From: Tejun Heo <tj@kernel.org>
To: Balbir Singh <bsingharora@gmail.com>
Cc: cgroups@vger.kernel.org, Oleg Nesterov <oleg@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [RFC][PATCH] cgroup_threadgroup_rwsem - affects scalability and OOM
Date: Tue, 9 Aug 2016 10:26:03 -0400 [thread overview]
Message-ID: <20160809142603.GE4906@mtj.duckdns.org> (raw)
In-Reply-To: <0a7ffe43-c0c6-85df-9bc2-d00fc837e284@gmail.com>
Hello, Balbir.
On Tue, Aug 09, 2016 at 05:02:47PM +1000, Balbir Singh wrote:
> > Hmm? Where does mem_cgroup_iter grab cgroup_mutex? cgroup_mutex nests
> > outside cgroup_threadgroup_rwsem or most other mutexes for that matter
> > and isn't exposed from cgroup core.
> >
>
> I based my theory on the code
>
> mem_cgroup_iter -> css_next_descendant_pre which asserts
>
> cgroup_assert_mutex_or_rcu_locked(),
>
> although you are right, we hold RCU lock while calling css_* routines.
That's "or". The iterator can be called either with RCU lock or
cgroup_mutex. cgroup core may use it under cgroup_mutex. Everyone
else uses it with rcu.
Thanks.
--
tejun
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next prev parent reply other threads:[~2016-08-09 14:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-09 4:19 [RFC][PATCH] cgroup_threadgroup_rwsem - affects scalability and OOM Balbir Singh
2016-08-09 6:29 ` Tejun Heo
2016-08-09 7:02 ` Balbir Singh
2016-08-09 14:26 ` Tejun Heo [this message]
2016-08-10 1:21 ` Balbir Singh
2016-08-09 9:00 ` Zefan Li
2016-08-09 13:57 ` Balbir Singh
2016-08-10 1:31 ` Zefan Li
2016-08-09 18:09 ` Oleg Nesterov
2016-08-10 19:43 ` Tejun Heo
2016-08-11 23:47 ` Balbir Singh
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