bpo-40514: Drop EXPERIMENTAL_ISOLATED_SUBINTERPRETERS (gh-93185)

This was added for bpo-40514 (gh-84694) to test out a per-interpreter GIL. However, it has since proven unnecessary to keep the experiment in the repo. (It can be done as a branch in a fork like normal.) So here we are removing:

* the configure option
* the macro
* the code enabled by the macro

Author: ericsnowcurrently

Doc/whatsnew/3.12.rst

@@ -115,6 +115,10 @@ Removed
 
   (Contributed by Erlend E. Aasland in :gh:`92548`)
 
+* The ``--experimental-isolated-subinterpreters`` configure flag
+  (and corresponding ``EXPERIMENTAL_ISOLATED_SUBINTERPRETERS``)
+  have been removed.
+
 
 Porting to Python 3.12
 ======================

Include/internal/pycore_ceval.h

@@ -81,11 +81,7 @@ _PyEval_Vector(PyThreadState *tstate,
             PyObject* const* args, size_t argcount,
             PyObject *kwnames);
 
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-extern int _PyEval_ThreadsInitialized(PyInterpreterState *interp);
-#else
 extern int _PyEval_ThreadsInitialized(struct pyruntimestate *runtime);
-#endif
 extern PyStatus _PyEval_InitGIL(PyThreadState *tstate);
 extern void _PyEval_FiniGIL(PyInterpreterState *interp);
 

Include/internal/pycore_interp.h

@@ -51,9 +51,6 @@ struct _ceval_state {
     /* Request for dropping the GIL */
     _Py_atomic_int gil_drop_request;
     struct _pending_calls pending;
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-    struct _gil_runtime_state gil;
-#endif
 };
 
 

Include/internal/pycore_pystate.h

@@ -64,18 +64,10 @@ _Py_ThreadCanHandlePendingCalls(void)
 /* Variable and macro for in-line access to current thread
    and interpreter state */
 
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-PyAPI_FUNC(PyThreadState*) _PyThreadState_GetTSS(void);
-#endif
-
 static inline PyThreadState*
 _PyRuntimeState_GetThreadState(_PyRuntimeState *runtime)
 {
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-    return _PyThreadState_GetTSS();
-#else
     return (PyThreadState*)_Py_atomic_load_relaxed(&runtime->gilstate.tstate_current);
-#endif
 }
 
 /* Get the current Python thread state.
@@ -90,11 +82,7 @@ _PyRuntimeState_GetThreadState(_PyRuntimeState *runtime)
 static inline PyThreadState*
 _PyThreadState_GET(void)
 {
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-    return _PyThreadState_GetTSS();
-#else
     return _PyRuntimeState_GetThreadState(&_PyRuntime);
-#endif
 }
 
 PyAPI_FUNC(void) _Py_NO_RETURN _Py_FatalError_TstateNULL(const char *func);

Include/internal/pycore_runtime.h

@@ -23,9 +23,7 @@ struct _ceval_runtime_state {
        the main thread of the main interpreter can handle signals: see
        _Py_ThreadCanHandleSignals(). */
     _Py_atomic_int signals_pending;
-#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
     struct _gil_runtime_state gil;
-#endif
 };
 
 /* GIL state */

Misc/NEWS.d/next/Core and Builtins/2022-05-25-12-30-12.gh-issue-84694.5sjy2w.rst

@@ -0,0 +1,2 @@
+The ``--experimental-isolated-subinterpreters`` configure option and
+``EXPERIMENTAL_ISOLATED_SUBINTERPRETERS`` macro have been removed.

Modules/_xxsubinterpretersmodule.c

@@ -1932,20 +1932,6 @@ _run_script_in_interpreter(PyInterpreterState *interp, const char *codestr,
         return -1;
     }
 
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-    // Switch to interpreter.
-    PyThreadState *new_tstate = PyInterpreterState_ThreadHead(interp);
-    PyThreadState *save1 = PyEval_SaveThread();
-
-    (void)PyThreadState_Swap(new_tstate);
-
-    // Run the script.
-    _sharedexception *exc = NULL;
-    int result = _run_script(interp, codestr, shared, &exc);
-
-    // Switch back.
-    PyEval_RestoreThread(save1);
-#else
     // Switch to interpreter.
     PyThreadState *save_tstate = NULL;
     if (interp != PyInterpreterState_Get()) {
@@ -1963,7 +1949,6 @@ _run_script_in_interpreter(PyInterpreterState *interp, const char *codestr,
     if (save_tstate != NULL) {
         PyThreadState_Swap(save_tstate);
     }
-#endif
 
     // Propagate any exception out to the caller.
     if (exc != NULL) {

Modules/gcmodule.c

@@ -1195,14 +1195,6 @@ gc_collect_main(PyThreadState *tstate, int generation,
     assert(gcstate->garbage != NULL);
     assert(!_PyErr_Occurred(tstate));
 
-#ifdef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-    if (tstate->interp->config._isolated_interpreter) {
-        // bpo-40533: The garbage collector must not be run on parallel on
-        // Python objects shared by multiple interpreters.
-        return 0;
-    }
-#endif
-
     if (gcstate->debug & DEBUG_STATS) {
         PySys_WriteStderr("gc: collecting generation %d...\n", generation);
         show_stats_each_generations(gcstate);

Objects/typeobject.c

@@ -54,11 +54,6 @@ typedef struct PySlot_Offset {
 } PySlot_Offset;
 
 
-/* bpo-40521: Interned strings are shared by all subinterpreters */
-#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-#  define INTERN_NAME_STRINGS
-#endif
-
 static PyObject *
 slot_tp_new(PyTypeObject *type, PyObject *args, PyObject *kwds);
 
@@ -4027,7 +4022,7 @@ type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
             if (name == NULL)
                 return -1;
         }
-#ifdef INTERN_NAME_STRINGS
+        /* bpo-40521: Interned strings are shared by all subinterpreters */
         if (!PyUnicode_CHECK_INTERNED(name)) {
             PyUnicode_InternInPlace(&name);
             if (!PyUnicode_CHECK_INTERNED(name)) {
@@ -4037,7 +4032,6 @@ type_setattro(PyTypeObject *type, PyObject *name, PyObject *value)
                 return -1;
             }
         }
-#endif
     }
     else {
         /* Will fail in _PyObject_GenericSetAttrWithDict. */
@@ -8474,17 +8468,11 @@ _PyTypes_InitSlotDefs(void)
     for (slotdef *p = slotdefs; p->name; p++) {
         /* Slots must be ordered by their offset in the PyHeapTypeObject. */
         assert(!p[1].name || p->offset <= p[1].offset);
-#ifdef INTERN_NAME_STRINGS
+        /* bpo-40521: Interned strings are shared by all subinterpreters */
         p->name_strobj = PyUnicode_InternFromString(p->name);
         if (!p->name_strobj || !PyUnicode_CHECK_INTERNED(p->name_strobj)) {
             return _PyStatus_NO_MEMORY();
         }
-#else
-        p->name_strobj = PyUnicode_FromString(p->name);
-        if (!p->name_strobj) {
-            return _PyStatus_NO_MEMORY();
-        }
-#endif
     }
     slotdefs_initialized = 1;
     return _PyStatus_OK();
@@ -8509,24 +8497,17 @@ update_slot(PyTypeObject *type, PyObject *name)
     int offset;
 
     assert(PyUnicode_CheckExact(name));
-#ifdef INTERN_NAME_STRINGS
     assert(PyUnicode_CHECK_INTERNED(name));
-#endif
 
     assert(slotdefs_initialized);
     pp = ptrs;
     for (p = slotdefs; p->name; p++) {
         assert(PyUnicode_CheckExact(p->name_strobj));
         assert(PyUnicode_CheckExact(name));
-#ifdef INTERN_NAME_STRINGS
+        /* bpo-40521: Using interned strings. */
         if (p->name_strobj == name) {
             *pp++ = p;
         }
-#else
-        if (p->name_strobj == name || _PyUnicode_EQ(p->name_strobj, name)) {
-            *pp++ = p;
-        }
-#endif
     }
     *pp = NULL;
     for (pp = ptrs; *pp; pp++) {

Objects/unicodeobject.c

@@ -190,11 +190,6 @@ extern "C" {
 #  define OVERALLOCATE_FACTOR 4
 #endif
 
-/* bpo-40521: Interned strings are shared by all interpreters. */
-#ifndef EXPERIMENTAL_ISOLATED_SUBINTERPRETERS
-#  define INTERNED_STRINGS
-#endif
-
 /* This dictionary holds all interned unicode strings.  Note that references
    to strings in this dictionary are *not* counted in the string's ob_refcnt.
    When the interned string reaches a refcnt of 0 the string deallocation
@@ -203,9 +198,7 @@ extern "C" {
    Another way to look at this is that to say that the actual reference
    count of a string is:  s->ob_refcnt + (s->state ? 2 : 0)
 */
-#ifdef INTERNED_STRINGS
 static PyObject *interned = NULL;
-#endif
 
 /* Forward declaration */
 static inline int
@@ -1530,7 +1523,6 @@ unicode_dealloc(PyObject *unicode)
     }
 #endif
 
-#ifdef INTERNED_STRINGS
     if (PyUnicode_CHECK_INTERNED(unicode)) {
         /* Revive the dead object temporarily. PyDict_DelItem() removes two
            references (key and value) which were ignored by
@@ -1546,7 +1538,6 @@ unicode_dealloc(PyObject *unicode)
         assert(Py_REFCNT(unicode) == 1);
         Py_SET_REFCNT(unicode, 0);
     }
-#endif
 
     if (_PyUnicode_HAS_UTF8_MEMORY(unicode)) {
         PyObject_Free(_PyUnicode_UTF8(unicode));
@@ -10568,13 +10559,11 @@ _PyUnicode_EqualToASCIIId(PyObject *left, _Py_Identifier *right)
     if (PyUnicode_CHECK_INTERNED(left))
         return 0;
 
-#ifdef INTERNED_STRINGS
     assert(_PyUnicode_HASH(right_uni) != -1);
     Py_hash_t hash = _PyUnicode_HASH(left);
     if (hash != -1 && hash != _PyUnicode_HASH(right_uni)) {
         return 0;
     }
-#endif
 
     return unicode_compare_eq(left, right_uni);
 }
@@ -14645,7 +14634,6 @@ PyUnicode_InternInPlace(PyObject **p)
         return;
     }
 
-#ifdef INTERNED_STRINGS
     if (interned == NULL) {
         interned = PyDict_New();
         if (interned == NULL) {
@@ -14671,11 +14659,6 @@ PyUnicode_InternInPlace(PyObject **p)
        this. */
     Py_SET_REFCNT(s, Py_REFCNT(s) - 2);
     _PyUnicode_STATE(s).interned = 1;
-#else
-    // PyDict expects that interned strings have their hash
-    // (PyASCIIObject.hash) already computed.
-    (void)unicode_hash(s);
-#endif
 }
 
 // Function kept for the stable ABI.