Use of Py_BEGIN_ALLOW_THREADS?

[Aahz Maruch]

In article <3AD42A5F.73AE10EC at rfa.org>, Bill Eldridge  <bill at rfa.org> wrote:
>
>I'm calling a C function from Python, and that C function in turn calls
>another C function #2 with a C callback function.
>
>Somewhere it seems like with threads it disappears - all of the debug
>messages in function #2 come out, but the C callback never gets called.

So you're saying that this works correctly if you don't use threads?
What happens if you have multiple threads, but only one thread calls the
original C function?  My suspicion is that you're getting cross-thread
contamination in your C code because it isn't thread-safe.  

Note that you should *ONLY* use Py_BEGIN_ALLOW_THREADS if your code is
"thread hot"; that is, not just thread-safe, but designed to allow
multiple threads into the same code at the same time.  In the absence of
Py_BEGIN_ALLOW_THREADS, your C code is considered to be one Python
bytecode and executes as a single unit.
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