A safe SCHED_IDLE implementation

A safe SCHED_IDLE implementation

Digital Equipment Corporations (DEC) VAXELN Real Time OS scheduling incorporated JOB and PROCESS Execution thread creation. A master PROCESS could create a single JOB (created by CREATE_JOB) and multiple PROCESS (with CREATE_PROCESS). The JOB is the background thread and runs only when there were no ready/running PROCESS threads. The earlier RSX-IAS OS from the late '70s implmented a similar scheduling algorithm and was "Batch" based.