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GH-127705: Fix _Py_RefcntAdd to handle objects becoming immortal #131140

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Merged
merged 3 commits into from
Mar 12, 2025
Merged

GH-127705: Fix _Py_RefcntAdd to handle objects becoming immortal #131140

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b915df3
Fix _Py_RefcntAdd to handle objects becoming immortal
markshannon Mar 12, 2025
c4bf588
Restore no-gil behavior
markshannon Mar 12, 2025
13d5be0
Remove redundant check
markshannon Mar 12, 2025
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26 changes: 17 additions & 9 deletions Include/internal/pycore_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -135,15 +135,20 @@ static inline void _Py_RefcntAdd(PyObject* op, Py_ssize_t n)
_Py_INCREF_IMMORTAL_STAT_INC();
return;
}
#ifdef Py_REF_DEBUG
_Py_AddRefTotal(_PyThreadState_GET(), n);
#endif
#if !defined(Py_GIL_DISABLED)
#if SIZEOF_VOID_P > 4
op->ob_refcnt += (PY_UINT32_T)n;
#else
op->ob_refcnt += n;
#endif
#ifndef Py_GIL_DISABLED
Py_ssize_t refcnt = _Py_REFCNT(op);
Py_ssize_t new_refcnt = refcnt + n;
if (new_refcnt >= (Py_ssize_t)_Py_IMMORTAL_MINIMUM_REFCNT) {
new_refcnt = _Py_IMMORTAL_INITIAL_REFCNT;
}
# if SIZEOF_VOID_P > 4
op->ob_refcnt = (PY_UINT32_T)new_refcnt;
# else
op->ob_refcnt = new_refcnt;
# endif
# ifdef Py_REF_DEBUG
_Py_AddRefTotal(_PyThreadState_GET(), new_refcnt - refcnt);
# endif
#else
if (_Py_IsOwnedByCurrentThread(op)) {
uint32_t local = op->ob_ref_local;
Expand All @@ -160,6 +165,9 @@ static inline void _Py_RefcntAdd(PyObject* op, Py_ssize_t n)
else {
_Py_atomic_add_ssize(&op->ob_ref_shared, (n << _Py_REF_SHARED_SHIFT));
}
# ifdef Py_REF_DEBUG
_Py_AddRefTotal(_PyThreadState_GET(), n);
# endif
#endif
// Although the ref count was increased by `n` (which may be greater than 1)
// it is only a single increment (i.e. addition) operation, so only 1 refcnt
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3 changes: 2 additions & 1 deletion Include/refcount.h
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Expand Up @@ -42,7 +42,8 @@ beyond the refcount limit. Immortality checks for reference count decreases will
be done by checking the bit sign flag in the lower 32 bits.

*/
#define _Py_IMMORTAL_INITIAL_REFCNT (3UL << 30)
#define _Py_IMMORTAL_INITIAL_REFCNT (3ULL << 30)
#define _Py_IMMORTAL_MINIMUM_REFCNT (1ULL << 31)
#define _Py_STATIC_FLAG_BITS ((Py_ssize_t)(_Py_STATICALLY_ALLOCATED_FLAG | _Py_IMMORTAL_FLAGS))
#define _Py_STATIC_IMMORTAL_INITIAL_REFCNT (((Py_ssize_t)_Py_IMMORTAL_INITIAL_REFCNT) | (_Py_STATIC_FLAG_BITS << 48))

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2 changes: 1 addition & 1 deletion Objects/unicodeobject.c
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Expand Up @@ -15982,7 +15982,7 @@ _PyUnicode_ClearInterned(PyInterpreterState *interp)
case SSTATE_INTERNED_MORTAL:
// Restore 2 references held by the interned dict; these will
// be decref'd by clear_interned_dict's PyDict_Clear.
Py_SET_REFCNT(s, Py_REFCNT(s) + 2);
_Py_RefcntAdd(s, 2);
#ifdef Py_REF_DEBUG
/* let's be pedantic with the ref total */
_Py_IncRefTotal(_PyThreadState_GET());
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