--- a/src/share/classes/com/sun/jmx/remote/internal/ServerNotifForwarder.java	Fri Dec 28 03:50:57 2012 -0800
+++ b/src/share/classes/com/sun/jmx/remote/internal/ServerNotifForwarder.java	Fri Dec 28 16:44:27 2012 +0100
@@ -25,16 +25,15 @@
 
 package com.sun.jmx.remote.internal;
 
-import com.sun.jmx.mbeanserver.Util;
 import com.sun.jmx.remote.security.NotificationAccessController;
 import com.sun.jmx.remote.util.ClassLogger;
 import com.sun.jmx.remote.util.EnvHelp;
 import java.io.IOException;
 import java.security.AccessControlContext;
 import java.security.AccessController;
-import java.security.PrivilegedAction;
 import java.security.PrivilegedActionException;
 import java.security.PrivilegedExceptionAction;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -291,13 +290,18 @@
     // so that we can know too, and remove the corresponding entry from the listenerMap.
     // See 6957378.
     private void snoopOnUnregister(NotificationResult nr) {
-        Set<IdAndFilter> delegateSet = listenerMap.get(MBeanServerDelegate.DELEGATE_NAME);
-        if (delegateSet == null || delegateSet.isEmpty()) {
-            return;
+        List<IdAndFilter> copy = null;
+        synchronized (listenerMap) {
+            Set<IdAndFilter> delegateSet = listenerMap.get(MBeanServerDelegate.DELEGATE_NAME);
+            if (delegateSet == null || delegateSet.isEmpty()) {
+                return;
+            }
+            copy = new ArrayList<>(delegateSet);
         }
+
         for (TargetedNotification tn : nr.getTargetedNotifications()) {
             Integer id = tn.getListenerID();
-            for (IdAndFilter idaf : delegateSet) {
+            for (IdAndFilter idaf : copy) {
                 if (idaf.id == id) {
                     // This is a notification from the MBeanServerDelegate.
                     Notification n = tn.getNotification();

--- a/test/ProblemList.txt	Fri Dec 28 03:50:57 2012 -0800
+++ b/test/ProblemList.txt	Fri Dec 28 16:44:27 2012 +0100
@@ -148,9 +148,6 @@
 # 6959636
 javax/management/loading/LibraryLoader/LibraryLoaderTest.java	windows-all
 
-# 7120365
-javax/management/remote/mandatory/notif/DiffHBTest.java 	generic-all
-
 ############################################################################
 
 # jdk_math

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/javax/management/remote/mandatory/notif/ConcurrentModificationTest.java	Fri Dec 28 16:44:27 2012 +0100
@@ -0,0 +1,167 @@
+/*
+ * Copyright (c) 2012, 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.
+ */
+
+/*
+ * @test
+ * @bug 7120365
+ * @summary test on Concurrent Modification
+ * @author Shanliang JIANG
+ * @run main ConcurrentModificationTest
+ */
+
+import java.net.MalformedURLException;
+import java.util.ConcurrentModificationException;
+import javax.management.MBeanServer;
+import javax.management.MBeanServerConnection;
+import javax.management.MBeanServerFactory;
+import javax.management.Notification;
+import javax.management.NotificationListener;
+import javax.management.ObjectName;
+import javax.management.remote.JMXConnector;
+import javax.management.remote.JMXConnectorFactory;
+import javax.management.remote.JMXConnectorServer;
+import javax.management.remote.JMXConnectorServerFactory;
+import javax.management.remote.JMXServiceURL;
+
+/**
+ *
+ */
+public class ConcurrentModificationTest {
+    private static final String[] protocols = {"rmi", "iiop", "jmxmp"};
+    private static int number = 100;
+
+    private static final MBeanServer mbs = MBeanServerFactory.createMBeanServer();
+    private static ObjectName delegateName;
+    private static ObjectName[] timerNames = new ObjectName[number];
+    private static NotificationListener[] listeners = new NotificationListener[number];
+
+    private static Throwable uncaughtException = null;
+
+    public static void main(String[] args) throws Exception {
+        System.out.println(">>> test on Concurrent Modification.");
+
+        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
+            @Override
+            public void uncaughtException(Thread t, Throwable e) {
+                e.printStackTrace();
+                if (e instanceof ConcurrentModificationException) {
+                    uncaughtException = e;
+                }
+            }
+        });
+
+        delegateName = new ObjectName("JMImplementation:type=MBeanServerDelegate");
+        for (int i=0; i<number; i++) {
+            timerNames[i] = new ObjectName("MBean:name=Timer"+i);
+            listeners[i] = new NotificationListener() {
+                @Override
+                public void handleNotification(Notification notification, Object handback) {
+                    // nothing
+                }
+            };
+        }
+        String errors = "";
+
+        for (int i = 0; i < protocols.length; i++) {
+            uncaughtException = null;
+            System.out.println(">>> Test for protocol " + protocols[i]);
+            test(protocols[i]);
+            if (uncaughtException != null) {
+                if ("".equals(errors)) {
+                    errors = "Failed to " + protocols[i] + ": "+uncaughtException;
+                } else {
+                    errors = errors+", failed to " + protocols[i] + ": "+uncaughtException;
+                }
+                System.out.println(">>> FAILED for protocol " + protocols[i]);
+            } else {
+                System.out.println(">>> PASSED for protocol " + protocols[i]);
+            }
+        }
+
+        if ("".equals(errors)) {
+            System.out.println("All Passed!");
+        } else {
+            System.out.println("!!!!!! Failed.");
+
+            throw new RuntimeException(errors);
+        }
+    }
+
+    private static void test(String proto) throws Exception {
+        JMXServiceURL u = new JMXServiceURL(proto, null, 0);
+        JMXConnectorServer server;
+        JMXConnector client;
+
+        try {
+            server =
+                    JMXConnectorServerFactory.newJMXConnectorServer(u, null, mbs);
+            server.start();
+            JMXServiceURL addr = server.getAddress();
+            client = JMXConnectorFactory.connect(addr, null);
+        } catch (MalformedURLException e) {
+            System.out.println(">>> not support: " + proto);
+            return;
+        }
+
+        final MBeanServerConnection mserver = client.getMBeanServerConnection();
+
+        int count = 0;
+        boolean adding = true;
+        while (uncaughtException == null && count++ < 10) {
+            for (int i = 0; i < number; i++) {
+                listenerOp(mserver, listeners[i], adding);
+                mbeanOp(mserver, timerNames[i], adding);
+            }
+            adding = !adding;
+        }
+
+        if (uncaughtException != null) { // clean
+            for (int i = 0; i < number; i++) {
+                try {
+                    mbeanOp(mserver, timerNames[i], false);
+                } catch (Exception e) {
+                }
+            }
+        }
+        client.close();
+        server.stop();
+    }
+
+    private static void mbeanOp(MBeanServerConnection mserver, ObjectName name, boolean adding)
+            throws Exception {
+        if (adding) {
+            mserver.createMBean("javax.management.timer.Timer", name);
+        } else {
+            mserver.unregisterMBean(name);
+        }
+    }
+
+    private static void listenerOp(MBeanServerConnection mserver, NotificationListener listener, boolean adding)
+            throws Exception {
+        if (adding) {
+            mserver.addNotificationListener(delegateName, listener, null, null);
+        } else {
+            mserver.removeNotificationListener(delegateName, listener);
+        }
+    }
+}
\ No newline at end of file