0N/A/*
2362N/A * Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
0N/A * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
0N/A *
0N/A * This code is free software; you can redistribute it and/or modify it
0N/A * under the terms of the GNU General Public License version 2 only, as
0N/A * published by the Free Software Foundation.
0N/A *
0N/A * This code is distributed in the hope that it will be useful, but WITHOUT
0N/A * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
0N/A * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
0N/A * version 2 for more details (a copy is included in the LICENSE file that
0N/A * accompanied this code).
0N/A *
0N/A * You should have received a copy of the GNU General Public License version
0N/A * 2 along with this work; if not, write to the Free Software Foundation,
0N/A * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
0N/A *
2362N/A * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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0N/A */
0N/A
0N/A/*
0N/A *
0N/A * @summary Thiseclass is used to synchronize execution off two threads.
0N/A * @author Swamy Venkataramanappa
0N/A */
0N/A
0N/Aimport java.util.concurrent.Semaphore;
0N/A
0N/Apublic class ThreadExecutionSynchronizer {
0N/A
0N/A private boolean waiting;
0N/A private Semaphore semaphore;
0N/A
0N/A public ThreadExecutionSynchronizer() {
0N/A semaphore = new Semaphore(1);
0N/A waiting = false;
0N/A }
0N/A
0N/A // Synchronizes two threads execution points.
0N/A // Basically any thread could get scheduled to run and
0N/A // it is not possible to know which thread reaches expected
0N/A // execution point. So whichever thread reaches a execution
0N/A // point first wait for the second thread. When the second thread
0N/A // reaches the expected execution point will wake up
0N/A // the thread which is waiting here.
0N/A void stopOrGo() {
0N/A semaphore.acquireUninterruptibly(); // Thread can get blocked.
0N/A if (!waiting) {
0N/A waiting = true;
0N/A // Wait for second thread to enter this method.
0N/A while(!semaphore.hasQueuedThreads()) {
0N/A try {
0N/A Thread.sleep(20);
0N/A } catch (InterruptedException xx) {}
0N/A }
0N/A semaphore.release();
0N/A } else {
0N/A waiting = false;
0N/A semaphore.release();
0N/A }
0N/A }
0N/A
0N/A // Wrapper function just for code readability.
0N/A void waitForSignal() {
0N/A stopOrGo();
0N/A goSleep(50);
0N/A }
0N/A
0N/A void signal() {
0N/A stopOrGo();
0N/A goSleep(50);
0N/A }
0N/A
0N/A private static void goSleep(long ms) {
0N/A try {
0N/A Thread.sleep(ms);
0N/A } catch (InterruptedException e) {
0N/A e.printStackTrace();
0N/A System.out.println("Unexpected exception.");
0N/A }
0N/A }
0N/A}