gh-94673: More Per-Interpreter Fields for Builtin Static Types (gh-103912)

his involves moving tp_dict, tp_bases, and tp_mro to PyInterpreterState, in the same way we did for tp_subclasses.  Those three fields are effectively const for builtin static types (unlike tp_subclasses).  In theory we only need to make their values immortal, along with their contents.  However, that isn't such a simple proposition.  (See gh-103823.)  In the meantime the simplest solution is to move the fields into the interpreter.

One alternative is to statically allocate the values, but that's its own can of worms.

Author: ericsnowcurrently

Include/internal/pycore_typeobject.h

@@ -44,6 +44,13 @@ struct type_cache {
 
 typedef struct {
     PyTypeObject *type;
+    int readying;
+    int ready;
+    // XXX tp_dict, tp_bases, and tp_mro can probably be statically
+    // allocated, instead of dynamically and stored on the interpreter.
+    PyObject *tp_dict;
+    PyObject *tp_bases;
+    PyObject *tp_mro;
     PyObject *tp_subclasses;
     /* We never clean up weakrefs for static builtin types since
        they will effectively never get triggered.  However, there

Modules/_abc.c

@@ -7,6 +7,7 @@
 #include "pycore_moduleobject.h"  // _PyModule_GetState()
 #include "pycore_object.h"        // _PyType_GetSubclasses()
 #include "pycore_runtime.h"       // _Py_ID()
+#include "pycore_typeobject.h"    // _PyType_GetMRO()
 #include "clinic/_abc.c.h"
 
 /*[clinic input]

Modules/gcmodule.c

@@ -2174,41 +2174,16 @@ _PyGC_DumpShutdownStats(PyInterpreterState *interp)
 }
 
 
-static void
-gc_fini_untrack(PyGC_Head *list)
-{
-    PyGC_Head *gc;
-    for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(list)) {
-        PyObject *op = FROM_GC(gc);
-        _PyObject_GC_UNTRACK(op);
-        // gh-92036: If a deallocator function expect the object to be tracked
-        // by the GC (ex: func_dealloc()), it can crash if called on an object
-        // which is no longer tracked by the GC. Leak one strong reference on
-        // purpose so the object is never deleted and its deallocator is not
-        // called.
-        Py_INCREF(op);
-    }
-}
-
-
 void
 _PyGC_Fini(PyInterpreterState *interp)
 {
     GCState *gcstate = &interp->gc;
     Py_CLEAR(gcstate->garbage);
     Py_CLEAR(gcstate->callbacks);
 
-    if (!_Py_IsMainInterpreter(interp)) {
-        // bpo-46070: Explicitly untrack all objects currently tracked by the
-        // GC. Otherwise, if an object is used later by another interpreter,
-        // calling PyObject_GC_UnTrack() on the object crashs if the previous
-        // or the next object of the PyGC_Head structure became a dangling
-        // pointer.
-        for (int i = 0; i < NUM_GENERATIONS; i++) {
-            PyGC_Head *gen = GEN_HEAD(gcstate, i);
-            gc_fini_untrack(gen);
-        }
-    }
+    /* We expect that none of this interpreters objects are shared
+       with other interpreters.
+       See https://github.com/python/cpython/issues/90228. */
 }
 
 /* for debugging */

Objects/structseq.c

@@ -511,7 +511,6 @@ _PyStructSequence_InitBuiltinWithFlags(PyInterpreterState *interp,
     Py_ssize_t n_members = count_members(desc, &n_unnamed_members);
     PyMemberDef *members = NULL;
 
-    int initialized = 1;
     if ((type->tp_flags & Py_TPFLAGS_READY) == 0) {
         assert(type->tp_name == NULL);
         assert(type->tp_members == NULL);
@@ -524,7 +523,6 @@ _PyStructSequence_InitBuiltinWithFlags(PyInterpreterState *interp,
         initialize_static_fields(type, desc, members, tp_flags);
 
         _Py_SetImmortal(type);
-        initialized = 0;
     }
 #ifndef NDEBUG
     else {
@@ -543,13 +541,10 @@ _PyStructSequence_InitBuiltinWithFlags(PyInterpreterState *interp,
                      desc->name);
         goto error;
     }
-    // This should be dropped if tp_dict is made per-interpreter.
-    if (initialized) {
-        return 0;
-    }
 
     if (initialize_structseq_dict(
-            desc, _PyType_GetDict(type), n_members, n_unnamed_members) < 0) {
+            desc, _PyType_GetDict(type), n_members, n_unnamed_members) < 0)
+    {
         goto error;
     }