/*
* Get the current Fiber reference on the current thread. The first time this
* function is called on a given (real) thread, the main Fiber is created.
*/
static Fiber *
get_current(void)
{
Fiber *current;
PyObject *tstate_dict;
/* get current Fiber from the active thread-state */
tstate_dict = PyThreadState_GetDict();
if (tstate_dict == NULL) {
if (!PyErr_Occurred()) {
PyErr_NoMemory();
}
return NULL;
}
current = (Fiber *)PyDict_GetItem(tstate_dict, current_fiber_key);
if (current == NULL) {
current = fiber_create_main();
if (current == NULL) {
return NULL;
}
/* Keep a reference to the main fiber in the thread dict. The main
* fiber is special because we don't require the user to keep a
* reference to it. It should be deleted when the thread exits. */
if (PyDict_SetItem(tstate_dict, main_fiber_key, (PyObject *) current) < 0) {
Py_DECREF(current);
return NULL;
}
/* current starts out as main */
if (PyDict_SetItem(tstate_dict, current_fiber_key, (PyObject *) current) < 0) {
Py_DECREF(current);
return NULL;
}
/* return a borrowed ref. refcount should be 2 after this */
Py_DECREF(current);
}
ASSERT(current != NULL);
return current;
}
/*
* Update the current Fiber reference on the current thread. The first time this
* function is called on a given (real) thread, the main Fiber is created.
*/
static Fiber *
update_current(void)
{
Fiber *current, *previous;
PyObject *exc, *val, *tb, *tstate_dict;
restart:
/* save current exception */
PyErr_Fetch(&exc, &val, &tb);
/* get current Fiber from the active thread-state */
tstate_dict = PyThreadState_GetDict();
if (tstate_dict == NULL) {
if (!PyErr_Occurred()) {
PyErr_NoMemory();
}
return NULL;
}
current = (Fiber *)PyDict_GetItem(tstate_dict, current_fiber_key);
if (current) {
/* found - remove it, to avoid keeping a ref */
Py_INCREF(current);
PyDict_DelItem(tstate_dict, current_fiber_key);
} else {
/* first time we see this thread-state, create main Fiber */
current = fiber_create_main();
if (current == NULL) {
Py_XDECREF(exc);
Py_XDECREF(val);
Py_XDECREF(tb);
return NULL;
}
if (_global_state.current == NULL) {
/* First time a main Fiber is allocated in any thread */
_global_state.current = current;
}
}
ASSERT(current->ts_dict == tstate_dict);
retry:
Py_INCREF(current);
previous = _global_state.current;
_global_state.current = current;
if (PyDict_GetItem(previous->ts_dict, current_fiber_key) != (PyObject *)previous) {
/* save previous as the current Fiber of its own (real) thread */
if (PyDict_SetItem(previous->ts_dict, current_fiber_key, (PyObject*) previous) < 0) {
Py_DECREF(previous);
Py_DECREF(current);
Py_XDECREF(exc);
Py_XDECREF(val);
Py_XDECREF(tb);
return NULL;
}
Py_DECREF(previous);
}
ASSERT(Py_REFCNT(previous) >= 1);
if (_global_state.current != current) {
/* some Python code executed above and there was a thread switch,
* so the global current points to some other Fiber again. We need to
* delete current_fiber_key and retry. */
PyDict_DelItem(tstate_dict, current_fiber_key);
goto retry;
}
/* release the extra reference */
Py_DECREF(current);
/* restore current exception */
PyErr_Restore(exc, val, tb);
/* thread switch could happen during PyErr_Restore, in that
case there's nothing to do except restart from scratch. */
if (_global_state.current->ts_dict != tstate_dict) {
goto restart;
}
return current;
}
