From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH v2 3/5] change number_of_cpusets to an atomic
Date: Tue, 24 Apr 2012 10:02:02 -0500 (CDT)
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Cc: Tejun Heo <tj@kernel.org>, netdev@vger.kernel.org,
	cgroups@vger.kernel.org, Li Zefan <lizefan@huawei.com>,
	kamezawa.hiroyu@jp.fujitsu.com, David Miller <davem@davemloft.net>,
	devel@openvz.org
To: Glauber Costa <glommer@parallels.com>
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On Mon, 23 Apr 2012, Glauber Costa wrote:

> This will allow us to call destroy() without holding the
> cgroup_mutex(). Other important updates inside update_flags()
> are protected by the callback_mutex.
>
> We could protect this variable with the callback_mutex as well,
> as suggested by Li Zefan, but we need to make sure we are protected
> by that mutex at all times, and some of its updates happen inside the
> cgroup_mutex - which means we would deadlock.

Would this not also be a good case to introduce static branching?

number_of_cpusets is used to avoid going through unnecessary processing
should there be no cpusets in use.