Immortal Threads: Multithreaded Event-driven Intermittent Computing on Ultra-Low-Power Microcontrollers

We introduce Immortal Threads, a novel programming model that brings pseudo-stackful multithreaded processing to intermittent computing. Programmers using Immortal Threads are oblivious to intermittent execution and write their applications in a multithreaded fashion using common event-driven multithreading primitives. Our compiler fronted transforms the stackful threads into stackless threads that waste a minimum amount of computational progress upon power failures. Our runtime implements fair scheduling to switch between threads efficiently. We evaluated Immortal Threads on real hardware by comparing it against the stateof-the-art intermittent runtimes. Our comparison showed that the price paid for the Immortal Threads is a runtime overhead comparable to existing intermittent computing runtimes.