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Mastering Linux Kernel Development

Mastering Linux Kernel Development

By : CH Raghav Maruthi
2.9 (10)
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Mastering Linux Kernel Development

Mastering Linux Kernel Development

2.9 (10)
By: CH Raghav Maruthi

Overview of this book

Mastering Linux Kernel Development looks at the Linux kernel, its internal arrangement and design, and various core subsystems, helping you to gain significant understanding of this open source marvel. You will look at how the Linux kernel, which possesses a kind of collective intelligence thanks to its scores of contributors, remains so elegant owing to its great design. This book also looks at all the key kernel code, core data structures, functions, and macros, giving you a comprehensive foundation of the implementation details of the kernel’s core services and mechanisms. You will also look at the Linux kernel as well-designed software, which gives us insights into software design in general that are easily scalable yet fundamentally strong and safe. By the end of this book, you will have considerable understanding of and appreciation for the Linux kernel.
Table of Contents (12 chapters)
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Linux timekeeping data structures, macros, and helper routines


We will now broaden our awareness by looking at some key timekeeping structures, macros, and helper routines that can assist programmers in extracting specific time-related data.

Jiffies

Thejiffies variable holds the number of ticks elapsed since system bootup. Every time a tick occurs, jiffies is incremented by one. It's a 32-bit variable, meaning for a tick rate of 100 Hz, overflow will occur in approximately 497 days (and in 49 days, 17 hours for a 1000 Hz tick rate).

To overcome this issue, a 64-bit variable jiffies_64 is used instead, which allows for thousands of millions of years before the overflow occurs. The jiffies variable is equated to the 32 least significant bits of jiffies_64. The reason for having both jiffies and jiffies_64 variables is that in 32-bit machines, a 64-bit variable can not be accessed atomically; some synchronization is required in order to avoid any counter update while these two 32-bit halves are...

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