Hands-On Concurrency with Rust

Racing threads

You can also mark types as thread-safe, effectively promising the compiler that you've arranged all the data races in such a way as to make them safe. This is relatively rare in practice but it's worth seeing what it takes to make a type thread-safe in Rust before we start building on top of safe primitives. First, let's take a look at code that's intentionally sideways:

use std::{mem, thread};
use std::ops::{Deref, DerefMut};

unsafe impl Send for Ring {}
unsafe impl Sync for Ring {}

struct InnerRing {
    capacity: isize,
    size: usize,
    data: *mut Option<u32>,
}

#[derive(Clone)]
struct Ring {
    inner: *mut InnerRing,
}

What we have here is a ring, or a circular buffer, of u32. InnerRing holds a raw mutable pointer and is not automatically ...