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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

By : Frank Vasquez, Chris Simmonds
4.6 (23)
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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

4.6 (23)
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)
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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

Preemptible kernel locks

Making the majority of kernel locks preemptible is the most intrusive change that PREEMPT_RT makes, and this code remains outside of the mainline kernel.

The problem occurs with spin locks, which are used for much of the kernel locking. A spin lock is a busy-wait mutex that does not require a context switch in the contended case, and so it is very efficient as long as the lock is held for a short time. Ideally, they should be locked for less than the time it would take to reschedule twice. The following diagram shows threads running on two different CPUs contending the same spin lock. CPU 0 gets it first, forcing CPU 1 to spin, waiting until it is unlocked:

Figure 21.3 – Spin lock

Figure 21.3 – Spin lock

The thread that holds the spin lock cannot be preempted since doing so may make the new thread enter the same code and deadlock when it tries to lock the same spin lock. Consequently, in mainline Linux, locking a spin lock disables kernel preemption...

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