Ingo
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