On Thu, 2011-12-22 at 11:10 +0800, Shaohua Li wrote:
> scsi_run_queue() picks off all sdev from host starved_list to a local list,
> then handle them. If there are multiple threads running scsi_run_queue(),
> the starved_list will get messed. This is quite common, because request
> rq_affinity is on by default.
>
> Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>
> ---
> drivers/scsi/scsi_lib.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> Index: linux/drivers/scsi/scsi_lib.c
> ===================================================================
> --- linux.orig/drivers/scsi/scsi_lib.c 2011-12-21 16:56:23.000000000 +0800
> +++ linux/drivers/scsi/scsi_lib.c 2011-12-22 09:33:09.000000000 +0800
> @@ -401,9 +401,8 @@ static inline int scsi_host_is_busy(stru
> */
> static void scsi_run_queue(struct request_queue *q)
> {
> - struct scsi_device *sdev = q->queuedata;
> + struct scsi_device *sdev = q->queuedata, *head_sdev = NULL;
> struct Scsi_Host *shost;
> - LIST_HEAD(starved_list);
> unsigned long flags;
>
> /* if the device is dead, sdev will be NULL, so no queue to run */
> @@ -415,9 +414,8 @@ static void scsi_run_queue(struct reques
> scsi_single_lun_run(sdev);
>
> spin_lock_irqsave(shost->host_lock, flags);
> - list_splice_init(&shost->starved_list, &starved_list);
>
> - while (!list_empty(&starved_list)) {
> + while (!list_empty(&shost->starved_list)) {
The original reason for working from a copy instead of the original list
was that the device can end up back on the starved list because of a
variety of conditions in the HBA and so this would cause the loop not to
exit, so this piece of the patch doesn't look right to me.
James
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