linux-kernel - Re: [PATCH] block: fix intermittent dm timeout based oops

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Date:	Fri, 3 Apr 2009 16:32:08 +0200
From:	Christof Schmitt <christof.schmitt@...ibm.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
	Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH] block: fix intermittent dm timeout based oops

On Tue, Mar 24, 2009 at 08:17:30AM +0100, Hannes Reinecke wrote:
> Very rarely under stress testing of dm, oopses are occuring as
> something tampers with an old stack frame.  This has been traced back
> to blk_abort_queue() leaving a timeout_list pointing to the stack.
> The reason is that sometimes blk_abort_request() won't delete the
> timer (if the request is marked as complete but before the timer has
> been removed, a small race window).  Fix this by splicing back from
> the ususally empty list to the q->timeout_list.
> 
> Signed-off-by: Hannes Reinecke <hare@...e.de>
> ---
>  block/blk-timeout.c |    6 ++++++
>  1 files changed, 6 insertions(+), 0 deletions(-)
> 
> diff --git a/block/blk-timeout.c b/block/blk-timeout.c
> index bbbdc4b..6213123 100644
> --- a/block/blk-timeout.c
> +++ b/block/blk-timeout.c
> @@ -224,6 +224,12 @@ void blk_abort_queue(struct request_queue *q)
>  	list_for_each_entry_safe(rq, tmp, &list, timeout_list)
>  		blk_abort_request(rq);
> 
> +	/*
> +	 * Occasionally, blk_abort_request() will return without
> +	 * deleting the element from the list
> +	 */
> +	list_splice(&list, &q->timeout_list);
> +
>  	spin_unlock_irqrestore(q->queue_lock, flags);
> 
>  }
> -- 
> 1.5.3.2

I just noticed that this fix is not upstream yet and i have seen test
cases hitting this problem.

Jens, are you going to included this patch, or should this go through
the SCSI tree?

--
Christof Schmitt
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