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Linux Kernel Programming

You're reading from  Linux Kernel Programming

Product type Book
Published in Mar 2021
Publisher Packt
ISBN-13 9781789953435
Pages 754 pages
Edition 1st Edition
Languages
Author (1):
Kaiwan N. Billimoria Kaiwan N. Billimoria
Profile icon Kaiwan N. Billimoria
Toc

Table of Contents (19) Chapters close

Preface 1. Section 1: The Basics
2. Kernel Workspace Setup 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

CPU scheduler entry points

The detailed comments present in (just before) the core kernel scheduling function kernel/sched/core.c:__schedule() are well worth reading through; they specify all the possible entry points to the kernel CPU scheduler. We have simply reproduced them here directly from the 5.4 kernel code base, so do take a look. Keep in mind: the following code is being run in process context by the process (thread, really) that's going to kick itself off the CPU by ultimately context-switching to some other thread! And this thread is who? Why, it's current, of course!

The __schedule() function has (among others) two local variables, pointer to struct task_struct named prev and next. The pointer named prev is set to rq->curr, which is nothing but current! The pointer named next will be set to the task that's going to be context-switched to, that's going to run next! So, you see: current runs the scheduler code, performing the...

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