Handle state changes atomically

src/dtlstransport.cpp

@@ -112,8 +112,8 @@ bool DtlsTransport::send(message_ptr message) {
 void DtlsTransport::incoming(message_ptr message) { mIncomingQueue.push(message); }
 
 void DtlsTransport::changeState(State state) {
-	mState = state;
-	mStateChangeCallback(state);
+	if (mState.exchange(state) != state)
+		mStateChangeCallback(state);
 }
 
 void DtlsTransport::runRecvLoop() {

src/icetransport.cpp

@@ -226,8 +226,8 @@ void IceTransport::outgoing(message_ptr message) {
 }
 
 void IceTransport::changeState(State state) {
-	mState = state;
-	mStateChangeCallback(mState);
+	if (mState.exchange(state) != state)
+		mStateChangeCallback(mState);
 }
 
 void IceTransport::changeGatheringState(GatheringState state) {

src/peerconnection.cpp

@@ -363,14 +363,12 @@ void PeerConnection::triggerDataChannel(weak_ptr<PeerConnection> weak_this, weak
 }
 
 void PeerConnection::changeState(State state) {
-	mState = state;
-	if (mStateChangeCallback)
+	if (mState.exchange(state) != state && mStateChangeCallback)
 		mStateChangeCallback(state);
 }
 
 void PeerConnection::changeGatheringState(GatheringState state) {
-	mGatheringState = state;
-	if (mGatheringStateChangeCallback)
+	if (mGatheringState.exchange(state) != state && mGatheringStateChangeCallback)
 		mGatheringStateChangeCallback(state);
 }
 

src/sctptransport.cpp

@@ -178,8 +178,8 @@ void SctpTransport::incoming(message_ptr message) {
 }
 
 void SctpTransport::changeState(State state) {
-	mState = state;
-	mStateChangeCallback(state);
+	if (mState.exchange(state) != state)
+		mStateChangeCallback(state);
 }
 
 void SctpTransport::runConnectAndSendLoop() {