linux-kernel - Re: [PATCH 1/2] cgroup: no need to check css refs for release notification

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Message-ID: <20130304180508.GF30413@htj.dyndns.org>
Date:	Mon, 4 Mar 2013 10:05:08 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH 1/2] cgroup: no need to check css refs for release
 notification

On Fri, Mar 01, 2013 at 03:06:07PM +0800, Li Zefan wrote:
> We no longer fail rmdir() when there're still css refs, so we don't
> need to check css refs in check_for_release().
> 
> This also voids a bug. cgroup_has_css_refs() accesses subsys[i]
> without cgroup_mutex, so it can race with cgroup_unload_subsys().
> 
> cgroup_has_css_refs()
> ...
>   if (ss == NULL || ss->root != cgrp->root)
> 
> if ss pointers to net_cls_subsys, and cls_cgroup module is unloaded
> right after the former check but before the latter, the memory that
> net_cls_subsys resides has become invalid.
> 
> Signed-off-by: Li Zefan <lizefan@...wei.com>

Applied to cgroup/for-3.10.

Thanks.

-- 
tejun
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