| /* |
| * Copyright (c) 2004, 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. |
| */ |
| |
| /* |
| * |
| * @summary Thiseclass is used to synchronize execution off two threads. |
| * @author Swamy Venkataramanappa |
| */ |
| |
| import java.util.concurrent.Semaphore; |
| |
| public class ThreadExecutionSynchronizer { |
| |
| private boolean waiting; |
| private Semaphore semaphore; |
| |
| public ThreadExecutionSynchronizer() { |
| semaphore = new Semaphore(1); |
| waiting = false; |
| } |
| |
| // Synchronizes two threads execution points. |
| // Basically any thread could get scheduled to run and |
| // it is not possible to know which thread reaches expected |
| // execution point. So whichever thread reaches a execution |
| // point first wait for the second thread. When the second thread |
| // reaches the expected execution point will wake up |
| // the thread which is waiting here. |
| void stopOrGo() { |
| semaphore.acquireUninterruptibly(); // Thread can get blocked. |
| if (!waiting) { |
| waiting = true; |
| // Wait for second thread to enter this method. |
| while(!semaphore.hasQueuedThreads()) { |
| try { |
| Thread.sleep(20); |
| } catch (InterruptedException xx) {} |
| } |
| semaphore.release(); |
| } else { |
| waiting = false; |
| semaphore.release(); |
| } |
| } |
| |
| // Wrapper function just for code readability. |
| void waitForSignal() { |
| stopOrGo(); |
| goSleep(50); |
| } |
| |
| void signal() { |
| stopOrGo(); |
| goSleep(50); |
| } |
| |
| private static void goSleep(long ms) { |
| try { |
| Thread.sleep(ms); |
| } catch (InterruptedException e) { |
| e.printStackTrace(); |
| System.out.println("Unexpected exception."); |
| } |
| } |
| } |