---

yaml
---
r: 254004
b: refs/heads/master
c: fdd514e
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c3af54afbac3675337cedf326b7b127ffa7f7327
+refs/heads/master: fdd514e16bb2531c0c61ae8a1f87740ce217f630

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);