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[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: <alex.shi@intel.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
This commit is contained in:
Mike Christie 2008-11-11 13:42:35 -06:00 committed by James Bottomley
parent 9bf1a2445f
commit 2a3a59e5c9
1 changed files with 11 additions and 12 deletions
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23
drivers/scsi/scsi_lib.c
View File

@ -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);