A new implementation method of timer for periodic tasks
Journal of Embedded Computing - Advanced Topics on Embedded Computing
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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, allowingthe execution of emergency jobs requested by real-time tasks. Weimplemented a prototype system in Linux 2.6.20. Experimental resultsshowed that the timer interrupt latency is reduced to 2.2\% of theoriginal Linux kernel and the latency time for executing anemergency real-time job is 27.9$\mu$s in the worst case. Comparingto existing real-time systems, the results showed that proposedtechnique is efficient enough for a future real-time operatingsystem.