To be a bit more constructive, why not add something like this in paragraph to http://docs.python.org/library/ctypes.html#callback-functions:

"Note that if the callback function is called in a new thread that has been created outside of Python's control (i.e., by the foreign code that calls the callback), ctypes creates a new dummy Python thread on every invocation. That means that values stored with `threading.local` will *not* survive across different callbacks.