From: Hans Verkuil hverkuil@xs4all.nl
[ Upstream commit 6bc5a4a1927556ff9adce1aa95ea408c95453225 ]
This driver has three locking issues:
- The wait_event_interruptible() condition calls hdpvr_get_next_buffer(dev) which uses a mutex, which is not allowed. Rewrite with list_empty_careful() that doesn't need locking.
- In hdpvr_read() the call to hdpvr_stop_streaming() didn't lock io_mutex, but it should have since stop_streaming expects that.
- In hdpvr_device_release() io_mutex was locked when calling flush_work(), but there it shouldn't take that mutex since the work done by flush_work() also wants to lock that mutex.
There are also two other changes (suggested by Keith):
- msecs_to_jiffies(4000); (a NOP) should have been msleep(4000). - Change v4l2_dbg to v4l2_info to always log if streaming had to be restarted.
Reported-by: Keith Pyle kpyle@austin.rr.com Suggested-by: Keith Pyle kpyle@austin.rr.com Signed-off-by: Hans Verkuil hverkuil-cisco@xs4all.nl Signed-off-by: Mauro Carvalho Chehab mchehab+samsung@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/usb/hdpvr/hdpvr-video.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/drivers/media/usb/hdpvr/hdpvr-video.c b/drivers/media/usb/hdpvr/hdpvr-video.c index 1b89c77bad66..0615996572e4 100644 --- a/drivers/media/usb/hdpvr/hdpvr-video.c +++ b/drivers/media/usb/hdpvr/hdpvr-video.c @@ -439,7 +439,7 @@ static ssize_t hdpvr_read(struct file *file, char __user *buffer, size_t count, /* wait for the first buffer */ if (!(file->f_flags & O_NONBLOCK)) { if (wait_event_interruptible(dev->wait_data, - hdpvr_get_next_buffer(dev))) + !list_empty_careful(&dev->rec_buff_list))) return -ERESTARTSYS; }
@@ -465,10 +465,17 @@ static ssize_t hdpvr_read(struct file *file, char __user *buffer, size_t count, goto err; } if (!err) { - v4l2_dbg(MSG_INFO, hdpvr_debug, &dev->v4l2_dev, - "timeout: restart streaming\n"); + v4l2_info(&dev->v4l2_dev, + "timeout: restart streaming\n"); + mutex_lock(&dev->io_mutex); hdpvr_stop_streaming(dev); - msecs_to_jiffies(4000); + mutex_unlock(&dev->io_mutex); + /* + * The FW needs about 4 seconds after streaming + * stopped before it is ready to restart + * streaming. + */ + msleep(4000); err = hdpvr_start_streaming(dev); if (err) { ret = err; @@ -1133,9 +1140,7 @@ static void hdpvr_device_release(struct video_device *vdev) struct hdpvr_device *dev = video_get_drvdata(vdev);
hdpvr_delete(dev); - mutex_lock(&dev->io_mutex); flush_work(&dev->worker); - mutex_unlock(&dev->io_mutex);
v4l2_device_unregister(&dev->v4l2_dev); v4l2_ctrl_handler_free(&dev->hdl);