linux-kernel - Re: [PATCH cgroup/for-3.14-fixes] cgroup: update cgroup_enable_task_cg

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Date:	Tue, 18 Feb 2014 18:25:56 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH cgroup/for-3.14-fixes] cgroup: update
 cgroup_enable_task_cg_lists() to grab siglock

On Thu, Feb 13, 2014 at 01:29:31PM -0500, Tejun Heo wrote:
> Currently, there's nothing preventing cgroup_enable_task_cg_lists()
> from missing set PF_EXITING and race against cgroup_exit().  Depending
> on the timing, cgroup_exit() may finish with the task still linked on
> css_set leading to list corruption.  Fix it by grabbing siglock in
> cgroup_enable_task_cg_lists() so that PF_EXITING is guaranteed to be
> visible.
> 
> This whole on-demand cg_list optimization is extremely fragile and has
> ample possibility to lead to bugs which can cause things like
> once-a-year oops during boot.  I'm wondering whether the better
> approach would be just adding "cgroup_disable=all" handling which
> disables the whole cgroup rather than tempting fate with this
> on-demand craziness.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: stable@...r.kernel.org

Applied to cgroup/for-3.14-fixes.

Thanks.

-- 
tejun
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