[PATCH 7/9] ALSA: usb-audio: Add spinlock to stop_urbs()

[Takashi Iwai]

In theory, stop_urbs() may be called concurrently.
Although we have the state check beforehand, it's safer to apply
ep->lock during the critical list head manipulations.

Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/usb/endpoint.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 1f757a7eeafe..c32022672319 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -927,6 +927,7 @@ void snd_usb_endpoint_sync_pending_stop(struct snd_usb_endpoint *ep)
 static int stop_urbs(struct snd_usb_endpoint *ep, bool force)
 {
 	unsigned int i;
+	unsigned long flags;
 
 	if (!force && atomic_read(&ep->running))
 		return -EBUSY;
@@ -934,9 +935,11 @@ static int stop_urbs(struct snd_usb_endpoint *ep, bool force)
 	if (!ep_state_update(ep, EP_STATE_RUNNING, EP_STATE_STOPPING))
 		return 0;
 
+	spin_lock_irqsave(&ep->lock, flags);
 	INIT_LIST_HEAD(&ep->ready_playback_urbs);
 	ep->next_packet_head = 0;
 	ep->next_packet_queued = 0;
+	spin_unlock_irqrestore(&ep->lock, flags);
 
 	for (i = 0; i < ep->nurbs; i++) {
 		if (test_bit(i, &ep->active_mask)) {
-- 
2.26.2