| /* |
| * Copyright (c) 2005, 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 MonitorDeadlock creates threads that are deadlocked on |
| * object monitors. |
| * @author Mandy Chung |
| * @build Barrier |
| */ |
| |
| import java.lang.management.*; |
| import java.util.*; |
| |
| public class MonitorDeadlock { |
| |
| private final int EXPECTED_THREADS = 3; |
| private Barrier go = new Barrier(1); |
| private Barrier barr = new Barrier(EXPECTED_THREADS); |
| |
| private Object a = new Object(); |
| private Object b = new Object(); |
| private Object c = new Object(); |
| private Thread[] dThreads = new Thread[EXPECTED_THREADS]; |
| |
| public MonitorDeadlock() { |
| dThreads[0] = new DeadlockingThread("MThread-1", a, b); |
| dThreads[1] = new DeadlockingThread("MThread-2", b, c); |
| dThreads[2] = new DeadlockingThread("MThread-3", c, a); |
| |
| // make them daemon threads so that the test will exit |
| for (int i = 0; i < EXPECTED_THREADS; i++) { |
| dThreads[i].setDaemon(true); |
| dThreads[i].start(); |
| } |
| } |
| |
| void goDeadlock() { |
| // Wait until all threads have started |
| barr.await(); |
| |
| // reset for later signals |
| barr.set(EXPECTED_THREADS); |
| |
| while (go.getWaiterCount() != EXPECTED_THREADS) { |
| synchronized(this) { |
| try { |
| wait(100); |
| } catch (InterruptedException e) { |
| // ignore |
| } |
| } |
| } |
| |
| // sleep a little so that all threads are blocked before notified. |
| try { |
| Thread.sleep(100); |
| } catch (InterruptedException e) { |
| // ignore |
| } |
| go.signal(); |
| |
| } |
| |
| void waitUntilDeadlock() { |
| barr.await(); |
| |
| for (int i=0; i < 100; i++) { |
| // sleep a little while to wait until threads are blocked. |
| try { |
| Thread.sleep(100); |
| } catch (InterruptedException e) { |
| // ignore |
| } |
| boolean retry = false; |
| for (Thread t: dThreads) { |
| if (t.getState() == Thread.State.RUNNABLE) { |
| retry = true; |
| break; |
| } |
| } |
| if (!retry) { |
| break; |
| } |
| } |
| } |
| |
| private class DeadlockingThread extends Thread { |
| private final Object lock1; |
| private final Object lock2; |
| |
| DeadlockingThread(String name, Object lock1, Object lock2) { |
| super(name); |
| this.lock1 = lock1; |
| this.lock2 = lock2; |
| } |
| public void run() { |
| f(); |
| } |
| private void f() { |
| synchronized (lock1) { |
| barr.signal(); |
| go.await(); |
| g(); |
| } |
| } |
| private void g() { |
| barr.signal(); |
| synchronized (lock2) { |
| throw new RuntimeException("should not reach here."); |
| } |
| } |
| } |
| |
| void checkResult(long[] threads) { |
| if (threads.length != EXPECTED_THREADS) { |
| throw new RuntimeException("Expected to have " + |
| EXPECTED_THREADS + " to be in the deadlock list"); |
| } |
| boolean[] found = new boolean[EXPECTED_THREADS]; |
| for (int i = 0; i < threads.length; i++) { |
| for (int j = 0; j < dThreads.length; j++) { |
| if (dThreads[j].getId() == threads[i]) { |
| found[j] = true; |
| } |
| } |
| } |
| boolean ok = true; |
| for (int j = 0; j < found.length; j++) { |
| ok = ok && found[j]; |
| } |
| |
| if (!ok) { |
| System.out.print("Returned result is ["); |
| for (int j = 0; j < threads.length; j++) { |
| System.out.print(threads[j] + " "); |
| } |
| System.out.println("]"); |
| |
| System.out.print("Expected result is ["); |
| for (int j = 0; j < threads.length; j++) { |
| System.out.print(dThreads[j] + " "); |
| } |
| System.out.println("]"); |
| throw new RuntimeException("Unexpected result returned " + |
| " by findMonitorDeadlockedThreads method."); |
| } |
| } |
| } |