From 6d88154402d82fcc27195dc597c8a1e916628384 Mon Sep 17 00:00:00 2001
From: David Zhao <david@davidzhao.com>
Date: Thu, 24 Feb 2022 15:09:34 -0800
Subject: [PATCH] Reduce lock scope, avoid callbacks under lock (#462)

---
 pkg/rtc/mediatrackreceiver.go | 32 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 19 deletions(-)

diff --git a/pkg/rtc/mediatrackreceiver.go b/pkg/rtc/mediatrackreceiver.go
index badd0fc6b..219ef849b 100644
--- a/pkg/rtc/mediatrackreceiver.go
+++ b/pkg/rtc/mediatrackreceiver.go
@@ -158,11 +158,10 @@ func (t *MediaTrackReceiver) IsMuted() bool {
 func (t *MediaTrackReceiver) SetMuted(muted bool) {
 	t.muted.TrySet(muted)
 
-	t.lock.RLock()
-	if t.receiver != nil {
-		t.receiver.SetUpTrackPaused(muted)
+	receiver := t.Receiver()
+	if receiver != nil {
+		receiver.SetUpTrackPaused(muted)
 	}
-	t.lock.RUnlock()
 
 	t.MediaTrackSubscriptions.SetMuted(muted)
 }
@@ -179,10 +178,9 @@ func (t *MediaTrackReceiver) AddOnClose(f func()) {
 
 // AddSubscriber subscribes sub to current mediaTrack
 func (t *MediaTrackReceiver) AddSubscriber(sub types.LocalParticipant) error {
-	t.lock.RLock()
-	defer t.lock.RUnlock()
+	receiver := t.Receiver()
 
-	if t.receiver == nil {
+	if receiver == nil {
 		// cannot add, no receiver
 		return errors.New("cannot subscribe without a receiver in place")
 	}
@@ -195,7 +193,7 @@ func (t *MediaTrackReceiver) AddSubscriber(sub types.LocalParticipant) error {
 		streamId = PackStreamID(t.PublisherID(), t.ID())
 	}
 
-	downTrack, err := t.MediaTrackSubscriptions.AddSubscriber(sub, t.receiver.Codec(), NewWrappedReceiver(t.receiver, t.ID(), streamId))
+	downTrack, err := t.MediaTrackSubscriptions.AddSubscriber(sub, receiver.Codec(), NewWrappedReceiver(receiver, t.ID(), streamId))
 	if err != nil {
 		return err
 	}
@@ -205,7 +203,7 @@ func (t *MediaTrackReceiver) AddSubscriber(sub types.LocalParticipant) error {
 			downTrack.AddReceiverReportListener(t.handleMaxLossFeedback)
 		}
 
-		t.receiver.AddDownTrack(downTrack)
+		receiver.AddDownTrack(downTrack)
 	}
 	return nil
 }
@@ -346,15 +344,13 @@ func (t *MediaTrackReceiver) DebugInfo() map[string]interface{} {
 
 	info["DownTracks"] = t.MediaTrackSubscriptions.DebugInfo()
 
-	t.lock.RLock()
-	if t.receiver != nil {
-		receiverInfo := t.receiver.DebugInfo()
+	receiver := t.Receiver()
+	if receiver != nil {
+		receiverInfo := receiver.DebugInfo()
 		for k, v := range receiverInfo {
 			info[k] = v
 		}
 	}
-	t.lock.RUnlock()
-
 	return info
 }
 
@@ -370,12 +366,10 @@ func (t *MediaTrackReceiver) OnSubscribedMaxQualityChange(f func(trackID livekit
 		if f != nil && !t.IsMuted() {
 			_ = f(t.ID(), subscribedQualities, maxSubscribedQuality)
 		}
-
-		t.lock.RLock()
-		if t.receiver != nil {
-			t.receiver.SetMaxExpectedSpatialLayer(SpatialLayerForQuality(maxSubscribedQuality))
+		receiver := t.Receiver()
+		if receiver != nil {
+			receiver.SetMaxExpectedSpatialLayer(SpatialLayerForQuality(maxSubscribedQuality))
 		}
-		t.lock.RUnlock()
 	})
 }