Optimality Results for Multiprocessor Real-Time Locking

Abstract

When locking protocols are used in real-time systems, bounds on blocking times are required when ensuring timing constraints. While the term "blocking" is well-understood in the context of uniprocessor real-time systems, the same is not true in the multiprocessor case. In this paper, two definitions of blocking are presented that are applicable to suspensionbased multiprocessor locking protocols. The need for two definitions arises because of differences in how suspensions are handled in existing schedulability analysis. For each definition, locking protocols are presented that have asymptotically optimal blocking behavior. In particular, protocols are presented for any job-level static-priority global or partitioned scheduling algorithm.

Multiprocessor Real-Time Systems with Shared Resources: Utilization Bound and Mapping

“…Moreover, in [18], Easwaran et al studied a parallel PCP (P-PCP) resource-sharing protocol for fixed-priority tasks in multiprocessor systems and developed the corresponding schedulability conditions. Recently, Block et al introduced a Flexible Multiprocessor Locking Protocol (FMLP) [10] and Brandenburg et al studied an asymptotically optimal locking protocol (OMLP) [11].…”

“…Moreover, for the resource access protocol, although the suspension-based mechanism adopted in OMLP can improve system efficiency at runtime [11], it cannot improve the off-line schedulability analysis that needs to consider the worst case scenario. Therefore, we focus on the spin-lock based MSRP resource access protocol, where the basic rules can be summarized as follows [20]:…”

“…Therefore, from [11], we can directly get the following proposition regarding to the interference among tasks under partitioned-EDF scheduling.…”

A Fully Preemptive Multiprocessor Semaphore Protocol for Latency-Sensitive Real-Time Applications

“…Most closely related to this paper are optimality results [8,12,13] pertaining to the intuitive goal of "minimal blocking" in multiprocessor real-time semaphore protocols under job-level fixed-priority (JLFP) scheduling, a broad category of schedulers that includes the FP and earliest-deadline first (EDF) policies. Specifically, recent work [12] investigated asymptotic bounds on maximum priority-inversion blocking (pi-blocking), which (intuitively) occurs whenever a high-priority task is delayed by a lowerpriority one.…”

“…Specifically, recent work [12] investigated asymptotic bounds on maximum priority-inversion blocking (pi-blocking), which (intuitively) occurs whenever a high-priority task is delayed by a lowerpriority one. Surprisingly, there exist two classes of schedulability analysis, called suspension-aware and suspensionoblivious analysis [12], resp., that give rise to different lower bounds on worst-case pi-blocking, namely Ω(n) and Ω(m), resp., where n denotes the number of tasks and m the number of processors. In brief, the difference arises due to how semaphore-induced self-suspensions are accounted for.…”