Hi Kieran,
On Wed, Mar 28, 2018 at 1:47 AM Kieran Bingham
<kieran.bingham@xxxxxxxxxxxxxxxx> wrote:
[snip]
> @@ -1544,25 +1594,29 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream,
> */
> static void uvc_uninit_video(struct uvc_streaming *stream, int free_buffers)
> {
> - struct urb *urb;
> - unsigned int i;
> + struct uvc_urb *uvc_urb;
>
> uvc_video_stats_stop(stream);
>
> - for (i = 0; i < UVC_URBS; ++i) {
> - struct uvc_urb *uvc_urb = &stream->uvc_urb[i];
> + /*
> + * We must poison the URBs rather than kill them to ensure that even
> + * after the completion handler returns, any asynchronous workqueues
> + * will be prevented from resubmitting the URBs
> + */
> + for_each_uvc_urb(uvc_urb, stream)
> + usb_poison_urb(uvc_urb->urb);
>
> - urb = uvc_urb->urb;
> - if (urb == NULL)
> - continue;
> + flush_workqueue(stream->async_wq);
>
> - usb_kill_urb(urb);
> - usb_free_urb(urb);
> + for_each_uvc_urb(uvc_urb, stream) {
> + usb_free_urb(uvc_urb->urb);
> uvc_urb->urb = NULL;
> }
>
> if (free_buffers)
> uvc_free_urb_buffers(stream);
> +
> + destroy_workqueue(stream->async_wq);
In our testing, this function ends up being called twice, if before
suspend the camera is streaming and if the camera disconnects between
suspend and resume. This is because uvc_video_suspend() calls this
function (with free_buffers = 0), but uvc_video_resume() wouldn't call
uvc_init_video() due to an earlier failure and uvc_v4l2_release()
would end up calling this function again, while the workqueue is
already destroyed.
The following diff seems to take care of it:
8<~~~
diff --git a/drivers/media/usb/uvc/uvc_video.c
b/drivers/media/usb/uvc/uvc_video.c
index c5e0ab564b1a..6fb890c8ba67 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1493,10 +1493,11 @@ static void uvc_uninit_video(struct
uvc_streaming *stream, int free_buffers)
uvc_urb->urb = NULL;
}
- if (free_buffers)
+ if (free_buffers) {
uvc_free_urb_buffers(stream);
-
- destroy_workqueue(stream->async_wq);
+ destroy_workqueue(stream->async_wq);
+ stream->async_wq = NULL;
+ }
}
/*
@@ -1648,10 +1649,12 @@ static int uvc_init_video(struct uvc_streaming
*stream, gfp_t gfp_flags)
uvc_video_stats_start(stream);
- stream->async_wq = alloc_workqueue("uvcvideo", WQ_UNBOUND | WQ_HIGHPRI,
- 0);
- if (!stream->async_wq)
- return -ENOMEM;
+ if (!stream->async_wq) {
+ stream->async_wq = alloc_workqueue("uvcvideo",
+ WQ_UNBOUND | WQ_HIGHPRI, 0);
+ if (!stream->async_wq)
+ return -ENOMEM;
+ }
if (intf->num_altsetting > 1) {
struct usb_host_endpoint *best_ep = NULL;
~~~>8
Best regards,
Tomasz
