Hi, @pwendell , this was added last night, 

as I explained, now, actorOf is non-blocking, I found it because sometimes DAGScheduler.submitJob() is called before eventProcessActor is well initialized causing NPE in https://github.com/CodingCat/spark/blob/SPARK-1235/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala#L428, though we are building eventProcessActor in the constructor of DAGScheduler....

I agree that ....ah...busy waiting here need to be fixed

for why we set a global status in supervisorActor....I think it's just to minimize the modification.....I can move declaration of eventProcessActor to supervisor....