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8260366: ExtendedSocketOptions <clinit> can deadlock in some circumst…
…ances

Reviewed-by: dfuchs
  • Loading branch information
Jaikiran Pai committed Feb 26, 2021
1 parent de3f519 commit 240f2a1bb7c982f7bda15c62abe2313d87654ed5
Showing with 182 additions and 14 deletions.
  1. +24 −14 src/java.base/share/classes/sun/net/ext/ExtendedSocketOptions.java
  2. +158 −0 test/jdk/sun/net/ext/ExtendedSocketOptionsTest.java
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2016, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2016, 2021, 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
@@ -167,25 +167,35 @@ protected ExtendedSocketOptions(Set<SocketOption<?>> options) {

private static volatile ExtendedSocketOptions instance;

public static final ExtendedSocketOptions getInstance() { return instance; }

/** Registers support for extended socket options. Invoked by the jdk.net module. */
public static final void register(ExtendedSocketOptions extOptions) {
if (instance != null)
throw new InternalError("Attempting to reregister extended options");

instance = extOptions;
}

static {
public static ExtendedSocketOptions getInstance() {
ExtendedSocketOptions ext = instance;
if (ext != null) {
return ext;
}
try {
// If the class is present, it will be initialized which
// triggers registration of the extended socket options.
Class<?> c = Class.forName("jdk.net.ExtendedSocketOptions");
ext = instance;
} catch (ClassNotFoundException e) {
// the jdk.net module is not present => no extended socket options
instance = new NoExtendedSocketOptions();
synchronized (ExtendedSocketOptions.class) {
ext = instance;
if (ext != null) {
return ext;
}
// the jdk.net module is not present => no extended socket options
ext = instance = new NoExtendedSocketOptions();
}
}
return ext;
}

/** Registers support for extended socket options. Invoked by the jdk.net module. */
public static synchronized void register(ExtendedSocketOptions extOptions) {
if (instance != null)
throw new InternalError("Attempting to reregister extended options");

instance = extOptions;
}

static final class NoExtendedSocketOptions extends ExtendedSocketOptions {
@@ -0,0 +1,158 @@
/*
* Copyright (c) 2021, 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.
*/

import org.testng.Assert;
import org.testng.annotations.Test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
* @test
* @bug 8260366
* @summary Verify that concurrent classloading of sun.net.ext.ExtendedSocketOptions and
* jdk.net.ExtendedSocketOptions doesn't lead to a deadlock
* @modules java.base/sun.net.ext:open
* jdk.net
* @run testng/othervm ExtendedSocketOptionsTest
* @run testng/othervm ExtendedSocketOptionsTest
* @run testng/othervm ExtendedSocketOptionsTest
* @run testng/othervm ExtendedSocketOptionsTest
* @run testng/othervm ExtendedSocketOptionsTest
*/
public class ExtendedSocketOptionsTest {

/**
* Loads {@code jdk.net.ExtendedSocketOptions} and {@code sun.net.ext.ExtendedSocketOptions}
* and invokes {@code sun.net.ext.ExtendedSocketOptions#getInstance()} concurrently in a thread
* of their own and expects the classloading of both those classes
* to succeed. Additionally, after these tasks are done, calls the
* sun.net.ext.ExtendedSocketOptions#getInstance() and expects it to return a registered
* ExtendedSocketOptions instance.
*/
@Test
public void testConcurrentClassLoad() throws Exception {
final CountDownLatch taskTriggerLatch = new CountDownLatch(4);
final List<Callable<?>> tasks = new ArrayList<>();
tasks.add(new Task("jdk.net.ExtendedSocketOptions", taskTriggerLatch));
tasks.add(new Task("sun.net.ext.ExtendedSocketOptions", taskTriggerLatch));
// add a couple of tasks which call sun.net.ext.ExtendedSocketOptions#getInstance
tasks.add(new GetInstanceTask(taskTriggerLatch));
tasks.add(new GetInstanceTask(taskTriggerLatch));
final ExecutorService executor = Executors.newFixedThreadPool(tasks.size());
try {
final Future<?>[] results = new Future[tasks.size()];
// submit
int i = 0;
for (final Callable<?> task : tasks) {
results[i++] = executor.submit(task);
}
// wait for completion
for (i = 0; i < tasks.size(); i++) {
results[i].get();
}
} finally {
executor.shutdownNow();
}
// check that the sun.net.ext.ExtendedSocketOptions#getInstance() does indeed return
// the registered instance
final Object extSocketOptions = callSunNetExtSocketOptionsGetInstance();
Assert.assertNotNull(extSocketOptions, "sun.net.ext.ExtendedSocketOptions#getInstance()" +
" unexpectedly returned null");
// now verify that each call to getInstance(), either in the tasks or here, returned the exact
// same instance of ExtendedSocketOptions
Assert.assertEquals(2, GetInstanceTask.extendedSocketOptionsInstances.size());
for (final Object inst : GetInstanceTask.extendedSocketOptionsInstances) {
Assert.assertSame(inst, extSocketOptions, "sun.net.ext.ExtendedSocketOptions#getInstance()" +
" returned different instances");
}
}

/**
* Reflectively calls sun.net.ext.ExtendedSocketOptions#getInstance() and returns
* the result
*/
private static Object callSunNetExtSocketOptionsGetInstance() throws Exception {
final Class<?> k = Class.forName("sun.net.ext.ExtendedSocketOptions");
return k.getDeclaredMethod("getInstance").invoke(null);
}

private static class Task implements Callable<Class<?>> {
private final String className;
private final CountDownLatch latch;

private Task(final String className, final CountDownLatch latch) {
this.className = className;
this.latch = latch;
}

@Override
public Class<?> call() {
System.out.println(Thread.currentThread().getName() + " loading " + this.className);
try {
// let the other tasks know we are ready to trigger our work
latch.countDown();
// wait for the other task to let us know they are ready to trigger their work too
latch.await();
return Class.forName(this.className);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}

private static class GetInstanceTask implements Callable<Object> {
// keeps track of the instances returned by calls to sun.nex.ext.ExtendedSocketOptions#getInstance()
// by the GetInstanceTask(s)
private static final List<Object> extendedSocketOptionsInstances = Collections.synchronizedList(new ArrayList<>());
private final CountDownLatch latch;

private GetInstanceTask(final CountDownLatch latch) {
this.latch = latch;
}

@Override
public Object call() {
System.out.println(Thread.currentThread().getName()
+ " calling sun.net.ext.ExtendedSocketOptions#getInstance()");
try {
// let the other tasks know we are ready to trigger our work
latch.countDown();
// wait for the other task to let us know they are ready to trigger their work too
latch.await();
// let's call getInstance on sun.net.ext.ExtendedSocketOptions
final Object inst = callSunNetExtSocketOptionsGetInstance();
extendedSocketOptionsInstances.add(inst);
return inst;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
}

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