Embedded Linux for Developers

Identifying the sources of non-determinism

Fundamentally, real-time programming is about making sure that the threads controlling the output in real-time are scheduled when needed and so can complete the job before the deadline. Anything that prevents this is a problem. Here are some problem areas:

• Scheduling: Real-time threads must be scheduled before others so they must have a real-time policy, SCHED_FIFO, or SCHED_RR. Additionally they should have priorities assigned in descending order starting with the one with the shortest deadline, according to the theory of Rate Monotonic Analysis that I described in Chapter 10, Learning About Processes and Threads.
• Scheduling latency: The kernel must be able to reschedule as soon as an event such as an ...