Threading bug in TaskGroup.java

Some people have complained about iteration() not returning. I had that problem and think I've solved it. In TaskGroup.waitForComplete(), the check is performed before the lock is acquired, so if the final worker completes after the main thread does the check but before it gets the lock, the main thread will sit in this.mightBeDone.await() forever without being notified.

I added a second check after the lock is acquired :

try {
if (!getNoTasks()) {
this.mightBeDone.await();
}
} catch (InterruptedException e) {
...


Since doing this, iteration() has always returned over millions of trials.

Hope this helps.