Implementing priority inheritance semaphore on uC/OS real-time kernel

Abstract

In a preemptive priority based RTOS, the priority inversion problem is among the major sources of deadline violations. The priority inheritance protocol is one of the approaches to reduce priority inversion. Unfortunately, RTOS like uC/OS cannot support the priority inheritance protocol since it does not allow the kernel to have multiple tasks at the same priority. Although it has different ways to avoid priority inversion such as the priority ceiling protocol, developers still have some difficulties in programming real time applications with it. In this paper, we redesign the uC/OS kernel to provide the ability to support round robin scheduling and implement the priority inheritance semaphore on the modified kernel. As a result, we port the new kernel with the priority inheritance semaphore to an evaluation board, and evaluate the execution time of each kernel service as well as verifying the operation of our implementation.