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Linux Kernel Programming

You're reading from   Linux Kernel Programming A comprehensive guide to kernel internals, writing kernel modules, and kernel synchronization

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Product type Paperback
Published in Mar 2021
Publisher Packt
ISBN-13 9781789953435
Length 754 pages
Edition 1st Edition
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Author (1):
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Kaiwan N. Billimoria Kaiwan N. Billimoria
Author Profile Icon Kaiwan N. Billimoria
Kaiwan N. Billimoria
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Table of Contents (19) Chapters Close

Preface 1. Section 1: The Basics
2. Kernel Workspace Setup FREE CHAPTER 3. Building the 5.x Linux Kernel from Source - Part 1 4. Building the 5.x Linux Kernel from Source - Part 2 5. Writing Your First Kernel Module - LKMs Part 1 6. Writing Your First Kernel Module - LKMs Part 2 7. Section 2: Understanding and Working with the Kernel
8. Kernel Internals Essentials - Processes and Threads 9. Memory Management Internals - Essentials 10. Kernel Memory Allocation for Module Authors - Part 1 11. Kernel Memory Allocation for Module Authors - Part 2 12. The CPU Scheduler - Part 1 13. The CPU Scheduler - Part 2 14. Section 3: Delving Deeper
15. Kernel Synchronization - Part 1 16. Kernel Synchronization - Part 2 17. About Packt 18. Other Books You May Enjoy

Mutex lock and unlock APIs and their usage

The actual locking and unlocking APIs for the mutex lock are as follows. The following code shows how to lock and unlock a mutex, respectively:

void __sched mutex_lock(struct mutex *lock);
void __sched mutex_unlock(struct mutex *lock);

(Ignore __sched here; it's just a compiler attribute that has this function disappear in the WCHAN output, which shows up in procfs and with certain option switches to ps(1) (such as -l)).

Again, the comments within the source code in kernel/locking/mutex.c are very detailed and descriptive; I encourage you to take a look at this file in more detail. We've only shown some of its code here, which has been taken directly from the 5.4 Linux kernel source tree:

// kernel/locking/mutex.c
[ ... ]
/**
* mutex_lock - acquire the mutex
* @lock: the mutex to be acquired
*
* Lock the mutex exclusively for this task. If the mutex is not
* available right now, it will sleep until it can get it...
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