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

Interrupt shielding

Using threaded interrupt handlers helps mitigate interrupt overhead by running some threads at a higher priority than interrupt handlers that do not impact the real-time tasks. If you are using a multi-core processor, you can take a different approach and shield one or more cores from processing interrupts completely, allowing them to be dedicated to real-time tasks instead. This works either with a normal Linux kernel or a PREEMPT_RT kernel.

Achieving this is a question of pinning the real-time threads to one CPU and the interrupt handlers to a different one. You can set the CPU affinity off a thread or process using the command line tool taskset, or you can use the sched_setaffinity(2) and pthread_setaffinity_np(3) functions.

To set the affinity of an interrupt, first note that there is a subdirectory for each interrupt number in /proc/irq/<IRQ number>. The control files for the interrupt are in there, including a CPU mask in smp_affinity. Write a bitmask to that...