--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/hotspot/jtreg/vmTestbase/nsk/share/gc/lock/CriticalSectionLocker.java	Mon Apr 30 18:10:24 2018 -0700
@@ -0,0 +1,127 @@
+/*
+ * Copyright (c) 2007, 2018, 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.
+ */
+
+package nsk.share.gc.lock;
+
+import nsk.share.TestBug;
+import nsk.share.gc.lock.Locker;
+
+/**
+ * CriticalSectionLocker represents a way to lock a resource
+ * by entering some critical section.
+ */
+public abstract class CriticalSectionLocker<T> implements Locker<T> {
+        private transient boolean enabled = false;
+        private transient boolean locked = false;
+        private Object sync = new Object();
+        private Thread thread;
+        private Throwable exception;
+
+        private final Runnable runnable = new Runnable() {
+                public void run() {
+                        //System.out.println("Running");
+                        try {
+                                do {
+                                        synchronized (sync) {
+                                                while (enabled && !locked) {
+                                                        try {
+                                                                sync.wait();
+                                                        } catch (InterruptedException e) {
+                                                        }
+                                                }
+                                                if (!enabled)
+                                                        break;
+                                        }
+                                        do {
+                                                criticalSection();
+                                        } while (locked);
+                                } while (enabled);
+                        //      System.out.println("Exiting");
+                        } catch (RuntimeException t) {
+                                t.printStackTrace();
+                                exception = t;
+                                throw t;
+                        }
+                }
+        };
+
+        public CriticalSectionLocker() {
+        }
+
+        /**
+         * Enter critical section.
+         *
+         */
+        protected abstract void criticalSection();
+
+        public void enable() {
+                synchronized (sync) {
+                        if (enabled)
+                                throw new TestBug("Locker already enabled.");
+//                      System.out.println("Enabling " + this);
+                        enabled = true;
+                        thread = new Thread(runnable, "Locker: " + runnable);
+                        thread.setDaemon(true);
+                        thread.start();
+                }
+        }
+
+        public void lock() {
+                synchronized (sync) {
+                        if (locked)
+                                throw new TestBug("Locker already locked.");
+//                      System.out.println("Locking " + this);
+                        locked = true;
+                        sync.notifyAll();
+                }
+        }
+
+        public void unlock() {
+                synchronized (sync) {
+                        if (!locked)
+                                throw new TestBug("Locker not locked.");
+//                      System.out.println("Unocking " + this);
+                        locked = false;
+                        sync.notifyAll();
+                }
+        }
+
+        public void disable() {
+                synchronized (sync) {
+                        if (!enabled)
+                                throw new TestBug("Locker not enabled.");
+//                      System.out.println("Disabling " + this);
+                        enabled = false;
+                        sync.notifyAll();
+                }
+                try {
+                        thread.join();
+                } catch (InterruptedException e) {
+                        throw new TestBug(e);
+                }
+        }
+
+        public Throwable getException() {
+                return exception;
+        }
+}