Computing maximum blocking times with explicit path analysis under non-local flow bounds

Abstract

Worst-case time (WCET) analyses for single tasks are well established and their results ultimately serve the purpose of providing execution time parameters for schedulability analyses. Besides WCET analysis, an important problem is maximum blocking time (MBT) analysis which is essential in deferred preemption schedules for the selection of preemption points. Among the most pressing problems in this context is the need for good path analyses, which are a fundamental bottleneck for selecting these points. Current state of the art relies on ILP-based or severely constrained explicit path analyses, both of which are unsatisfactory in general.In this paper, we propose a general explicit path analysis to compute maximum blocking times, specifically for scheduling policies with deferred preemption. The proposal improves the current state of the art significantly for both WCET and MBT analysis, as it is efficient, accurate, easily extensible and computes path lengths between all program points, without imposing any artificial constraints, and under a general flow bound model, unmatched by other existing explicit path analyses, while significantly outperforming the ILP-based approach. To the best of the authors' knowledge, no explicit path analysis for MBT has been proposed yet.