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/*
* Copyright 2014 Google Inc. 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.
*/
/**
* @test
* @bug 8062771 8016236
* @summary Test publication of Class objects via a data race
* @run testng ThreadSafety
*/
import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Collections;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.Callable;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeoutException;
import static java.util.concurrent.TimeUnit.SECONDS;
import static org.testng.Assert.*;
import org.testng.annotations.Test;
/**
* A test resulting from an attempt to repro this failure (in guice):
*
* java.lang.NullPointerException
* at sun.reflect.generics.visitor.Reifier.visitClassTypeSignature(Reifier.java:125)
* at sun.reflect.generics.tree.ClassTypeSignature.accept(ClassTypeSignature.java:49)
* at sun.reflect.generics.repository.ClassRepository.getSuperclass(ClassRepository.java:84)
* at java.lang.Class.getGenericSuperclass(Class.java:692)
* at com.google.inject.TypeLiteral.getSuperclassTypeParameter(TypeLiteral.java:99)
* at com.google.inject.TypeLiteral.<init>(TypeLiteral.java:79)
*
* However, as one would expect with thread safety problems in reflection, these
* are very hard to reproduce. This very test has never been observed to fail,
* but a similar test has been observed to fail about once in 2000 executions
* (about once every 6 CPU-hours), in jdk7 only. It appears to be fixed in jdk8+ by:
*
* 8016236: Class.getGenericInterfaces performance improvement.
* (by making Class.genericInfo volatile)
*/
public class ThreadSafety {
public static class EmptyClass {
public static class EmptyGenericSuperclass<T> {}
public static class EmptyGenericSubclass<T> extends EmptyGenericSuperclass<T> {}
}
/** published via data race */
private Class<?> racyClass = Object.class;
private Class<?> createNewEmptyGenericSubclassClass() throws Exception {
String[] cpaths = System.getProperty("test.classes", ".")
.split(File.pathSeparator);
URL[] urls = new URL[cpaths.length];
for (int i=0; i < cpaths.length; i++) {
urls[i] = Paths.get(cpaths[i]).toUri().toURL();
}
URLClassLoader ucl = new URLClassLoader(urls, null);
return Class.forName("ThreadSafety$EmptyClass$EmptyGenericSubclass", true, ucl);
}
@Test
public void testRacy_getGenericSuperclass() throws Exception {
final int nThreads = 10;
final int iterations = 30;
final int timeout = 10;
final CyclicBarrier newCycle = new CyclicBarrier(nThreads);
final Callable<Void> task = new Callable<Void>() {
public Void call() throws Exception {
for (int i = 0; i < iterations; i++) {
final int threadId;
try {
threadId = newCycle.await(timeout, SECONDS);
} catch (BrokenBarrierException e) {
return null;
}
for (int j = 0; j < iterations; j++) {
// one thread publishes the class object via a data
// race, for the other threads to consume.
if (threadId == 0) {
racyClass = createNewEmptyGenericSubclassClass();
} else {
racyClass.getGenericSuperclass();
}
}
}
return null;
}};
final ExecutorService pool = Executors.newFixedThreadPool(nThreads);
try {
for (Future<Void> future :
pool.invokeAll(Collections.nCopies(nThreads, task))) {
try {
future.get(iterations * timeout, SECONDS);
} catch (ExecutionException e) {
// ignore "collateral damage"
if (!(e.getCause() instanceof BrokenBarrierException)
&&
!(e.getCause() instanceof TimeoutException)) {
throw e;
}
}
}
} finally {
pool.shutdownNow();
assertTrue(pool.awaitTermination(2 * timeout, SECONDS));
}
}
}
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