Re: [RFC][PATCH 7/9 v2] cgroup: avoid attaching task to a cgroupunder rmdir()

[Tejun Heo]

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@xxxxxxxxxxxxxx>

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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