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

Delaying for a given time in the kernel

Often, your kernel or driver code will need to wait for a given time before moving on to the next instruction. This can be achieved within the Linux kernel space via a set of delay APIs. Right from the outset, a key point to understand is that you can enforce a delay in two broad ways:

  • Delay via non-blocking or atomic APIs that will never cause a sleep process to occur (in other words, it will never schedule out)
  • Delay via blocking APIs that cause the current process context to sleep (in other words, by scheduling out)

(As we covered in detail in the companion guide Linux Kernel Programming, our chapters on CPU scheduling  Chapter 10, The CPU Scheduler Part 1, and Chapter 11, The CPU Scheduler Part 2), putting a process context to sleep internally implies that the kernel's core schedule() function is invoked at some point, ultimately causing a context switch to occur. This leads up...