Rust Concurrency: Synchronizing Access to Shared State

This article was originally published on our website https://isab.run. The Medium version offers the same in-depth content and insights.

Rust’s built-in concurrency model, based on message-passing and thread ownership, makes it easy to write concurrent and parallel code that is both safe and efficient. However, when multiple threads need to access and modify shared state, we need to take extra care to ensure that the data remains consistent and that the access is properly synchronized.

One common way to synchronize access to shared state in Rust is to use a Mutex. A Mutex is a type that allows only one thread to hold the lock at a time, and blocks other threads that try to acquire the lock until it is released. To use a Mutex, we first need to create an instance of it, wrapping the shared state:

let shared_state = Mutex::new(0);

Then, to access or modify the shared state, we need to acquire the lock by calling the lock method:

let mut state = shared_state.lock().unwrap();
*state += 1;

The lock method returns a LockResult which contains a MutexGuard that holds the lock and allows access to the shared state. We need to call unwrap to get the actual MutexGuard and thus access the shared state.

When we’re done with the shared state, the lock is automatically released when the MutexGuard goes out of scope.

It’s important to keep in mind that while the Mutex provides a way to synchronize access to shared state, it can also lead to performance issues if used excessively or improperly. So, it's best practice to use it as little as possible and only when necessary.

In conclusion, Rust’s Mutex is a powerful tool that allows us to synchronize access to shared state, but it's important to use it judiciously to maintain good performance and avoid deadlocks.