linux-kernel - Re: 2.6.19-rc6 -- dm: possible recursive locking detected

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Date:	Mon, 20 Nov 2006 09:49:06 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Alasdair G Kergon <agk@...hat.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	dm-devel@...hat.com, Andrew Morton <akpm@...l.org>,
	Neil Brown <neilb@...e.de>
Subject: Re: 2.6.19-rc6 -- dm: possible recursive locking detected

On Fri, Nov 17, 2006 at 07:43:03PM +0000, Alasdair G Kergon wrote:
> On Fri, Nov 17, 2006 at 04:30:03PM +0100, Heiko Carstens wrote:
> > =============================================
> > [ INFO: possible recursive locking detected ]
> > 2.6.19-rc6-g1b9bb3c1 #28
> > ---------------------------------------------
> > kpartx/945 is trying to acquire lock:
> >  (&md->io_lock){----}, at: [<00000000001f8faa>] dm_request+0x42/0x24c
> > 
> > but task is already holding lock:
> >  (&md->io_lock){----}, at: [<00000000001f8faa>] dm_request+0x42/0x24c
> 
> Known problem - nobody's written a patch to fix it yet to my knowledge,
> but I don't recall any reports of real world lock-ups related to this - just
> several reports of the debug warning messages:-)
> 
> Simply ignore the message for now - or submit a patch that fixes the
> underlying problem:-)

Ignoring would be good, but this problem renders lockdep useless since it
stops working after it found the first possible bug.

While we are at it:

this one is sitting since ages in -mm and probably waiting for your approval:
http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.19-rc5/2.6.19-rc5-mm2/broken-out/md-dm-reduce-stack-usage-with-stacked-block-devices.patch
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