linux-kernel - Re: [PATCH v2] block: Mitigate lock unbalance caused by lock disconnect

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Message-ID: <20120528102214.GB15202@dhcp-172-17-108-109.mtv.corp.google.com>
Date:	Mon, 28 May 2012 19:22:14 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Asias He <asias@...hat.com>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] block: Mitigate lock unbalance caused by lock
 disconnect

On Mon, May 28, 2012 at 10:20:03AM +0800, Asias He wrote:
> Commit 777eb1bf15b8532c396821774bf6451e563438f5 disconnects externally
> supplied queue_lock before blk_drain_queue(). This would introduce lock
> unbalance because theads which have taken the external lock might unlock
> the internal lock in the during the queue drain.
> 
> This patch mitigate this by disconnecting the lock after the queue
> draining since queue draining makes a lot of request_queue users go
> away.

Can you please point out how the code is broken and that the code is
still broken after the patch but somewhat less likely to actually
fail?

Thanks.

-- 
tejun
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