From: Tejun Heo  <htejun@gmail.com>
Date: Fri, 13 May 2005 15:46:08 +0000 (+0900)
Subject: [SCSI] remove a timer race in scsi_queue_insert()
X-Git-Tag: v2.6.13-rc1~90^2~583^2~62^2^2~27^2~15
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8c37e7b9a619855e05d5d4e56c68f799b1f539c;p=linux-2.6

[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>
---

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 05d2bd075f..0d730f646b 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 c3bb28c3fe..9f996499fa 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.