Book Image

Mastering Embedded Linux Programming - Third Edition

By : Frank Vasquez, Chris Simmonds
5 (3)
Book Image

Mastering Embedded Linux Programming - Third Edition

5 (3)
By: Frank Vasquez, Chris Simmonds

Overview of this book

If you’re looking for a book that will demystify embedded Linux, then you’ve come to the right place. Mastering Embedded Linux Programming is a fully comprehensive guide that can serve both as means to learn new things or as a handy reference. The first few chapters of this book will break down the fundamental elements that underpin all embedded Linux projects: the toolchain, the bootloader, the kernel, and the root filesystem. After that, you will learn how to create each of these elements from scratch and automate the process using Buildroot and the Yocto Project. As you progress, the book will show you how to implement an effective storage strategy for flash memory chips and install updates to a device remotely once it’s deployed. You’ll also learn about the key aspects of writing code for embedded Linux, such as how to access hardware from apps, the implications of writing multi-threaded code, and techniques to manage memory in an efficient way. The final chapters demonstrate how to debug your code, whether it resides in apps or in the Linux kernel itself. You’ll also cover the different tracers and profilers that are available for Linux so that you can quickly pinpoint any performance bottlenecks in your system. By the end of this Linux book, you’ll be able to create efficient and secure embedded devices using Linux.
Table of Contents (27 chapters)
1
Section 1: Elements of Embedded Linux
10
Section 2: System Architecture and Design Decisions
18
Section 3: Writing Embedded Applications
22
Section 4: Debugging and Optimizing Performance

Understanding scheduling latency

Real-time threads need to be scheduled as soon as they have something to do. However, even if there are no other threads of the same or higher priority, there is always a delay from the point at which the wake-up event occurs—an interrupt or system timer—to the time that the thread starts to run. This is called scheduling latency. It can be broken down into several components, as shown in the following diagram:

Figure 21.1 – Scheduling latency

Figure 21.1 – Scheduling latency

Firstly, there is the hardware interrupt latency from the point at which an interrupt is asserted until the interrupt service routine (ISR) begins to run. A small part of this is the delay in the interrupt hardware itself, but the biggest problem is due to interrupts being disabled in software. Minimizing this IRQ off time is important.

The next is interrupt latency, which is the length of time until the ISR has serviced the interrupt and woken up any threads...