You know it often is the case that APIs like this both in C++ and Rust don't offer you enough knobs when your usecase deviates from being trivial.

It happens with locking APIs, it happens with socket APIs, anything platform dependent.

Does the C++ standard give you an idiomatic way to set PTHREAD_RWLOCK_PREFER_READER_NP or PTHREAD_RWLOCK_PREFER_WRITER_NP explicitly when initializing a rwlock? Nope. Then you either roll your own or in Rust you reach for a crate where someone did the work of making a smarter primitive for you.