1/*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.  Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25/*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36package java.util.concurrent.locks;
37
38/**
39 * A synchronizer that may be exclusively owned by a thread.  This
40 * class provides a basis for creating locks and related synchronizers
41 * that may entail a notion of ownership.  The
42 * {@code AbstractOwnableSynchronizer} class itself does not manage or
43 * use this information. However, subclasses and tools may use
44 * appropriately maintained values to help control and monitor access
45 * and provide diagnostics.
46 *
47 * @since 1.6
48 * @author Doug Lea
49 */
50public abstract class AbstractOwnableSynchronizer
51    implements java.io.Serializable {
52
53    /** Use serial ID even though all fields transient. */
54    private static final long serialVersionUID = 3737899427754241961L;
55
56    /**
57     * Empty constructor for use by subclasses.
58     */
59    protected AbstractOwnableSynchronizer() { }
60
61    /**
62     * The current owner of exclusive mode synchronization.
63     */
64    private transient Thread exclusiveOwnerThread;
65
66    /**
67     * Sets the thread that currently owns exclusive access.
68     * A {@code null} argument indicates that no thread owns access.
69     * This method does not otherwise impose any synchronization or
70     * {@code volatile} field accesses.
71     * @param thread the owner thread
72     */
73    protected final void setExclusiveOwnerThread(Thread thread) {
74        exclusiveOwnerThread = thread;
75    }
76
77    /**
78     * Returns the thread last set by {@code setExclusiveOwnerThread},
79     * or {@code null} if never set.  This method does not otherwise
80     * impose any synchronization or {@code volatile} field accesses.
81     * @return the owner thread
82     */
83    protected final Thread getExclusiveOwnerThread() {
84        return exclusiveOwnerThread;
85    }
86}
87