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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

Product type Book
Published in Mar 2021
Publisher Packt
ISBN-13 9781801079518
Pages 452 pages
Edition 1st Edition
Languages
Author (1):
Kaiwan N. Billimoria Kaiwan N. Billimoria
Profile icon Kaiwan N. Billimoria
Toc

Table of Contents (11) Chapters close

Preface 1. Section 1: Character Device Driver Basics
2. Writing a Simple misc Character Device Driver 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

Fully figuring out the context

The Interrupt context guidelines what to do and what not to do section made this clear: when you're in any kind of interrupt (or atomic) context, do not invoke any possibly blocking APIs (that end up calling schedule()); this really boils down to a few key points (as we saw). One is that you should not make any kernel to user space (or vice versa) data transfers; another, if you must allocate memory, do so with the GFP_ATOMIC flag.

This, of course, begs the question: how do I know if my driver (or module) code is currently running in process or interrupt (atomic) context? Furthermore, if it's running in interrupt context, is it in a top or bottom half? The short answer to all this is that the kernel provides several macros that you can use to figure this out. These macros are defined in the linux/preempt.h header. Instead of unnecessarily duplicating information, we...

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