Right way to initialize python embedded in a multi-threaded application

[Mark Hammond]

On 17/05/2012 10:08 PM, shooshx wrote:
> I'm embedding python in a multi-threaded C application.
> I've taken care to wrap every call to the Python C API with
>
> gstate = PyGILState_Ensure();
> // call python code
> PyGILState_Release(gstate);
>
> But I'm stumped with what to do in the initialization.
> Right after the call to Py_IsInitialized() I've added a call:
>
> PyEval_InitThreads();
>
> The docs say that this function leaves the GIL locked when it returns.
> I do some more initializations like importing modules and then I call
>
> PyEval_ReleaseLock();
>
> This seems to cause a problem since not long after a call to
> PyGILState_Release(gstate) that's made in a different thread crashes.
> with
>
> "Fatal Python error: This thread state must be current when releasing"
>
> If I don't do the call to PyEval_ReleaseLock() in the main thread
> right after initialization, the GIL seems to be released
> after the first PyGILState_Ensure() - PyGILState_Release() pair.
>
> So what am I doing wrong here?
> What is the correct way of initializing a multi-threaded application?

Try replacing the PyEval_ReleaseLock() call with PyEval_SaveThread(); - 
that works for pythoncom, which has the same basic requirement - see 
http://pywin32.hg.sourceforge.net/hgweb/pywin32/pywin32/raw-file/b8c62cf04c5a/com/win32com/src/dllmain.cpp 
for how it works.

HTH,

Mark
>
>