Thread suspension system and method

Abstract

In processor architectures that support allocation of register windows to called procedures, functions or methods, register windowing mechanisms can be used to facilitate suspension of a mutator thread (or mutator threads) while imposing negligible overhead on the mutator computation during periods when thread suspension is not requested. Reduced Instruction Set Computer-(RISC)-oriented processor architectures often employ register windows (typically partially-overlapped register windows) and can therefore benefit from the technique. Variations can be employed even in processors (RISC or otherwise) that do not employ register windowing as long as the processor (by itself or in cooperation with software) provides facilities for allocating and reclaiming resources in correspondence with calls to, and returns from, procedures, functions or methods. Mechanisms are provided to spill values from the fixed set of resources to a secondary store and to fill values from the secondary store into the fixed set in correspondence with function call triggered overflows and function return triggered underflows. In some configurations, modified spill and/or fill mechanism(s) are used to suspend threads at safe points coinciding with call and/or return sites. Because the modified spill and/or fill mechanism(s) impose negligible overhead when not employed and can be engaged in response to an event (e.g., a start garbage collection event), safe points can be defined at call and/or return points throughout mutator code to reduce the latency between the event and suspension of threads.