Make MuJoCo Python bindings compatible with free-threading.

Introduce a new header `gil.h` defining `MutexLockIfGilDisabled` to support thread-safety in both standard and free-threaded CPython builds.

Protect critical shared states and registries:
- Guard global Python callback pointers in `callbacks.cc` using a mutex. Move `gil_scoped_acquire` into local blocks around refcount modifications to prevent `longjmp` from bypassing destructors.
- Protect raw pointer maps in `structs_wrappers.cc` with static mutexes.
- Replace TOCTOU race in `mjcb_time` initialization with thread-safe `std::call_once`.
- Add synchronization to lazy indexer array cache initialization in `indexers.cc` and `indexer_xmacro.h`.
- Protect vector mutations in `StructListBase::PopulateUpTo` in `structs.h` with a mutex.
- Revert unnecessary atomic changes to threadpool counters.
- Declare free-threading compatibility by passing `pybind11::mod_gil_not_used()` to all extension modules.

Fixes #3259
Fixes #3256
Fixes #2978

PiperOrigin-RevId: 941101502
Change-Id: Iec4ce58afcbc75d4b0be6a9a21fc8a47854242e3

This commit is contained in:

Saran Tunyasuvunakool

2026-07-01 08:08:10 -07:00

committed by

Copybara-Service

parent cab191755a

commit a07ae6f849

21 changed files with 489 additions and 66 deletions

									
										python/mujoco/structs.cc
									
		+1
		-1
	
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				@@ -101,7 +101,7 @@ py::tuple RecompileSpec(raw::MjSpec* spec, const MjModelWrapper& old_m,

				}  // namespace

				PYBIND11_MODULE(_structs, m) {

				PYBIND11_MODULE(_structs, m, pybind11::mod_gil_not_used()) {

				  py::module_::import("mujoco._enums");

				  // ==================== MJOPTION =============================================