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authorDonghee Na <donghee.na@python.org>2024-01-03 13:25:27 (GMT)
committerGitHub <noreply@github.com>2024-01-03 13:25:27 (GMT)
commit0c3455a9693cfabcd991c4c33db7cccb1387de58 (patch)
treee9238f84d22a24a8ea8a31eb0a86f0b854f22bb2
parentfab7ad62ceca1f88767bca4e1f06f8e4b1faef2f (diff)
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gh-111926: Set up basic sementics of weakref API for freethreading (gh-113621)
--------- Co-authored-by: Sam Gross <colesbury@gmail.com>
-rw-r--r--Include/internal/pycore_weakref.h56
1 files changed, 37 insertions, 19 deletions
diff --git a/Include/internal/pycore_weakref.h b/Include/internal/pycore_weakref.h
index eacbe14..dea267b 100644
--- a/Include/internal/pycore_weakref.h
+++ b/Include/internal/pycore_weakref.h
@@ -9,48 +9,66 @@ extern "C" {
#endif
#include "pycore_critical_section.h" // Py_BEGIN_CRITICAL_SECTION()
+#include "pycore_object.h" // _Py_REF_IS_MERGED()
-static inline PyObject* _PyWeakref_GET_REF(PyObject *ref_obj) {
+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));
+ PyObject *ret = NULL;
+ Py_BEGIN_CRITICAL_SECTION(ref_obj);
PyWeakReference *ref = _Py_CAST(PyWeakReference*, ref_obj);
PyObject *obj = ref->wr_object;
if (obj == Py_None) {
// clear_weakref() was called
- return NULL;
+ goto end;
}
- // 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.
- Py_ssize_t refcnt = Py_REFCNT(obj);
- if (refcnt == 0) {
- return NULL;
+ if (_is_dead(obj)) {
+ goto end;
}
-
- assert(refcnt > 0);
- return Py_NewRef(obj);
+#if !defined(Py_GIL_DISABLED)
+ assert(Py_REFCNT(obj) > 0);
+#endif
+ ret = Py_NewRef(obj);
+end:
+ Py_END_CRITICAL_SECTION();
+ return ret;
}
-static inline int _PyWeakref_IS_DEAD(PyObject *ref_obj) {
+static inline int _PyWeakref_IS_DEAD(PyObject *ref_obj)
+{
assert(PyWeakref_Check(ref_obj));
- int is_dead;
+ int ret = 0;
Py_BEGIN_CRITICAL_SECTION(ref_obj);
PyWeakReference *ref = _Py_CAST(PyWeakReference*, ref_obj);
PyObject *obj = ref->wr_object;
if (obj == Py_None) {
// clear_weakref() was called
- is_dead = 1;
+ ret = 1;
}
else {
// See _PyWeakref_GET_REF() for the rationale of this test
- is_dead = (Py_REFCNT(obj) == 0);
+ ret = _is_dead(obj);
}
Py_END_CRITICAL_SECTION();
- return is_dead;
+ return ret;
}
extern Py_ssize_t _PyWeakref_GetWeakrefCount(PyWeakReference *head);