[alsa-devel] [PATCH v2] usb-audio: not submit urb for stopped endpoint

[Henry Lin]

While output urb's snd_complete_urb() is executing, calling
prepare_outbound_urb() may cause endpoint stopped before
prepare_outbound_urb() returns and result in next urb submitted
to stopped endpoint. usb-audio driver cannot re-use it afterwards as
the urb is still hold by usb stack.

This change checks EP_FLAG_RUNNING flag after prepare_outbound_urb() again
to let snd_complete_urb() know the endpoint already stopped and does not
submit next urb. Below kind of error will be fixed:

[  213.153103] usb 1-2: timeout: still 1 active urbs on EP #1
[  213.164121] usb 1-2: cannot submit urb 0, error -16: unknown error

Signed-off-by: Henry Lin <henryl at nvidia.com>
---
 sound/usb/endpoint.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index a2ab8e8d3a93..4a9a2f6ef5a4 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -388,6 +388,9 @@ static void snd_complete_urb(struct urb *urb)
 		}
 
 		prepare_outbound_urb(ep, ctx);
+		/* can be stopped during prepare callback */
+		if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
+			goto exit_clear;
 	} else {
 		retire_inbound_urb(ep, ctx);
 		/* can be stopped during retire callback */
-- 
2.17.1