tree 92b490f4d8e3d3ea039503602a9480adc11f6632
parent 59d7cb28c1f5a014bb17ad4a8e80da2fb51a6159
author Henry Schreiner <HenrySchreinerIII@gmail.com> 1782265706 -0400
committer GitHub <noreply@github.com> 1782265706 -0400
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fix: data race on last_storage_ptr_ cache in gil_safe_call_once_and_store (#6087)

Under free-threaded CPython (Py_GIL_DISABLED) the GIL provides no mutual
exclusion, so the plain pointer last_storage_ptr_ was read and written
concurrently without synchronization, a C++ data race. Make it a
std::atomic<T *>.

Also reorder get_stored() to check is_last_storage_valid() before loading
the cached pointer. The writer publishes the pointer before setting the
validity flag, so the flag must be observed first for correct
acquire/release ordering.

Assisted-by: ClaudeCode:claude-fable-5