Sync Primitives

RwLock (Reader Writer Lock)

Reference video | Rust Doc

  • An RwLock is basically a RefCell whose counters are kept using atomics
  • the read (borrow equivalent for RefCell) and write (borrow_mut equivalent of Refcell) always return the ref/refmut instead of an option so that we dont have to manually poll in a loop. They block the current thread till its available if the borrow cannot succeed yet


  • A Mutex can be considered as a simplified version of RwLock where ther is only borrow_mut. So a Mutex doesnt have to keep a state to count the no. of readers becuse its either we have the reference or someone else has it. Mutex also blocks the thread till it gets a value

Arc (Atomic reference counted)

Reference Video timestamp | Rust doc Arc

  • Thread safe reference counting pointer
  • Almost similar to Rc except that it uses thread safe atomic operations to manage the reference count