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Subject: Re: 2.6.32-rc5-git1 -- INFO: possible circular locking dependency
 detected
From: Johannes Berg <johannes@sipsolutions.net>
To: Miles Lane <miles.lane@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Holger Schurig <hs4233@mail.mn-solutions.de>,
	Alan Jenkins <sourcejedi.lkml@googlemail.com>
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Date: Thu, 22 Oct 2009 10:34:43 +0200
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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>]=20
> __cancel_work_timer+0x81/0x181
> =20
>  but task is already holding lock:
>   (&ehotk->hotplug_lock){+.+.+.}, at: [<f8587708>]=20
> eeepc_rfkill_hotplug+0x45/0xda [eeepc_laptop]
> =20
>  which lock already depends on the new lock.
> =20
>=20
>  the existing dependency chain (in reverse order) is:
> =20
>  -> #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
> =20
>  -> #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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