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Date: Wed, 10 Dec 2008 10:26:28 -0800
Message-ID: <6599ad830812101026g7d2813acvec7cdb3e0321f780@mail.gmail.com>
Subject: Re: [RFC][PATCH 1/6] memcg: fix pre_destory handler
From: Paul Menage <menage@google.com>
To: nishimura@mxp.nes.nec.co.jp
Cc: balbir@linux.vnet.ibm.com,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>,
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       "kosaki.motohiro@jp.fujitsu.com" <kosaki.motohiro@jp.fujitsu.com>,
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On Wed, Dec 10, 2008 at 5:47 AM, Daisuke Nishimura
<d-nishimura@mtf.biglobe.ne.jp> wrote:
> Hmm.. but doesn't per-hierarchy-mutex solve the problem if memory and cpuset
> mounted on the same hierarchy ?
>

It's not a per-hierarchy mutex - it's a per-subsystem lock against
changes on that subsystem's hierarchy. So each subsystem just has to
take its own lock, rather than a global or per-hierarchy lock. The
cgroups code takes care of acquiring the multiple locks in a safe
order when necessary.

Paul