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Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization

You're reading from   Linux Kernel Programming Part 2 - Char Device Drivers and Kernel Synchronization Create user-kernel interfaces, work with peripheral I/O, and handle hardware interrupts

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Product type Paperback
Published in Mar 2021
Publisher Packt
ISBN-13 9781801079518
Length 452 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 (11) Chapters Close

Preface 1. Section 1: Character Device Driver Basics
2. Writing a Simple misc Character Device Driver FREE CHAPTER 3. User-Kernel Communication Pathways 4. Working with Hardware I/O Memory 5. Handling Hardware Interrupts 6. Working with Kernel Timers, Threads, and Workqueues 7. Section 2: Delving Deeper
8. Kernel Synchronization - Part 1 9. Kernel Synchronization - Part 2 10. Other Books You May Enjoy

Example 2 – catching an AB-BA deadlock with lockdep

As one more example, let's check out a (demo) kernel module that quite deliberately creates a circular dependency, which will ultimately result in a deadlock. The code is here: ch13/3_lockdep/deadlock_eg_AB-BA. We've based this module on our earlier one (ch13/2_percpu); as you'll recall, we create two kernel threads and ensure (by using a hacked sched_setaffinity()) that each kernel thread runs on a unique CPU core (the first kernel thread on CPU core 0 and the second on core 1).

This way, we have concurrency. Now, within the threads, we have them work with two spinlocks, lockA and lockB. Understanding that we have a process context with two or more locks, we document and follow a lock ordering rule: first take lockA, then lockB. Great; so, one way it should not be done is like this:

kthread 0 on CPU #0                kthread 1 on CPU #1
Take lockA ...
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