/*
* Copyright (c) 2004, 2011, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This source code is provided to illustrate the usage of a given feature
* or technique and has been deliberately simplified. Additional steps
* required for a production-quality application, such as security checks,
* input validation and proper error handling, might not be present in
* this sample code.
*/
/*
*/
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import java.io.IOException;
/**
* This Deadlock class demonstrates the capability of performing
* deadlock detection programmatically within the application using
* the java.lang.management API.
*
* See ThreadMonitor.java for the use of java.lang.management.ThreadMXBean
* API.
*/
public class Deadlock {
public static void main(String[] argv) {
new Deadlock();
// Now find deadlock
ThreadMonitor monitor = new ThreadMonitor();
boolean found = false;
while (!found) {
found = monitor.findDeadlock();
try {
Thread.sleep(500);
} catch (InterruptedException e) {
System.exit(1);
}
}
System.out.println("\nPress <Enter> to exit this Deadlock program.\n");
waitForEnterPressed();
}
private CyclicBarrier barrier = new CyclicBarrier(6);
public Deadlock() {
DeadlockThread[] dThreads = new DeadlockThread[6];
Monitor a = new Monitor("a");
Monitor b = new Monitor("b");
Monitor c = new Monitor("c");
dThreads[0] = new DeadlockThread("MThread-1", a, b);
dThreads[1] = new DeadlockThread("MThread-2", b, c);
dThreads[2] = new DeadlockThread("MThread-3", c, a);
Lock d = new ReentrantLock();
Lock e = new ReentrantLock();
Lock f = new ReentrantLock();
dThreads[3] = new DeadlockThread("SThread-4", d, e);
dThreads[4] = new DeadlockThread("SThread-5", e, f);
dThreads[5] = new DeadlockThread("SThread-6", f, d);
// make them daemon threads so that the test will exit
for (int i = 0; i < 6; i++) {
dThreads[i].setDaemon(true);
dThreads[i].start();
}
}
class DeadlockThread extends Thread {
private Lock lock1 = null;
private Lock lock2 = null;
private Monitor mon1 = null;
private Monitor mon2 = null;
private boolean useSync;
DeadlockThread(String name, Lock lock1, Lock lock2) {
super(name);
this.lock1 = lock1;
this.lock2 = lock2;
this.useSync = true;
}
DeadlockThread(String name, Monitor mon1, Monitor mon2) {
super(name);
this.mon1 = mon1;
this.mon2 = mon2;
this.useSync = false;
}
@Override
public void run() {
if (useSync) {
syncLock();
} else {
monitorLock();
}
}
private void syncLock() {
lock1.lock();
try {
try {
barrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
System.exit(1);
} catch (BrokenBarrierException e) {
e.printStackTrace();
System.exit(1);
}
goSyncDeadlock();
} finally {
lock1.unlock();
}
}
private void goSyncDeadlock() {
try {
barrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
System.exit(1);
} catch (BrokenBarrierException e) {
e.printStackTrace();
System.exit(1);
}
lock2.lock();
throw new RuntimeException("should not reach here.");
}
private void monitorLock() {
synchronized (mon1) {
try {
barrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
System.exit(1);
} catch (BrokenBarrierException e) {
e.printStackTrace();
System.exit(1);
}
goMonitorDeadlock();
}
}
private void goMonitorDeadlock() {
try {
barrier.await();
} catch (InterruptedException e) {
e.printStackTrace();
System.exit(1);
} catch (BrokenBarrierException e) {
e.printStackTrace();
System.exit(1);
}
synchronized (mon2) {
throw new RuntimeException(getName() + " should not reach here.");
}
}
}
class Monitor {
String name;
Monitor(String name) {
this.name = name;
}
}
private static void waitForEnterPressed() {
try {
boolean done = false;
while (!done) {
char ch = (char) System.in.read();
if (ch<0||ch=='\n') {
done = true;
}
}
}
catch (IOException e) {
e.printStackTrace();
System.exit(0);
}
}
}