Concurrency, I guess

[Stormcoder]

Using candygram you can send the sync thread a message telling it to
reread the config file or you could send a message that changes the
setting directly. Candygram is much better than the standard threading
module which is designed after the Java threading library. Java
recently added another threading library because the old one was not
adequate.

The reason you can't simply share a global variable is that threads do
not share state. You have to go through a lot of trouble to share that
state. First you have to setup some form of interprocess communications
such as a memory mapped file, shared mem, pipe, socket etc. You then
have to implement locking and try to debug what you have done.
Debugging multi threaded programs is inherently difficult.
I would highly recommend using candygram or an asynchronous library,
since it sounds like you haven't done any multi-threaded programming
before. In candygram you can send threads messages which don't require
any synchronization or IPC setup.