PyThreadState_Swap(NULL)

[Bryan]

Jack Diederich wrote:
> On Fri, Aug 18, 2006 at 02:21:40PM -0700, Bryan wrote:
>> i've written a program that uses python c api code that lives in a 
>> shared library that is loaded by a custom apache module (mod_xxx).  this 
>> python c api code all works correctly under our test server and under 
>> apache but only if mod_python isn't loaded.  when apache loads 
>> mod_python as shown in the http.conf snippet below, 
>> PyThreadState_Swap(NULL) in mod_xxx returns NULL.  when the snippet of 
>> code in http.conf is commented out, it works again.  what do i have to 
>> do to have mod_xxx code work correctly when apache loads mod_python?
>>
>>
>> failure case when apache loads mod_python:
>>      Py_Initialize() succeeded
>>      PyThreadState_Swap(NULL) failed
>>
>>
>> sucess case when apache doesn't load mod_python:
>>      Py_Initialize() succeeded
>>      PyThreadState_Swap(NULL) succeeded
>>
> 
> Running multiple python interpreters in the same process isn't supported.
> It works OK for most things but some low-level guts are shared between
> interpreters so it is possible to run into trouble.
> 
> You aren't running multiple interpreters in the same process.  You and
> mod_python both think you are in charge and end up nuking each other's 
> states. Py_Initialize() resets the global state and shouldn't be called 
> more than once.  You can create more than one sub-interpreter (check out
> the mod_python source for how, the source is small and readable).
> 
> The best thing to do would be to load your module last and conitionally
> call Py_Initialize() if someone else hasn't already.
> 
> -Jack


thanks for replying jack. i tested what you suggested.

i put our module after mod_python, commented out Py_Initialize(), and 
Py_IsInitialized() returned True, but PyThreadState_Swap() failed.

i put our module before mod_python, called Py_Initialize(), and 
Py_IsInitialized() returned True, but PyThreadState_Swap() failed.

i removed mod_python and our module succeeded.

i even tested combinations of calling and PyEval_InitThreads() but didn't work 
either.


bryan