ALSA: line6: Fix -EBUSY error during active monitoring

When a monitor stream is active, the next PCM stream access results in
EBUSY error because of the check in line6_stream_start().  Fix this by
just skipping the submission of pending URBs when the stream is
already running instead.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=101431
Cc: <stable@vger.kernel.org> # v4.0+
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/line6/pcm.c

@@ -186,12 +186,8 @@ static int line6_stream_start(struct snd_line6_pcm *line6pcm, int direction,
 	int ret = 0;
 
 	spin_lock_irqsave(&pstr->lock, flags);
-	if (!test_and_set_bit(type, &pstr->running)) {
-		if (pstr->active_urbs || pstr->unlink_urbs) {
-			ret = -EBUSY;
-			goto error;
-		}
-
+	if (!test_and_set_bit(type, &pstr->running) &&
+	    !(pstr->active_urbs || pstr->unlink_urbs)) {
 		pstr->count = 0;
 		/* Submit all currently available URBs */
 		if (direction == SNDRV_PCM_STREAM_PLAYBACK)
@@ -199,7 +195,6 @@ static int line6_stream_start(struct snd_line6_pcm *line6pcm, int direction,
 		else
 			ret = line6_submit_audio_in_all_urbs(line6pcm);
 	}
- error:
 	if (ret < 0)
 		clear_bit(type, &pstr->running);
 	spin_unlock_irqrestore(&pstr->lock, flags);