From: t_jeang <devnull@localhost>
Date: Tue, 6 Jan 2009 12:06:01 +0000 (+0000)
Subject: imported patch CA-12483-fix-forced-shutdown-race
X-Git-Tag: CA-9002-blktap-plug
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=46f4f3637f790befa40abcaedde67c116c2cf306;p=xenclient%2Fkernel.git

imported patch CA-12483-fix-forced-shutdown-race
---

diff --git a/drivers/xen/blktap/backdev.c b/drivers/xen/blktap/backdev.c
index 3ebed59f..1bdcfded 100644
--- a/drivers/xen/blktap/backdev.c
+++ b/drivers/xen/blktap/backdev.c
@@ -96,6 +96,7 @@ destroy_backdev(struct tap_blkif *uinfo)
 	spin_lock_irq(&backdev_io_lock);
 	/* No more blkif_request(). */
 	blk_stop_queue(info->gd->queue);
+	uinfo->backdev = NULL;
 	spin_unlock_irq(&backdev_io_lock);
 
 	del_gendisk(info->gd);
@@ -108,7 +109,6 @@ destroy_backdev(struct tap_blkif *uinfo)
 
 	blkif_put(uinfo->blkif);
 
-	uinfo->backdev = NULL;
 	kfree(info);
 
 	clear_bit(4, &uinfo->dev_inuse);
@@ -505,19 +505,22 @@ backdev_restart_queue(struct tap_blkif *uinfo)
 {
 	struct backdev_info *info;
 
+	spin_lock_irq(&backdev_io_lock);
+
 	info = uinfo->backdev;
 	if (info == NULL || info->gd == NULL || info->gd->queue == NULL)
-		return;
+		goto out;
 
 	if (!RING_FULL(&uinfo->ufe_ring)) {
-		spin_lock_irq(&backdev_io_lock);
 		/* Re-enable calldowns. */
 		if (blk_queue_stopped(info->gd->queue))
 			blk_start_queue(info->gd->queue);
 		/* Kick things off immediately. */
 		process_backdev_request(uinfo, info);
-		spin_unlock_irq(&backdev_io_lock);
 	}
+
+out:
+	spin_unlock_irq(&backdev_io_lock);
 	return;
 }