When the video device is unregistered any filehandles waiting on
an event (i.e. in VIDIOC_DQEVENT) will never wake up.
Wake them up and detect that the video device is unregistered in
__v4l2_event_dequeue() and return -ENODEV in that case.
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
Note: this is a quick hack, just for events. We have the same problem
with vb2 (waiting for a buffer) and cec (waiting for an event). Not sure if rc
or dvb are also suffering from the same problem.
I wonder if there is an easier way to wake up all fhs that are waiting for
some event.
Michael: most applications use non-blocking mode and poll/select to wait
for something to happen. In such applications the poll/select will return
when the device is unregistered and this problem does not occur.
---
diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index d5e0e536ef04..42574ccbd770 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -1017,6 +1017,9 @@ EXPORT_SYMBOL(__video_register_device);
*/
void video_unregister_device(struct video_device *vdev)
{
+ unsigned long flags;
+ struct v4l2_fh *fh;
+
/* Check if vdev was ever registered at all */
if (!vdev || !video_is_registered(vdev))
return;
@@ -1027,6 +1030,12 @@ void video_unregister_device(struct video_device *vdev)
*/
clear_bit(V4L2_FL_REGISTERED, &vdev->flags);
mutex_unlock(&videodev_lock);
+
+ spin_lock_irqsave(&vdev->fh_lock, flags);
+ list_for_each_entry(fh, &vdev->fh_list, list)
+ wake_up_all(&fh->wait);
+ spin_unlock_irqrestore(&vdev->fh_lock, flags);
+
device_unregister(&vdev->dev);
}
EXPORT_SYMBOL(video_unregister_device);
diff --git a/drivers/media/v4l2-core/v4l2-event.c b/drivers/media/v4l2-core/v4l2-event.c
index 968c2eb08b5a..d04977cd1bfb 100644
--- a/drivers/media/v4l2-core/v4l2-event.c
+++ b/drivers/media/v4l2-core/v4l2-event.c
@@ -36,12 +36,17 @@ static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
{
struct v4l2_kevent *kev;
unsigned long flags;
+ int ret = 0;
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
+ if (!video_is_registered(fh->vdev)) {
+ ret = -ENODEV;
+ goto err;
+ }
if (list_empty(&fh->available)) {
- spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
- return -ENOENT;
+ ret = -ENOENT;
+ goto err;
}
WARN_ON(fh->navailable == 0);
@@ -54,10 +59,10 @@ static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
*event = kev->event;
kev->sev->first = sev_pos(kev->sev, 1);
kev->sev->in_use--;
-
+err:
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
- return 0;
+ return ret;
}
int v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event,
