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Commit b485462a authored by Bart Van Assche's avatar Bart Van Assche Committed by James Bottomley
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[SCSI] Stop accepting SCSI requests before removing a device 



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: default avatarBart Van Assche <bvanassche@acm.org>
Reviewed-by: default avatarMike Christie <michaelc@cs.wisc.edu>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarJames Bottomley <JBottomley@Parallels.com>
parent 84feb166

drivers/scsi/scsi_lib.c

+4 −3
Original line number Diff line number Diff line
@@ -155,13 +155,14 @@ static void __scsi_queue_insert(struct scsi_cmnd *cmd, int reason, int unbusy) 


	/*

	 * Requeue this command.  It will go before all other commands

	 * that are already in the queue.

	 * that are already in the queue. Schedule requeue work under

	 * lock such that the kblockd_schedule_work() call happens

	 * before blk_cleanup_queue() finishes.

	 */

	spin_lock_irqsave(q->queue_lock, flags);

	blk_requeue_request(q, cmd->request);

	spin_unlock_irqrestore(q->queue_lock, flags);



	kblockd_schedule_work(q, &device->requeue_work);

	spin_unlock_irqrestore(q->queue_lock, flags);

}



/*

drivers/scsi/scsi_sysfs.c

+9 −2
Original line number Diff line number Diff line
@@ -967,13 +967,20 @@ void __scsi_remove_device(struct scsi_device *sdev) 
		device_del(dev);

	} else

		put_device(&sdev->sdev_dev);



	/*

	 * Stop accepting new requests and wait until all queuecommand() and

	 * scsi_run_queue() invocations have finished before tearing down the

	 * device.

	 */

	scsi_device_set_state(sdev, SDEV_DEL);

	blk_cleanup_queue(sdev->request_queue);

	cancel_work_sync(&sdev->requeue_work);



	if (sdev->host->hostt->slave_destroy)

		sdev->host->hostt->slave_destroy(sdev);

	transport_destroy_device(dev);



	/* Freeing the queue signals to block that we're done */

	blk_cleanup_queue(sdev->request_queue);

	put_device(dev);

}