The Priority Ceiling Protocol (PCP) of Sha, Rajkumar and Lehoczky is a policy for locking binary semaphores that bounds priority inversion (i.e., the blocking of a job while a lower priority job executes), and thereby improves schedulability under fixed priority preemptive scheduling. We show how to extend the PCP to handle: multiunit resources, which… (More)
The Stack Resource Policy (SRP) is a resource allocation policy which permits processes with different priorities to share a single runtime stack. It is a refinement of the Priority Ceiling Protocol (PCP) of Sha, Rajkumar and Lehoczky, which strictly bounds priority inversion and permits simple schedulability tests. With or without stack sharing, the SRP… (More)
Schedulability tests are presented for preemptive earliest-deadline-first and deadline-monotonic scheduling of periodic or sporadic real-time tasks on a single-queue Ñ-server system, in which the deadline of a task may be less than or equal to the task period. These results subsume and generalize several known utilization-based mul-tiprocessor… (More)
A schedulability test is derived for the global Earliest Deadline Zero Laxity (EDZL) scheduling algorithm on a platform with multiple identical processors. The test is sufficient, but not necessary, to guarantee that a system of independent sporadic tasks with arbitrary deadlines will be successfully scheduled, with no missed deadlines, by the… (More)
A polynomial-time algorithm is presented for partitioning a collection of sporadic tasks among the processors of an identical multiprocessor platform with static-priority scheduling on each individual processor. Since the partitioning problem is easily seen to be NP-hard in the strong sense, this algorithm is not optimal. A quantitative characterization of… (More)
In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key results in real time scheduling theory and the historical events that led to the establishment of the current real time computing infrastructure. We conclude this paper by looking at the challenges ahead of us.
We consider the schedulability of a set of independent periodic tasks under xed priority preemptive scheduling on homogeneous multiprocessor systems. Assuming there is no task migration between processors and each processor schedules tasks preemptively according to xed priorities assigned by the Rate Monotonic policy, the scheduling problem reduces to… (More)
Improvements in schedulability tests for global fixed-priority and EDF scheduling in a homogeneous mul-tiprocessor (symmetric multiprocessing) environment have shown that the worst-case guaranteed achievable utilization levels for global EDF scheduling equals what can be achieved with partitioned scheduling, and both ways of applying EDF scheduling… (More)