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Subject: Re: [2.6.33-rc5] Weird deadlock when shutting down
From: Johannes Berg <johannes@sipsolutions.net>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>, Peter Zijlstra <peterz@infradead.org>,
       Linus Torvalds <torvalds@linux-foundation.org>
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Date: Thu, 18 Feb 2010 10:36:15 +0100
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On Fri, 2010-01-29 at 15:41 +1100, Benjamin Herrenschmidt wrote:
> Hi Ingo !
> 
> Johannes and I see this on our quad G5s... it -could- be similar to
> one reported a short while ago by Xiaotian Feng <xtfeng@gmail.com>
> under the subject [2.6.33-rc4] sysfs lockdep warnings on cpu hotplug.
>  
> Basically, the machine deadlocks right after printing the following
> when doing a shutdown:
> 
> halt/4071 is trying to acquire lock:
>  (s_active){++++.+}, at: [<c0000000001ef868>]
> .sysfs_addrm_finish+0x58/0xc0
> 
> but task is already holding lock:
>  (&per_cpu(cpu_policy_rwsem, cpu)){+.+.+.}, at: [<c0000000004cd6ac>]
> .lock_policy_rwsem_write+0x84/0xf4
> 
> which lock already depends on the new lock.
> 
> the existing dependency chain (in reverse order) is:

This is still happening with -rc8. Any news?

johannes

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