rcu-clean  

This crate provides easy to use smart-pointers with interior mutability. These smart pointers use RCU to allow simultaneous reads and updates. They implement Deref for reads, which makes them both convenient (ergonomic) and fast on reads, particularly for the Arc version that would otherwise require taking a Mutex or RwLock in order to read the pointer. The downside is that old versions of the data are only freed when you have called the clean method on each copy of the pointer.