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Message-ID: <20120427203159.GL26595@google.com>
Date: Fri, 27 Apr 2012 13:31:59 -0700
From: Tejun Heo <tj@...nel.org>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: Linux Kernel <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
Michal Hocko <mhocko@...e.cz>,
Johannes Weiner <hannes@...xchg.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Glauber Costa <glommer@...allels.com>,
Han Ying <yinghan@...gle.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
kamezawa.hiroyuki@...il.com
Subject: Re: [RFC][PATCH 7/9 v2] cgroup: avoid attaching task to a cgroup
under rmdir()
On Fri, Apr 27, 2012 at 03:02:22PM +0900, KAMEZAWA Hiroyuki wrote:
> attach_task() is done under cgroup_mutex() but ->pre_destroy() callback
> in rmdir() isn't called under cgroup_mutex().
>
> It's better to avoid attaching a task to a cgroup which
> is under pre_destroy(). Considering memcg, the attached task may
> increase resource usage after memcg's pre_destroy() confirms that
> memcg is empty. This is not good.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Hmm... once memcg's pre_destroy() can't fail, I think what we should
do is marking a cgroup DEAD before calling pre_destroy() and the
existing cgroup_is_removed() check should be enough. Patches upto
this point already make ->pre_destroy() not fail, right?
Thanks.
--
tejun
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