A purely functional mutex.

A mutex is a concurrency primitive that can be used to give access to a resource to only one fiber at a time; e.g. a cats.effect.kernel.Ref.

// Assuming some resource r that should not be used concurrently.

Mutex[IO].flatMap { mutex =>
  mutex.lock.surround {
    // Here you can use r safely.
    IO(r.mutate(...))
  }
}

Note: This lock is not reentrant, thus this mutex.lock.surround(mutex.lock.use_) will deadlock.