Race condition in Promise

[trumpetinc]

The Promise class needs the get() method to check to see if the value has already been set BEFORE calling wait(). If no thread is waiting when the other thread calls calls notifyAll(), then it's a NOP and the wait()ing thread will wait forever. Classic race condition. I sometimes see an RPC call that waits forever because the response comes back faster than the client thread can call enter get() and call wait().