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Posted to mod_python-dev@quetz.apache.org by "Graham Dumpleton (JIRA)" <ji...@apache.org> on 2006/03/05 07:45:42 UTC
[jira] Work started: (MODPYTHON-77) The multiple interpreter
concept of mod_python is broken for Python extension modules since Python
2.3
[ http://issues.apache.org/jira/browse/MODPYTHON-77?page=all ]
Work on MODPYTHON-77 started by Graham Dumpleton
> 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
> Assignee: Graham Dumpleton
> Fix For: 3.3
> Attachments: diff.txt, diff2.txt, diff3.txt, gil_test.c, gilstate.tar.gz, grahamd_20051105.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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