From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH] memcg: add RCU locking around
 css_for_each_descendant_pre() in memcg_offline_kmem()
Date: Thu, 26 May 2016 14:02:02 -0700
Message-ID: <20160526140202.077d611dbe0926ce290b4e53@linux-foundation.org>
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To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Vladimir Davydov <vdavydov-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org

On Thu, 26 May 2016 16:30:18 -0400 Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:

> memcg_offline_kmem() may be called from memcg_free_kmem() after a css
> init failure.  memcg_free_kmem() is a ->css_free callback which is
> called without cgroup_mutex and memcg_offline_kmem() ends up using
> css_for_each_descendant_pre() without any locking.  Fix it by adding
> rcu read locking around it.
> 
>  mkdir: cannot create directory ___65530___: No space left on device
>  [  527.241361] ===============================
>  [  527.241845] [ INFO: suspicious RCU usage. ]
>  [  527.242367] 4.6.0-work+ #321 Not tainted
>  [  527.242730] -------------------------------
>  [  527.243220] kernel/cgroup.c:4008 cgroup_mutex or RCU read lock required!

cc:stable?