8 - Real-Time Operating Systems for DSP

Abstract

Modern DSP systems are managed by real-time operating systems that manage multiple tasks, service events from the environment based on an interrupt structure, and effectively manage the system resources. An operating system must have certain properties to qualify as a real-time operating system (RTOS). Most importantly, a RTOS must be multithreaded and preemptible. The RTOS must also support task priorities. Many DSP RTOSs and most commercial RTOSs in general use static-scheduling algorithms because they are simple to implement, easy to understand and support, and have a rich set of analysis techniques to draw from. DSP software developers can use Rate Monotonic Analysis to determine if the system task set is schedulable or not. If it is not schedulable, the analysis can be used to determine if there are any shared-resource blocking issues that can be used to re-design the system task set and resource requirements and is especially useful for a first cut feasibility review. Most existing commercial RTOSs such as VxWorks, VRTX, and DSP RTOSs such as DSP/BIOS use Rate Monotonic Scheduling, with some form of priority inheritance or priority ceiling protocol to limit resource blocking and priority inversion.