Deadlock in nested contexts
---------------------------
Key: CAY-957
URL: https://issues.apache.org/cayenne/browse/CAY-957
Project: Cayenne
Issue Type: Bug
Components: Cayenne Core Library
Affects Versions: 1.2 [STABLE], 2.0 [STABLE], 3.0
Reporter: Andrus Adamchik
Assignee: Andrus Adamchik
Fix For: 3.0
There is a deadlock condition when two peer nested contexts commit
simultaneously. Here is a small test case:
package org.test;
import java.util.Date;
import java.util.List;
import java.util.Random;
import org.apache.cayenne.access.DataContext;
import org.apache.cayenne.query.EJBQLQuery;
public class Main {
public static void main(String[] args) {
DataContext parent = DataContext.createDataContext();
parent.performGenericQuery(new EJBQLQuery("delete from
Artist"));
for (int i = 0; i < 300; i++) {
Artist a = parent.newObject(Artist.class);
a.setArtistName("X" + i);
a.setDateOfBirth(new Date());
}
parent.commitChanges();
Random rnd = new Random(System.currentTimeMillis());
for (int i = 0; i < 2; i++) {
new UpdateThread(parent.createChildDataContext(),
rnd).start();
}
synchronized (parent) {
try {
parent.wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
static class UpdateThread extends Thread {
protected DataContext context;
protected Random rnd;
UpdateThread(DataContext context, Random rnd) {
super("UpdateThread-" + context.hashCode());
setDaemon(true);
this.context = context;
this.rnd = rnd;
}
@Override
public void run() {
List<Artist> artists = context.performQuery(new
EJBQLQuery(
"select a FROM Artist a"));
for (int i = 0; i < 1000; i++) {
for (int j = 0; j < 5; j++) {
int index = rnd.nextInt(artists.size());
Artist a = artists.get(index);
a.setArtistName("Y" + rnd.nextInt());
}
context.commitChanges();
System.out.println(getId() + ": " + i);
}
}
}
}
It deadlocks almost immediately with only two threads... Here is the stacks
from Jconsole:
Name: UpdateThread-9684455
State: BLOCKED on [EMAIL PROTECTED] owned by: UpdateThread-10872036
Total blocked: 7 Total waited: 1
Stack trace:
org.apache.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:54)
org.apache.cayenne.event.EventManager.dispatchEvent(EventManager.java:348)
org.apache.cayenne.event.EventManager.postEvent(EventManager.java:319)
org.apache.cayenne.access.DataContext.fireDataChannelChanged(DataContext.java:1457)
org.apache.cayenne.access.DataContext.onContextFlush(DataContext.java:1121)
org.apache.cayenne.access.DataContext.onSync(DataContext.java:1102)
org.apache.cayenne.access.DataContext.flushToParent(DataContext.java:1160)
org.apache.cayenne.access.DataContext.commitChanges(DataContext.java:1073)
org.test.Main$UpdateThread.run(Main.java:66)
Name: UpdateThread-10872036
State: BLOCKED on [EMAIL PROTECTED] owned by: UpdateThread-9684455
Total blocked: 9 Total waited: 0
Stack trace:
org.apache.cayenne.access.DataContextMergeHandler.graphChanged(DataContextMergeHandler.java:104)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
java.lang.reflect.Method.invoke(Method.java:585)
org.apache.cayenne.util.Invocation.fire(Invocation.java:204)
org.apache.cayenne.event.EventManager$Dispatch.fire(EventManager.java:409)
org.apache.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:162)
org.apache.cayenne.event.DispatchQueue.dispatchEvent(DispatchQueue.java:58)
org.apache.cayenne.event.EventManager.dispatchEvent(EventManager.java:348)
org.apache.cayenne.event.EventManager.postEvent(EventManager.java:319)
org.apache.cayenne.access.DataContext.fireDataChannelChanged(DataContext.java:1457)
org.apache.cayenne.access.DataContext.onContextFlush(DataContext.java:1121)
org.apache.cayenne.access.DataContext.onSync(DataContext.java:1102)
org.apache.cayenne.access.DataContext.flushToParent(DataContext.java:1160)
org.apache.cayenne.access.DataContext.commitChanges(DataContext.java:1073)
org.test.Main$UpdateThread.run(Main.java:66)
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