For the same reason that motivated this ticket, I think the functions should be inline functions. They should also take the current thread-state as argument, because that's probably known on the caller side already.

I guess a macro would be fine, too. :)

Cython previously used "use_tracing" directly because it needs to implement the exact same tracing/profiling behaviour as CPython, regardless of who called a Cython implemented function (Cython or CPython).

Naming nit: Get/Is/UsesTracing?

Also, given that a common use case seems to be "make sure tracing is disabled, do something, enable tracing if it was enabled", I think DisableTracing() should return the previous state.