and here is an (untest) patch that should fix this problem:
Koos, can you apply this to your kernel tree and report back if this
fixes your deadlock?
From: Arjan van de Ven <arjan@linux.intel.com>
Subject: [PATCH] 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.
Reported-by: Koos Vriezen <koos.vriezen@gmail.com>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
drivers/media/video/bt8xx/bttv-driver.c | 2 +-
drivers/media/video/videobuf-core.c | 3 ++-
include/media/videobuf-core.h | 3 +++
3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/media/video/bt8xx/bttv-driver.c b/drivers/media/video/bt8xx/bttv-driver.c
index 2ca3e9c..0165aac 100644
--- a/drivers/media/video/bt8xx/bttv-driver.c
+++ b/drivers/media/video/bt8xx/bttv-driver.c
@@ -2613,7 +2613,7 @@ static int vidiocgmbuf(struct file *file, void *priv, struct video_mbuf *mbuf)
struct bttv_fh *fh = priv;
mutex_lock(&fh->cap.vb_lock);
- retval = videobuf_mmap_setup(&fh->cap, gbuffers, gbufsize,
+ retval = __videobuf_mmap_setup(&fh->cap, gbuffers, gbufsize,
V4L2_MEMORY_MMAP);
if (retval < 0) {
mutex_unlock(&fh->cap.vb_lock);
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 @@ int videobuf_mmap_free(struct videobuf_queue *q)
}
/* 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_stream);
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);
diff --git a/include/media/videobuf-core.h b/include/media/videobuf-core.h
index 5b39a22..874f134 100644
--- a/include/media/videobuf-core.h
+++ b/include/media/videobuf-core.h
@@ -237,6 +237,9 @@ unsigned int videobuf_poll_stream(struct file *file,
int videobuf_mmap_setup(struct videobuf_queue *q,
unsigned int bcount, unsigned int bsize,
enum v4l2_memory memory);
+int __videobuf_mmap_setup(struct videobuf_queue *q,
+ unsigned int bcount, unsigned int bsize,
+ enum v4l2_memory memory);
int videobuf_mmap_free(struct videobuf_queue *q);
int videobuf_mmap_mapper(struct videobuf_queue *q,
struct vm_area_struct *vma);
--
1.5.4.5
--
