Re: [PATCH v1] media: uvcvideo: handle urb completion in a work queue

[Hans de Goede <hdegoede@xxxxxxxxxx>]

Hi,

On 09/07/2015 06:23 PM, Mian Yousaf Kaukab wrote:
> urb completion callback is executed in host controllers interrupt
> context. To keep preempt disable time short, add urbs to a list on
> completion and schedule work to process the list.
>
> Moreover, save timestamp and sof number in the urb completion callback
> to avoid any delays.

Erm, I thought that we had already moved to using threaded interrupt
handling for the urb completion a while (1-2 years ?) back. Is this then
still needed ?

Regards,

Hans


> Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@xxxxxxxxx>
> ---
> History:
> v1:
>   - Use global work queue instead of creating ordered queue.
>   - Add completed urbs to a list and process all on the list when work
>     is scheduled
>   - Save timestamp and sof number in urb completion callback and use
>     in uvc_video_clock_decode() and uvc_video_decode_start()
>   - Fix race between usb_submit_urb() from uvc_video_complete() and
>     usb_kill_urb() from uvc_uninit_video()
>
>   drivers/media/usb/uvc/uvc_isight.c |   3 +-
>   drivers/media/usb/uvc/uvc_video.c  | 132 +++++++++++++++++++++++++++----------
>   drivers/media/usb/uvc/uvcvideo.h   |  17 ++++-
>   3 files changed, 113 insertions(+), 39 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_isight.c b/drivers/media/usb/uvc/uvc_isight.c
> index 8510e725..7f93d09 100644
> --- a/drivers/media/usb/uvc/uvc_isight.c
> +++ b/drivers/media/usb/uvc/uvc_isight.c
> @@ -99,9 +99,10 @@ static int isight_decode(struct uvc_video_queue *queue, struct uvc_buffer *buf,
>   	return 0;
>   }
>
> -void uvc_video_decode_isight(struct urb *urb, struct uvc_streaming *stream,
> +void uvc_video_decode_isight(struct uvc_urb *uu, struct uvc_streaming *stream,
>   		struct uvc_buffer *buf)
>   {
> +	struct urb *urb = uu->urb;
>   	int ret, i;
>
>   	for (i = 0; i < urb->number_of_packets; ++i) {
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index f839654..71354ec 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -379,15 +379,14 @@ static inline void uvc_video_get_ts(struct timespec *ts)
>
>   static void
>   uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
> -		       const __u8 *data, int len)
> +		       const __u8 *data, int len, u16 host_sof,
> +		       struct timespec *ts)
>   {
>   	struct uvc_clock_sample *sample;
>   	unsigned int header_size;
>   	bool has_pts = false;
>   	bool has_scr = false;
>   	unsigned long flags;
> -	struct timespec ts;
> -	u16 host_sof;
>   	u16 dev_sof;
>
>   	switch (data[1] & (UVC_STREAM_PTS | UVC_STREAM_SCR)) {
> @@ -435,9 +434,6 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>
>   	stream->clock.last_sof = dev_sof;
>
> -	host_sof = usb_get_current_frame_number(stream->dev->udev);
> -	uvc_video_get_ts(&ts);
> -
>   	/* The UVC specification allows device implementations that can't obtain
>   	 * the USB frame number to keep their own frame counters as long as they
>   	 * match the size and frequency of the frame number associated with USB
> @@ -473,7 +469,7 @@ uvc_video_clock_decode(struct uvc_streaming *stream, struct uvc_buffer *buf,
>   	sample->dev_stc = get_unaligned_le32(&data[header_size - 6]);
>   	sample->dev_sof = dev_sof;
>   	sample->host_sof = host_sof;
> -	sample->host_ts = ts;
> +	sample->host_ts = *ts;
>
>   	/* Update the sliding window head and count. */
>   	stream->clock.head = (stream->clock.head + 1) % stream->clock.size;
> @@ -964,7 +960,8 @@ static void uvc_video_stats_stop(struct uvc_streaming *stream)
>    * uvc_video_decode_end will never be called with a NULL buffer.
>    */
>   static int uvc_video_decode_start(struct uvc_streaming *stream,
> -		struct uvc_buffer *buf, const __u8 *data, int len)
> +		struct uvc_buffer *buf, const __u8 *data, int len,
> +		u16 host_sof, struct timespec *ts)
>   {
>   	__u8 fid;
>
> @@ -989,7 +986,7 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
>   			uvc_video_stats_update(stream);
>   	}
>
> -	uvc_video_clock_decode(stream, buf, data, len);
> +	uvc_video_clock_decode(stream, buf, data, len, host_sof, ts);
>   	uvc_video_stats_decode(stream, data, len);
>
>   	/* Store the payload FID bit and return immediately when the buffer is
> @@ -1016,8 +1013,6 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
>   	 * when the EOF bit is set to force synchronisation on the next packet.
>   	 */
>   	if (buf->state != UVC_BUF_STATE_ACTIVE) {
> -		struct timespec ts;
> -
>   		if (fid == stream->last_fid) {
>   			uvc_trace(UVC_TRACE_FRAME, "Dropping payload (out of "
>   				"sync).\n");
> @@ -1027,13 +1022,11 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
>   			return -ENODATA;
>   		}
>
> -		uvc_video_get_ts(&ts);
> -
>   		buf->buf.v4l2_buf.field = V4L2_FIELD_NONE;
>   		buf->buf.v4l2_buf.sequence = stream->sequence;
> -		buf->buf.v4l2_buf.timestamp.tv_sec = ts.tv_sec;
> +		buf->buf.v4l2_buf.timestamp.tv_sec = ts->tv_sec;
>   		buf->buf.v4l2_buf.timestamp.tv_usec =
> -			ts.tv_nsec / NSEC_PER_USEC;
> +			ts->tv_nsec / NSEC_PER_USEC;
>
>   		/* TODO: Handle PTS and SCR. */
>   		buf->state = UVC_BUF_STATE_ACTIVE;
> @@ -1160,9 +1153,10 @@ static void uvc_video_validate_buffer(const struct uvc_streaming *stream,
>   /*
>    * Completion handler for video URBs.
>    */
> -static void uvc_video_decode_isoc(struct urb *urb, struct uvc_streaming *stream,
> -	struct uvc_buffer *buf)
> +static void uvc_video_decode_isoc(struct uvc_urb *uu,
> +		struct uvc_streaming *stream, struct uvc_buffer *buf)
>   {
> +	struct urb *urb = uu->urb;
>   	u8 *mem;
>   	int ret, i;
>
> @@ -1180,7 +1174,8 @@ static void uvc_video_decode_isoc(struct urb *urb, struct uvc_streaming *stream,
>   		mem = urb->transfer_buffer + urb->iso_frame_desc[i].offset;
>   		do {
>   			ret = uvc_video_decode_start(stream, buf, mem,
> -				urb->iso_frame_desc[i].actual_length);
> +				urb->iso_frame_desc[i].actual_length, uu->sof,
> +				&uu->ts);
>   			if (ret == -EAGAIN) {
>   				uvc_video_validate_buffer(stream, buf);
>   				buf = uvc_queue_next_buffer(&stream->queue,
> @@ -1206,9 +1201,10 @@ static void uvc_video_decode_isoc(struct urb *urb, struct uvc_streaming *stream,
>   	}
>   }
>
> -static void uvc_video_decode_bulk(struct urb *urb, struct uvc_streaming *stream,
> -	struct uvc_buffer *buf)
> +static void uvc_video_decode_bulk(struct uvc_urb *uu,
> +		struct uvc_streaming *stream, struct uvc_buffer *buf)
>   {
> +	struct urb *urb = uu->urb;
>   	u8 *mem;
>   	int len, ret;
>
> @@ -1228,7 +1224,8 @@ static void uvc_video_decode_bulk(struct urb *urb, struct uvc_streaming *stream,
>   	 */
>   	if (stream->bulk.header_size == 0 && !stream->bulk.skip_payload) {
>   		do {
> -			ret = uvc_video_decode_start(stream, buf, mem, len);
> +			ret = uvc_video_decode_start(stream, buf, mem, len,
> +				uu->sof, &uu->ts);
>   			if (ret == -EAGAIN)
>   				buf = uvc_queue_next_buffer(&stream->queue,
>   							    buf);
> @@ -1274,9 +1271,10 @@ static void uvc_video_decode_bulk(struct urb *urb, struct uvc_streaming *stream,
>   	}
>   }
>
> -static void uvc_video_encode_bulk(struct urb *urb, struct uvc_streaming *stream,
> -	struct uvc_buffer *buf)
> +static void uvc_video_encode_bulk(struct uvc_urb *uu,
> +		struct uvc_streaming *stream, struct uvc_buffer *buf)
>   {
> +	struct urb *urb = uu->urb;
>   	u8 *mem = urb->transfer_buffer;
>   	int len = stream->urb_size, ret;
>
> @@ -1317,9 +1315,26 @@ static void uvc_video_encode_bulk(struct urb *urb, struct uvc_streaming *stream,
>   	urb->transfer_buffer_length = stream->urb_size - len;
>   }
>
> -static void uvc_video_complete(struct urb *urb)
> +static void uvc_urb_complete(struct urb *urb)
>   {
> -	struct uvc_streaming *stream = urb->context;
> +	struct uvc_urb *uu = urb->context;
> +	struct uvc_streaming *stream = uu->stream;
> +	unsigned long flags;
> +
> +	uu->sof = usb_get_current_frame_number(stream->dev->udev);
> +	uvc_video_get_ts(&uu->ts);
> +
> +	spin_lock_irqsave(&stream->urb_list_lock, flags);
> +	list_add_tail(&urb->urb_list, &stream->urb_complete_list);
> +	spin_unlock_irqrestore(&stream->urb_list_lock, flags);
> +
> +	schedule_work(&stream->urb_work);
> +}
> +
> +static void uvc_video_complete(struct uvc_urb *uu)
> +{
> +	struct urb *urb = uu->urb;
> +	struct uvc_streaming *stream = uu->stream;
>   	struct uvc_video_queue *queue = &stream->queue;
>   	struct uvc_buffer *buf = NULL;
>   	unsigned long flags;
> @@ -1349,7 +1364,10 @@ static void uvc_video_complete(struct urb *urb)
>   				       queue);
>   	spin_unlock_irqrestore(&queue->irqlock, flags);
>
> -	stream->decode(urb, stream, buf);
> +	stream->decode(uu, stream, buf);
> +
> +	if (stream->stop)
> +		return;
>
>   	if ((ret = usb_submit_urb(urb, GFP_ATOMIC)) < 0) {
>   		uvc_printk(KERN_ERR, "Failed to resubmit video URB (%d).\n",
> @@ -1357,6 +1375,29 @@ static void uvc_video_complete(struct urb *urb)
>   	}
>   }
>
> +static void uvc_video_complete_work(struct work_struct *work)
> +{
> +	struct uvc_streaming *stream = container_of(work, struct uvc_streaming,
> +								urb_work);
> +	struct urb *urb;
> +	unsigned long flags;
> +	int i;
> +
> +	for (i = 0; i < UVC_URBS; i++) {
> +		spin_lock_irqsave(&stream->urb_list_lock, flags);
> +		if (list_empty(&stream->urb_complete_list)) {
> +			spin_unlock_irqrestore(&stream->urb_list_lock, flags);
> +			return;
> +		}
> +		urb = list_first_entry(&stream->urb_complete_list,
> +							struct urb, urb_list);
> +		list_del(&urb->urb_list);
> +		spin_unlock_irqrestore(&stream->urb_list_lock, flags);
> +
> +		uvc_video_complete(urb->context);
> +	}
> +}
> +
>   /*
>    * Free transfer buffers.
>    */
> @@ -1448,14 +1489,28 @@ static void uvc_uninit_video(struct uvc_streaming *stream, int free_buffers)
>
>   	uvc_video_stats_stop(stream);
>
> +	/* set stop and make sure no urb is being submitted.*/
> +	stream->stop = true;
> +	flush_work(&stream->urb_work);
> +
>   	for (i = 0; i < UVC_URBS; ++i) {
> -		urb = stream->urb[i];
> +		urb = stream->uvc_urb[i].urb;
>   		if (urb == NULL)
>   			continue;
>
>   		usb_kill_urb(urb);
> +	}
> +
> +	/* Finish all kill callbacks */
> +	flush_work(&stream->urb_work);
> +
> +	for (i = 0; i < UVC_URBS; ++i) {
> +		urb = stream->uvc_urb[i].urb;
> +		if (urb == NULL)
> +			continue;
> +
>   		usb_free_urb(urb);
> -		stream->urb[i] = NULL;
> +		stream->uvc_urb[i].urb = NULL;
>   	}
>
>   	if (free_buffers)
> @@ -1514,7 +1569,7 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream,
>   		}
>
>   		urb->dev = stream->dev->udev;
> -		urb->context = stream;
> +		urb->context = &stream->uvc_urb[i];
>   		urb->pipe = usb_rcvisocpipe(stream->dev->udev,
>   				ep->desc.bEndpointAddress);
>   #ifndef CONFIG_DMA_NONCOHERENT
> @@ -1525,7 +1580,7 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream,
>   #endif
>   		urb->interval = ep->desc.bInterval;
>   		urb->transfer_buffer = stream->urb_buffer[i];
> -		urb->complete = uvc_video_complete;
> +		urb->complete = uvc_urb_complete;
>   		urb->number_of_packets = npackets;
>   		urb->transfer_buffer_length = size;
>
> @@ -1534,7 +1589,8 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream,
>   			urb->iso_frame_desc[j].length = psize;
>   		}
>
> -		stream->urb[i] = urb;
> +		stream->uvc_urb[i].urb = urb;
> +		stream->uvc_urb[i].stream = stream;
>   	}
>
>   	return 0;
> @@ -1580,14 +1636,15 @@ static int uvc_init_video_bulk(struct uvc_streaming *stream,
>   		}
>
>   		usb_fill_bulk_urb(urb, stream->dev->udev, pipe,
> -			stream->urb_buffer[i], size, uvc_video_complete,
> -			stream);
> +			stream->urb_buffer[i], size, uvc_urb_complete,
> +			&stream->uvc_urb[i]);
>   #ifndef CONFIG_DMA_NONCOHERENT
>   		urb->transfer_flags = URB_NO_TRANSFER_DMA_MAP;
>   		urb->transfer_dma = stream->urb_dma[i];
>   #endif
>
> -		stream->urb[i] = urb;
> +		stream->uvc_urb[i].urb = urb;
> +		stream->uvc_urb[i].stream = stream;
>   	}
>
>   	return 0;
> @@ -1611,6 +1668,11 @@ static int uvc_init_video(struct uvc_streaming *stream, gfp_t gfp_flags)
>
>   	uvc_video_stats_start(stream);
>
> +	INIT_WORK(&stream->urb_work, uvc_video_complete_work);
> +	INIT_LIST_HEAD(&stream->urb_complete_list);
> +	spin_lock_init(&stream->urb_list_lock);
> +	stream->stop = false;
> +
>   	if (intf->num_altsetting > 1) {
>   		struct usb_host_endpoint *best_ep = NULL;
>   		unsigned int best_psize = UINT_MAX;
> @@ -1678,7 +1740,7 @@ static int uvc_init_video(struct uvc_streaming *stream, gfp_t gfp_flags)
>
>   	/* Submit the URBs. */
>   	for (i = 0; i < UVC_URBS; ++i) {
> -		ret = usb_submit_urb(stream->urb[i], gfp_flags);
> +		ret = usb_submit_urb(stream->uvc_urb[i].urb, gfp_flags);
>   		if (ret < 0) {
>   			uvc_printk(KERN_ERR, "Failed to submit URB %u "
>   					"(%d).\n", i, ret);
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index 816dd1a..b73c0ab 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -440,6 +440,13 @@ struct uvc_stats_stream {
>   	unsigned int max_sof;		/* Maximum STC.SOF value */
>   };
>
> +struct uvc_urb {
> +	struct urb *urb;
> +	struct uvc_streaming *stream;
> +	struct timespec ts;
> +	u16 sof;
> +};
> +
>   struct uvc_streaming {
>   	struct list_head list;
>   	struct uvc_device *dev;
> @@ -470,7 +477,7 @@ struct uvc_streaming {
>   	/* Buffers queue. */
>   	unsigned int frozen : 1;
>   	struct uvc_video_queue queue;
> -	void (*decode) (struct urb *urb, struct uvc_streaming *video,
> +	void (*decode)(struct uvc_urb *uu, struct uvc_streaming *video,
>   			struct uvc_buffer *buf);
>
>   	/* Context data used by the bulk completion handler. */
> @@ -482,7 +489,11 @@ struct uvc_streaming {
>   		__u32 max_payload_size;
>   	} bulk;
>
> -	struct urb *urb[UVC_URBS];
> +	bool stop;
> +	spinlock_t urb_list_lock;
> +	struct list_head urb_complete_list;
> +	struct work_struct urb_work;
> +	struct uvc_urb uvc_urb[UVC_URBS];
>   	char *urb_buffer[UVC_URBS];
>   	dma_addr_t urb_dma[UVC_URBS];
>   	unsigned int urb_size;
> @@ -728,7 +739,7 @@ extern struct usb_host_endpoint *uvc_find_endpoint(
>   		struct usb_host_interface *alts, __u8 epaddr);
>
>   /* Quirks support */
> -void uvc_video_decode_isight(struct urb *urb, struct uvc_streaming *stream,
> +void uvc_video_decode_isight(struct uvc_urb *uu, struct uvc_streaming *stream,
>   		struct uvc_buffer *buf);
>
>   /* debugfs and statistics */
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html