From: Tejun Heo <tj@kernel.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>,
Brian Christiansen <brian.o.christiansen@gmail.com>,
Michal Hocko <mhocko@kernel.org>,
cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: PROBLEM: BUG when using memory.kmem.limit_in_bytes
Date: Fri, 22 Jan 2016 10:51:04 -0500 [thread overview]
Message-ID: <20160122155104.GG32380@htj.duckdns.org> (raw)
In-Reply-To: <20160122144854.GA14432@cmpxchg.org>
On Fri, Jan 22, 2016 at 09:48:54AM -0500, Johannes Weiner wrote:
> On Fri, Jan 22, 2016 at 04:50:42PM +0300, Vladimir Davydov wrote:
> > From first glance, it looks like the bug was triggered, because
> > mem_cgroup_css_offline was run for a child cgroup earlier than for its
> > parent. This couldn't happen for sure before the cgroup was switched to
> > percpu_ref, because cgroup_destroy_wq has always had max_active == 1.
> > Now, however, it looks like this is perfectly possible for
> > css_killed_ref_fn is called from an rcu callback - see kill_css ->
> > percpu_ref_kill_and_confirm. This breaks kmemcg assumptions.
> >
> > I'll take a look what can be done about that.
>
> It's an acknowledged problem in the cgroup core then, and not an issue
> with kmemcg. Tejun sent a fix to correct the offlining order here:
>
> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1056544.html
Patche descriptions updated and applied to cgroup/for-4.5-fixes.
http://lkml.kernel.org/g/20160122154503.GD32380@htj.duckdns.org
http://lkml.kernel.org/g/20160122154552.GE32380@htj.duckdns.org
Thanks.
--
tejun
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next prev parent reply other threads:[~2016-01-22 15:51 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-21 19:49 PROBLEM: BUG when using memory.kmem.limit_in_bytes Brian Christiansen
2016-01-22 13:50 ` Vladimir Davydov
2016-01-22 14:48 ` Johannes Weiner
2016-01-22 15:51 ` Tejun Heo [this message]
2016-01-22 16:33 ` Vladimir Davydov
2016-01-22 18:35 ` Brian Christiansen
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