| /* |
| * Copyright (c) 2007, 2018, 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 nsk.share.locks; |
| |
| /* |
| * Thread intended to hold given lock until method releaseLock() not called |
| * |
| * Example of usage: |
| * |
| * Object lockToHold = new Object(); |
| * MonitorLockingThread lockingThread = new MonitorLockingThread(lockToHold); |
| * |
| * // after calling this method lock 'lockToHold' is acquired by lockingThread |
| * lockingThread.acquireLock(); |
| * |
| * // after calling this method lockingThread releases 'lockToHold' and finishes execution |
| * lockingThread.releaseLock(); |
| */ |
| public class MonitorLockingThread extends Thread { |
| /* |
| * Class MonitorLockingThread is written for usage in tests provoking monitor contention. |
| * Typically in these tests exists thread holding lock (MonitorLockingThread) and another |
| * thread trying to acquire the same lock. But this scenario also requires one more thread |
| * which will force MonitorLockingThread to release lock when contention occurred, for this purpose |
| * auxiliary thread class LockFreeThread is written. |
| * |
| * Example of usage of MonitorLockingThread and LockFreeThread: |
| * |
| * Object lock = new Object(); |
| * MonitorLockingThread monitorLockingThread = new MonitorLockingThread(lock); |
| * |
| * MonitorLockingThread.LockFreeThread lockFreeThread = |
| * new MonitorLockingThread.LockFreeThread(Thread.currentThread(), monitorLockingThread); |
| * |
| * monitorLockingThread.acquireLock(); |
| * |
| * lockFreeThread.start(); |
| * |
| * // try to acquire lock which is already held by MonitorLockingThread (here monitor contention should occur), |
| * // when LockFreeThread finds that contention occurred it forces MonitorLockingThread to release lock |
| * // and current thread is able to continue execution |
| * synchronized (lock) { |
| * } |
| */ |
| public static class LockFreeThread extends Thread { |
| private Thread blockedThread; |
| |
| private MonitorLockingThread lockingThread; |
| |
| public LockFreeThread(Thread blockedThread, MonitorLockingThread lockingThread) { |
| this.blockedThread = blockedThread; |
| this.lockingThread = lockingThread; |
| } |
| |
| public void run() { |
| /* |
| * Wait when blockedThread's state will switch to 'BLOCKED' (at that moment monitor contention |
| * should already occur) and then force MonitorLockingThread to release lock |
| */ |
| while (blockedThread.getState() != Thread.State.BLOCKED) |
| yield(); |
| |
| lockingThread.releaseLock(); |
| } |
| } |
| |
| private volatile boolean isRunning = true; |
| |
| private volatile boolean holdsLock; |
| |
| private Object lockToHold; |
| |
| public MonitorLockingThread(Object lockToHold) { |
| this.lockToHold = lockToHold; |
| } |
| |
| public void run() { |
| synchronized (lockToHold) { |
| holdsLock = true; |
| while (isRunning) |
| yield(); |
| } |
| holdsLock = false; |
| } |
| |
| public void releaseLock() { |
| isRunning = false; |
| while (holdsLock) |
| yield(); |
| } |
| |
| public void acquireLock() { |
| start(); |
| while (!holdsLock) |
| yield(); |
| } |
| } |