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Subject: Re: 2.6.24-rc7 lockdep warning when poweroff
From: Peter Zijlstra <peterz@infradead.org>
To: Dave Young <hidave.darkstar@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>, Johannes Berg <johannes@sipsolutions.net>
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On Mon, 2008-01-14 at 17:04 +0800, Dave Young wrote:
> Hi,
> 
> When I "halt -p", lockdep warnings triggered as following (hand copy):
> 
> WARNING : at kernel/lockdep.c: 700 lookup_lock_class()
> 
> <snip>
> lock_acquire
> cleanup_workqueue_thread
> workqueue_cpu_callback
> notifier_call_chain
> __raw_notifier_call_chain
> raw_notifier_call_chain
> __cpu_down
> disable_nonboot_cpus
> kernel_power_off
> sys_reboot
> <snip>

My first guess would be a __create_workqueue_key() where a key is
re-used with a different workqueue name.

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