Probabilistic schedulability guarantees for dependable real-time systems under error bursts

• The fundamental requirement for the design of effective and efficient fault-tolerance mechanisms in dependable real-time systems is a realistic and applicable model of potential faults, their manifestations and consequences. Fault and error models also need to be evolved based on the characteristics of the operational environments or even based on technological advances. In this paper we propose a probabilistic burst error model in lieu of the commonly used simplistic fault assumptions in the context of processor scheduling. We present a novel schedulability analysis that accounts for the worst case interference caused by error bursts on the response times of tasks scheduled under the fixed priority scheduling (FPS) policy. Further, we describe a methodology for the calculation of probabilistic schedulability guarantees as a weighted sum of the conditional probabilities of schedulability under specified error burst characteristics. Finally, we identify potential sources of pessimism in the worst case response time calculations and discuss potential means for circumventing these issues.

Nyckelord

dependability

error bursts

fault tolerant scheduling

real-time systems

Burst errors

Conditional probabilities

Error model

Fault tolerance mechanisms

Fixed priority scheduling

Operational environments

Potential faults

Potential sources

Processor scheduling

Schedulability

Schedulability analysis

Technological advances

Weighted Sum

Worst case

Worst case response time

Embedded software

Embedded systems

Fault tolerance

Response time (computer systems)

Scheduling

Real time systems

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