Eliminating Interrupt Overload in Embedded Systems

Embedded systems can fail to operate correctly due to interrupt overload: starvation caused by too many interrupt requests. This paper describes three new techniques, two software-based and one hardware-based, for creating systems that delay or drop excessive interrupt requests before they can overload a processor. Our solutions to the interrupt overload problem have several desirable properties. During underload, overhead is proportional to interrupt load. During overload, both the amount of work performed in interrupt context and its granularity are bounded, making it possible to provide strong progress guarantees to low-priority interrupts and noninterrupt tasks. These guarantees permit developers to avoid making assumptions about the worst-case interrupt rates of peripherals such as sensors and network interfaces, filling an important gap in the chain of reasoning leading to a validated embedded system. We show that our solutions successfully prevent interrupt overload with modest overhead by evaluating them on embedded processors. We have also taken a description for a microprocessor in VHDL, modified it to include logic that prevents interrupt overload, synthesized the processor, and verified that it works using simulation.