From ee6869afc922a9849979e49bb3bbcad794872fcb Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Sun, 26 Sep 2010 08:47:38 -0300 Subject: V4L/DVB: v4l2: add core serialization lock Drivers can optionally set a pointer to a mutex in struct video_device. The core will use that to lock before calling open, read, write, unlocked_ioctl, poll, mmap or release. Updated the documentation as well and ensure that v4l2-event knows about the lock: it will unlock it before doing a blocking wait on an event and relock it afterwards. Ensure that the 'video_is_registered' check is done when the lock is held: a typical disconnect will take the lock as well before unregistering the device nodes, so to prevent race conditions the video_is_registered check should also be done with the lock held. Signed-off-by: Hans Verkuil Signed-off-by: Mauro Carvalho Chehab --- drivers/media/video/v4l2-event.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'drivers/media/video/v4l2-event.c') diff --git a/drivers/media/video/v4l2-event.c b/drivers/media/video/v4l2-event.c index de74ce07b5e2..69fd343d4774 100644 --- a/drivers/media/video/v4l2-event.c +++ b/drivers/media/video/v4l2-event.c @@ -134,15 +134,22 @@ int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event, if (nonblocking) return __v4l2_event_dequeue(fh, event); + /* Release the vdev lock while waiting */ + if (fh->vdev->lock) + mutex_unlock(fh->vdev->lock); + do { ret = wait_event_interruptible(events->wait, events->navailable != 0); if (ret < 0) - return ret; + break; ret = __v4l2_event_dequeue(fh, event); } while (ret == -ENOENT); + if (fh->vdev->lock) + mutex_lock(fh->vdev->lock); + return ret; } EXPORT_SYMBOL_GPL(v4l2_event_dequeue); -- cgit v1.2.3