bpo-40521: Disable free lists in subinterpreters (GH-19937)
When Python is built with experimental isolated interpreters, disable
tuple, dict and free free lists.
Temporary workaround until these caches are made per-interpreter.
Add frame_alloc() and frame_get_builtins() subfunctions to simplify
_PyFrame_New_NoTrack().
diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 4f5054d..af32276 100644
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -556,12 +556,20 @@
free_list. Else programs creating lots of cyclic trash involving
frames could provoke free_list into growing without bound.
*/
-
-static PyFrameObject *free_list = NULL;
-static int numfree = 0; /* number of frames currently in free_list */
/* max value for numfree */
#define PyFrame_MAXFREELIST 200
+/* bpo-40521: frame free lists are shared by all interpreters. */
+#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
+# undef PyFrame_MAXFREELIST
+# define PyFrame_MAXFREELIST 0
+#endif
+
+#if PyFrame_MAXFREELIST > 0
+static PyFrameObject *free_list = NULL;
+static int numfree = 0; /* number of frames currently in free_list */
+#endif
+
static void _Py_HOT_FUNCTION
frame_dealloc(PyFrameObject *f)
{
@@ -590,15 +598,19 @@
Py_CLEAR(f->f_trace);
co = f->f_code;
- if (co->co_zombieframe == NULL)
+ if (co->co_zombieframe == NULL) {
co->co_zombieframe = f;
+ }
+#if PyFrame_MAXFREELIST > 0
else if (numfree < PyFrame_MAXFREELIST) {
++numfree;
f->f_back = free_list;
free_list = f;
}
- else
+#endif
+ else {
PyObject_GC_Del(f);
+ }
Py_DECREF(co);
Py_TRASHCAN_SAFE_END(f)
@@ -759,15 +771,107 @@
_Py_IDENTIFIER(__builtins__);
+static inline PyFrameObject*
+frame_alloc(PyCodeObject *code)
+{
+ PyFrameObject *f;
+
+ f = code->co_zombieframe;
+ if (f != NULL) {
+ code->co_zombieframe = NULL;
+ _Py_NewReference((PyObject *)f);
+ assert(f->f_code == code);
+ return f;
+ }
+
+ Py_ssize_t ncells = PyTuple_GET_SIZE(code->co_cellvars);
+ Py_ssize_t nfrees = PyTuple_GET_SIZE(code->co_freevars);
+ Py_ssize_t extras = code->co_stacksize + code->co_nlocals + ncells + nfrees;
+#if PyFrame_MAXFREELIST > 0
+ if (free_list == NULL)
+#endif
+ {
+ f = PyObject_GC_NewVar(PyFrameObject, &PyFrame_Type, extras);
+ if (f == NULL) {
+ return NULL;
+ }
+ }
+#if PyFrame_MAXFREELIST > 0
+ else {
+ assert(numfree > 0);
+ --numfree;
+ f = free_list;
+ free_list = free_list->f_back;
+ if (Py_SIZE(f) < extras) {
+ PyFrameObject *new_f = PyObject_GC_Resize(PyFrameObject, f, extras);
+ if (new_f == NULL) {
+ PyObject_GC_Del(f);
+ return NULL;
+ }
+ f = new_f;
+ }
+ _Py_NewReference((PyObject *)f);
+ }
+#endif
+
+ f->f_code = code;
+ extras = code->co_nlocals + ncells + nfrees;
+ f->f_valuestack = f->f_localsplus + extras;
+ for (Py_ssize_t i=0; i<extras; i++) {
+ f->f_localsplus[i] = NULL;
+ }
+ f->f_locals = NULL;
+ f->f_trace = NULL;
+ return f;
+}
+
+
+static inline PyObject *
+frame_get_builtins(PyFrameObject *back, PyObject *globals)
+{
+ PyObject *builtins;
+
+ if (back != NULL && back->f_globals == globals) {
+ /* If we share the globals, we share the builtins.
+ Save a lookup and a call. */
+ builtins = back->f_builtins;
+ assert(builtins != NULL);
+ Py_INCREF(builtins);
+ return builtins;
+ }
+
+ builtins = _PyDict_GetItemIdWithError(globals, &PyId___builtins__);
+ if (builtins != NULL && PyModule_Check(builtins)) {
+ builtins = PyModule_GetDict(builtins);
+ assert(builtins != NULL);
+ }
+ if (builtins != NULL) {
+ Py_INCREF(builtins);
+ return builtins;
+ }
+
+ if (PyErr_Occurred()) {
+ return NULL;
+ }
+
+ /* No builtins! Make up a minimal one.
+ Give them 'None', at least. */
+ builtins = PyDict_New();
+ if (builtins == NULL) {
+ return NULL;
+ }
+ if (PyDict_SetItemString(builtins, "None", Py_None) < 0) {
+ Py_DECREF(builtins);
+ return NULL;
+ }
+ return builtins;
+}
+
+
PyFrameObject* _Py_HOT_FUNCTION
_PyFrame_New_NoTrack(PyThreadState *tstate, PyCodeObject *code,
PyObject *globals, PyObject *locals)
{
- PyFrameObject *back = tstate->frame;
- PyFrameObject *f;
- PyObject *builtins;
- Py_ssize_t i;
-
#ifdef Py_DEBUG
if (code == NULL || globals == NULL || !PyDict_Check(globals) ||
(locals != NULL && !PyMapping_Check(locals))) {
@@ -775,82 +879,19 @@
return NULL;
}
#endif
- if (back == NULL || back->f_globals != globals) {
- builtins = _PyDict_GetItemIdWithError(globals, &PyId___builtins__);
- if (builtins) {
- if (PyModule_Check(builtins)) {
- builtins = PyModule_GetDict(builtins);
- assert(builtins != NULL);
- }
- }
- if (builtins == NULL) {
- if (PyErr_Occurred()) {
- return NULL;
- }
- /* No builtins! Make up a minimal one
- Give them 'None', at least. */
- builtins = PyDict_New();
- if (builtins == NULL ||
- PyDict_SetItemString(
- builtins, "None", Py_None) < 0)
- return NULL;
- }
- else
- Py_INCREF(builtins);
+ PyFrameObject *back = tstate->frame;
+ PyObject *builtins = frame_get_builtins(back, globals);
+ if (builtins == NULL) {
+ return NULL;
}
- else {
- /* If we share the globals, we share the builtins.
- Save a lookup and a call. */
- builtins = back->f_builtins;
- assert(builtins != NULL);
- Py_INCREF(builtins);
- }
- if (code->co_zombieframe != NULL) {
- f = code->co_zombieframe;
- code->co_zombieframe = NULL;
- _Py_NewReference((PyObject *)f);
- assert(f->f_code == code);
- }
- else {
- Py_ssize_t extras, ncells, nfrees;
- ncells = PyTuple_GET_SIZE(code->co_cellvars);
- nfrees = PyTuple_GET_SIZE(code->co_freevars);
- extras = code->co_stacksize + code->co_nlocals + ncells +
- nfrees;
- if (free_list == NULL) {
- f = PyObject_GC_NewVar(PyFrameObject, &PyFrame_Type,
- extras);
- if (f == NULL) {
- Py_DECREF(builtins);
- return NULL;
- }
- }
- else {
- assert(numfree > 0);
- --numfree;
- f = free_list;
- free_list = free_list->f_back;
- if (Py_SIZE(f) < extras) {
- PyFrameObject *new_f = PyObject_GC_Resize(PyFrameObject, f, extras);
- if (new_f == NULL) {
- PyObject_GC_Del(f);
- Py_DECREF(builtins);
- return NULL;
- }
- f = new_f;
- }
- _Py_NewReference((PyObject *)f);
- }
- f->f_code = code;
- extras = code->co_nlocals + ncells + nfrees;
- f->f_valuestack = f->f_localsplus + extras;
- for (i=0; i<extras; i++)
- f->f_localsplus[i] = NULL;
- f->f_locals = NULL;
- f->f_trace = NULL;
+ PyFrameObject *f = frame_alloc(code);
+ if (f == NULL) {
+ Py_DECREF(builtins);
+ return NULL;
}
+
f->f_stacktop = f->f_valuestack;
f->f_builtins = builtins;
Py_XINCREF(back);
@@ -1142,6 +1183,7 @@
void
_PyFrame_ClearFreeList(void)
{
+#if PyFrame_MAXFREELIST > 0
while (free_list != NULL) {
PyFrameObject *f = free_list;
free_list = free_list->f_back;
@@ -1149,6 +1191,7 @@
--numfree;
}
assert(numfree == 0);
+#endif
}
void
@@ -1161,9 +1204,11 @@
void
_PyFrame_DebugMallocStats(FILE *out)
{
+#if PyFrame_MAXFREELIST > 0
_PyDebugAllocatorStats(out,
"free PyFrameObject",
numfree, sizeof(PyFrameObject));
+#endif
}