Using PyGILState_Ensure

[Ralf Riemer]

Hi,

I have some questions concerning the global interpreter lock:

I am working with Windows XP Professional Version 5.1, Python version 2.4.1
and Microsoft Visual C++.Net Version 7.1.[color=blue]
>From Python I call a function from a C++ dll using[/color]
calldll.call_fo reign_function. This C++ function does a callback of a python
function.
Do get it running I use PyGILState_Ensu re before PyEval_CallObje ct and
PyGILState_Rele ase afterwards.
The code looks like this:

static PyObject *my_callback = NULL;

...

// my_callback is set from Python using a function SetCallback
...


/* Time to call the callback */
ppyobjArgList = Py_BuildValue(" ()", NULL);

//General Interpreter Lock (essential for succesful
calling of any python function)
PyGILState_STAT E gstate;
//Ensure that the current thread is ready to call
the Python C API
gstate = PyGILState_Ensu re();

ppyobjResult = PyEval_CallObje ct(my_callback,
ppyobjArgList);
if (!((DWORD_PTR)p pyobjResult))
{
//Error handling
...
} else {
Py_DECREF(ppyob jResult);
}

Py_DECREF(ppyob jArgList);

PyGILState_Rele ase(gstate);

Now my questions:
Are there any risks aquiring the global interpreter lock?
Do I invoke by PyEval_CallObje ct a new python process? (I suppose not)
How long my this call of PyEval_CallObje ct last? Are there restictions to
the code I use in the called function.
Is it allowed to force the thread to wait (by aquiring the GIL)?
Is there a risk that windows hangs up?
Doing several calls of my dll function with the callback, is there a risk
that the calls overlap and information gets lost?

Thanks for your help!
Ralf

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