Author: lbernardo
Date: Thu Oct 9 20:21:09 2014
New Revision: 1630586
URL: http://svn.apache.org/r1630586
Log:
FOP-2157: Deadlock in CompareUtil class; patch by Jacopo Cappellato based on
original proposal by Morten Knudsen.
Added:
xmlgraphics/fop/trunk/test/java/org/apache/fop/util/CompareUtilTestCase.java
(with props)
Modified:
xmlgraphics/fop/trunk/src/java/org/apache/fop/util/CompareUtil.java
Modified: xmlgraphics/fop/trunk/src/java/org/apache/fop/util/CompareUtil.java
URL:
http://svn.apache.org/viewvc/xmlgraphics/fop/trunk/src/java/org/apache/fop/util/CompareUtil.java?rev=1630586&r1=1630585&r2=1630586&view=diff
==============================================================================
--- xmlgraphics/fop/trunk/src/java/org/apache/fop/util/CompareUtil.java
(original)
+++ xmlgraphics/fop/trunk/src/java/org/apache/fop/util/CompareUtil.java Thu Oct
9 20:21:09 2014
@@ -24,17 +24,39 @@ package org.apache.fop.util;
*/
public final class CompareUtil {
+ private static final Object TIE_LOCK = new Object();
+
private CompareUtil() {
}
/**
* Compares two objects for equality.
+ * In order to prevent lock-ordering deadlocks the following strategy is
used:
+ * when two non null objects are passed to the method, the comparison
+ * is done by calling the {@link Object#equals(Object)} method of the
object
+ * with the lower hash code ({@link System#identityHashCode(Object)});
+ * in the rare case that two different objects have the same hash code, a
lock
+ * is used.
*
* @param o1 an object
* @param o2 another object
* @return true if either o1 and o2 are null or if o1.equals(o2)
*/
public static boolean equal(Object o1, Object o2) {
+ int o1Hash = System.identityHashCode(o1);
+ int o2Hash = System.identityHashCode(o1);
+ if (o1Hash == o2Hash && o1 != o2 && o1Hash != 0) {
+ // in the rare case of different objects with the same hash code,
+ // the tieLock object is used to synchronize access
+ synchronized (TIE_LOCK) {
+ return o1.equals(o2);
+ }
+ }
+ if (o1Hash > o2Hash) {
+ Object tmp = o1;
+ o1 = o2;
+ o2 = tmp;
+ }
return o1 == null ? o2 == null : o1 == o2 || o1.equals(o2);
}
Added:
xmlgraphics/fop/trunk/test/java/org/apache/fop/util/CompareUtilTestCase.java
URL:
http://svn.apache.org/viewvc/xmlgraphics/fop/trunk/test/java/org/apache/fop/util/CompareUtilTestCase.java?rev=1630586&view=auto
==============================================================================
---
xmlgraphics/fop/trunk/test/java/org/apache/fop/util/CompareUtilTestCase.java
(added)
+++
xmlgraphics/fop/trunk/test/java/org/apache/fop/util/CompareUtilTestCase.java
Thu Oct 9 20:21:09 2014
@@ -0,0 +1,98 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* $Id$ */
+
+package org.apache.fop.util;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Vector;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNull;
+
+public class CompareUtilTestCase {
+
+ @Test
+ public void testEqual() {
+ int numberOfParallelThreads =
Runtime.getRuntime().availableProcessors();
+ long numberOfEqualOperations = 100;
+ double probabilityOf12 = 0.5;
+
+ ExecutorService executor =
Executors.newFixedThreadPool(numberOfParallelThreads);
+
+ final Vector object1 = new Vector();
+ object1.add(new Object());
+ object1.add(new Object());
+ object1.add(new Object());
+ object1.add(new Object());
+ object1.add(new Object());
+ final Vector object2 = new Vector();
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ object2.add(new Object());
+ final boolean areEqual = object1.equals(object2);
+ final AtomicBoolean wrongResult = new AtomicBoolean(false);
+
+ Runnable equal12 = new Runnable() {
+ public void run() {
+ if (areEqual != CompareUtil.equal(object1, object2)) {
+ wrongResult.set(true);
+ }
+ }
+ };
+ Runnable equal21 = new Runnable() {
+ public void run() {
+ if (areEqual != CompareUtil.equal(object2, object1)) {
+ wrongResult.set(true);
+ }
+ }
+ };
+
+ List<Future<?>> futures = new ArrayList<Future<?>>();
+ for (int i = 1; i <= numberOfEqualOperations; i++) {
+ Runnable randomTask = Math.random() < probabilityOf12 ? equal12 :
equal21;
+ futures.add(executor.submit(randomTask));
+ }
+
+ Exception exception = null;
+ try {
+ for (Future<?> future : futures) {
+ future.get();
+ }
+ } catch (Exception e) {
+ exception = e;
+ }
+
+ assertNull(exception);
+ assertFalse(wrongResult.get());
+ }
+}
Propchange:
xmlgraphics/fop/trunk/test/java/org/apache/fop/util/CompareUtilTestCase.java
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