remove synchronized locks that may be held while blocking

websocket-resources/src/main/java/org/whispersystems/websocket/session/WebSocketSessionContext.java

@@ -6,6 +6,7 @@ package org.whispersystems.websocket.session;
 
 import java.util.LinkedList;
 import java.util.List;
+import java.util.concurrent.locks.ReentrantLock;
 import javax.annotation.Nullable;
 import org.whispersystems.websocket.WebSocketClient;
 
@@ -13,6 +14,8 @@ public class WebSocketSessionContext {
 
   private final List<WebSocketEventListener> closeListeners = new LinkedList<>();
 
+  private final ReentrantLock lock = new ReentrantLock();
+
   private final WebSocketClient webSocketClient;
 
   private Object authenticated;
@@ -39,21 +42,33 @@ public class WebSocketSessionContext {
     return authenticated;
   }
 
-  public synchronized void addWebsocketClosedListener(WebSocketEventListener listener) {
-    if (!closed) this.closeListeners.add(listener);
-    else         listener.onWebSocketClose(this, 1000, "Closed");
+  public void addWebsocketClosedListener(WebSocketEventListener listener) {
+    lock.lock();
+    try {
+      if (!closed)
+        this.closeListeners.add(listener);
+      else
+        listener.onWebSocketClose(this, 1000, "Closed");
+    } finally {
+      lock.unlock();
+    }
   }
 
   public WebSocketClient getClient() {
     return webSocketClient;
   }
 
-  public synchronized void notifyClosed(int statusCode, String reason) {
-    for (WebSocketEventListener listener : closeListeners) {
-      listener.onWebSocketClose(this, statusCode, reason);
-    }
+  public void notifyClosed(int statusCode, String reason) {
+    lock.lock();
+    try {
+      for (WebSocketEventListener listener : closeListeners) {
+        listener.onWebSocketClose(this, statusCode, reason);
+      }
 
-    closed = true;
+      closed = true;
+    } finally {
+      lock.unlock();
+    }
   }
 
   public interface WebSocketEventListener {