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From: Rusty Russell <rusty@rustcorp.com.au>
To: Johannes Berg <johannes@sipsolutions.net>
Subject: Re: circular locking dependency on shutdown
Date: Fri, 30 Jan 2009 15:13:35 +1030
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Cc: Linux Kernel list <linux-kernel@vger.kernel.org>,
       Heiko Carstens <heiko.carstens@de.ibm.com>,
       Pekka Enberg <penberg@cs.helsinki.fi>, Ingo Molnar <mingo@elte.hu>,
       Manfred Spraul <manfred@colorfullife.com>,
       Peter Zijlstra <peterz@infradead.org>, cpufreq@vger.kernel.org
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On Friday 30 January 2009 05:20:49 Johannes Berg wrote:
> Hi,
> 
> Every time I shut down my machine with a 2.6.29-rc2 kernel, I get a
> lockdep report that scrolls off.
...
> halt is trying to acquire lock
> 	(&per_cpu(cpu_policy_rwsem, cpu)){---}
> 
> but task is already holding lock
> 	(&cpu_hotplug.lock){--..}

Hi Johannes,

   This looks much like the work_on_cpu()-getting-hotplug-lock problem which caused us to stop work_on_cpu doing that.  -rc3 has that fix; any chance of a re-test?

Thanks,
Rusty.