Modifying the kernel using RT-PREEMPT

To dive into the real time realm, we'll begin by exploring a piece of code that you apply to the Linux kernel directly, one which is often considered the de facto standard for real-time applications, a patch called PREEMPT_RT.

First, nomenclature. In the literature, our patch can be found referred to as CONFIG_PREEMPT_RT, PREEMPT_RT, RT-Preempt, or simply Linux RT patch. Whew! Can't anyone decide? We'll default to calling it RT-PREEMPT since that is the most common usage.

The RT-PREEMPT patch forces onto our system what is known as native real time pre-emption. This means that the patch is applied directly—or natively—onto the kernel, and allows you to preempt the entire kernel's events and processes in favor of targeted events or tasks. It makes sections of the Linux kernel pre-emptible that are ordinarily blocking.

For example, let's say we have two processes. We assign a higher priority to the second process than the first one. The patch enables a time...