[PATCH for v4.9 LTS 51/87] ALSA: usb-audio: test EP_FLAG_RUNNING at urb completion

From: Levin, Alexander (Sasha Levin)
Date: Fri Jul 14 2017 - 21:40:49 EST

From: Ioan-Adrian Ratiu <adi@xxxxxxxxxx>

[ Upstream commit 13a6c8328e6056932dc680e447d4c5e8ad9add17 ]

Testing EP_FLAG_RUNNING in snd_complete_urb() before running the completion
logic allows us to save a few cpu cycles by returning early, skipping the
pending urb in case the stream was stopped; the stop logic handles the urb
and sets the completion callbacks to NULL.

Signed-off-by: Ioan-Adrian Ratiu <adi@xxxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
sound/usb/endpoint.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index c5251aaad844..b8044c6034b3 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -384,6 +384,9 @@ static void snd_complete_urb(struct urb *urb)
if (unlikely(atomic_read(&ep->chip->shutdown)))
goto exit_clear;

+ if (unlikely(!test_bit(EP_FLAG_RUNNING, &ep->flags)))
+ goto exit_clear;
if (usb_pipeout(ep->pipe)) {
retire_outbound_urb(ep, ctx);
/* can be stopped during retire callback */