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Date: Fri, 4 Mar 2011 16:43:59 -0500
From: Mike Snitzer <snitzer@redhat.com>
To: Shaohua Li <shli@kernel.org>
Cc: Jens Axboe <jaxboe@fusionio.com>, linux-kernel@vger.kernel.org,
        hch@infradead.org
Subject: Re: [PATCH 05/10] block: remove per-queue plugging
Message-ID: <20110304214359.GA18442@redhat.com>
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On Fri, Mar 04 2011 at  8:02am -0500,
Shaohua Li <shli@kernel.org> wrote:

> 2011/3/4 Mike Snitzer <snitzer@redhat.com>:
> > I'm now hitting a lockdep issue, while running a 'for-2.6.39/stack-plug'
> > kernel, when I try an fsync heavy workload to a request-based mpath
> > device (the kernel ultimately goes down in flames, I've yet to look at
> > the crashdump I took)
> >
> >
> > =======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 2.6.38-rc6-snitm+ #2
> > -------------------------------------------------------
> > ffsb/3110 is trying to acquire lock:
> > ?(&(&q->__queue_lock)->rlock){..-...}, at: [<ffffffff811b4c4d>] flush_plug_list+0xbc/0x135
> >
> > but task is already holding lock:
> > ?(&rq->lock){-.-.-.}, at: [<ffffffff8137132f>] schedule+0x16a/0x725
> >
> > which lock already depends on the new lock.
> I hit this too. Can you check if attached debug patch fixes it?

Fixes it for me.

Thanks,
Mike
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