gh-153290: Fix data race in BytesIO.__setstate__ installing __dict__#153376
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bhuvi27 wants to merge 1 commit into
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gh-153290: Fix data race in BytesIO.__setstate__ installing __dict__#153376bhuvi27 wants to merge 1 commit into
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…ict__ On the free-threaded build, __setstate__() installed the instance dictionary with a plain store while the lock-free LOAD_ATTR method fast path reads the same dict slot with an atomic acquire load. Use a release store to pair with that acquire load, matching ensure_nonmanaged_dict() in Objects/dictobject.c.
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Fixes #153290
On the free-threaded build,
BytesIO.__setstate__()installed the instance__dict__with a plain pointer store, while the lock-free LOAD_ATTR methodfast path (
_CHECK_ATTR_METHOD_LAZY_DICT) reads the same dict slot with anatomic acquire load. ThreadSanitizer reports a data race between the two, and
an unordered store could publish the dict pointer before its contents are
visible to the reading thread.
Use
FT_ATOMIC_STORE_PTR_RELEASEfor the store, pairing it with the acquireload, the same way
ensure_nonmanaged_dict()inObjects/dictobject.chandles non-managed dict slots. This is a no-op on the default build.
Verified with TSAN on a
--disable-gil --with-pydebugbuild: the issue'sreproducer reports the race before the change and is clean after. Added a
regression test in
test_free_threading/test_io.py.BytesIO.__setstate__and lock-free LOAD_ATTR method #153290