wait until change

[Matthew Wilson]

I just took a midterm in my operating systems class, and a big topic was
"busy waiting" and semaphores.

And now, today, a real-world example!  Anyway, the time.sleep() method
is probably good enough, but how would a semaphore solution work in
python?  A semaphore solution is one where the process that uses the
updated file is asleep until another process says "Hey! Wake up! I
updated the file!".  This avoids all those check_for_update() calls
which bog down the CPU.

Anyone?