Testing, Checking, and Hardware Syndrome

Abstract

In previous chapters we introduced the processes of checking and testing, the first of the three main processes of generalized algorithm of fault tolerance—GAFT. In this chapter we further discuss the process of checking hardware, at first software-based hardware checking and at second hardware-based checking. For the software-based hardware checking, we show what a software-based test should include, when they are the preferred choice over hardware-based checking schemes and especially how such tests can be scheduled in the system without interfering with ongoing real-time tasks. Further to support handling of hardware -based checking we introduce a new system condition descriptor—a so-called syndrome—and illustrate how it can be used as a mechanism to signal to the operating system hardware condition, including manifestation of detected error. We then show the steps the run-time system performs to eliminate the fault and in case of permanent errors how the software can reconfigure the hardware to exclude the faulty element. We also explain in which cases software has to adapt to the new hardware topology. We start by explaining how software-based checks can be used to detect hardware faults. Run-time systems use online or off-line scheduling mechanisms for task management of programs—own—system software ones and user application ones. Since in Kirby et al. (Softw Pract Exp 15(1):87–103, 1985, [2]), Serlin (Comput C 7(8):19–30, 1984, [3]), Blazewicz et al. (Handbook on scheduling, from theory to applications, 2007, [4]), Ingo (Linux kernel archive, 2002, [8]) it is expected that run-time system provides a special session of task scheduling (off-line or online during execution) for the purposes of diagnostic of hardware conditions—recall Apple and Microsoft system starting delays. Later for some systems that operate in domain of real-time monitoring scheduling of tasks, critical in time of execution especially criticality of hardware availability and efficiency of process scheduling, become crucial. In turn testing itself become “hot” in terms of required time and coverage of hardware. Thus in this chapter we initially analyze simple sequences of testing of hardware elements of computer systems. Further, we introduce a concept of transparent for user application procedure of hardware testing. This enables to prove the integrity of computer system hardware, and guarantee it within reasonable time, without delays of service of execution of user tasks.