Avoid locking in callback (#588)

pkg/rtc/mediatracksubscriptions.go

@@ -109,13 +109,13 @@ func (t *MediaTrackSubscriptions) AddSubscriber(sub types.LocalParticipant, code
 	trackID := t.params.MediaTrack.ID()
 	subscriberID := sub.ID()
 
-	t.subscribedTracksMu.Lock()
-	defer t.subscribedTracksMu.Unlock()
-
 	// don't subscribe to the same track multiple times
+	t.subscribedTracksMu.Lock()
 	if _, ok := t.subscribedTracks[subscriberID]; ok {
+		t.subscribedTracksMu.Unlock()
 		return nil, nil
 	}
+	t.subscribedTracksMu.Unlock()
 
 	var rtcpFeedback []webrtc.RTCPFeedback
 	switch t.params.MediaTrack.Kind() {
@@ -257,7 +257,9 @@ func (t *MediaTrackSubscriptions) AddSubscriber(sub types.LocalParticipant, code
 		sub.Negotiate()
 	})
 
+	t.subscribedTracksMu.Lock()
 	t.subscribedTracks[subscriberID] = subTrack
+	t.subscribedTracksMu.Unlock()
 	subTrack.SetPublisherMuted(t.params.MediaTrack.IsMuted())
 
 	// since sub will lock, run it in a goroutine to avoid deadlocks

pkg/rtc/participant.go

@@ -1216,8 +1216,22 @@ func (p *ParticipantImpl) onSubscribedMaxQualityChange(trackID livekit.TrackID,
 		SubscribedQualities: subscribedQualities,
 	}
 
-	p.params.Telemetry.TrackMaxSubscribedVideoQuality(context.Background(), p.ID(), &livekit.TrackInfo{Sid: string(trackID), Type: livekit.TrackType_VIDEO}, maxSubscribedQuality)
+	p.params.Telemetry.TrackMaxSubscribedVideoQuality(
+		context.Background(),
+		p.ID(),
+		&livekit.TrackInfo{
+			Sid:  string(trackID),
+			Type: livekit.TrackType_VIDEO,
+		},
+		maxSubscribedQuality,
+	)
 
+	p.params.Logger.Debugw(
+		"sending max subscribed quality",
+		"trackID", trackID,
+		"qualities", subscribedQualities,
+		"max", maxSubscribedQuality,
+	)
 	return p.writeMessage(&livekit.SignalResponse{
 		Message: &livekit.SignalResponse_SubscribedQualityUpdate{
 			SubscribedQualityUpdate: subscribedQualityUpdate,