8173743: Failures during class definition can lead to memory leaks in metaspace
Reviewed-by: dholmes, coleenp, acorn, ddmitriev
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*/
/**
* @test
* @bug 8173743
* @summary Failures during class definition can lead to memory leaks in metaspace
* @library /test/lib
* @run main/othervm test.DefineClass defineClass
* @run main/othervm test.DefineClass defineSystemClass
* @run main/othervm -XX:+UnlockDiagnosticVMOptions
-XX:+UnsyncloadClass -XX:+AllowParallelDefineClass
test.DefineClass defineClassParallel
* @run main/othervm -XX:+UnlockDiagnosticVMOptions
-XX:+UnsyncloadClass -XX:-AllowParallelDefineClass
test.DefineClass defineClassParallel
* @run main/othervm -XX:+UnlockDiagnosticVMOptions
-XX:-UnsyncloadClass -XX:+AllowParallelDefineClass
test.DefineClass defineClassParallel
* @run main/othervm -XX:+UnlockDiagnosticVMOptions
-XX:-UnsyncloadClass -XX:-AllowParallelDefineClass
test.DefineClass defineClassParallel
* @run main/othervm test.DefineClass redefineClass
* @run main/othervm test.DefineClass redefineClassWithError
* @author volker.simonis@gmail.com
*/
package test;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.lang.instrument.ClassDefinition;
import java.lang.instrument.Instrumentation;
import java.lang.management.ManagementFactory;
import java.util.Scanner;
import java.util.concurrent.CountDownLatch;
import java.util.jar.Attributes;
import java.util.jar.JarEntry;
import java.util.jar.JarOutputStream;
import java.util.jar.Manifest;
import javax.management.MBeanServer;
import javax.management.ObjectName;
import com.sun.tools.attach.VirtualMachine;
import jdk.test.lib.process.ProcessTools;
public class DefineClass {
private static Instrumentation instrumentation;
public void getID(CountDownLatch start, CountDownLatch stop) {
String id = "AAAAAAAA";
System.out.println(id);
try {
// Signal that we've entered the activation..
start.countDown();
//..and wait until we can leave it.
stop.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(id);
return;
}
private static class MyThread extends Thread {
private DefineClass dc;
private CountDownLatch start, stop;
public MyThread(DefineClass dc, CountDownLatch start, CountDownLatch stop) {
this.dc = dc;
this.start = start;
this.stop = stop;
}
public void run() {
dc.getID(start, stop);
}
}
private static class ParallelLoadingThread extends Thread {
private MyParallelClassLoader pcl;
private CountDownLatch stop;
private byte[] buf;
public ParallelLoadingThread(MyParallelClassLoader pcl, byte[] buf, CountDownLatch stop) {
this.pcl = pcl;
this.stop = stop;
this.buf = buf;
}
public void run() {
try {
stop.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
try {
@SuppressWarnings("unchecked")
Class<DefineClass> dc = (Class<DefineClass>) pcl.myDefineClass(DefineClass.class.getName(), buf, 0, buf.length);
}
catch (LinkageError jle) {
// Expected with a parallel capable class loader and
// -XX:+UnsyncloadClass or -XX:+AllowParallelDefineClass
pcl.incrementLinkageErrors();
}
}
}
static private class MyClassLoader extends ClassLoader {
public Class<?> myDefineClass(String name, byte[] b, int off, int len) throws ClassFormatError {
return defineClass(name, b, off, len, null);
}
}
static private class MyParallelClassLoader extends ClassLoader {
static {
System.out.println("parallelCapable : " + registerAsParallelCapable());
}
public Class<?> myDefineClass(String name, byte[] b, int off, int len) throws ClassFormatError {
return defineClass(name, b, off, len, null);
}
public synchronized void incrementLinkageErrors() {
linkageErrors++;
}
public int getLinkageErrors() {
return linkageErrors;
}
private volatile int linkageErrors;
}
public static void agentmain(String args, Instrumentation inst) {
System.out.println("Loading Java Agent.");
instrumentation = inst;
}
private static void loadInstrumentationAgent(String myName, byte[] buf) throws Exception {
// Create agent jar file on the fly
Manifest m = new Manifest();
m.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
m.getMainAttributes().put(new Attributes.Name("Agent-Class"), myName);
m.getMainAttributes().put(new Attributes.Name("Can-Redefine-Classes"), "true");
File jarFile = File.createTempFile("agent", ".jar");
jarFile.deleteOnExit();
JarOutputStream jar = new JarOutputStream(new FileOutputStream(jarFile), m);
jar.putNextEntry(new JarEntry(myName.replace('.', '/') + ".class"));
jar.write(buf);
jar.close();
String pid = Long.toString(ProcessTools.getProcessId());
System.out.println("Our pid is = " + pid);
VirtualMachine vm = VirtualMachine.attach(pid);
vm.loadAgent(jarFile.getAbsolutePath());
}
private static byte[] getBytecodes(String myName) throws Exception {
InputStream is = DefineClass.class.getResourceAsStream(myName + ".class");
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buf = new byte[4096];
int len;
while ((len = is.read(buf)) != -1) baos.write(buf, 0, len);
buf = baos.toByteArray();
System.out.println("sizeof(" + myName + ".class) == " + buf.length);
return buf;
}
private static int getStringIndex(String needle, byte[] buf) {
return getStringIndex(needle, buf, 0);
}
private static int getStringIndex(String needle, byte[] buf, int offset) {
outer:
for (int i = offset; i < buf.length - offset - needle.length(); i++) {
for (int j = 0; j < needle.length(); j++) {
if (buf[i + j] != (byte)needle.charAt(j)) continue outer;
}
return i;
}
return 0;
}
private static void replaceString(byte[] buf, String name, int index) {
for (int i = index; i < index + name.length(); i++) {
buf[i] = (byte)name.charAt(i - index);
}
}
private static MBeanServer mbserver = ManagementFactory.getPlatformMBeanServer();
private static int getClassStats(String pattern) {
try {
ObjectName diagCmd = new ObjectName("com.sun.management:type=DiagnosticCommand");
String result = (String)mbserver.invoke(diagCmd , "gcClassStats" , new Object[] { null }, new String[] {String[].class.getName()});
int count = 0;
try (Scanner s = new Scanner(result)) {
if (s.hasNextLine()) {
System.out.println(s.nextLine());
}
while (s.hasNextLine()) {
String l = s.nextLine();
if (l.endsWith(pattern)) {
count++;
System.out.println(l);
}
}
}
return count;
}
catch (Exception e) {
throw new RuntimeException("Test failed because we can't read the class statistics!", e);
}
}
private static void printClassStats(int expectedCount, boolean reportError) {
int count = getClassStats("DefineClass");
String res = "Should have " + expectedCount +
" DefineClass instances and we have: " + count;
System.out.println(res);
if (reportError && count != expectedCount) {
throw new RuntimeException(res);
}
}
public static final int ITERATIONS = 10;
public static void main(String[] args) throws Exception {
String myName = DefineClass.class.getName();
byte[] buf = getBytecodes(myName.substring(myName.lastIndexOf(".") + 1));
int iterations = (args.length > 1 ? Integer.parseInt(args[1]) : ITERATIONS);
if (args.length == 0 || "defineClass".equals(args[0])) {
MyClassLoader cl = new MyClassLoader();
for (int i = 0; i < iterations; i++) {
try {
@SuppressWarnings("unchecked")
Class<DefineClass> dc = (Class<DefineClass>) cl.myDefineClass(myName, buf, 0, buf.length);
System.out.println(dc);
}
catch (LinkageError jle) {
// Can only define once!
if (i == 0) throw new Exception("Should succeed the first time.");
}
}
// We expect to have two instances of DefineClass here: the initial version in which we are
// executing and another version which was loaded into our own classloader 'MyClassLoader'.
// All the subsequent attempts to reload DefineClass into our 'MyClassLoader' should have failed.
printClassStats(2, false);
System.gc();
System.out.println("System.gc()");
// At least after System.gc() the failed loading attempts should leave no instances around!
printClassStats(2, true);
}
else if ("defineSystemClass".equals(args[0])) {
MyClassLoader cl = new MyClassLoader();
int index = getStringIndex("test/DefineClass", buf);
replaceString(buf, "java/DefineClass", index);
while ((index = getStringIndex("Ltest/DefineClass;", buf, index + 1)) != 0) {
replaceString(buf, "Ljava/DefineClass;", index);
}
index = getStringIndex("test.DefineClass", buf);
replaceString(buf, "java.DefineClass", index);
for (int i = 0; i < iterations; i++) {
try {
@SuppressWarnings("unchecked")
Class<DefineClass> dc = (Class<DefineClass>) cl.myDefineClass(null, buf, 0, buf.length);
throw new RuntimeException("Defining a class in the 'java' package should fail!");
}
catch (java.lang.SecurityException jlse) {
// Expected, because we're not allowed to define a class in the 'java' package
}
}
// We expect to stay with one (the initial) instances of DefineClass.
// All the subsequent attempts to reload DefineClass into the 'java' package should have failed.
printClassStats(1, false);
System.gc();
System.out.println("System.gc()");
// At least after System.gc() the failed loading attempts should leave no instances around!
printClassStats(1, true);
}
else if ("defineClassParallel".equals(args[0])) {
MyParallelClassLoader pcl = new MyParallelClassLoader();
CountDownLatch stop = new CountDownLatch(1);
Thread[] threads = new Thread[iterations];
for (int i = 0; i < iterations; i++) {
(threads[i] = new ParallelLoadingThread(pcl, buf, stop)).start();
}
stop.countDown(); // start parallel class loading..
// ..and wait until all threads loaded the class
for (int i = 0; i < iterations; i++) {
threads[i].join();
}
System.out.print("Counted " + pcl.getLinkageErrors() + " LinkageErrors ");
System.out.println(pcl.getLinkageErrors() == 0 ?
"" : "(use -XX:+UnsyncloadClass and/or -XX:+AllowParallelDefineClass to avoid this)");
System.gc();
System.out.println("System.gc()");
// After System.gc() we expect to remain with two instances: one is the initial version which is
// kept alive by this main method and another one in the parallel class loader.
printClassStats(2, true);
}
else if ("redefineClass".equals(args[0])) {
loadInstrumentationAgent(myName, buf);
int index = getStringIndex("AAAAAAAA", buf);
CountDownLatch stop = new CountDownLatch(1);
Thread[] threads = new Thread[iterations];
for (int i = 0; i < iterations; i++) {
buf[index] = (byte) ('A' + i + 1); // Change string constant in getID() which is legal in redefinition
instrumentation.redefineClasses(new ClassDefinition(DefineClass.class, buf));
DefineClass dc = DefineClass.class.newInstance();
CountDownLatch start = new CountDownLatch(1);
(threads[i] = new MyThread(dc, start, stop)).start();
start.await(); // Wait until the new thread entered the getID() method
}
// We expect to have one instance for each redefinition because they are all kept alive by an activation
// plus the initial version which is kept active by this main method.
printClassStats(iterations + 1, false);
stop.countDown(); // Let all threads leave the DefineClass.getID() activation..
// ..and wait until really all of them returned from DefineClass.getID()
for (int i = 0; i < iterations; i++) {
threads[i].join();
}
System.gc();
System.out.println("System.gc()");
// After System.gc() we expect to remain with two instances: one is the initial version which is
// kept alive by this main method and another one which is the latest redefined version.
printClassStats(2, true);
}
else if ("redefineClassWithError".equals(args[0])) {
loadInstrumentationAgent(myName, buf);
int index = getStringIndex("getID", buf);
for (int i = 0; i < iterations; i++) {
buf[index] = (byte) 'X'; // Change getID() to XetID() which is illegal in redefinition
try {
instrumentation.redefineClasses(new ClassDefinition(DefineClass.class, buf));
throw new RuntimeException("Class redefinition isn't allowed to change method names!");
}
catch (UnsupportedOperationException uoe) {
// Expected because redefinition can't change the name of methods
}
}
// We expect just a single DefineClass instance because failed redefinitions should
// leave no garbage around.
printClassStats(1, false);
System.gc();
System.out.println("System.gc()");
// At least after a System.gc() we should definitely stay with a single instance!
printClassStats(1, true);
}
}
}