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

Does the kernel maintain separate IRQ stacks?

In the companion guide Linux Kernel Programming in Chapter 6, Kernel Internals and Essentials  Processes and Threads, in the Organizing process, threads, and their stacks user and kernel space section, we covered some key points: every single user space thread has two stacks: a user space stack and a kernel space stack. When the thread runs in non-privileged user space, it makes use of the user mode stack, while when it switches to privileged kernel space (via a system call or exception), it works with its kernel-mode stack (refer back to Figure 6.3 in the companion guide Linux Kernel Programming). Next, the kernel-mode stack is very limited and fixed in size it's only 2 or 4 pages long (depending on whether your arch is 32- or 64-bit, respectively)!

So, imagine your driver code's (let's say, the ioctl() method) is running within a deeply nested code...