1 /*
2  * Copyright 2014 Google Inc.  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  * @test
26  * @bug 8062771 8016236
27  * @summary Test publication of Class objects via a data race
28  * @run testng ThreadSafety
29  */
30 
31 import java.io.File;
32 import java.net.URL;
33 import java.net.URLClassLoader;
34 import java.nio.file.Path;
35 import java.nio.file.Paths;
36 import java.util.Collections;
37 import java.util.concurrent.BrokenBarrierException;
38 import java.util.concurrent.Callable;
39 import java.util.concurrent.CyclicBarrier;
40 import java.util.concurrent.ExecutionException;
41 import java.util.concurrent.ExecutorService;
42 import java.util.concurrent.Executors;
43 import java.util.concurrent.Future;
44 import java.util.concurrent.TimeoutException;
45 import static java.util.concurrent.TimeUnit.SECONDS;
46 import static org.testng.Assert.*;
47 import org.testng.annotations.Test;
48 
49 /**
50  * A test resulting from an attempt to repro this failure (in guice):
51  *
52  * java.lang.NullPointerException
53  *   at sun.reflect.generics.visitor.Reifier.visitClassTypeSignature(Reifier.java:125)
54  *   at sun.reflect.generics.tree.ClassTypeSignature.accept(ClassTypeSignature.java:49)
55  *   at sun.reflect.generics.repository.ClassRepository.getSuperclass(ClassRepository.java:84)
56  *   at java.lang.Class.getGenericSuperclass(Class.java:692)
57  *   at com.google.inject.TypeLiteral.getSuperclassTypeParameter(TypeLiteral.java:99)
58  *   at com.google.inject.TypeLiteral.<init>(TypeLiteral.java:79)
59  *
60  * However, as one would expect with thread safety problems in reflection, these
61  * are very hard to reproduce.  This very test has never been observed to fail,
62  * but a similar test has been observed to fail about once in 2000 executions
63  * (about once every 6 CPU-hours), in jdk7 only.  It appears to be fixed in jdk8+ by:
64  *
65  * 8016236: Class.getGenericInterfaces performance improvement.
66  * (by making Class.genericInfo volatile)
67  */
68 public class ThreadSafety {
69     public static class EmptyClass {
70         public static class EmptyGenericSuperclass<T> {}
71         public static class EmptyGenericSubclass<T> extends EmptyGenericSuperclass<T> {}
72     }
73 
74     /** published via data race */
75     private Class<?> racyClass = Object.class;
76 
createNewEmptyGenericSubclassClass()77     private Class<?> createNewEmptyGenericSubclassClass() throws Exception {
78         String[] cpaths = System.getProperty("test.classes", ".")
79                                 .split(File.pathSeparator);
80         URL[] urls = new URL[cpaths.length];
81         for (int i=0; i < cpaths.length; i++) {
82             urls[i] = Paths.get(cpaths[i]).toUri().toURL();
83         }
84         URLClassLoader ucl = new URLClassLoader(urls, null);
85         return Class.forName("ThreadSafety$EmptyClass$EmptyGenericSubclass", true, ucl);
86     }
87 
88     @Test
testRacy_getGenericSuperclass()89     public void testRacy_getGenericSuperclass() throws Exception {
90         final int nThreads = 10;
91         final int iterations = 30;
92         final int timeout = 10;
93         final CyclicBarrier newCycle = new CyclicBarrier(nThreads);
94         final Callable<Void> task = new Callable<Void>() {
95             public Void call() throws Exception {
96                 for (int i = 0; i < iterations; i++) {
97                     final int threadId;
98                     try {
99                         threadId = newCycle.await(timeout, SECONDS);
100                     } catch (BrokenBarrierException e) {
101                         return null;
102                     }
103                     for (int j = 0; j < iterations; j++) {
104                         // one thread publishes the class object via a data
105                         // race, for the other threads to consume.
106                         if (threadId == 0) {
107                             racyClass = createNewEmptyGenericSubclassClass();
108                         } else {
109                             racyClass.getGenericSuperclass();
110                         }
111                     }
112                 }
113                 return null;
114             }};
115 
116         final ExecutorService pool = Executors.newFixedThreadPool(nThreads);
117         try {
118             for (Future<Void> future :
119                      pool.invokeAll(Collections.nCopies(nThreads, task))) {
120                 try {
121                     future.get(iterations * timeout, SECONDS);
122                 } catch (ExecutionException e) {
123                     // ignore "collateral damage"
124                     if (!(e.getCause() instanceof BrokenBarrierException)
125                         &&
126                         !(e.getCause() instanceof TimeoutException)) {
127                         throw e;
128                     }
129                 }
130             }
131         } finally {
132             pool.shutdownNow();
133             assertTrue(pool.awaitTermination(2 * timeout, SECONDS));
134         }
135     }
136 }
137