| /* |
| * 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; |
| |
| import nsk.share.*; |
| |
| /* |
| * DeadlockLocker - class used for deadlock creation |
| * |
| * To create deadlock second 'inner' instance of DeadlockLocker is required. |
| * |
| * Deadlock creation scenario: |
| * - object acquires its resource |
| * - notify 'inner' through Wicket step1 that resource is locked and 'inner' can try to acquire this object's resource |
| * - wait notification through Wicket step2 from 'inner' that 'inner' acquired its resource |
| * - call readyWicket.unlock to notify thread waiting deadlock creation |
| * - try acquire locked inner's resource, at the same time inner trying to acquire locked this object's resource - deadlock is created |
| * |
| * Subclasses should implement method doLock() taking in account described scenario. |
| * |
| * Objects of DeadlockLocker should not be created directly, to create deadlocked threads use class DeadlockMaker |
| */ |
| abstract public class DeadlockLocker { |
| protected DeadlockLocker inner; |
| |
| protected Wicket step1; |
| |
| protected Wicket step2; |
| |
| // 'readyWicket' is used to notify DeadlockMacker that deadlock is almost created |
| protected Wicket readyWicket; |
| |
| public DeadlockLocker(Wicket step1, Wicket step2, Wicket readyWicket) { |
| this.step1 = step1; |
| this.step2 = step2; |
| this.readyWicket = readyWicket; |
| } |
| |
| public void setInner(DeadlockLocker inner) { |
| this.inner = inner; |
| } |
| |
| protected void checkInnerLocker() { |
| if (inner == null) { |
| throw new IllegalStateException(getClass().getName() + " deadlockLocker's inner locker is null"); |
| } |
| } |
| |
| protected abstract void doLock(); |
| |
| abstract public Object getLock(); |
| |
| private int lockCount; |
| |
| final public void lock() { |
| // call this method once |
| if (lockCount++ > 1) |
| return; |
| |
| // check that inner locker was set |
| checkInnerLocker(); |
| |
| doLock(); |
| } |
| |
| } |