Embedding Python in a C extension

[Paul]

I have a problem with embedding Python into a C extension in Windows
Vista. I have implemented a timer routine in C as an extension, which
I can import into Python 2.6.5 and run. Each timer interval, the
extension calls a C CALLBACK function. I want to be able to have this
CALLBACK function call a Python function, so that I can write the
timer handler in Python.

I can write Python functions and call them from a C extension function
with no trouble in all cases EXCEPT when the function that calls the
Python code is the timer's CALLBACK function. That is, if I call
PyRun_SimpleString or PyRun_SimpleFile, or PyImport_ImportModule, or
basically any Python-y function in the CALLBACK function, Python
crashes and I get a window saying "Python has stopped working. Windows
is searching for a solution to the problem."

The Python code runs fine if I call it from a function in the
extension that is not the CALLBACK function. And regular C code runs
in the CALLBACK function properly. It only crashes if I try to run the
Python code from the timer CALLBACK function (or any C function I call
from the CALLBACK function).

Does anybody know how to fix this? Is there a workaround of some sort?