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8263108: Class initialization deadlock in java.lang.constant
Reviewed-by: vtewari, plevart, chegar
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jaikiran committed Mar 18, 2021
1 parent 5d5813a commit 9225a23023f3f18122247e85027146014ab2a07b
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Showing 2 changed files with 171 additions and 11 deletions.
@@ -1,5 +1,5 @@
/*
* Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2018, 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
@@ -64,15 +64,6 @@
private final String constantName;
private final ClassDesc constantType;

private static final Map<MethodHandleDesc, Function<DynamicConstantDesc<?>, ConstantDesc>> canonicalMap
= Map.ofEntries(Map.entry(ConstantDescs.BSM_PRIMITIVE_CLASS, DynamicConstantDesc::canonicalizePrimitiveClass),
Map.entry(ConstantDescs.BSM_ENUM_CONSTANT, DynamicConstantDesc::canonicalizeEnum),
Map.entry(ConstantDescs.BSM_NULL_CONSTANT, DynamicConstantDesc::canonicalizeNull),
Map.entry(ConstantDescs.BSM_VARHANDLE_STATIC_FIELD, DynamicConstantDesc::canonicalizeStaticFieldVarHandle),
Map.entry(ConstantDescs.BSM_VARHANDLE_FIELD, DynamicConstantDesc::canonicalizeFieldVarHandle),
Map.entry(ConstantDescs.BSM_VARHANDLE_ARRAY, DynamicConstantDesc::canonicalizeArrayVarHandle)
);

/**
* Creates a nominal descriptor for a dynamic constant.
*
@@ -137,6 +128,8 @@ protected DynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod,
* format
* @jvms 4.2.2 Unqualified Names
*/
// Do not call this method from the static initialization of java.lang.constant.ConstantDescs
// since that can lead to potential deadlock during multi-threaded concurrent execution
public static<T> ConstantDesc ofCanonical(DirectMethodHandleDesc bootstrapMethod,
String constantName,
ClassDesc constantType,
@@ -281,7 +274,7 @@ public T resolveConstantDesc(MethodHandles.Lookup lookup) throws ReflectiveOpera
}

private ConstantDesc tryCanonicalize() {
Function<DynamicConstantDesc<?>, ConstantDesc> f = canonicalMap.get(bootstrapMethod);
Function<DynamicConstantDesc<?>, ConstantDesc> f = CanonicalMapHolder.CANONICAL_MAP.get(bootstrapMethod);
if (f != null) {
try {
return f.apply(this);
@@ -394,4 +387,15 @@ public String toString() {
super(bootstrapMethod, constantName, constantType, bootstrapArgs);
}
}

private static final class CanonicalMapHolder {
static final Map<MethodHandleDesc, Function<DynamicConstantDesc<?>, ConstantDesc>> CANONICAL_MAP =
Map.ofEntries(
Map.entry(ConstantDescs.BSM_PRIMITIVE_CLASS, DynamicConstantDesc::canonicalizePrimitiveClass),
Map.entry(ConstantDescs.BSM_ENUM_CONSTANT, DynamicConstantDesc::canonicalizeEnum),
Map.entry(ConstantDescs.BSM_NULL_CONSTANT, DynamicConstantDesc::canonicalizeNull),
Map.entry(ConstantDescs.BSM_VARHANDLE_STATIC_FIELD, DynamicConstantDesc::canonicalizeStaticFieldVarHandle),
Map.entry(ConstantDescs.BSM_VARHANDLE_FIELD, DynamicConstantDesc::canonicalizeFieldVarHandle),
Map.entry(ConstantDescs.BSM_VARHANDLE_ARRAY, DynamicConstantDesc::canonicalizeArrayVarHandle));
}
}
@@ -0,0 +1,156 @@
/*
* 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 java.lang.constant.ClassDesc;
import java.lang.constant.ConstantDesc;
import java.lang.constant.DirectMethodHandleDesc;
import java.lang.constant.DynamicConstantDesc;
import java.lang.constant.MethodHandleDesc;
import java.lang.constant.MethodTypeDesc;
import java.lang.invoke.MethodHandles;
import java.util.ArrayList;
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 8263108
* @summary Verify that concurrent classloading of java.lang.constant.DynamicConstantDesc and
* java.lang.constant.ConstantDescs doesn't lead to a deadlock
* @run main/othervm DynamicConstantDescTest
* @run main/othervm DynamicConstantDescTest
* @run main/othervm DynamicConstantDescTest
* @run main/othervm DynamicConstantDescTest
* @run main/othervm DynamicConstantDescTest
*/
// Implementation note: This test cannot use testng, since by the time this test gets a chance
// to trigger a concurrent classloading of the classes it's interested in, the testng infrastructure
// would already have loaded those classes in a single main thread.
public class DynamicConstantDescTest {

/**
* Loads {@code java.lang.constant.DynamicConstantDesc} and {@code java.lang.constant.ConstantDescs}
* and invokes {@code java.lang.constant.DynamicConstantDesc#ofCanonical()} concurrently in a thread
* of their own and expects the classloading of both those classes
* to succeed.
*/
public static void main(final String[] args) throws Exception {
final CountDownLatch taskTriggerLatch = new CountDownLatch(4);
final List<Callable<?>> tasks = new ArrayList<>();
// a bunch of tasks - some doing just Class.forName and some
// invoking DynamicConstantDesc.ofCanonical
tasks.add(new Task("java.lang.constant.DynamicConstantDesc", taskTriggerLatch));
tasks.add(new InvokeOfCanonical(taskTriggerLatch));
tasks.add(new Task("java.lang.constant.ConstantDescs", taskTriggerLatch));
tasks.add(new InvokeOfCanonical(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();
}
}

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);
}
}
}

enum MyEnum {A, B}

private static class InvokeOfCanonical implements Callable<Object> {
private final CountDownLatch latch;

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

@Override
public Object call() {
System.out.println(Thread.currentThread().getName()
+ " calling DynamicConstantDesc.ofCanonical()");
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();
ConstantDesc desc = DynamicConstantDesc.ofCanonical(boostrapMethodForEnumConstant(),
"A", ClassDesc.of("DynamicConstantDescTest").nested("MyEnum"),
new ConstantDesc[0]);
if (desc == null) {
throw new Exception("DynamicConstantDesc.ofCanonical unexpectedly returned null");
}
if (!MyEnum.A.equals(desc.resolveConstantDesc(MethodHandles.lookup()))) {
throw new Exception("DynamicConstantDesc.ofCanonical returned unexpected result " + desc);
}
return desc;
} catch (Exception e) {
throw new RuntimeException(e);
}
}

private static DirectMethodHandleDesc boostrapMethodForEnumConstant() {
ClassDesc[] args = {ClassDesc.of("java.lang.invoke.MethodHandles").nested("Lookup"),
ClassDesc.of("java.lang.String"),
ClassDesc.of("java.lang.Class")};
return MethodHandleDesc.ofMethod(java.lang.constant.DirectMethodHandleDesc.Kind.STATIC,
ClassDesc.of("java.lang.invoke.ConstantBootstraps"),
"enumConstant", MethodTypeDesc.of(ClassDesc.of("java.lang.Enum"), new ClassDesc[0])
.insertParameterTypes(0, args));
}

}

}

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