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)
1
Section 1: Character Device Driver Basics
3
User-Kernel Communication Pathways
5
Handling Hardware Interrupts
6
Working with Kernel Timers, Threads, and Workqueues
7
Section 2: Delving Deeper

Using Ftrace to get a handle on system latencies

Linux has a very powerful tracing engine built into the kernel itself called Ftrace. Just as you can trace system calls via the (oh so useful) strace(1) (and library APIs via ltrace(1)) utility in user space, you can also trace pretty much every function running in kernel space via Ftrace. Ftrace, though, is much more than simply a function tracer – it's a framework, a linchpin of the kernel's underlying tracing infrastructure.

Steven Rostedt is the original author of Ftrace. His paper entitled Finding Origins of Latencies Using Ftrace is a very good read. You can find it here: https://static.lwn.net/images/conf/rtlws11/papers/proc/p02.pdf.

In this section, we don't intend to cover how to use Ftrace in an in-depth manner as it's really not part of the subject matter here. Learning to use Ftrace isn't difficult, and is a valuable weapon in your kernel...