A dynamic scheduling approach to designing flexible safety-critical systems

Abstract

The design of safety-critical systems has typically adopted static techniques to simplify error detection and fault tolerance. However, economic pressure to reduce costs is exposing the limitations of those techniques in terms of efficiency in the use of system resources. In some industrial domains, such as the automotive, this pressure is too high, and other approaches to safety must be found, e.g., capable of providing some kind of fault tolerance but with graceful degradation to lower costs, or also capable of adapting to instantaneous requirements to better use the computational/communication resources. This paper analyzes the development of systems that exhibit such level of flexibility, allowing the system configuration to evolve within a well-defined space. Two options are possible, one starting from the typical static approach but introducing choice points that are evaluated only at runtime, and another one starting from an open systems approach but delimiting the space of possible adaptations. The paper follows the latter and presents a specific contribution, namely, the concept of local utilization bound, which supports a fast and efficient schedulability analysis for on-line resource management that assures continued safe operation. Such local bound is derived off-line for the specific set of possible configurations, and can be significantly higher than any generic non-necessary utilization bound such as the well known Liu and Layland's bound for RateMonotonic scheduling. Comments Postprint version. Published in ABSTRACTThe design of safety-critical systems has typically adopted static techniques to simplify error detection and fault tolerance. However, economic pressure to reduce costs is exposing the limitations of those techniques in terms of efficiency in the use of system resources. In some industrial domains, such as the automotive, this pressure is too high, and other approaches to safety must be found, e.g., capable of providing some kind of fault tolerance but with graceful degradation to lower costs, or also capable of adapting to instantaneous requirements to better use the computational/communication resources. This paper analyses the development of systems that exhibit such level of flexibility, allowing the system configuration to evolve within a well-defined space. Two options are possible, one starting from the typical static approach but introducing choice points that are evaluated only at runtime, and another one starting from an open systems approach but delimiting the space of possible adaptations. The paper follows the latter and presents a specific contribution, namely, the concept of local utilization bound, which supports a fast and efficient schedulability analysis for on-line resource management that assures continued safe operation. Such local bound is derived off-line for the specific set of possible configurations, and can be significantly higher than any generic non-necessary utilization bound such as the well known Liu and Layland's bound for Rate-Monotonic sche...

Preliminary design of future reconfigurable IMA platforms

“…Our approach is close from the one proposed by the authors of [1] although our context is different (they study time triggered systems and dynamic QoS management). The authors propose a bounded flexibility solution meaning that the reconfiguration evolves in a bounded and predefined configuration space.…”

QoS management for dependable sensory environments

“…In this sense, this work empowers the dynamism and do not restrict to a well known set of possible configurations known at design time, as in [8]. This is why online feasibility tests based on utilization factor as the well known utilization bound test of Liu and Layland [25] or the more efficient response time analysis [23] can be used.…”

“…Another possible QoS management policy is the one proposed in [8]. It is called prioritized QoS management policy, and it is the inspiration for the QoS policy that has been adopted in this work, as far as it provides some advantages over the elastic QoS management policy from the safety point of view, which is a key issue in this work.…”

Topological design of industrial Ethernet networks with a fast heuristic

“…The weighting of the above mentioned criteria in the design process depends on the actual automation applications [12] [13]. In practice, users usually have multiple requirements of network performance for a single application.…”