mirror of
https://github.com/python/cpython.git
synced 2024-11-28 16:45:42 +01:00
e8752d7b80
This exposes `PyUnstable_Object_ClearWeakRefsNoCallbacks` as an unstable C-API function to provide a thread-safe mechanism for clearing weakrefs without executing callbacks. Some C-API extensions need to clear weakrefs without calling callbacks, such as after running finalizers like we do in subtype_dealloc. Previously they could use `_PyWeakref_ClearRef` on each weakref, but that's not thread-safe in the free-threaded build. Co-authored-by: Petr Viktorin <encukou@gmail.com>
120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
#ifndef Py_INTERNAL_WEAKREF_H
|
|
#define Py_INTERNAL_WEAKREF_H
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
#ifndef Py_BUILD_CORE
|
|
# error "this header requires Py_BUILD_CORE define"
|
|
#endif
|
|
|
|
#include "pycore_critical_section.h" // Py_BEGIN_CRITICAL_SECTION()
|
|
#include "pycore_lock.h"
|
|
#include "pycore_object.h" // _Py_REF_IS_MERGED()
|
|
#include "pycore_pyatomic_ft_wrappers.h"
|
|
|
|
#ifdef Py_GIL_DISABLED
|
|
|
|
#define WEAKREF_LIST_LOCK(obj) \
|
|
_PyInterpreterState_GET() \
|
|
->weakref_locks[((uintptr_t)obj) % NUM_WEAKREF_LIST_LOCKS]
|
|
|
|
// Lock using the referenced object
|
|
#define LOCK_WEAKREFS(obj) \
|
|
PyMutex_LockFlags(&WEAKREF_LIST_LOCK(obj), _Py_LOCK_DONT_DETACH)
|
|
#define UNLOCK_WEAKREFS(obj) PyMutex_Unlock(&WEAKREF_LIST_LOCK(obj))
|
|
|
|
// Lock using a weakref
|
|
#define LOCK_WEAKREFS_FOR_WR(wr) \
|
|
PyMutex_LockFlags(wr->weakrefs_lock, _Py_LOCK_DONT_DETACH)
|
|
#define UNLOCK_WEAKREFS_FOR_WR(wr) PyMutex_Unlock(wr->weakrefs_lock)
|
|
|
|
#else
|
|
|
|
#define LOCK_WEAKREFS(obj)
|
|
#define UNLOCK_WEAKREFS(obj)
|
|
|
|
#define LOCK_WEAKREFS_FOR_WR(wr)
|
|
#define UNLOCK_WEAKREFS_FOR_WR(wr)
|
|
|
|
#endif
|
|
|
|
static inline int _is_dead(PyObject *obj)
|
|
{
|
|
// Explanation for the Py_REFCNT() check: when a weakref's target is part
|
|
// of a long chain of deallocations which triggers the trashcan mechanism,
|
|
// clearing the weakrefs can be delayed long after the target's refcount
|
|
// has dropped to zero. In the meantime, code accessing the weakref will
|
|
// be able to "see" the target object even though it is supposed to be
|
|
// unreachable. See issue gh-60806.
|
|
#if defined(Py_GIL_DISABLED)
|
|
Py_ssize_t shared = _Py_atomic_load_ssize_relaxed(&obj->ob_ref_shared);
|
|
return shared == _Py_REF_SHARED(0, _Py_REF_MERGED);
|
|
#else
|
|
return (Py_REFCNT(obj) == 0);
|
|
#endif
|
|
}
|
|
|
|
static inline PyObject* _PyWeakref_GET_REF(PyObject *ref_obj)
|
|
{
|
|
assert(PyWeakref_Check(ref_obj));
|
|
PyWeakReference *ref = _Py_CAST(PyWeakReference*, ref_obj);
|
|
|
|
PyObject *obj = FT_ATOMIC_LOAD_PTR(ref->wr_object);
|
|
if (obj == Py_None) {
|
|
// clear_weakref() was called
|
|
return NULL;
|
|
}
|
|
|
|
LOCK_WEAKREFS(obj);
|
|
#ifdef Py_GIL_DISABLED
|
|
if (ref->wr_object == Py_None) {
|
|
// clear_weakref() was called
|
|
UNLOCK_WEAKREFS(obj);
|
|
return NULL;
|
|
}
|
|
#endif
|
|
if (_Py_TryIncref(obj)) {
|
|
UNLOCK_WEAKREFS(obj);
|
|
return obj;
|
|
}
|
|
UNLOCK_WEAKREFS(obj);
|
|
return NULL;
|
|
}
|
|
|
|
static inline int _PyWeakref_IS_DEAD(PyObject *ref_obj)
|
|
{
|
|
assert(PyWeakref_Check(ref_obj));
|
|
int ret = 0;
|
|
PyWeakReference *ref = _Py_CAST(PyWeakReference*, ref_obj);
|
|
PyObject *obj = FT_ATOMIC_LOAD_PTR(ref->wr_object);
|
|
if (obj == Py_None) {
|
|
// clear_weakref() was called
|
|
ret = 1;
|
|
}
|
|
else {
|
|
LOCK_WEAKREFS(obj);
|
|
// See _PyWeakref_GET_REF() for the rationale of this test
|
|
#ifdef Py_GIL_DISABLED
|
|
ret = (ref->wr_object == Py_None) || _is_dead(obj);
|
|
#else
|
|
ret = _is_dead(obj);
|
|
#endif
|
|
UNLOCK_WEAKREFS(obj);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
extern Py_ssize_t _PyWeakref_GetWeakrefCount(PyObject *obj);
|
|
|
|
// Clear all the weak references to obj but leave their callbacks uncalled and
|
|
// intact.
|
|
extern void _PyWeakref_ClearWeakRefsNoCallbacks(PyObject *obj);
|
|
|
|
PyAPI_FUNC(int) _PyWeakref_IsDead(PyObject *weakref);
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
#endif /* !Py_INTERNAL_WEAKREF_H */
|