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/*
* Copyright (c) 2007, 2018, 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.
*/
package nsk.share.gc.lock;
import nsk.share.TestBug;
import nsk.share.gc.lock.Locker;
/**
* CriticalSectionLocker represents a way to lock a resource
* by entering some critical section.
*/
public abstract class CriticalSectionLocker<T> implements Locker<T> {
private transient boolean enabled = false;
private transient boolean locked = false;
private Object sync = new Object();
private Thread thread;
private Throwable exception;
private final Runnable runnable = new Runnable() {
public void run() {
//System.out.println("Running");
try {
do {
synchronized (sync) {
while (enabled && !locked) {
try {
sync.wait();
} catch (InterruptedException e) {
}
}
if (!enabled)
break;
}
do {
criticalSection();
} while (locked);
} while (enabled);
// System.out.println("Exiting");
} catch (RuntimeException t) {
t.printStackTrace();
exception = t;
throw t;
}
}
};
public CriticalSectionLocker() {
}
/**
* Enter critical section.
*
*/
protected abstract void criticalSection();
public void enable() {
synchronized (sync) {
if (enabled)
throw new TestBug("Locker already enabled.");
// System.out.println("Enabling " + this);
enabled = true;
thread = new Thread(runnable, "Locker: " + runnable);
thread.setDaemon(true);
thread.start();
}
}
public void lock() {
synchronized (sync) {
if (locked)
throw new TestBug("Locker already locked.");
// System.out.println("Locking " + this);
locked = true;
sync.notifyAll();
}
}
public void unlock() {
synchronized (sync) {
if (!locked)
throw new TestBug("Locker not locked.");
// System.out.println("Unocking " + this);
locked = false;
sync.notifyAll();
}
}
public void disable() {
synchronized (sync) {
if (!enabled)
throw new TestBug("Locker not enabled.");
// System.out.println("Disabling " + this);
enabled = false;
sync.notifyAll();
}
try {
thread.join();
} catch (InterruptedException e) {
throw new TestBug(e);
}
}
public Throwable getException() {
return exception;
}
}
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