But `Mutex::get_mut` takes `&mut Mutex`. In this case the exclusivity and safety is ensured by the exclusive reference `&mut`. So get_mut can be called from any

But `Mutex::get_mut` takes `&mut Mutex`. In this case the exclusivity and safety is ensured by the exclusive reference `&mut`. So get_mut can be called from any thread where you can get hold of a `&mut Mutex`.