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[3.13] gh-119525: Fix deadlock with _PyType_Lookup and the GIL (GH-119527) #119746

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Merged
merged 1 commit into from
May 29, 2024
Merged

[3.13] gh-119525: Fix deadlock with _PyType_Lookup and the GIL (GH-119527) #119746

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2024-05-24-21-04-00.gh-issue-119525.zLFLf1.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix deadlock involving ``_PyType_Lookup()`` cache in the free-threaded build
when the GIL is dynamically enabled at runtime.
11 changes: 7 additions & 4 deletions Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5062,7 +5062,7 @@ is_dunder_name(PyObject *name)
return 0;
}

static void
static PyObject *
update_cache(struct type_cache_entry *entry, PyObject *name, unsigned int version_tag, PyObject *value)
{
_Py_atomic_store_uint32_relaxed(&entry->version, version_tag);
Expand All @@ -5073,7 +5073,7 @@ update_cache(struct type_cache_entry *entry, PyObject *name, unsigned int versio
// exact unicode object or Py_None so it's safe to do so.
PyObject *old_name = entry->name;
_Py_atomic_store_ptr_relaxed(&entry->name, Py_NewRef(name));
Py_DECREF(old_name);
return old_name;
}

#if Py_GIL_DISABLED
Expand All @@ -5093,10 +5093,12 @@ update_cache_gil_disabled(struct type_cache_entry *entry, PyObject *name,
return;
}

update_cache(entry, name, version_tag, value);
PyObject *old_value = update_cache(entry, name, version_tag, value);

// Then update sequence to the next valid value
_PySeqLock_UnlockWrite(&entry->sequence);

Py_DECREF(old_value);
}

#endif
Expand Down Expand Up @@ -5208,7 +5210,8 @@ _PyType_LookupRef(PyTypeObject *type, PyObject *name)
#if Py_GIL_DISABLED
update_cache_gil_disabled(entry, name, version, res);
#else
update_cache(entry, name, version, res);
PyObject *old_value = update_cache(entry, name, version, res);
Py_DECREF(old_value);
#endif
}
return res;
Expand Down