Merge git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/ieee1394/dv1394.c b/drivers/ieee1394/dv1394.c
index 965cfdb84ebc..c19f23267157 100644
--- a/drivers/ieee1394/dv1394.c
+++ b/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);