Delayed Interrupt Processing Technique for Reducing Latency of Timer Interrupt in Embedded Linux

Abstract

In real-time operating systems, timer interrupts are usually used for indicating when a real-time task should be started. Critical sections with interrupts disabled can, however, cause an unacceptable delay in the execution of these tasks. Existing approaches for overcoming this issue either require modifications to many places in the kernel source or introduce a new structural design. In this paper, we propose a simple interrupt management technique for reducing the latency of timer interrupts. The locking mechanism and the timer interrupt handler have been modified so that timer interrupts are not disabled during critical sections, allowing the execution of emergency jobs requested by real-time tasks. We implemented a prototype system in Linux 2.6.20. Experimental results showed that the timer interrupt latency is reduced to 2.2\% of the original Linux kernel and the latency time for executing an emergency real-time job is 27.9$\mu$s in the worst case. Comparing to existing real-time systems, the results showed that proposed technique is efficient enough for a future real-time operating system.