From f3a6d4145342d2e3eb723787e974dbec16c64fff Mon Sep 17 00:00:00 2001 From: Sam Gross Date: Tue, 16 Jul 2024 14:06:54 -0400 Subject: [PATCH] fix: make gil_safe_call_once thread-safe in free-threaded CPython (#5246) * fix: Make gil_safe_call_once thread-safe in free-threaded CPython The "is_initialized_" flags is not protected by the GIL in free-threaded Python, so it needs to be an atomic field. Fixes #5245 * style: pre-commit fixes * Apply changes from code review --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> --- include/pybind11/gil_safe_call_once.h | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/include/pybind11/gil_safe_call_once.h b/include/pybind11/gil_safe_call_once.h index eaf84d16e..5f9e1b03c 100644 --- a/include/pybind11/gil_safe_call_once.h +++ b/include/pybind11/gil_safe_call_once.h @@ -8,6 +8,10 @@ #include #include +#ifdef Py_GIL_DISABLED +# include +#endif + PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE) // Use the `gil_safe_call_once_and_store` class below instead of the naive @@ -82,7 +86,12 @@ public: private: alignas(T) char storage_[sizeof(T)] = {}; std::once_flag once_flag_ = {}; - bool is_initialized_ = false; +#ifdef Py_GIL_DISABLED + std::atomic_bool +#else + bool +#endif + is_initialized_{false}; // The `is_initialized_`-`storage_` pair is very similar to `std::optional`, // but the latter does not have the triviality properties of former, // therefore `std::optional` is not a viable alternative here.