src/patches/suse-2.6.27.25/patches.fixes/scsi-fix-hang-in-starved-list-processing

   1 Subject: [SCSI] Fix hang in starved list processing
   2 From: Mike Christie <michaelc@cs.wisc.edu>
   3 Date: Sun Nov 16 08:13:58 2008 -0600:
   4 Git: 2a3a59e5c977654d3aad5bc11cc0aca2303a7f44
   5 References: bnc#464155
   6
   7 Close possible infinite loop with interrupts off when devices are
   8 added back to the starved list.
   9
  10 Fixes: http://bugzilla.kernel.org/show_bug.cgi?id=11898
  11
  12 Reported-by: <alex.shi@intel.com>
  13 Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
  14 Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
  15 Signed-off-by: Hannes Reinecke <hare@suse.de>
  16
  17 diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
  18 index f5d3b96..fa45a1a 100644
  19 --- a/drivers/scsi/scsi_lib.c
  20 +++ b/drivers/scsi/scsi_lib.c
  21 @@ -567,15 +567,18 @@ static inline int scsi_host_is_busy(struct Scsi_Host *shost)
  22   */
  23  static void scsi_run_queue(struct request_queue *q)
  24  {
  25 -       struct scsi_device *starved_head = NULL, *sdev = q->queuedata;
  26 +       struct scsi_device *sdev = q->queuedata;
  27         struct Scsi_Host *shost = sdev->host;
  28 +       LIST_HEAD(starved_list);
  29         unsigned long flags;
  30
  31         if (scsi_target(sdev)->single_lun)
  32                 scsi_single_lun_run(sdev);
  33
  34         spin_lock_irqsave(shost->host_lock, flags);
  35 -       while (!list_empty(&shost->starved_list) && !scsi_host_is_busy(shost)) {
  36 +       list_splice_init(&shost->starved_list, &starved_list);
  37 +
  38 +       while (!list_empty(&starved_list)) {
  39                 int flagset;
  40
  41                 /*
  42 @@ -588,24 +591,18 @@ static void scsi_run_queue(struct request_queue *q)
  43                  * scsi_request_fn must get the host_lock before checking
  44                  * or modifying starved_list or starved_entry.
  45                  */
  46 -               sdev = list_entry(shost->starved_list.next,
  47 -                                         struct scsi_device, starved_entry);
  48 -               /*
  49 -                * The *queue_ready functions can add a device back onto the
  50 -                * starved list's tail, so we must check for a infinite loop.
  51 -                */
  52 -               if (sdev == starved_head)
  53 +               if (scsi_host_is_busy(shost))
  54                         break;
  55 -               if (!starved_head)
  56 -                       starved_head = sdev;
  57
  58 +               sdev = list_entry(starved_list.next,
  59 +                                 struct scsi_device, starved_entry);
  60 +               list_del_init(&sdev->starved_entry);
  61                 if (scsi_target_is_busy(scsi_target(sdev))) {
  62                         list_move_tail(&sdev->starved_entry,
  63                                        &shost->starved_list);
  64                         continue;
  65                 }
  66
  67 -               list_del_init(&sdev->starved_entry);
  68                 spin_unlock(shost->host_lock);
  69
  70                 spin_lock(sdev->request_queue->queue_lock);
  71 @@ -621,6 +618,8 @@ static void scsi_run_queue(struct request_queue *q)
  72
  73                 spin_lock(shost->host_lock);
  74         }
  75 +       /* put any unprocessed entries back */
  76 +       list_splice(&starved_list, &shost->starved_list);
  77         spin_unlock_irqrestore(shost->host_lock, flags);
  78
  79         blk_run_queue(q);