button threads

gistfile1.txt

parent                           child
request lock on mutex            :loop
create child thread              request lock on mutex (may be a timeout)

:loop
poll for button change

release lock on mutex
wait on barrier                  release lock on mutex (if not timeout)
                                 wait on barrier (if not timeout)
request lock on mutex            wait on barrier (if not timeout)
wait on barrier                  process button state based on button change
goto :loop                       goto :loop