Book Image

Linux Kernel Programming

By : Kaiwan N. Billimoria
Book Image

Linux Kernel Programming

By: Kaiwan N. Billimoria

Overview of this book

Linux Kernel Programming is a comprehensive introduction for those new to Linux kernel and module development. This easy-to-follow guide will have you up and running with writing kernel code in next-to-no time. This book uses the latest 5.4 Long-Term Support (LTS) Linux kernel, which will be maintained from November 2019 through to December 2025. By working with the 5.4 LTS kernel throughout the book, you can be confident that your knowledge will continue to be valid for years to come. You’ll start the journey by learning how to build the kernel from the source. Next, you’ll write your first kernel module using the powerful Loadable Kernel Module (LKM) framework. The following chapters will cover key kernel internals topics including Linux kernel architecture, memory management, and CPU scheduling. During the course of this book, you’ll delve into the fairly complex topic of concurrency within the kernel, understand the issues it can cause, and learn how they can be addressed with various locking technologies (mutexes, spinlocks, atomic, and refcount operators). You’ll also benefit from more advanced material on cache effects, a primer on lock-free techniques within the kernel, deadlock avoidance (with lockdep), and kernel lock debugging techniques. By the end of this kernel book, you’ll have a detailed understanding of the fundamentals of writing Linux kernel module code for real-world projects and products.
Table of Contents (19 chapters)
Section 1: The Basics
Writing Your First Kernel Module - LKMs Part 2
Section 2: Understanding and Working with the Kernel
Kernel Memory Allocation for Module Authors - Part 1
Kernel Memory Allocation for Module Authors - Part 2
Section 3: Delving Deeper
About Packt

Preemptible kernel

Let's take a hypothetical situation: you're running on a system with one CPU. An analog clock app is running on the GUI along with a C program, a.out, whose one line of code is (groan) while(1);. So, what do you think: will the CPU hogger while 1 process indefinitely hog the CPU, thus causing the GUI clock app to stop ticking (will its second hand stop moving altogether)?

A little thought (and experimentation) will reveal that, indeed, the GUI clock app keeps ticking in spite of the naughty CPU hogger app! Actually, this is really the whole point of having an OS-level scheduler: it can, and does, preempt the CPU-hogging user space process. (We briefly discussed the CFS algorithm previously; CFS will cause the aggressive CPU hogger process to accumulate a huge vruntime value and thus move more to the right on its rb-tree runqueue, thus penalizing itself!) All modern OSes support this type of preemption – it's called user-mode preemption...