Book Image

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

By : Kaiwan N Billimoria
Book Image

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

By: Kaiwan N Billimoria

Overview of this book

Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization is an ideal companion guide to the Linux Kernel Programming book. This book provides a comprehensive introduction for those new to Linux device driver development and will have you up and running with writing misc class character device driver code (on the 5.4 LTS Linux kernel) in next to no time. You'll begin by learning how to write a simple and complete misc class character driver before interfacing your driver with user-mode processes via procfs, sysfs, debugfs, netlink sockets, and ioctl. You'll then find out how to work with hardware I/O memory. The book covers working with hardware interrupts in depth and helps you understand interrupt request (IRQ) allocation, threaded IRQ handlers, tasklets, and softirqs. You'll also explore the practical usage of useful kernel mechanisms, setting up delays, timers, kernel threads, and workqueues. Finally, you'll discover how to deal with the complexity of kernel synchronization with locking technologies (mutexes, spinlocks, and atomic/refcount operators), including more advanced topics such as cache effects, a primer on lock-free techniques, deadlock avoidance (with lockdep), and kernel lock debugging techniques. By the end of this Linux kernel book, you'll have learned the fundamentals of writing Linux character device driver code for real-world projects and products.
Table of Contents (11 chapters)
Section 1: Character Device Driver Basics
User-Kernel Communication Pathways
Handling Hardware Interrupts
Working with Kernel Timers, Threads, and Workqueues
Section 2: Delving Deeper

Threaded interrupts to really make it real time

This is a key point and requires some explanation.

Prioritization on the standard Linux OS goes from highest to lowest priority as follows (we'll suffix each bullet point with the context it runs in; it will be either process or interrupt. If you're unclear on this point, it's very important you understand this; do refer to the companion guide Linux Kernel Programming - Chapter 6, Kernel Internals Essentials  Processes and Threads, the Understanding Process and Interrupt Contexts section, for more information):

  • Hardware interrupts: These preempt anything and everything. The hardirq handler runs atomically (to completion, without interruption) on the CPU; context:interrupt.
  • Real-time threads (the SCHED_FIFO or SCHED_RR scheduling policy), both kernel and user space, with positive real-time priority (rtprio); context:process:
    • A kernel...