[XMLBEANS-345] Setting the same variable to multiple properties in multi-threaded environment causes deadlocking

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Invalid
• Affects Version/s: Version 2.3, Version 2.3.1
• Component/s: XmlObject
• Environment: Microsoft Windows XP [Version 5.1.2600], single-core; java version "1.5.0_10"; Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_10-b03); Java HotSpot(TM) Client VM (build 1.5.0_10-b03, mixed mode)
• Assignee: Unassigned
• Reporter: Ian Sollars
• Created: 18/Oct/07 13:25
• Updated: 28/Mar/08 00:18
• Resolved: 28/Mar/08 00:18

Description

When setting a property on many XmlBeans objects with a single large variable, all threads concerned will block with this stacktrace:

java.lang.Object.wait:-2
java.lang.Object.wait:-1
org.apache.xmlbeans.impl.common.Mutex.acquire:33
org.apache.xmlbeans.impl.common.GlobalLock.acquire:27
org.apache.xmlbeans.impl.values.XmlObjectBase.set:1944

The test below sets a Type on it's Document and illustrates the problem. I can't publish the actual schema and namespace, but to give an idea of size, the XML object is about 90 KB of complex data (multiple namespaces, hundreds of elements, embedded CDATA).

A workaround has been included in commented-out form.

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.xmlbeans.XmlException;

import tests.LargeDataStructureType;
import tests.LargeDataStructureDocument;

public class BlockingExample {

public static void main(String[] args) throws InterruptedException, XmlException, IOException {

LargeDataStructureDocument doc = LargeDataStructureDocument.Factory.parse(new File("exampleFile.xml"));

LargeDataStructureType type = doc.getLargeDataStructureType();

List<Setter> setters = new ArrayList<Setter>();

for(int i = 0; i != 20; i++) setters.add(new Setter(key));

for(Setter s : setters) s.start();

Thread.sleep(10000);

Map<Thread,StackTraceElement[]> map=Thread.getAllStackTraces();
for(Thread t:map.keySet()){
StackTraceElement[] ss=map.get(t);
System.out.println("Thread:"t.getName()":"t.getState()":"+t.isAlive());

if(ss!=null) {
for(StackTraceElement s:ss)

{ System.out.println("\t"+s.getClassName()+"."+s.getMethodName()+":"+s.getLineNumber()); }

}
}

System.exit(0);

}
}

class Setter extends Thread {

private static int counter = 0;

private LargeDataStructureType type;

Setter(LargeDataStructureType type)

{ /* * This reproduces the behaviour */ this.type = type; /* * This also reproduces the behaviour */ // this.type = (LargeDataStructureType)type.copy(); /* * This is a reliable workaround. */ // this.type = LargeDataStructureType.Factory.newInstance(); // type.set(type); }

public void run() {
while(true) {
LargeDataStructureDocument obj = LargeDataStructureDocument.Factory.newInstance();
obj.setLargeDataStructure(key);

if(counter++ % 10000 == 0)

{ System.out.print("."); }

}
}

}

This produces the following output:

.Thread:Thread-7:WAITING:true
java.lang.Object.wait:-2
java.lang.Object.wait:-1
org.apache.xmlbeans.impl.common.Mutex.acquire:33
org.apache.xmlbeans.impl.common.GlobalLock.acquire:27
org.apache.xmlbeans.impl.values.XmlObjectBase.set:1944
tests.LargeDataStructureTypeImpl.setLargeDataStructure:xx
be.inglease.wel.Setter.run:64
Thread:Thread-13:WAITING:true
java.lang.Object.wait:-2
java.lang.Object.wait:-1
org.apache.xmlbeans.impl.common.Mutex.acquire:33
org.apache.xmlbeans.impl.common.GlobalLock.acquire:27
org.apache.xmlbeans.impl.values.XmlObjectBase.set:1944
tests.LargeDataStructureTypeImpl.setLargeDataStructure:xx
be.inglease.wel.Setter.run:64

(...etc. for 20 threads)

The expected output would just be lots of dots followed by various stacktraces.