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.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  */
  22 
  23 /*
  24  * @test
  25  * @run main/othervm/timeout=60 ReadersUnlockAfterWriteUnlock
  26  * @bug 8023234
  27  * @summary StampedLock serializes readers on writer unlock
  28  * @author Dmitry Chyuko
  29  * @author Aleksey Shipilev
  30  */
  31 
  32 import java.util.concurrent.CyclicBarrier;
  33 import java.util.concurrent.locks.StampedLock;
  34 
  35 public class ReadersUnlockAfterWriteUnlock {
  36     static final int RNUM = 2;
  37     static final StampedLock sl = new StampedLock();
  38     static volatile boolean isDone;
  39 
  40     static CyclicBarrier iterationStart = new CyclicBarrier(RNUM + 1);
  41     static CyclicBarrier readersHaveLocks = new CyclicBarrier(RNUM);
  42     static CyclicBarrier writerHasLock = new CyclicBarrier(RNUM + 1);
  43 
  44     static class Reader extends Thread {
  45         final String name;
  46         Reader(String name) {
  47             super();
  48             this.name = name;
  49         }
  50         public void run() {
  51             while (!isDone && !isInterrupted()) {
  52                 try {
  53                     iterationStart.await();
  54                     writerHasLock.await();
  55                     long rs = sl.readLock();
  56 
  57                     // single reader blocks here indefinitely if readers
  58                     // are serialized
  59                     readersHaveLocks.await();
  60 
  61                     sl.unlockRead(rs);
  62                 } catch (Exception e) {
  63                     throw new IllegalStateException(e);
  64                 }
  65             }
  66         }
  67     }
  68 
  69     public static void main(String[] args) throws InterruptedException {
  70         for (int r = 0 ; r < RNUM; ++r) {
  71             new Reader("r" + r).start();
  72         }
  73         int i;
  74         for (i = 0; i < 1024; ++i) {
  75             try {
  76                 iterationStart.await();
  77                 long ws = sl.writeLock();
  78                 writerHasLock.await();
  79                 Thread.sleep(10);
  80                 sl.unlockWrite(ws);
  81             } catch (Exception e) {
  82                 throw new IllegalStateException(e);
  83             }
  84         }
  85         isDone = true;
  86     }
  87 
  88 }