128 lines
4.8 KiB
Java
128 lines
4.8 KiB
Java
/*
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* Copyright (c) 2007, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package nsk.share.gc.lock;
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import nsk.share.TestBug;
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import nsk.share.gc.lock.Locker;
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/**
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* CriticalSectionLocker represents a way to lock a resource
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* by entering some critical section.
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*/
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public abstract class CriticalSectionLocker<T> implements Locker<T> {
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private transient boolean enabled = false;
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private transient boolean locked = false;
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private Object sync = new Object();
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private Thread thread;
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private Throwable exception;
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private final Runnable runnable = new Runnable() {
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public void run() {
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//System.out.println("Running");
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try {
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do {
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synchronized (sync) {
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while (enabled && !locked) {
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try {
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sync.wait();
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} catch (InterruptedException e) {
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}
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}
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if (!enabled)
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break;
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}
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do {
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criticalSection();
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} while (locked);
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} while (enabled);
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// System.out.println("Exiting");
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} catch (RuntimeException t) {
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t.printStackTrace();
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exception = t;
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throw t;
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}
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}
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};
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public CriticalSectionLocker() {
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}
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/**
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* Enter critical section.
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*
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*/
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protected abstract void criticalSection();
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public void enable() {
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synchronized (sync) {
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if (enabled)
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throw new TestBug("Locker already enabled.");
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// System.out.println("Enabling " + this);
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enabled = true;
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thread = new Thread(runnable, "Locker: " + runnable);
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thread.setDaemon(true);
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thread.start();
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}
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}
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public void lock() {
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synchronized (sync) {
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if (locked)
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throw new TestBug("Locker already locked.");
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// System.out.println("Locking " + this);
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locked = true;
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sync.notifyAll();
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}
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}
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public void unlock() {
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synchronized (sync) {
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if (!locked)
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throw new TestBug("Locker not locked.");
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// System.out.println("Unocking " + this);
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locked = false;
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sync.notifyAll();
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}
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}
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public void disable() {
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synchronized (sync) {
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if (!enabled)
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throw new TestBug("Locker not enabled.");
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// System.out.println("Disabling " + this);
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enabled = false;
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sync.notifyAll();
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}
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try {
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thread.join();
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} catch (InterruptedException e) {
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throw new TestBug(e);
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}
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}
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public Throwable getException() {
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return exception;
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}
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}
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