linux-kernel - [PATCH v2] usb-audio: not submit urb for stopped endpoint

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Date:   Wed, 13 Nov 2019 10:14:19 +0800
From:   Henry Lin <henryl@...dia.com>
To:     unlisted-recipients:; (no To-header on input)
CC:     Henry Lin <henryl@...dia.com>, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Allison Randal <allison@...utok.net>,
        Richard Fontana <rfontana@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] usb-audio: not submit urb for stopped endpoint

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@...dia.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