diff -r fd16c54261b3 -r 90ce3da70b43 jdk/src/share/classes/com/sun/tools/jdi/MonitorInfoImpl.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/com/sun/tools/jdi/MonitorInfoImpl.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2005 Sun Microsystems, Inc.  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.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package com.sun.tools.jdi;
+
+import com.sun.jdi.*;
+
+public class MonitorInfoImpl extends MirrorImpl
+    implements MonitorInfo, ThreadListener {
+
+    /* Once false, monitorInfo should not be used.
+     * access synchronized on (vm.state())
+     */
+    private boolean isValid = true;
+
+    ObjectReference monitor;
+    ThreadReference thread;
+    int  stack_depth;
+
+    MonitorInfoImpl(VirtualMachine vm, ObjectReference mon,
+                    ThreadReference thread, int dpth) {
+        super(vm);
+        this.monitor = mon;
+        this.thread = thread;
+        this.stack_depth = dpth;
+    }
+
+
+    /*
+     * ThreadListener implementation
+     * Must be synchronized since we must protect against
+     * sending defunct (isValid == false) stack ids to the back-end.
+     */
+    public boolean threadResumable(ThreadAction action) {
+        synchronized (vm.state()) {
+            if (isValid) {
+                isValid = false;
+                return false;   /* remove this stack frame as a listener */
+            } else {
+                throw new InternalException(
+                                  "Invalid stack frame thread listener");
+            }
+        }
+    }
+
+    private void validateMonitorInfo() {
+        if (!isValid) {
+            throw new InvalidStackFrameException("Thread has been resumed");
+        }
+    }
+
+    public ObjectReference monitor() {
+        validateMonitorInfo();
+        return monitor;
+    }
+
+    public int stackDepth() {
+        validateMonitorInfo();
+        return stack_depth;
+    }
+
+    public ThreadReference thread() {
+        validateMonitorInfo();
+        return thread;
+    }
+}