Which concurrent operations are allowed when using atomic types?

[vigna]

The documentation refers several times to support for atomic types, that is, building a BitVec with AtomicUsize backend.

However, I expected in this case that set would use a &self instead of &mut self reference and would make me able to set and get bits concurrently, passing a reference to multiple threads, as it happens with AtomicUsize. I couldn't do it and I cannot find any documentation about it.

So: which are the additional concurrent features one gets when using AtomicUsize as a backend?