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Re: [PATCH] repair: avoid ABBA deadlocks on prefetched buffers

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH] repair: avoid ABBA deadlocks on prefetched buffers
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 17 Nov 2011 15:25:43 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20111115210953.GA6670@xxxxxxxxxxxxx>
References: <20111115210953.GA6670@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Tue, Nov 15, 2011 at 04:09:53PM -0500, Christoph Hellwig wrote:
> Both the prefetch threads and actual repair processing threads can have
> multiple buffers at a time locked, but they do no use a common locker
> order, which can lead to ABBA deadlocks while trying to lock the buffers.
> 
> Switch the prefetch code to do a trylock and skip buffers that have
> already been locked to avoid this deadlock.
> 
> Reported-by: Arkadiusz Mi??kiewicz <arekm@xxxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Looks sane to me.

Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>

-- 
Dave Chinner
david@xxxxxxxxxxxxx

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