How Software Works

8Concurrency

Usually we can tell when software is doing something interesting, even if we don’t know how it’s done. We know that computers make graphics, encrypt our transmissions, and stream our videos. What we miss, though, is that these tasks often involve multiple programs, multiple processors, or even multiple computers connected via a network, accessing the same data at the same time.

This overlapping access of data, known as concurrency, is a vital part of modern technology. High-performance tasks like graphics and shared resources like websites wouldn’t be possible without it. But concurrency causes big problems when it’s not carefully ...