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 31import java.io.File; 32import java.net.URL; 33import java.net.URLClassLoader; 34import java.nio.file.Path; 35import java.nio.file.Paths; 36import java.util.Collections; 37import java.util.concurrent.BrokenBarrierException; 38import java.util.concurrent.Callable; 39import java.util.concurrent.CyclicBarrier; 40import java.util.concurrent.ExecutionException; 41import java.util.concurrent.ExecutorService; 42import java.util.concurrent.Executors; 43import java.util.concurrent.Future; 44import java.util.concurrent.TimeoutException; 45import static java.util.concurrent.TimeUnit.SECONDS; 46import static org.testng.Assert.*; 47import 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 */ 68public 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 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 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