1 /*
   2  * Copyright (c) 2013, 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 
  31 import java.lang.ref.*;
  32 
  33 public 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 }