Re: [PATCH] cgroup: use an ordered workqueue for cgroup destruction

Tejun Heo
2014-02-07T15:22:06Z

On Thu, Feb 06, 2014 at 03:56:01PM -0800, Hugh Dickins wrote:
> Sometimes the cleanup after memcg hierarchy testing gets stuck in
> mem_cgroup_reparent_charges(), unable to bring non-kmem usage down to 0.
>
> There may turn out to be several causes, but a major cause is this: the
> workitem to offline parent can get run before workitem to offline child;
> parent's mem_cgroup_reparent_charges() circles around waiting for the
> child's pages to be reparented to its lrus, but it's holding cgroup_mutex
> which prevents the child from reaching its mem_cgroup_reparent_charges().
>
> Just use an ordered workqueue for cgroup_destroy_wq.
>
> Fixes: e5fca243abae ("cgroup: use a dedicated workqueue for cgroup destruction")
> Suggested-by: Filipe Brandenburger <filbranden@google.com>
> Signed-off-by: Hugh Dickins <hughd@google.com>
> Cc: stable@vger.kernel.org # 3.10+

Applied to cgroup/for-3.14-fixes with comment updated to indicate that
this is temporary.

Thanks.

--
tejun