Short and sweet module doing something very useful: for event loop

based threads, release the GIL when the event loop goes to sleep,
and acquire it again when the event loop wakes up again. OSX-only.

diff --git a/Mac/Modules/autoGIL.c b/Mac/Modules/autoGIL.c
new file mode 100644 (file)
index 0000000..4ee1e75
--- /dev/null
+++ b/Mac/Modules/autoGIL.c
@@ -0,0 +1,149 @@
+#include "Python.h"
+#include <CoreFoundation/CFRunLoop.h>
+
+/* These macros are defined in Python 2.3 but not 2.2 */
+#ifndef PyMODINIT_FUNC
+#define PyMODINIT_FUNC void
+#endif
+#ifndef PyDoc_STRVAR
+#define PyDoc_STRVAR(Var,Str) static char Var[] = Str
+#endif
+
+
+#undef AUTOGIL_DEBUG
+
+static PyObject *AutoGILError;
+
+
+static void autoGILCallback(CFRunLoopObserverRef observer,
+                           CFRunLoopActivity activity,
+                           void *info) {
+       PyThreadState **p_tstate = (PyThreadState **)info;
+
+       switch (activity) {
+       case kCFRunLoopBeforeWaiting:
+               /* going to sleep, release GIL */
+#ifdef AUTOGIL_DEBUG
+               fprintf(stderr, "going to sleep, release GIL\n");
+#endif
+               *p_tstate = PyEval_SaveThread();
+               break;
+       case kCFRunLoopAfterWaiting:
+               /* waking up, acquire GIL */
+#ifdef AUTOGIL_DEBUG
+               fprintf(stderr, "waking up, acquire GIL\n");
+#endif
+               PyEval_RestoreThread(*p_tstate);
+               *p_tstate = NULL;
+               break;
+       default:
+               break;
+       }
+}
+
+static void infoRelease(const void *info) {
+       /* XXX This should get called when the run loop is deallocated,
+          but this doesn't seem to happen. So for now: leak. */
+       PyMem_Free((void *)info);
+}
+
+static PyObject *
+autoGIL_installAutoGIL(PyObject *self)
+{
+       PyObject *tstate_dict = PyThreadState_GetDict();
+       PyObject *v;
+       CFRunLoopRef rl;
+       PyThreadState **p_tstate;  /* for use in the info field */
+       CFRunLoopObserverContext context = {0, NULL, NULL, NULL, NULL};
+       CFRunLoopObserverRef observer;
+
+       if (tstate_dict == NULL)
+               return NULL;
+       v = PyDict_GetItemString(tstate_dict, "autoGIL.InstalledAutoGIL");
+       if (v != NULL) {
+               /* we've already installed a callback for this thread */
+               Py_INCREF(Py_None);
+               return Py_None;
+       }
+
+       rl = CFRunLoopGetCurrent();
+       if (rl == NULL) {
+               PyErr_SetString(AutoGILError,
+                               "can't get run loop for current thread");
+               return NULL;
+       }
+
+       p_tstate = PyMem_Malloc(sizeof(PyThreadState *));
+       if (p_tstate == NULL) {
+               PyErr_SetString(PyExc_MemoryError,
+                               "not enough memory to allocate "
+                               "tstate pointer");
+               return NULL;
+       }
+       *p_tstate = NULL;
+       context.info = (void *)p_tstate;
+       context.release = infoRelease;
+
+       observer = CFRunLoopObserverCreate(
+               NULL,
+               kCFRunLoopBeforeWaiting | kCFRunLoopAfterWaiting,
+               1, 0, autoGILCallback, &context);
+       if (observer == NULL) {
+               PyErr_SetString(AutoGILError,
+                               "can't create event loop observer");
+               return NULL;
+       }
+       CFRunLoopAddObserver(rl, observer, kCFRunLoopDefaultMode);
+       /* XXX how to check for errors? */
+
+       /* register that we have installed a callback for this thread */
+       if (PyDict_SetItemString(tstate_dict, "autoGIL.InstalledAutoGIL",
+                                Py_None) < 0)
+               return NULL;
+
+       Py_INCREF(Py_None);
+       return Py_None;
+}
+
+PyDoc_STRVAR(autoGIL_installAutoGIL_doc,
+"installAutoGIL() -> None\n\
+Install an observer callback in the event loop (CFRunLoop) for the\n\
+current thread that will lock and unlock the Global Interpreter Lock\n\
+(GIL) at appropriate times, allowing other Python threads to run while\n\
+the event loop is running."
+);
+
+static PyMethodDef autoGIL_methods[] = {
+       {
+               "installAutoGIL",
+               (PyCFunction)autoGIL_installAutoGIL,
+               METH_NOARGS,
+               autoGIL_installAutoGIL_doc
+       },
+       { 0, 0, 0, 0 } /* sentinel */
+};
+
+PyDoc_STRVAR(autoGIL_docs,
+"The autoGIL module provides a function (installAutoGIL) that\n\
+automatically locks and unlocks Python's Global Interpreter Lock\n\
+when running an event loop."
+);
+
+PyMODINIT_FUNC
+initautoGIL(void)
+{
+       PyObject *mod;
+
+       mod = Py_InitModule4("autoGIL", autoGIL_methods, autoGIL_docs,
+                            NULL, PYTHON_API_VERSION);
+       if (mod == NULL)
+               return;
+       AutoGILError = PyErr_NewException("autoGIL.AutoGILError",
+                                         PyExc_Exception, NULL);
+       if (AutoGILError == NULL)
+               return;
+       Py_INCREF(AutoGILError);
+       if (PyModule_AddObject(mod, "AutoGILError",
+                              AutoGILError) < 0)
+               return;
+}