1 /*
   2  * Copyright (c) 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 
  25 package rtm;
  26 
  27 import java.util.concurrent.BrokenBarrierException;
  28 import java.util.concurrent.CyclicBarrier;
  29 
  30 /**
  31  * To force transactional execution abort due to memory conflict
  32  * one thread should access memory region from transactional region
  33  * while another thread should modify the same memory region.
  34  * Since this scenario is based on the race condition between threads
  35  * you should not expect some particular amount of aborts.
  36  */
  37 class MemoryConflictProvoker extends AbortProvoker {
  38     // Following field have to be static in order to avoid escape analysis.
  39     @SuppressWarnings("UnsuedDeclaration")
  40     private static int field = 0;
  41     private static final int INNER_ITERATIONS = 10000;
  42     private final CyclicBarrier barrier;
  43     /**
  44      * This thread will access and modify memory region
  45      * from outside of the transaction.
  46      */
  47     private final Runnable conflictingThread;
  48 
  49     public MemoryConflictProvoker() {
  50         this(new Object());
  51     }
  52 
  53     public MemoryConflictProvoker(Object monitor) {
  54         super(monitor);
  55         barrier = new CyclicBarrier(2);
  56         conflictingThread = () -> {
  57             try {
  58                 barrier.await();
  59             } catch (Exception e) {
  60                 throw new RuntimeException(e);
  61             }
  62             for (int i = 0; i < MemoryConflictProvoker.INNER_ITERATIONS; i++) {
  63                 MemoryConflictProvoker.field++;
  64             }
  65         };
  66     }
  67 
  68     /**
  69      * Accesses and modifies memory region from within the transaction.
  70      */
  71     public void transactionalRegion() {
  72         for (int i = 0; i < MemoryConflictProvoker.INNER_ITERATIONS; i++) {
  73             synchronized(monitor) {
  74                 MemoryConflictProvoker.field--;
  75             }
  76         }
  77     }
  78 
  79     @Override
  80     public void forceAbort() {
  81         try {
  82             Thread t = new Thread(conflictingThread);
  83             t.start();
  84             try {
  85                 barrier.await();
  86             } catch (InterruptedException | BrokenBarrierException e) {
  87                 throw new RuntimeException(e);
  88             }
  89             transactionalRegion();
  90             t.join();
  91         } catch (Exception e) {
  92             throw new RuntimeException(e);
  93         }
  94     }
  95 
  96     @Override
  97     public String getMethodWithLockName() {
  98         return this.getClass().getName() + "::transactionalRegion";
  99     }
 100 }