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Merge pull request #77 from SmallGiantGames/bug415838-test

Test for 1.9.6 concurrency bug in LocalVariableTable.unpack()
tags/V1_9_8_M1
Andy Clement 2 years ago
parent
commit
a8239df4c8
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+ 13
- 1
bcel-builder/src/main/java/org/aspectj/apache/bcel/classfile/LocalVariableTable.java View File

@@ -189,6 +189,18 @@ public class LocalVariableTable extends Attribute {
return buf.toString();
}

/**
* Returns copy of this attribute using same packed state. Used in unit tests.
*/
public synchronized LocalVariableTable copyFromPackedState() {
if (!isInPackedState) throw new IllegalStateException("No in packed state");
try {
return new LocalVariableTable(nameIndex, length, new DataInputStream(new ByteArrayInputStream(data)), getConstantPool());
} catch (IOException e) {
throw new RuntimeException("Failed to unpack clone", e);
}
}

/**
* @return deep copy of this attribute
*/
@@ -223,7 +235,7 @@ public class LocalVariableTable extends Attribute {
dis.close();
data = null; // throw it away now
} catch (IOException e) {
throw new RuntimeException("Unpacking of LocalVariableTable attribute failed");
throw new RuntimeException("Unpacking of LocalVariableTable attribute failed", e);
}
isInPackedState = false;
}

+ 95
- 0
bcel-builder/src/test/java/org/aspectj/apache/bcel/classfile/tests/LocalVariableTableConcurrencyTest.java View File

@@ -0,0 +1,95 @@
/* *******************************************************************
* Copyright (c) 2004 IBM
* All rights reserved.
* This program and the accompanying materials are made available
* under the terms of the Eclipse Public License v1.0
* which accompanies this distribution and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Dmitry Mikhaylov - initial implementation
* ******************************************************************/

package org.aspectj.apache.bcel.classfile.tests;

import org.aspectj.apache.bcel.classfile.Code;
import org.aspectj.apache.bcel.classfile.JavaClass;
import org.aspectj.apache.bcel.classfile.LocalVariableTable;
import org.aspectj.apache.bcel.classfile.Method;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicReference;


public class LocalVariableTableConcurrencyTest extends BcelTestCase {

private final int nThreads = Runtime.getRuntime().availableProcessors();

private final ExecutorService[] workers = new ExecutorService[nThreads];

private LocalVariableTable reference;

protected void setUp() throws Exception {
super.setUp();

for (int i = 0; i < nThreads; i++) workers[i] = Executors.newSingleThreadExecutor();

JavaClass clazz = getClassFromJar("SimpleGenericsProgram");
Method mainMethod = getMethod(clazz,"main");
Code codeAttr = (Code) findAttribute("Code",mainMethod.getAttributes());
reference = (LocalVariableTable) findAttribute("LocalVariableTable",codeAttr.getAttributes());
}

/**
* Try to hit concurrency bug in org.aspectj.apache.bcel.classfile.LocalVariableTable.unpack().
* We do so by running unpack() on same instance with multiple threads, and artificially
* delaying all threads but first so that they enter unpack() the moment first thread is about to leave it.
*
* Since this test relies on empirically obtained access pattern and number of iterations,
* it never has 100% probability of hitting the bug. If it fails - there is certainly a bug.
* If it passes, it could mean anything - fully correct code or slightly changed execution order preventing
* threads to collide at problematic location.
*
* As such, it is not really good for unit testing.
*/
public void testLocalVariableTableAttributeConcurrency() throws RuntimeException, InterruptedException {
final AtomicReference<RuntimeException> error = new AtomicReference<>();
for (int i = 0; i < 10000; i++) {
LocalVariableTable sharedInstance = reference.copyFromPackedState();
CountDownLatch preStart = new CountDownLatch(nThreads);
Semaphore start = new Semaphore(0);
CountDownLatch finish = new CountDownLatch(nThreads);

for (int j = 0; j < nThreads; j++) {
final boolean needsDelay = j > 0;
workers[j].execute(() -> {
preStart.countDown();
start.acquireUninterruptibly();
// trying to trigger concurrent unpacking bug - one tread should enter unpack() when other is about to leave it
if (needsDelay) reference.copyFromPackedState().getTableLength();
try {
sharedInstance.getTableLength();
}
catch (RuntimeException ex) {
error.compareAndSet(null, ex);
}
finish.countDown();
});
}

preStart.await();
start.release(nThreads);
finish.await();

if (error.get() != null) throw error.get();
}
}

protected void tearDown() throws Exception {
for (int i = 0; i < nThreads; i++) if (workers[i] != null) workers[i].shutdownNow();
super.tearDown();
}
}

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