Chapter 22: Fearless Concurrency

Concurrency is a cornerstone of modern software. Whether you’re building servers that handle many requests simultaneously or computational tools that leverage multiple CPU cores, concurrency can improve the responsiveness and throughput of your programs. However, it also brings challenges such as data races, deadlocks, and undefined behavior—often hard to debug in languages like C or C++.

Rust’s approach, often called fearless concurrency, combines its ownership model with compile-time checks that prevent data races. This significantly lowers the likelihood of subtle runtime bugs. In this chapter, we’ll explore concurrency with OS threads (leaving async tasks for a later chapter) and cover synchronization, data sharing, message passing, data parallelism (via Rayon), and SIMD optimizations. We’ll also compare Rust to C and C++ to highlight how Rust helps you avoid concurrency pitfalls from the start.