Make refleak checking thread-safe without the GIL

[colesbury]

Feature or enhancement

The refleak checking relies on per-interpreter "total" refcount tracking. It uses non-atomic operations and is not thread-safe without the GIL.

In the free-threaded build, I think we should primarily track counts in PyThreadState and occasionally aggregate the results into the per-interpreter total refcount using atomic operations.

See:

cpython/Objects/object.c

Lines 72 to 91 in 9dae05e

	# define REFTOTAL(interp) \
	interp->object_state.reftotal
	static inline void
	reftotal_increment(PyInterpreterState *interp)
	{
	REFTOTAL(interp)++;
	}
	static inline void
	reftotal_decrement(PyInterpreterState *interp)
	{
	REFTOTAL(interp)--;
	}
	static inline void
	reftotal_add(PyInterpreterState *interp, Py_ssize_t n)
	{
	REFTOTAL(interp) += n;
	}

There is also the legacy _Py_RefTotal, but that's just preserved for ABI compatibility. I don't think we have to do anything with that.

Linked PRs

• gh-117439: Make refleak checking thread-safe without the GIL #117469