linux-kernel - [PATCH 4.9 096/105] ALSA: usb-audio: test EP_FLAG

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Message-Id: <20170804231557.720738355@linuxfoundation.org>
Date:   Fri,  4 Aug 2017 16:16:04 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ioan-Adrian Ratiu <adi@...rat.com>,
        Takashi Iwai <tiwai@...e.de>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 096/105] ALSA: usb-audio: test EP_FLAG_RUNNING at urb completion

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ioan-Adrian Ratiu <adi@...rat.com>


[ 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@...rat.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 sound/usb/endpoint.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -384,6 +384,9 @@ static void snd_complete_urb(struct 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 */