/*

 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

package rtm;

import java.util.concurrent.BrokenBarrierException;

import java.util.concurrent.CyclicBarrier;

/**

 * To force transactional execution abort due to memory conflict

 * one thread should access memory region from transactional region

 * while another thread should modify the same memory region.

 * Since this scenario is based on the race condition between threads

 * you should not expect some particular amount of aborts.

 */

class MemoryConflictProvoker extends AbortProvoker {

    // Following field have to be static in order to avoid escape analysis.

    @SuppressWarnings("UnsuedDeclaration")

    private static int field = 0;

    private static final int INNER_ITERATIONS = 10000;

    private final CyclicBarrier barrier;

    /**

     * This thread will access and modify memory region

     * from outside of the transaction.

     */

    private final Runnable conflictingThread;

    public MemoryConflictProvoker() {

        this(new Object());

    }

    public MemoryConflictProvoker(Object monitor) {

        super(monitor);

        barrier = new CyclicBarrier(2);

        conflictingThread = () -> {

            try {

                barrier.await();

            } catch (Exception e) {

                throw new RuntimeException(e);

            }

            for (int i = 0; i < MemoryConflictProvoker.INNER_ITERATIONS; i++) {

                MemoryConflictProvoker.field++;

            }

        };

    }

    /**

     * Accesses and modifies memory region from within the transaction.

     */

    public void transactionalRegion() {

        for (int i = 0; i < MemoryConflictProvoker.INNER_ITERATIONS; i++) {

            synchronized(monitor) {

                MemoryConflictProvoker.field--;

            }

        }

    }

    @Override

    public void forceAbort() {

        try {

            Thread t = new Thread(conflictingThread);

            t.start();

            transactionalRegion();

            t.join();

        } catch (Exception e) {

            throw new RuntimeException(e);

        }

    }

    @Override

    public String getMethodWithLockName() {

        return this.getClass().getName() + "::transactionalRegion";

    }

}