8000 [3.13] gh-117657: Make Py_TYPE and Py_SET_TYPE thread safe (GH-120165… · python/cpython@91c4444 · GitHub
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[3.13] gh-117657: Make Py_TYPE and Py_SET_TYPE thread safe (GH-120165) (GH-120403)
gh-117657: Make Py_TYPE and Py_SET_TYPE thread safe (GH-120165) (cherry picked from commit e16aed6) Co-authored-by: Ken Jin <kenjin@python.org> Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com> Co-authored-by: Nadeshiko Manju <me@manjusaka.me>
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+45
-4
lines changed

5 files changed

+45
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lines changed

‎Include/internal/pycore_interp.h

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -401,7 +401,10 @@ PyAPI_FUNC(PyStatus) _PyInterpreterState_New(
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#define RARE_EVENT_INTERP_INC(interp, name) \
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do { \
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/* saturating add */ \
404-
if (interp->rare_events.name < UINT8_MAX) interp->rare_events.name++; \
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int val = FT_ATOMIC_LOAD_UINT8_RELAXED(interp->rare_events.name); \
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if (val < UINT8_MAX) { \
406+
FT_ATOMIC_STORE_UINT8(interp->rare_events.name, val + 1); \
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} \
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RARE_EVENT_STAT_INC(name); \
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} while (0); \
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‎Include/object.h

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -331,7 +331,11 @@ static inline Py_ssize_t Py_REFCNT(PyObject *ob) {
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// bpo-39573: The Py_SET_TYPE() function must be used to set an object type.
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static inline PyTypeObject* Py_TYPE(PyObject *ob) {
334+
#ifdef Py_GIL_DISABLED
335+
return (PyTypeObject *)_Py_atomic_load_ptr_relaxed(&ob->ob_type);
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#else
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return ob->ob_type;
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#endif
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}
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#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
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# define Py_TYPE(ob) Py_TYPE(_PyObject_CAST(ob))
@@ -421,7 +425,11 @@ static inline void Py_SET_REFCNT(PyObject *ob, Py_ssize_t refcnt) {
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static inline void Py_SET_TYPE(PyObject *ob, PyTypeObject *type) {
428+
#ifdef Py_GIL_DISABLED
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_Py_atomic_store_ptr(&ob->ob_type, type);
430+
#else
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ob->ob_type = type;
432+
#endif
425433
}
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#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 < 0x030b0000
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# define Py_SET_TYPE(ob, type) Py_SET_TYPE(_PyObject_CAST(ob), type)

‎Lib/test/test_free_threading/test_type.py

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -96,6 +96,32 @@ def reader_func():
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self.run_one(writer_func, reader_func)
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99+
def test___class___modification(self):
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class Foo:
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pass
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class Bar:
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pass
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thing = Foo()
107+
def work():
108+
foo = thing
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for _ in range(10000):
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foo.__class__ = Bar
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type(foo)
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foo.__class__ = Foo
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type(foo)
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threads = []
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for i in range(NTHREADS):
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thread = threading.Thread(target=work)
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thread.start()
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threads.append(thread)
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for thread in threads:
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thread.join()
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99125
def run_one(self, writer_func, reader_func):
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writer = Thread(target=writer_func)
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readers = []

‎Objects/typeobject.c

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -6474,9 +6474,15 @@ object_set_class(PyObject *self, PyObject *value, void *closure)
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if (newto->tp_flags & Py_TPFLAGS_HEAPTYPE) {
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Py_INCREF(newto);
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}
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Py_BEGIN_CRITICAL_SECTION(self);
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// The real Py_TYPE(self) (`oldto`) may have changed from
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// underneath us in another thread, so we re-fetch it here.
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oldto = Py_TYPE(self);
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Py_SET_TYPE(self, newto);
6478-
if (oldto->tp_flags & Py_TPFLAGS_HEAPTYPE)
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Py_END_CRITICAL_SECTION();
6483+
if (oldto->tp_flags & Py_TPFLAGS_HEAPTYPE) {
64796484
Py_DECREF(oldto);
6485+
}
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RARE_EVENT_INC(set_class);
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return 0;

‎Tools/tsan/suppressions_free_threading.txt

Lines changed: 0 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -37,7 +37,6 @@ race_top:set_contains_key
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# https://gist.github.com/colesbury/d13d033f413b4ad07929d044bed86c35
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race_top:set_discard_entry
3939
race_top:set_inheritable
40-
race_top:Py_SET_TYPE
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race_top:_PyDict_CheckConsistency
4241
race_top:_Py_dict_lookup_threadsafe
4342
race_top:_multiprocessing_SemLock_acquire_impl
@@ -58,7 +57,6 @@ race_top:_PyFrame_Initialize
5857
race_top:PyInterpreterState_ThreadHead
5958
race_top:_PyObject_TryGetInstanceAttribute
6059
race_top:PyThreadState_Next
61-
race_top:Py_TYPE
6260
race_top:PyUnstable_InterpreterFrame_GetLine
6361
race_top:sock_close
6462
race_top:tstate_delete_common

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