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

Using spinlocks  a quick summary

Let's quickly summarize spinlocks:

  • Simplest, lowest overhead: Use the non-irq spinlock primitives, spin_lock()/spin_unlock(), when protecting critical sections in the process context (there's either no interrupts to deal with or there are interrupts, but we do not race with them at all; in effect, use this when interrupts don't come into play or don't matter).
  • Medium overhead: Use the irq-disabling (as well as kernel preemption disabling) versions, spin_lock_irq() / spin_unlock_irq(), when interrupts are in play and do matter (the process and interrupt contexts can "race"; that is, they share global data).
  • Strongest (relatively), high overhead: This is the safest way to use a spinlock. It does the same as the medium overhead, except it performs a save-and-restore on the interrupt mask via the spin_lock_irqsave() / spin_unlock_irqrestore() pair, so as to guarantee that the...