media: hdpvr: fix locking and a missing msleep

[ 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>

diff --git a/drivers/media/usb/hdpvr/hdpvr-video.c b/drivers/media/usb/hdpvr/hdpvr-video.c
index 1b89c77..0615996 100644 (file)
--- 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);