commit 81b2dbcad86732ffc02bad87aa25c4651199fc77
author Arjan van de Ven <arjan@linux.intel.com> Tue May 20 09:53:52 2008 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Tue May 20 10:12:26 2008 -0700
tree 6c956c561fbaaa7e04ef612695bf5d3d0b5faef2
parent babd90b274e6b43a7dc7bb08562bf566cbabdbf8

Fix a deadlock in the bttv driver

vidiocgmbuf() does this:
        mutex_lock(&fh->cap.vb_lock);
        retval = videobuf_mmap_setup(&fh->cap, gbuffers, gbufsize,
                                     V4L2_MEMORY_MMAP);

and videobuf_mmap_setup() then just does
        mutex_lock(&q->vb_lock);
        ret = __videobuf_mmap_setup(q, bcount, bsize, memory);
        mutex_unlock(&q->vb_lock);

which is an obvious double-take deadlock.

This patch fixes this by having vidiocgmbuf() just call the
__videobuf_mmap_setup function instead.

Acked-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Reported-by: Koos Vriezen <koos.vriezen@gmail.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/media/video/videobuf-core.c

diff --git a/drivers/media/video/videobuf-core.c b/drivers/media/video/videobuf-core.c
index 982f446..0a88c44 100644
--- a/drivers/media/video/videobuf-core.c
+++ b/drivers/media/video/videobuf-core.c
@@ -331,7 +331,7 @@
 }
 
 /* Locking: Caller holds q->vb_lock */
-static int __videobuf_mmap_setup(struct videobuf_queue *q,
+int __videobuf_mmap_setup(struct videobuf_queue *q,
 			unsigned int bcount, unsigned int bsize,
 			enum v4l2_memory memory)
 {
@@ -1129,6 +1129,7 @@
 EXPORT_SYMBOL_GPL(videobuf_read_one);
 EXPORT_SYMBOL_GPL(videobuf_poll_stream);
 
+EXPORT_SYMBOL_GPL(__videobuf_mmap_setup);
 EXPORT_SYMBOL_GPL(videobuf_mmap_setup);
 EXPORT_SYMBOL_GPL(videobuf_mmap_free);
 EXPORT_SYMBOL_GPL(videobuf_mmap_mapper);