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Date: Sat, 1 Aug 2009 07:34:54 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
       Rusty Russell <rusty@rustcorp.com.au>, linux-kernel@vger.kernel.org,
       Li Zefan <lizf@cn.fujitsu.com>, Miao Xie <miaox@cn.fujitsu.com>,
       Paul Menage <menage@google.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Gautham R Shenoy <ego@in.ibm.com>
Subject: Re: [PATCH] cpusets: rework guarantee_online_cpus() to fix
	deadlock with cpu_down()
Message-ID: <20090801053454.GA26596@redhat.com>
References: <20090729023302.GA8899@redhat.com> <20090729212125.GA16970@redhat.com> <20090729212216.GB16970@redhat.com> <20090729230043.GA28175@redhat.com> <4A70FD26.1010800@cn.fujitsu.com> <20090730175108.GC3617@redhat.com> <4A725594.8020205@cn.fujitsu.com> <20090801044236.GA23975@redhat.com>
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Sorry for noise, forgot to mention...

On 08/01, Oleg Nesterov wrote:
>
> 	- adds cpuset->cpumask_lock, this lock is taken by
> 	  update_cpumask() around cpumask_copy(cs->cpus_allowed, newcpus).

Most probably there are other places where ->cpus_allowed is changed,
in that case they need ->cpumask_lock too. But this is trivial, the
patch I sent just explains what I meant.

Oleg.