Schedulability Analysis of Mode Changes with Arbitrary Deadlines

Abstract

Modern real-time systems are required to operate in complex applications and dynamically adapt to a wide range of changes in the environment. One strategy that allows the implementation of these systems in complex scenarios is the partitioning of their applications into modes of operation. Flexibility of operation is achieved by having the system execute in several modes of operation and undergo transitions between modes in response to external or internal events. A mode of operation can be seen as a specific configuration of the computational resources that is optimal for the operational phase that the system executes. As conditions in the environment change, resource allocations may become inadequate. Therefore, the systemmust reconfigure itself through amode change, reallocating its resources in an efficient manner. A classic example of modes lies in the area of aviation where most aircraft undergo at least three basic modes of operation: take-off, level-flight, and landing modes. Having the system designed with a single mode of operation does not explore the fact that some operations, and thus resource usage, are mutually exclusive. The allocation of all these resources, as if they could be needed at the same time, leads to inefficiency. More importantly, the resulting system is not scalable. The so called all-modes-in-one system is usually feasible for simple systems with limited functionality.