5031664: Increase thread safety of EventListenerList

Reviewed-by: azvegint

src/java.desktop/share/classes/javax/swing/event/EventListenerList.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -102,7 +102,7 @@ public class EventListenerList implements Serializable {
     /* A null array to be shared by all empty listener lists*/
     private static final Object[] NULL_ARRAY = new Object[0];
     /** The list of ListenerType - Listener pairs */
-    protected transient Object[] listenerList = NULL_ARRAY;
+    protected transient volatile Object[] listenerList = NULL_ARRAY;
 
     /**
      * Passes back the event listener list as an array

test/jdk/javax/swing/event/EventListenerList/GetUpToDateData.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+import java.awt.event.AWTEventListener;
+import java.util.EventListener;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import javax.swing.event.EventListenerList;
+
+/**
+ * @test
+ * @bug 5031664
+ * @summary EventListenerList.getXXX should always return up to date data
+ */
+public final class GetUpToDateData {
+
+    static final EventListenerList listeners = new EventListenerList();
+
+    static final EventListener o1 = new EventListener() {
+    };
+    static final AWTEventListener o2 = event -> {
+    };
+
+    public static void main(final String[] args) throws Exception {
+        CountDownLatch go = new CountDownLatch(3);
+
+        Thread t1 = new Thread(() -> {
+            try {
+                // Time to warm-up t3, t4, t5
+                Thread.sleep(2000);
+            } catch (InterruptedException e) {
+            }
+            listeners.add(EventListener.class, o1);
+        });
+        Thread t2 = new Thread(() -> {
+            try {
+                // Time to warm-up t3, t4, t5
+                Thread.sleep(2000);
+            } catch (InterruptedException e) {
+            }
+            listeners.add(AWTEventListener.class, o2);
+        });
+
+        Thread t3 = new Thread(() -> {
+            while (listeners.getListenerCount() != 2) {
+            }
+            go.countDown();
+        });
+        Thread t4 = new Thread(() -> {
+            while (listeners.getListeners(EventListener.class).length != 1
+                    || listeners.getListeners(EventListener.class)[0] != o1) {
+            }
+            go.countDown();
+        });
+        Thread t5 = new Thread(() -> {
+            while (listeners.getListeners(AWTEventListener.class).length != 1
+                    || listeners.getListeners(AWTEventListener.class)[0] != o2) {
+            }
+            go.countDown();
+        });
+
+        t1.setDaemon(true);
+        t2.setDaemon(true);
+        t3.setDaemon(true);
+        t4.setDaemon(true);
+        t5.setDaemon(true);
+
+        t1.start();
+        t2.start();
+        t3.start();
+        t4.start();
+        t5.start();
+        if (!go.await(10, TimeUnit.SECONDS)) {
+            throw new RuntimeException("The test hangs");
+        }
+    }
+}