linux-kernel - PKTCDVD: possible recursive locking detected with 2.6.24.4/3

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Message-Id: <200803242119.30840.chunkeey@web.de>
Date:	Mon, 24 Mar 2008 21:19:30 +0100
From:	Chr <chunkeey@....de>
To:	linux-kernel@...r.kernel.org
Cc:	petero2@...ia.com, mingo@...hat.com, peterz@...radead.org
Subject: PKTCDVD: possible recursive locking detected with 2.6.24.4/3

Hi,

Whenever I start /etc/init.d/udftools. I get a warning from lockdep about
a possible recursive lockup... It looks like this:

--- 

Clocksource tsc unstable (delta = -80671344 ns)
pktcdvd: writer pktcdvd0 mapped to sr0

=============================================
[ INFO: possible recursive locking detected ]
2.6.24.4 #1
---------------------------------------------
scsi_id/4705 is trying to acquire lock:
 (&bdev->bd_mutex){--..}, at: [<ffffffff802a71a8>] do_open+0x74/0x2a9

but task is already holding lock:
 (&bdev->bd_mutex){--..}, at: [<ffffffff802a71a8>] do_open+0x74/0x2a9

other info that might help us debug this:
2 locks held by scsi_id/4705:
 #0:  (&bdev->bd_mutex){--..}, at: [<ffffffff802a71a8>] do_open+0x74/0x2a9
 #1:  (&ctl_mutex#2){--..}, at: [<ffffffff881ecf2a>] pkt_open+0x27/0xda1 
[pktcdvd]

stack backtrace:
Pid: 4705, comm: scsi_id Not tainted 2.6.24.4 #1

Call Trace:
 [<ffffffff80253b08>] __lock_acquire+0x1db/0xd3f
 [<ffffffff802a71a8>] do_open+0x74/0x2a9
 [<ffffffff802546f0>] lock_acquire+0x84/0xa8
 [<ffffffff802a71a8>] do_open+0x74/0x2a9
[...]
(full dmesg + backtrace: http://www.pastebin.ca/955702 )
---
Well, as you can see the function that tries to get the lock... has it 
already?! This sounds a bit bogus, what's going on here? Is this really
a locking bug or just lockdep noise?
(BTW: the pktcdvd device seems to work nonetheless...)

Regards,
	Christian
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