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Date: Tue, 20 Sep 2011 16:20:31 +0200
From: Johannes Weiner <hannes@cmpxchg.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Christoph Lameter <cl@linux.com>, Greg Thelen <gthelen@google.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Subject: Re: [RFC][PATCH 3/5] memcg: Disable preemption in
 memcg_check_events()
Message-ID: <20110920142031.GB17198@cmpxchg.org>
References: <20110919212040.745370781@goodmis.org>
 <20110919212641.015320989@goodmis.org>
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On Mon, Sep 19, 2011 at 05:20:43PM -0400, Steven Rostedt 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.

Makes sense, thanks!

Since the atomic versions are no longer required with preemption
disabled explicitely, could you also make the this_cpu ops in
__memcg_event_check and __mem_cgroup_target_update non-atomic in the
same go?