RS.CLIPPY.MUTEX_ATOMIC

Using a mutex where an atomic value could be used instead.

This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: mutex_atomic. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Checks for usage of Mutex<X> where an atomic will do.

Why restrict this?

Using a mutex just to make access to a plain bool or reference sequential is shooting flies with cannons. std::sync::atomic::AtomicBool and std::sync::atomic::AtomicPtr are leaner and faster.

On the other hand, Mutexes are, in general, easier to verify correctness. An atomic does not behave the same as an equivalent mutex. See this issue's commentary for more details.

Known problems

  • This lint cannot detect if the mutex is actually used for waiting before a critical section.
  • This lint has a false positive that warns without considering the case where Mutex is used together with Condvar.

Example

let x = Mutex::new(&y);

Use instead:

let x = AtomicBool::new(y);