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
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  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  */
  29 
  30 import java.lang.ref.*;
  31 
  32 public class EnqueuePollRace {
  33 
  34     public static void main(String args[]) throws Exception {
  35         new WeakRef().run();
  36         System.out.println("Test passed.");
  37     }
  38 
  39     static class WeakRef {
  40         ReferenceQueue<Object> queue = new ReferenceQueue<Object>();
  41         final int numReferences = 100;
  42         final Reference refs[] = new Reference[numReferences];
  43         final int iterations = 1000;
  44 
  45         void run() throws InterruptedException {
  46             for (int i = 0; i < iterations; i++) {
  47                 queue = new ReferenceQueue<Object>();
  48 
  49                 for (int j = 0; j < refs.length; j++) {
  50                     refs[j] = new WeakReference(new Object(), queue);
  51                 }
  52 
  53                 System.gc(); // enqueues references into the list of discovered references
  54 
  55                 // now manually enqueue all of them
  56                 for (int j = 0; j < refs.length; j++) {
  57                     refs[j].enqueue();
  58                 }
  59                 // and get them back. There should be exactly numReferences
  60                 // entries in the queue now.
  61                 int foundReferences = 0;
  62                 while (queue.poll() != null) {
  63                     foundReferences++;
  64                 }
  65 
  66                 if (foundReferences != refs.length) {
  67                     throw new RuntimeException("Got " + foundReferences + " references in the queue, but expected " + refs.length);
  68                 }
  69             }
  70         }
  71     }
  72 }