From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Christie <michaelc@cs.wisc.edu>
Subject: Re: [PATCH 4/4] scsi: Stop accepting SCSI requests before removing
 a device
Date: Tue, 05 Jun 2012 16:36:09 -0500
Message-ID: <4FCE7BC9.1010504@cs.wisc.edu>
References: <4FCE3D20.4000205@acm.org> <4FCE3E63.7000002@acm.org>
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To: Bart Van Assche <bvanassche@acm.org>
Cc: linux-scsi <linux-scsi@vger.kernel.org>, James Bottomley <jbottomley@parallels.com>, Jun'ichi Nomura <j-nomura@ce.jp.nec.com>, Stefan Richter <stefanr@s5r6.in-berlin.de>, Jens Axboe <axboe@kernel.dk>, Joe Lawrence <jdl1291@gmail.com>

On 06/05/2012 12:14 PM, Bart Van Assche wrote:
> Avoid that the code for requeueing SCSI requests triggers a
> crash by making sure that that code isn't scheduled anymore
> after a device has been removed.
> 
> Also, source code inspection of __scsi_remove_device() revealed
> a race condition in this function: no new SCSI requests must be
> accepted for a SCSI device after device removal started.
> 
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> Cc: Mike Christie <michaelc@cs.wisc.edu>
> Cc: James Bottomley <JBottomley@parallels.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Joe Lawrence <jdl1291@gmail.com>
> Cc: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
> Cc: <stable@kernel.org>
> ---
>  drivers/scsi/scsi_lib.c   |    7 ++++---
>  drivers/scsi/scsi_sysfs.c |   11 +++++++++--
>  2 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index 082c1e5..b722a8b 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -158,10 +158,11 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy)
>  	 * that are already in the queue.
>  	 */
>  	spin_lock_irqsave(q->queue_lock, flags);
> -	blk_requeue_request(q, cmd->request);
> +	if (!blk_queue_dead(q)) {
> +		blk_requeue_request(q, cmd->request);
> +		kblockd_schedule_work(q, &device->requeue_work);
> +	}

If we do not requeue what eventually frees the request?