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

Threaded interrupt handlers

Not all interrupts are triggers for the real-time tasks but all interrupts steal cycles from the real-time task. Threaded interrupt handlers allow a priority to be associated with the interrupt and for it to be scheduled at an appropriate time as shown in the following diagram:

If the interrupt handler code is run as a kernel thread there is no reason why it cannot be preempted by a user space thread of higher priority, and so the interrupt handler does not contribute towards scheduling latency of the user space thread. Threaded interrupt handlers have been a feature of mainline Linux since 2.6.30. You can request that an individual interrupt handler is threaded by registering it with request_threaded_irq() in place of the normal request_irq(). You can make threaded IRQs the default by configuring the kernel with CONFIG_IRQ_FORCED_THREADING=y which makes all handlers into threads unless they have explicitly prevented this by setting the IRQF_NO_THREAD flag. When...