Concurrency Building Blocks

Mutex Counter

Lock Before Updating

Mutex protects shared data by requiring a lock before code can read or change the value.

Program

Play the program to choose the increment added while the counter is locked.

mutex_counter.rs 
use std::sync::Mutex;

fn main() {
    let increment = ;
    let counter = Mutex::new(10);
    {
        let mut value = counter.lock().unwrap();
        *value += increment;
    }
    let total = *counter.lock().unwrap();
    println!("total={total}");
}

use std::sync::Mutex;

fn main() {
    let increment = ;
    let counter = Mutex::new(10);
    {
        let mut value = counter.lock().unwrap();
        *value += increment;
    }
    let total = *counter.lock().unwrap();
    println!("total={total}");
}

use std::sync::Mutex;

fn main() {
    let increment = ;
    let counter = Mutex::new(10);
    {
        let mut value = counter.lock().unwrap();
        *value += increment;
    }
    let total = *counter.lock().unwrap();
    println!("total={total}");
}
Mutex `Mutex::new` wraps data that should be updated through a lock.
lock `lock().unwrap()` returns a guard that grants access while it is in scope.
scope The inner block releases the first lock before the final read.