/*
* The MIT License
*
* Copyright (c) 2004-2010, Sun Microsystems, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package org.jvnet.hudson.test;
/**
* Lock mechanism to let multiple threads execute phases sequentially.
*
* @author Kohsuke Kawaguchi
*/
public class SequenceLock {
/**
* Currently executing phase N.
*/
private int n;
/**
* This thread is executing the phase
*/
private Thread t;
private boolean aborted;
/**
* Blocks until all the previous phases are completed, and returns when the specified phase <i>i</i> is started.
* If the calling thread was executing an earlier phase, that phase is marked as completed.
*
* @throws IllegalStateException
* if the sequential lock protocol is aborted, or the thread that owns the current phase has quit.
*/
public synchronized void phase(int i) throws InterruptedException {
done(); // mark the previous phase done
while (i!=n) {
if (aborted)
throw new IllegalStateException("SequenceLock aborted");
if (t!=null && !t.isAlive())
throw new IllegalStateException("Owner thread of the current phase has quit"+t);
if (i<n)
throw new IllegalStateException("Phase "+i+" is already completed");
wait();
}
t = Thread.currentThread();
}
/**
* Marks the current phase completed that the calling thread was executing.
*
* <p>
* This is only necessary when the thread exits the last phase, as {@link #phase(int)} call implies the
* {@link #done()} call.
*/
public synchronized void done() {
if (t==Thread.currentThread()) {
// phase N done
n++;
t = null;
notifyAll();
}
}
/**
* Tell all the threads that this sequencing was aborted.
* Everyone waiting for future phases will receive an error.
*
* <p>
* Calling this method from the finally block prevents a dead lock if one of the participating thread
* aborts with an exception, as without the explicit abort operation, other threads will block forever
* for a phase that'll never come.
*/
public synchronized void abort() {
aborted = true;
notifyAll();
}
}