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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

Available softirqs and what they are for

The work that's carried out by a given softirq is statically compiled into the kernel image (it's fixed). This coupling of the softirq and the action it takes (in effect, the code it runs, via the action function pointer) is done via the following code:

// kernel/softirq.c
void open_softirq(int nr, void (*action)(struct softirq_action *))
{
softirq_vec[nr].action = action;
}

The following diagram is a conceptual representation of the available softirqs and their priority level on Linux (as of kernel version 5.4), with 0 being the highest and 9 the lowest softirq priority level:

Figure 4.11 – The 10 softirqs on Linux in order of priority (0:highest, 9:lowest)

The following table sums up the individual kernel's softirqs in order of their priority (0: HI_SOFTIRQ being the highest priority one), along with the action or vector, its functionality, and a comment mentioning what its use case is:

Softirq# Softirq Comment...
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