linux-kernel - Re: INFO: possible circular locking dependency at cleanup_workqueue

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Message-Id: <1242802064.31350.12.camel@johannes.local>
Date:	Wed, 20 May 2009 08:47:44 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Zdenek Kabelac <zdenek.kabelac@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: INFO: possible circular locking dependency at 
 cleanup_workqueue_thread

On Wed, 2009-05-20 at 11:36 +0800, Ming Lei wrote:

> > Anyway, you can have a deadlock like this:
> >
> > CPU 3                   CPU 2                           CPU 1
> >                                                        suspend/hibernate
> >                        something:
> >                        rtnl_lock()                     device_pm_lock()
> >                                                        -> mutex_lock(&dpm_list_mtx)
> >
> >                        mutex_lock(&dpm_list_mtx)
> 
> Would you give a explaination why mutex_lock(&dpm_list_mtx) runs in CPU2
> and depends on rtnl_lock?

Why not? Something is registering a hotplugged netdev.

johannes

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