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Subject: Re: [PATCH] memcg: Fix race condition in memcg_check_events() with
 this_cpu usage
From: Steven Rostedt <rostedt@goodmis.org>
To: Greg Thelen <gthelen@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        bsingharora@gmail.com, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        PeterZijlstra <peterz@infradead.org>, ChristophLameter <cl@linux.com>
Date: Fri, 23 Sep 2011 22:41:32 -0400
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On Fri, 2011-09-23 at 19:39 -0700, Greg Thelen wrote:
> cc: updated Balbir Singh email address
> 
> On Fri, Sep 23, 2011 at 7:34 PM, Greg Thelen <gthelen@google.com> wrote:
> > On Fri, Sep 23, 2011 at 5:54 PM, Steven Rostedt <rostedt@goodmis.org> wrote:
> >> From: Steven Rostedt <srostedt@redhat.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@google.com>
> >> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> >> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> 
> Correction:
> Cc: Balbir Singh <bsingharora@gmail.com>

Thanks, I was starting to hate that "return mail to sender" thing.

-- Steve

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