Avoid deadlock between SockJS heartbeat and XHR polling

Issue: SPR-14833
(cherry picked from commit 72e1f7e)

Author: jhoeller

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractHttpSockJsSession.java

@@ -51,6 +51,7 @@
  */
 public abstract class AbstractHttpSockJsSession extends AbstractSockJsSession {
 
+	private final Queue<String> messageCache;
 
 	private volatile URI uri;
 
@@ -64,20 +65,13 @@ public abstract class AbstractHttpSockJsSession extends AbstractSockJsSession {
 
 	private volatile String acceptedProtocol;
 
-
 	private volatile ServerHttpResponse response;
 
 	private volatile SockJsFrameFormat frameFormat;
 
-
 	private volatile ServerHttpAsyncRequestControl asyncRequestControl;
 
-	private final Object responseLock = new Object();
-
-	private volatile boolean readyToSend;
-
-
-	private final Queue<String> messageCache;
+	private boolean readyToSend;
 
 
 	public AbstractHttpSockJsSession(String id, SockJsServiceConfig config,
@@ -215,14 +209,10 @@ public void handleInitialRequest(ServerHttpRequest request, ServerHttpResponse r
 				this.frameFormat = frameFormat;
 				this.asyncRequestControl = request.getAsyncRequestControl(response);
 				this.asyncRequestControl.start(-1);
-
 				disableShallowEtagHeaderFilter(request);
-
 				// Let "our" handler know before sending the open frame to the remote handler
 				delegateConnectionEstablished();
-
 				handleRequestInternal(request, response, true);
-
 				// Request might have been reset (e.g. polling sessions do after writing)
 				this.readyToSend = isActive();
 			}
@@ -258,9 +248,7 @@ public void handleSuccessiveRequest(ServerHttpRequest request, ServerHttpRespons
 				this.frameFormat = frameFormat;
 				this.asyncRequestControl = request.getAsyncRequestControl(response);
 				this.asyncRequestControl.start(-1);
-
 				disableShallowEtagHeaderFilter(request);
-
 				handleRequestInternal(request, response, false);
 				this.readyToSend = isActive();
 			}
@@ -332,14 +320,11 @@ protected void disconnect(CloseStatus status) {
 
 	protected void resetRequest() {
 		synchronized (this.responseLock) {
-
 			ServerHttpAsyncRequestControl control = this.asyncRequestControl;
 			this.asyncRequestControl = null;
 			this.readyToSend = false;
 			this.response = null;
-
 			updateLastActiveTime();
-
 			if (control != null && !control.isCompleted()) {
 				if (control.isStarted()) {
 					try {

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/transport/session/AbstractSockJsSession.java

@@ -91,6 +91,8 @@ private enum State {NEW, OPEN, CLOSED}
 
 	protected final Log logger = LogFactory.getLog(getClass());
 
+	protected final Object responseLock = new Object();
+
 	private final String id;
 
 	private final SockJsServiceConfig config;
@@ -109,8 +111,6 @@ private enum State {NEW, OPEN, CLOSED}
 
 	private HeartbeatTask heartbeatTask;
 
-	private final Object heartbeatLock = new Object();
-
 	private volatile boolean heartbeatDisabled;
 
 
@@ -250,7 +250,7 @@ public void disableHeartbeat() {
 	}
 
 	public void sendHeartbeat() throws SockJsTransportFailureException {
-		synchronized (this.heartbeatLock) {
+		synchronized (this.responseLock) {
 			if (isActive() && !this.heartbeatDisabled) {
 				writeFrame(SockJsFrame.heartbeatFrame());
 				scheduleHeartbeat();
@@ -262,7 +262,7 @@ protected void scheduleHeartbeat() {
 		if (this.heartbeatDisabled) {
 			return;
 		}
-		synchronized (this.heartbeatLock) {
+		synchronized (this.responseLock) {
 			cancelHeartbeat();
 			if (!isActive()) {
 				return;
@@ -277,7 +277,7 @@ protected void scheduleHeartbeat() {
 	}
 
 	protected void cancelHeartbeat() {
-		synchronized (this.heartbeatLock) {
+		synchronized (this.responseLock) {
 			if (this.heartbeatFuture != null) {
 				if (logger.isTraceEnabled()) {
 					logger.trace("Cancelling heartbeat in session " + getId());
@@ -445,7 +445,7 @@ private class HeartbeatTask implements Runnable {
 
 		@Override
 		public void run() {
-			synchronized (heartbeatLock) {
+			synchronized (responseLock) {
 				if (!this.expired) {
 					try {
 						sendHeartbeat();