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Commit 2a3a59e5 authored by Mike Christie's avatar Mike Christie Committed by James Bottomley
Browse files

[SCSI] Fix hang in starved list processing 

Close possible infinite loop with interrupts off when devices are
added back to the starved list.

Fixes: http://bugzilla.kernel.org/show_bug.cgi?id=11898



Reported-by: default avatar <alex.shi@intel.com>
Signed-off-by: default avatarMike Christie <michaelc@cs.wisc.edu>
Signed-off-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
parent 9bf1a244

drivers/scsi/scsi_lib.c

+11 −12
Original line number Diff line number Diff line
@@ -567,15 +567,18 @@ static inline int scsi_host_is_busy(struct Scsi_Host *shost) 
 */

static void scsi_run_queue(struct request_queue *q)

{

	struct scsi_device *starved_head = NULL, *sdev = q->queuedata;

	struct scsi_device *sdev = q->queuedata;

	struct Scsi_Host *shost = sdev->host;

	LIST_HEAD(starved_list);

	unsigned long flags;



	if (scsi_target(sdev)->single_lun)

		scsi_single_lun_run(sdev);



	spin_lock_irqsave(shost->host_lock, flags);

	while (!list_empty(&shost->starved_list) && !scsi_host_is_busy(shost)) {

	list_splice_init(&shost->starved_list, &starved_list);



	while (!list_empty(&starved_list)) {

		int flagset;



		/*
@@ -588,24 +591,18 @@ static void scsi_run_queue(struct request_queue *q) 
		 * scsi_request_fn must get the host_lock before checking

		 * or modifying starved_list or starved_entry.

		 */

		sdev = list_entry(shost->starved_list.next,

					  struct scsi_device, starved_entry);

		/*

		 * The *queue_ready functions can add a device back onto the

		 * starved list's tail, so we must check for a infinite loop.

		 */

		if (sdev == starved_head)

		if (scsi_host_is_busy(shost))

			break;

		if (!starved_head)

			starved_head = sdev;



		sdev = list_entry(starved_list.next,

				  struct scsi_device, starved_entry);

		list_del_init(&sdev->starved_entry);

		if (scsi_target_is_busy(scsi_target(sdev))) {

			list_move_tail(&sdev->starved_entry,

				       &shost->starved_list);

			continue;

		}



		list_del_init(&sdev->starved_entry);

		spin_unlock(shost->host_lock);



		spin_lock(sdev->request_queue->queue_lock);
@@ -621,6 +618,8 @@ static void scsi_run_queue(struct request_queue *q) 


		spin_lock(shost->host_lock);

	}

	/* put any unprocessed entries back */

	list_splice(&starved_list, &shost->starved_list);

	spin_unlock_irqrestore(shost->host_lock, flags);



	blk_run_queue(q);