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http://issues.apache.org/jira/browse/MODPYTHON-77?page=comments#action_12356739
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Graham Dumpleton commented on MODPYTHON-77:
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There are now so many different suggestions on this that it is all too
confusing.
In respect of latest suggested change to release_interpreter(), this code
wasn't based on latest code from 3.2 betas and therefore doesn't include fix
for where Python doesn't support threading at all. Ie., the base code on which
it should have been made was:
static void release_interpreter(void)
{
PyThreadState *tstate = PyThreadState_Get();
#ifdef WITH_THREAD
PyEval_ReleaseThread(tstate);
#else
PyThreadState_Swap(NULL);
#endif
PyThreadState_Delete(tstate);
}
Ie., new call to PyThreadState_Swap() not factored in.
I will refrain from posting what it perhaps should be so as not to make things
worse.
In terms of the comment "smallest required change", I am currently taking this
to mean that the most minimal change is still to install first interpreter as
"main_interpreter" and then to change release_interpreter() as suggested in
previous post.
Before anyone else posts any code, let me independently work out some changes
from scratch and thus verify the fixes or not. :-(
> The multiple interpreter concept of mod_python is broken for Python extension
> modules since Python 2.3
> ------------------------------------------------------------------------------------------------------
>
> Key: MODPYTHON-77
> URL: http://issues.apache.org/jira/browse/MODPYTHON-77
> Project: mod_python
> Type: Bug
> Components: core
> Versions: 3.1.4
> Environment: Python >= 2.3
> Reporter: Boyan Boyadjiev
> Attachments: diff.txt, diff2.txt, diff3.txt, gil_test.c, gilstate.tar.gz,
> mod_python.c, mod_python.c.diff, mod_python.h.diff, src.zip
>
> The multiple interpreter concept of mod_python is broken for Python extension
> modules since Python 2.3 because of the PEP 311 (Simplified Global
> Interpreter Lock Acquisition for Extensions):
> ...
> Limitations and Exclusions
> This proposal identifies a solution for extension authors with
> complex multi-threaded requirements, but that only require a
> single "PyInterpreterState". There is no attempt to cater for
> extensions that require multiple interpreter states. At the time
> of writing, no extension has been identified that requires
> multiple PyInterpreterStates, and indeed it is not clear if that
> facility works correctly in Python itself.
> ...
> For mod_python this means, that complex Python extensions won't work any more
> with Python >= 2.3, because they are supposed to work only with the first
> interpreter state initialized for the current process (a problem we
> experienced). The first interpreter state is not used by mod_python after the
> python_init is called.
> One solution, which works fine for me, is to save the first interpreter state
> into the "interpreters" dictionary in the function python_init
> (MAIN_INTERPRETER is used as a key):
> static int python_init(apr_pool_t *p, apr_pool_t *ptemp,
> apr_pool_t *plog, server_rec *s)
> {
> ...
> /* initialize global Python interpreter if necessary */
> if (! Py_IsInitialized())
> {
> /* initialze the interpreter */
> Py_Initialize();
> #ifdef WITH_THREAD
> /* create and acquire the interpreter lock */
> PyEval_InitThreads();
> #endif
> /* create the obCallBack dictionary */
> interpreters = PyDict_New();
> if (! interpreters) {
> ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, 0, s,
> "python_init: PyDict_New() failed! No more memory?");
> exit(1);
> }
> {
> /*
> Workaround PEP 311 - Simplified Global Interpreter Lock
> Acquisition for Extensions
> BEGIN
> */
> PyObject *p = 0;
> interpreterdata * idata = (interpreterdata
> *)malloc(sizeof(interpreterdata));
> PyThreadState* currentThreadState = PyThreadState_Get();
> PyInterpreterState *istate = currentThreadState->interp;
> idata->istate = istate;
> /* obcallback will be created on first use */
> idata->obcallback = NULL;
> p = PyCObject_FromVoidPtr((void ) idata, NULL); /*p->refcout = 1*/
> PyDict_SetItemString(interpreters, MAIN_INTERPRETER, p);
> /*p->refcout = 2*/
> Py_DECREF(p); /*p->refcout = 1*/
> /*
> END
> Workaround PEP 311 - Simplified Global Interpreter Lock
> Acquisition for Extensions
> */
> }
> /* Release the thread state because we will never use
> * the main interpreter, only sub interpreters created later. */
> PyThreadState_Swap(NULL);
> #ifdef WITH_THREAD
> /* release the lock; now other threads can run */
> PyEval_ReleaseLock();
> #endif
> }
> return OK;
> }
> Another change I've made in the attached file is to Py_DECREF(p) in
> get_interpreter, which will remove leaky reference to the PyCObject with the
> interpreter data. This was not a real problem, but now I see fewer leaks in
> BoundsChecker :-).
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