The automotive industry, as well as other industrial branches, has a growing need to integrate consumer electronics applications (e.g. Linux based) and safety-relevant applications requiring an underlying hard real-time operating system. Some established concepts for mixed criticality systems can be found in the avionics domain.
In mixed-criticality systems it is necessary to separate applications with different levels of criticality such that they cannot affect each other in a more than acceptable degree.
Therefore, applications are usually assigned to partitions that limit their influence sphere. Different partitions are usually protected against each other in mixed-criticality system by separating them regarding space, i.e. memory, and regarding timing.
As this paper concentrates on the real-time aspects, the important issues to control are:
1 – At which points in time is a given partition allowed to obtain a shared resource?
2 – For which amount of time is a partition able to block out other partitions from accessing a particular resource?
This paper demonstrates that the principles behind these concepts are a dead end regarding innovations requiring a close interoperation.
The second contribution of the paper is to present a different solution approach as a potential remedy that allows the different developer groups (hard real-time and standard IT) to retain their attitude to software development.
The core of the novel approach is a worst-case execution time (WCET) directed OS service, which could serve as solution pattern for further problems in mixed-criticality systems.
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