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

Spinlock simple usage

For all the spinlock APIs, you must include the relevant header file; that is, include <linux/spinlock.h>.

Similar to the mutex lock, you must declare and initialize the spinlock to the unlocked state before use. The spinlock is an "object" that's declared via the typedef data type named spinlock_t (internally, it's a structure defined in include/linux/spinlock_types.h). It can be initialized dynamically via the spin_lock_init() macro:

spinlock_t lock;

Alternatively, this can be performed statically (declared and initialized) with DEFINE_SPINLOCK(lock);.

As with the mutex, declaring a spinlock within the (global/static) data structure is meant to protect against concurrent access, and is typically a very good idea. As we mentioned earlier, this very idea is made use of within the kernel often; as an example, the data structure representing an open file on the Linux kernel...