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  1. mod_python
  2. MODPYTHON-77

The multiple interpreter concept of mod_python is broken for Python extension modules since Python 2.3

    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 3.1.4
    • Fix Version/s: 3.3.1
    • Component/s: core
    • Labels:
      None
    • Environment:
      Python >= 2.3

      Description

      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 .

        Attachments

        1. src.zip
          17 kB
          Boyan Boyadjiev
        2. mod_python.h.diff
          0.5 kB
          Boyan Boyadjiev
        3. mod_python.c.diff
          9 kB
          Boyan Boyadjiev
        4. mod_python.c
          67 kB
          Boyan Boyadjiev
        5. grahamd_20051105.tar.gz
          16 kB
          Graham Dumpleton
        6. gilstate.tar.gz
          1 kB
          Graham Dumpleton
        7. gil_test.c
          2 kB
          Boyan Boyadjiev
        8. diff3.txt
          2 kB
          Boyan Boyadjiev
        9. diff2.txt
          2 kB
          Boyan Boyadjiev
        10. diff.txt
          1 kB
          Boyan Boyadjiev

          Activity

            People

            • Assignee:
              grahamd Graham Dumpleton
              Reporter:
              bb Boyan Boyadjiev
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              Dates

              • Created:
                Updated:
                Resolved: