How to Integrate Precedence Constraints and Shared Resources in Real-Time Scheduling

Formal results for precedence constrained, real-time scheduling of unit time tasks are extended to arbitrary timed tasks with preemp-tion. An exact characterisation of the EDF-like schedulers that can be used to transparently enforce precedence constraints among tasks is shown. These extended results are then integrated with a well-known protocol that handles real-time scheduling of tasks with shared resources , but does not consider precedence constraints. This results in schedulability formulas for task sets which allow preemption, shared resources, and precedence constraints, and a practical algorithm for many real-time uniprocessor systems.