gh-149110: Fix race in _PyFrame_IsIncomplete for FRAME_OWNED_BY_FRAME… - #156001
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gh-149110: Fix race in _PyFrame_IsIncomplete for FRAME_OWNED_BY_FRAME…#156001BHUVANSH855 wants to merge 1 commit into
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…_FRAME_OBJECT frames
markshannon
reviewed
Aug 19, 2026
| new_frame->instr_ptr = | ||
| _PyFrame_GetBytecode(new_frame) + code->_co_firsttraceable + 1; | ||
| } | ||
| /* Set owner BEFORE updating f->f_frame so any concurrent reader that |
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Does the C memory model guarantee this?
Why can't another thread see f->f_frame = new_frame before new_frame->owner = FRAME_OWNED_BY_FRAME_OBJECT?
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_PyFrame_IsIncompletewas checkinginstr_ptragainst a TLBC slot onframes already owned by a frame object, which races with
take_ownership()when another thread walks
frame.f_back(e.g. via pdb).Fix:
_PyFrame_IsIncompleteforFRAME_OWNED_BY_FRAME_OBJECTframes —
take_ownership()already guarantees they're completetake_ownership()soowneris set beforef->f_frameis visible to concurrent readersco_tlbc->entries[idx]writes/readsAdded a regression test in
test_free_threading/test_frame.py.Fixes issue #149110
!_PyFrame_IsIncomplete(frame->f_frame)#149110