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SubjectRe: [PATCH v4 6/6] media: uvcvideo: Move decode processing to process context
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Hi Tomasz,

On 07/08/18 10:54, Tomasz Figa wrote:
> Hi Kieran,
>
> On Wed, Mar 28, 2018 at 1:47 AM Kieran Bingham
> <kieran.bingham@ideasonboard.com> 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:

Thank you for the investigation and patch report ;D

I think moving the workqueue allocation might be a reasonable option as
suggested by Laurent in his review.

I'll look further into this when I get to another spin of the series.


>
> 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
>

--
Regards
--
Kieran

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