linux-kernel - Re: 2.6.32-rc5-git1 -- INFO: possible circular locking dependency detected

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Message-Id: <1256200483.12174.16.camel@johannes.local>
Date:	Thu, 22 Oct 2009 10:34:43 +0200
From:	Johannes Berg <johannes@...solutions.net>
To:	Miles Lane <miles.lane@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	Holger Schurig <hs4233@...l.mn-solutions.de>,
	Alan Jenkins <sourcejedi.lkml@...glemail.com>
Subject: Re: 2.6.32-rc5-git1 -- INFO: possible circular locking dependency
 detected

On Tue, 2009-10-20 at 09:37 -0400, Miles Lane wrote:
> Resending with wrapping off and time info removed:

Hey, thanks for that!

> [ INFO: possible circular locking dependency detected ]
>  2.6.32-rc5-git1 #1
>  -------------------------------------------------------
>  events/0/9 is trying to acquire lock:
>   (&rfkill->sync_work){+.+.+.}, at: [<c1039083>] 
> __cancel_work_timer+0x81/0x181
>  
>  but task is already holding lock:
>   (&ehotk->hotplug_lock){+.+.+.}, at: [<f8587708>] 
> eeepc_rfkill_hotplug+0x45/0xda [eeepc_laptop]
>  
>  which lock already depends on the new lock.
>  
> 
>  the existing dependency chain (in reverse order) is:
>  
>  -> #2 (&ehotk->hotplug_lock){+.+.+.}:

>         [<c129e5ee>] mutex_lock_nested+0x2b/0x33
>         [<f8587708>] eeepc_rfkill_hotplug+0x45/0xda [eeepc_laptop]
>         [<f858787c>] eeepc_rfkill_set+0x1d/0x2d [eeepc_laptop]
>         [<f83f4a9f>] rfkill_set_block+0x6f/0xb1 [rfkill]
>         [<f83f4b78>] __rfkill_switch_all+0x2e/0x51 [rfkill]
>         [<f83f4c12>] rfkill_switch_all+0x33/0x41 [rfkill]
>         [<f83f51b0>] rfkill_op_handler+0xf0/0x11e [rfkill]
>         [<c1038965>] worker_thread+0x161/0x233
>         [<c103b883>] kthread+0x5f/0x64
>         [<c1003613>] kernel_thread_helper+0x7/0x10
>  
>  -> #1 (rfkill_global_mutex){+.+.+.}:
>         [<c104ac60>] __lock_acquire+0x9fb/0xb6d
>         [<c104ae2e>] lock_acquire+0x5c/0x73
>         [<c129e223>] __mutex_lock_common+0x39/0x375
>         [<c129e5ee>] mutex_lock_nested+0x2b/0x33
>         [<f83f4c36>] rfkill_sync_work+0x16/0x35 [rfkill]

Hmm. It seems eeepc takes the hotplug lock in the set path, but also
elsewhere? Seems like a bug in eeepc, Alan?

johannes

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