Need some help with Python/C api and threading
theller at python.net
Thu Jun 17 17:58:46 CEST 2004
>>>>>> "Steve" == Steve Menard <steve.menard at videotron.ca> writes:
> Steve> Here is my problem. I have this library thats hosts
> Steve> another language within python, and allows that language to
> Steve> call back INTO python.
> Steve> All is good as long as the other languages calls back on
> Steve> the same thread. If the callback arrives on a different
> Steve> thread, all hell break loose and the program dies horribly.
> Steve> looking at the C api documentation, I came upon the
> Steve> following block of code :
> Steve> PyThreadState *tstate; PyObject *result;
> Steve> /* interp is your reference to an interpreter
> Steve> object. */ tstate = PyThreadState_New(interp);
> Steve> PyEval_AcquireThread(tstate);
> Steve> /* Perform Python actions here. */ result =
> Steve> CallSomeFunction(); /* evaluate result */
> Steve> /* Release the thread. No Python API allowed beyond
> Steve> this point. */ PyEval_ReleaseThread(tstate);
> Steve> /* You can either delete the thread state, or save it
> Steve> until you need it the next time. */
> Steve> PyThreadState_Delete(tstate);
> Steve> Which would seem to be what I need. However, I have no idea
> Steve> how to get at that interp pointer. I tried the following :
> Steve> PyInterpreterState* interp =
> Steve> PyInterpreterState_New(); PyThreadState *tstate =
> Steve> PyThreadState_New(interp); PyEval_AcquireThread(tstate);
> Steve> but then it crashes on the second line ...
> Steve> Anybody ever done this? As a side note, the hosted language
> Steve> can start an arbitrary number of threads ...
> Steve> Steve
If your library is a Python extension, you should get and save the
PyInterpreterState in the initxxx() function, which initializes the
If using Python 2.3 you could (should?) probably use the
PyGILState_Ensure() and PyGILState_Release() functions, which manage all
this for you. See PEP311 http://www.python.org/peps/pep-0311.html.
Maybe also it is needed to call PyEval_InitThreads() somewhere in the
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