From: Michal Hocko <mhocko@kernel.org>
To: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov@virtuozzo.com>,
cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com
Subject: Re: [PATCH] memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem()
Date: Tue, 31 May 2016 11:33:51 +0200 [thread overview]
Message-ID: <20160531093351.GG26128@dhcp22.suse.cz> (raw)
In-Reply-To: <20160527155140.GN23194@mtj.duckdns.org>
Sorry for a late response.
On Fri 27-05-16 11:51:40, Tejun Heo wrote:
> On Fri, May 27, 2016 at 05:31:24PM +0200, Michal Hocko wrote:
> > On Thu 26-05-16 14:02:02, Andrew Morton wrote:
> > > On Thu, 26 May 2016 16:30:18 -0400 Tejun Heo <tj@kernel.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?
> >
> > Also which kernel versions would be affected? I have tried to look and
> > got lost in the indirection of the css_free path.
>
> I think it's actually from 0b8f73e10428 ("mm: memcontrol: clean up
> alloc, online, offline, free functions") which got merged during this
> cycle, so no need for -stable.
yes you are right! memcg_free_kmem didn't call memcg_offline_kmem before
that commit. Thanks for the clarification.
Anyway
$ git describe --contains 0b8f73e10428
v4.5-rc1~30^2~11
So it would be stable # 4.5+
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-05-31 9:33 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-26 20:30 [PATCH] memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem() Tejun Heo
2016-05-26 21:02 ` Andrew Morton
2016-05-27 15:31 ` Michal Hocko
2016-05-27 15:51 ` Tejun Heo
2016-05-31 9:33 ` Michal Hocko [this message]
2016-05-27 8:17 ` Vladimir Davydov
2016-05-27 17:19 ` Johannes Weiner
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