Help with concurrency - traversing a DAG

[tbttfox]

On Friday, 18 October 2013 at 19:47:37 UTC, qznc wrote:
> Create a task for each node without a parent. Let the tasks 
> create new tasks for their children.

I was finally able to try this out, but I'm having a problem.
My test case right now is a simple linked list, and what I think 
happens is that the queue empties and makes it past the 
pool.finish() before the worker thread can add another task to 
the queue.

Here's the code:
http://pastebin.com/LLfMyKVp

Thanks again