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/* -*- Mode: Java; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*
* This file incorporates work covered by the following license notice:
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright
* ownership. The ASF licenses this file to you under the Apache
* License, Version 2.0 (the "License"); you may not use this file
* except in compliance with the License. You may obtain a copy of
* the License at http://www.apache.org/licenses/LICENSE-2.0 .
*/
package com.sun.star.lib.util;
import java.util.LinkedList;
/**
* Helper class to asynchronously execute finalize methods.
*
* <p>Current JVMs seem not to be robust against long-running finalize methods,
* in that such long-running finalize methods may lead to OutOfMemoryErrors.
* This class mitigates the problem by asynchronously shifting the bodies of
* potentially long-running finalize methods into an extra thread. Classes that
* make use of this in their finalize methods are the proxies used in the
* intra-process JNI UNO bridge and the inter-process Java URP UNO bridge (where
* in both cases finalizers lead to synchronous UNO release calls).</p>
*
* <p>Irrespective whether JVMs are getting more mature and should no longer
* have problems with long-running finalize methods, at least the JNI UNO bridge
* needs some way to stop finalization of proxies (to C++ objects) well before
* process exit, as provided by drain().</p>
*/
public final class AsynchronousFinalizer {
public AsynchronousFinalizer() {
thread = new Thread("AsynchronousFinalizer") {
@Override
public void run() {
for (;;) {
Job j;
synchronized (queue) {
for (;;) {
if (done) {
return;
}
if (!queue.isEmpty()) {
break;
}
try {
queue.wait();
} catch (InterruptedException e) {
return;
}
}
j = queue.remove(0);
}
try {
j.run();
} catch (Throwable e) {}
}
}
};
thread.start();
}
/**
* Add a job to be executed asynchronously.
*
* <p>The run method of the given job is called exactly once. If it terminates
* abnormally by throwing any Throwable, that is ignored.</p>
*
* @param job represents the body of some finalize method; must not be null.
*/
public void add(Job job) {
synchronized (queue) {
boolean first = queue.isEmpty();
queue.add(job);
if (first) {
queue.notify();
}
}
}
public void drain() throws InterruptedException {
synchronized (queue) {
done = true;
queue.notify();
}
// tdf#123481 Only join if we are not in our own thread, else we have a deadlock
if (Thread.currentThread() != thread)
thread.join();
}
/**
* An interface to represent bodies of finalize methods.
*
* Similar to <code>Runnable</code>, except that the run method may throw any
* <code>Throwable</code> (which is effectively ignored by
* <code>AsynchronousFinalizer.add</code>, similar to any <code>Throwables</code>
* raised by finalize being ignored).
*/
public interface Job {
void run() throws Throwable;
}
private final LinkedList<Job> queue = new LinkedList<Job>();
private final Thread thread;
private boolean done = false;
}
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