1/*
2 * Copyright (c) 2013, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24/* @test
25 * @bug 8014890
26 * @summary Verify that a race between ReferenceQueue.enqueue() and poll() does not occur.
27 * @author thomas.schatzl@oracle.com
28 * @run main/othervm -Xmx10M EnqueuePollRace
29 */
30
31import java.lang.ref.*;
32
33public class EnqueuePollRace {
34
35    public static void main(String args[]) throws Exception {
36        new WeakRef().run();
37        System.out.println("Test passed.");
38    }
39
40    static class WeakRef {
41        ReferenceQueue<Object> queue = new ReferenceQueue<Object>();
42        final int numReferences = 100;
43        final Reference refs[] = new Reference[numReferences];
44        final int iterations = 1000;
45
46        void run() throws InterruptedException {
47            for (int i = 0; i < iterations; i++) {
48                queue = new ReferenceQueue<Object>();
49
50                for (int j = 0; j < refs.length; j++) {
51                    refs[j] = new WeakReference(new Object(), queue);
52                }
53
54                System.gc(); // enqueues references into the list of discovered references
55
56                // now manually enqueue all of them
57                for (int j = 0; j < refs.length; j++) {
58                    refs[j].enqueue();
59                }
60                // and get them back. There should be exactly numReferences
61                // entries in the queue now.
62                int foundReferences = 0;
63                while (queue.poll() != null) {
64                    foundReferences++;
65                }
66
67                if (foundReferences != refs.length) {
68                    throw new RuntimeException("Got " + foundReferences + " references in the queue, but expected " + refs.length);
69                }
70            }
71        }
72    }
73}
74