It's indeed more common than RefCell, but it's not like you're using them everywhere either (as using multiple locks is a recipe for deadlocks, so you should al

It's indeed more common than RefCell, but it's not like you're using them everywhere either (as using multiple locks is a recipe for deadlocks, so you should always be very mindful about how you use shared memory between threads). I've run a quick analysis on the 1,145,666 lines of Rust code (excluding comments and blank lines) I have on my computer, which belong to several code bases I've worked on over the past few years (professional proprietary code, side projects and open source projects I just cloned to fiddle with), and here are the results: - unsafe: 8247 matches, 1 every 138 lines (though keep in mind most of those aren't about mutable aliasing at all, like FFI or SIMD intrinsic) - RefCell: 252 matches, 1 every 4546 lines - Arc<Mutex<: 199 matches, 1 every 5757 lines I think that's fair to say that “The typical Rust program has either no refcells, or a very small number, just as it has either no unsafe code or a very small amount”