Book Image

Mastering Embedded Linux Programming

By : Chris Simmonds
Book Image

Mastering Embedded Linux Programming

By: Chris Simmonds

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (22 chapters)
Mastering Embedded Linux Programming
About the Author
About the Reviewers


The second big topic I want to cover in this chapter is scheduling. The Linux scheduler has a queue of threads that are ready to run and its job is to schedule them on CPUs as they become available. Each thread has a scheduling policy which may be timeshared or real-time. The timeshared threads have a niceness value which increases or reduces their entitlement to CPU time. The real-time threads have a priority such that a higher priority thread will preempt a lower one. The scheduler works with threads, not processes. Each thread is scheduled regardless of which process it is running in.

The scheduler runs when:

  • A thread blocks by calling sleep() or in a blocking I/O call

  • A timeshare thread exhausts its time slice

  • An interrupt causes a thread to be unblocked, for example, because of I/O completing

For background information on the Linux scheduler, I recommend reading the chapter on process scheduling in Linux Kernel Development, 3rd edition by Robert Love, Addison-Wesley Professional...