linux-kernel - Re: [PATCH] memcg: Fix race condition in memcg_check_events() with this

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Message-ID: <CAHH2K0agLygD6cREazsTquCT=Whx97RxxhOneWpVF1cHwMwp3A@mail.gmail.com>
Date:	Fri, 23 Sep 2011 19:39:05 -0700
From:	Greg Thelen <gthelen@...gle.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	bsingharora@...il.com,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	PeterZijlstra <peterz@...radead.org>,
	ChristophLameter <cl@...ux.com>
Subject: Re: [PATCH] memcg: Fix race condition in memcg_check_events() with
 this_cpu usage

cc: updated Balbir Singh email address

On Fri, Sep 23, 2011 at 7:34 PM, Greg Thelen <gthelen@...gle.com> wrote:
> On Fri, Sep 23, 2011 at 5:54 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>> From: Steven Rostedt <srostedt@...hat.com>
>>
>> The code in memcg_check_events() calls this_cpu_read() on
>> different variables without disabling preemption, and can cause
>> the calculations to be done from two different CPU variables.
>>
>> Disable preemption throughout the check to keep apples and oranges
>> from becoming a mixed drink.
>>
>> [ Added this_cpu to __this_cpu conversion by Johannes ]
>>
>> Cc: Greg Thelen <gthelen@...gle.com>
>> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>> Cc: Balbir Singh <balbir@...ux.vnet.ibm.com>

Correction:
Cc: Balbir Singh <bsingharora@...il.com>

>> Cc: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Christoph Lameter <cl@...ux.com>
>> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
>> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
>> Link: http://lkml.kernel.org/r/20110919212641.015320989@goodmis.org
>
> Looks good to me.  Thanks.
>
> Reviewed-by: Greg Thelen <gthelen@...gle.com>
>
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