--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/test/javax/security/auth/Subject/Synch.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,74 @@
+/*
+ * Copyright 2003 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.
+ *
+ * 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.
+ */
+
+/*
+ * @test
+ * @bug 4893489
+ * @summary     Subject.doAs not thread-safe against changes to principals
+ */
+
+import java.security.Principal;
+import java.security.PrivilegedAction;
+import java.util.Collections;
+import java.util.Set;
+import javax.security.auth.Subject;
+import javax.security.auth.x500.X500Principal;
+
+public class Synch {
+    public static void main(String[] args) {
+        Subject subject = new Subject();
+        final Set principals = subject.getPrincipals();
+        principals.add(new X500Principal("CN=Alice"));
+        new Thread() {
+            { setDaemon(true); }
+            public void run() {
+                Principal last = new X500Principal("CN=Bob");
+                for (int i = 0; true; i++) {
+                    Principal next = new X500Principal("CN=Bob" + i);
+                    principals.add(next);
+                    principals.remove(last);
+                    last = next;
+                }
+            }
+        }.start();
+        for (int i = 0; i < 1000; i++) {
+            Subject.doAs(
+                subject,
+                new PrivilegedAction() {
+                    public Object run() {
+                        return Subject.doAs(
+                            new Subject(true,
+                                        Collections.singleton(
+                                            new X500Principal("CN=Claire")),
+                                        Collections.EMPTY_SET,
+                                        Collections.EMPTY_SET),
+                            new PrivilegedAction() {
+                                public Object run() {
+                                    return null;
+                                }
+                            });
+                    }
+                });
+        }
+    }
+}