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

The bare minimum workqueue internals

We don't go into too much depth about the internals of the workqueue here; in fact, we will merely scratch the surface (as we mentioned previously, our purpose here is to only focus on using the kernel-global workqueue).

It's always recommended that you use the default kernel-global (system) workqueue to consume your asynchronous background work. If this is deemed to be insufficient, don't worry  certain interfaces are exposed that let you create your workqueues. (Keep in mind that doing so will increase stress on the system!) To allocate a new workqueue instance, you can use the alloc_workqueue() API; this is the primary API that's used for creating (allocating) workqueues (via the modern cmwq framework):

include/linux/workqueue.h
struct workqueue_struct *alloc_workqueue(const char *fmt, unsigned int flags, int max_active, ...);

Note that it's exported via EXPORT_SYMBOL_GPL(), which means it's only available...