[SCSI] remove a timer race in scsi_queue_insert()

scsi_queue_insert() has four callers.  Three callers call with
timer disabled and one (the second invocation in
scsi_dispatch_cmd()) calls with timer activated.
scsi_queue_insert() used to always call scsi_delete_timer()
and ignore the return value.  This results in race with timer
expiration.  Remove scsi_delete_timer() call from
scsi_queue_insert() and make the caller delete timer and check
the return value.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

2 files changed, 7 insertions, 11 deletions

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 05d2bd075fd4..0d730f646bce 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -638,10 +638,12 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
         }
         spin_unlock_irqrestore(host->host_lock, flags);
         if (rtn) {
-                atomic_inc(&cmd->device->iodone_cnt);
-                scsi_queue_insert(cmd,
-                                (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
-                                 rtn : SCSI_MLQUEUE_HOST_BUSY);
+                if (scsi_delete_timer(cmd)) {
+                        atomic_inc(&cmd->device->iodone_cnt);
+                        scsi_queue_insert(cmd,
+                                          (rtn == SCSI_MLQUEUE_DEVICE_BUSY) ?
+                                          rtn : SCSI_MLQUEUE_HOST_BUSY);
+                }
                 SCSI_LOG_MLQUEUE(3,
                     printk("queuecommand : request rejected\n"));
         }
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index c3bb28c3feef..9f996499fa9d 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -128,13 +128,7 @@ int scsi_queue_insert(struct scsi_cmnd *cmd, int reason)
                  printk("Inserting command %p into mlqueue\n", cmd));
 
         /*
-         * We are inserting the command into the ml queue.  First, we
-         * cancel the timer, so it doesn't time out.
-         */
-        scsi_delete_timer(cmd);
-
-        /*
-         * Next, set the appropriate busy bit for the device/host.
+         * Set the appropriate busy bit for the device/host.
          *
          * If the host/device isn't busy, assume that something actually
          * completed, and that we should be able to queue a command now.