From e2bb771ae8b4041afe6320c0c85b763074746cf4 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Thu, 9 Jun 2011 20:43:59 +0200
Subject: [PATCH] --- yaml --- r: 254004 b: refs/heads/master c:
 fdd514e16bb2531c0c61ae8a1f87740ce217f630 h: refs/heads/master v: v3

---
 [refs]              |  2 +-
 trunk/block/genhd.c | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 08fe2a5f04ad..f2b40a5bb800 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c3af54afbac3675337cedf326b7b127ffa7f7327
+refs/heads/master: fdd514e16bb2531c0c61ae8a1f87740ce217f630
diff --git a/trunk/block/genhd.c b/trunk/block/genhd.c
index ab0731d8976d..3608289c8ecd 100644
--- a/trunk/block/genhd.c
+++ b/trunk/block/genhd.c
@@ -1371,6 +1371,7 @@ struct disk_events {
 	struct gendisk		*disk;		/* the associated disk */
 	spinlock_t		lock;
 
+	struct mutex		block_mutex;	/* protects blocking */
 	int			block;		/* event blocking depth */
 	unsigned int		pending;	/* events already sent out */
 	unsigned int		clearing;	/* events being cleared */
@@ -1438,12 +1439,20 @@ void disk_block_events(struct gendisk *disk)
 	if (!ev)
 		return;
 
+	/*
+	 * Outer mutex ensures that the first blocker completes canceling
+	 * the event work before further blockers are allowed to finish.
+	 */
+	mutex_lock(&ev->block_mutex);
+
 	spin_lock_irqsave(&ev->lock, flags);
 	cancel = !ev->block++;
 	spin_unlock_irqrestore(&ev->lock, flags);
 
 	if (cancel)
 		cancel_delayed_work_sync(&disk->ev->dwork);
+
+	mutex_unlock(&ev->block_mutex);
 }
 
 static void __disk_unblock_events(struct gendisk *disk, bool check_now)
@@ -1751,6 +1760,7 @@ static void disk_add_events(struct gendisk *disk)
 	INIT_LIST_HEAD(&ev->node);
 	ev->disk = disk;
 	spin_lock_init(&ev->lock);
+	mutex_init(&ev->block_mutex);
 	ev->block = 1;
 	ev->poll_msecs = -1;
 	INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);