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Subject: Re: 2.6.18-rc5-mm1 + all hotfixes -- INFO: possible recursive
	locking detected
From: Arjan van de Ven <arjan@infradead.org>
To: Miles Lane <miles.lane@gmail.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>,
       Herbert Xu <herbert@gondor.apana.org.au>
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Date: Wed, 06 Sep 2006 08:39:24 +0200
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On Tue, 2006-09-05 at 10:37 -0700, Miles Lane wrote:
> ieee1394: Node changed: 0-01:1023 -> 0-00:1023
> ieee1394: Node changed: 0-02:1023 -> 0-01:1023
> ieee1394: Node suspended: ID:BUS[0-00:1023]  GUID[0080880002103eae]
> 
> =============================================
> [ INFO: possible recursive locking detected ]
> 2.6.18-rc5-mm1 #2
> ---------------------------------------------
> knodemgrd_0/2321 is trying to acquire lock:
>  (&s->rwsem){----}, at: [<f8958897>] nodemgr_probe_ne+0x311/0x38d [ieee1394]
> 
> but task is already holding lock:
>  (&s->rwsem){----}, at: [<f8959078>] nodemgr_host_thread+0x717/0x883 [ieee1394]


looks like a real bug to me:

nodemgr_node_probe() takes down_read(&class->subsys.rwsem) and then
calls nodemgr_probe_ne() which calls nodemgr_update_pdrv() which does
down_read(&class->subsys.rwsem).

Such recursive taking of rwsems is not allowed (rwsems are fair, if a
write comes in in between then there is a deadlock).


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