From 09c4946a9198abd3850d32b207a44fbdbda295d0 Mon Sep 17 00:00:00 2001
From: Stefan Richter <stefanr@s5r6.in-berlin.de>
Date: Sun, 26 Oct 2008 12:02:03 +0100
Subject: [PATCH] --- yaml --- r: 118514 b: refs/heads/master c:
 8449fc3ae58bf8ee5acbd2280754cde67b5db128 h: refs/heads/master v: v3

---
 [refs]                          |  2 +-
 trunk/drivers/ieee1394/dv1394.c | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 215e21909b76..cbdc86307f35 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 638570b54346f140bc09b986d93e76025d35180f
+refs/heads/master: 8449fc3ae58bf8ee5acbd2280754cde67b5db128
diff --git a/trunk/drivers/ieee1394/dv1394.c b/trunk/drivers/ieee1394/dv1394.c
index df70f51279d8..53329972c7db 100644
--- a/trunk/drivers/ieee1394/dv1394.c
+++ b/trunk/drivers/ieee1394/dv1394.c
@@ -1270,8 +1270,14 @@ static int dv1394_mmap(struct file *file, struct vm_area_struct *vma)
 	struct video_card *video = file_to_video_card(file);
 	int retval = -EINVAL;
 
-	/* serialize mmap */
-	mutex_lock(&video->mtx);
+	/*
+	 * We cannot use the blocking variant mutex_lock here because .mmap
+	 * is called with mmap_sem held, while .ioctl, .read, .write acquire
+	 * video->mtx and subsequently call copy_to/from_user which will
+	 * grab mmap_sem in case of a page fault.
+	 */
+	if (!mutex_trylock(&video->mtx))
+		return -EAGAIN;
 
 	if ( ! video_card_initialized(video) ) {
 		retval = do_dv1394_init_default(video);