Flexible Real-Time Linux*: A Flexible Hard Real-Time Environment

This paper presents a framework appropriate for Flexible Real-Time Systems (FRTS) and a run-time support system based on that framework, called Flexible Real-Time Linux (FRTL). The framework proposes to build each task as a sequence of mandatory and optional components and to separate their execution in two scheduling levels. This approach is shown to provide both hard guarantees and flexible behavior. The FRTL system has been implemented by enhancing the original capabilities of Real-Time Linux (RT-Linux), while maintaining its predictability and efficiency features. This paper also shows a complete schedulability test on which all sources of overhead of the FRTL itself have been introduced. By applying this complete test, the designer is able to safely guarantee a real-time application running on the FRTL system.