Skip to content

gh-139716: Use the same StackRef flagging scheme for immortals on FT build as on GIL build #141675

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
efimov-mikhail wants to merge 4 commits into
base: main
Choose a base branch
from
Open

gh-139716: Use the same StackRef flagging scheme for immortals on FT build as on GIL build #141675

Show file tree
Hide file tree
Changes from 3 commits
Commits
Show all changes
4 commits
Select commit Hold shift + click to select a range
df6ea14
Another flag on immortal
efimov-mikhail Nov 17, 2025
fbda208
Use _Py_IMMORTAL_FLAGS == Py_TAG_REFCNT check on all builds
efimov-mikhail Nov 17, 2025
7b87fac
Use _PyGC_BITS_DEFERRED for all immortal objects
efimov-mikhail Nov 19, 2025
50e0fe3
Address review: add comment
efimov-mikhail Nov 19, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 14 additions & 9 deletions Include/internal/pycore_stackref.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,13 @@ extern "C" {

#define Py_TAGGED_SHIFT 2

/* References to immortal objects always have their tag bit set to Py_TAG_REFCNT
* as they can (must) have their reclamation deferred */

#if _Py_IMMORTAL_FLAGS != Py_TAG_REFCNT
# error "_Py_IMMORTAL_FLAGS != Py_TAG_REFCNT"
#endif

#if !defined(Py_GIL_DISABLED) && defined(Py_STACKREF_DEBUG)

PyAPI_FUNC(PyObject *) _Py_stackref_get_object(_PyStackRef ref);
Expand Down Expand Up @@ -502,7 +509,12 @@ _PyStackRef_FromPyObjectSteal(PyObject *obj)
assert(obj != NULL);
// Make sure we don't take an already tagged value.
assert(((uintptr_t)obj & Py_TAG_BITS) == 0);
return (_PyStackRef){ .bits = (uintptr_t)obj };
if (_Py_IsImmortal(obj)) {
return (_PyStackRef){ .bits = (uintptr_t)obj | Py_TAG_DEFERRED };
}
else {
return (_PyStackRef){ .bits = (uintptr_t)obj };
}
}
# define PyStackRef_FromPyObjectSteal(obj) _PyStackRef_FromPyObjectSteal(_PyObject_CAST(obj))

Expand All @@ -511,7 +523,7 @@ PyStackRef_IsHeapSafe(_PyStackRef stackref)
{
if (PyStackRef_IsDeferred(stackref)) {
PyObject *obj = PyStackRef_AsPyObjectBorrow(stackref);
return obj == NULL || _Py_IsImmortal(obj) || _PyObject_HasDeferredRefcount(obj);
return obj == NULL || _PyObject_HasDeferredRefcount(obj);
}
return true;
}
Expand Down Expand Up @@ -631,13 +643,6 @@ PyStackRef_AsStrongReference(_PyStackRef stackref)

// With GIL

/* References to immortal objects always have their tag bit set to Py_TAG_REFCNT
* as they can (must) have their reclamation deferred */

#if _Py_IMMORTAL_FLAGS != Py_TAG_REFCNT
# error "_Py_IMMORTAL_FLAGS != Py_TAG_REFCNT"
#endif

#define BITS_TO_PTR(REF) ((PyObject *)((REF).bits))
#define BITS_TO_PTR_MASKED(REF) ((PyObject *)(((REF).bits) & (~Py_TAG_REFCNT)))

Expand Down
4 changes: 3 additions & 1 deletion Objects/object.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2675,6 +2675,9 @@ _Py_SetImmortalUntracked(PyObject *op)
assert(PyUnicode_CHECK_INTERNED(op) == SSTATE_INTERNED_IMMORTAL
|| PyUnicode_CHECK_INTERNED(op) == SSTATE_INTERNED_IMMORTAL_STATIC);
}
#endif
#ifdef Py_GIL_DISABLED
_Py_atomic_or_uint8(&op->ob_gc_bits, _PyGC_BITS_DEFERRED);
#endif
// Check if already immortal to avoid degrading from static immortal to plain immortal
if (_Py_IsImmortal(op)) {
Expand All @@ -2684,7 +2687,6 @@ _Py_SetImmortalUntracked(PyObject *op)
op->ob_tid = _Py_UNOWNED_TID;
op->ob_ref_local = _Py_IMMORTAL_REFCNT_LOCAL;
op->ob_ref_shared = 0;
_Py_atomic_or_uint8(&op->ob_gc_bits, _PyGC_BITS_DEFERRED);
#elif SIZEOF_VOID_P > 4
op->ob_flags = _Py_IMMORTAL_FLAGS;
op->ob_refcnt = _Py_IMMORTAL_INITIAL_REFCNT;
Expand Down
Loading