In such systems, tasks must receive appropriate timeliness guarantees from the operating system independently from one another otherwise, the QoS experienced by the users may decrease. This paper presents an architecture for quality of service (QoS) control of time-sensitive applications in multi-programmed embedded systems.
Automaton tracer code#
This analysis is made possible due to the minimalistic nature of modern micro kernels, and properties of seL4's source code arising from the requirements of formal verification. We believe this is one of the largest code bases on which a fully context-aware WCET analysis has been performed. It creates a foundation for integrating hard real-time systems with less critical time-sharing components on the same processor, supporting enhanced functionality while keeping hardware and development costs low. Adding temporal guarantees makes seL4 also a compelling platform for safety- and timing-critical systems. This makes seL4 an ideal platform for security-critical systems. seL4 is the world's first formally-verified operating-system kernel, featuring machine-checked correctness proofs of its complete functionality. This paper presents a WCET analysis of seL4, a third-generation micro kernel. As a result, hard real-time systems are usually developed without memory protection, perhaps utilizing a lightweight real-time executive to provide OS abstractions. This is due to a combination of size, unstructured code and tight coupling with hardware. Operating systems offering virtual memory and protected address spaces have been an elusive target of static worst-case execution time (WCET) analysis. This illustrates how it is possible to take advantage of the model for analyzing the preemption model of Linux. As an example of the usage of the model, the analysis of the events involved in the activation of the highest priority thread is presented, describing the delays occurred in this operation in the same granularity used by kernel developers.
Indeed, we describe in details three problems in the kernel revealed by using the proposed technique, along with a short summary on how we reported and proposed fixes to the Linux kernel community. This enables cross-checking of a kernel behavior against the formalized one, and in case of inconsistency, it pinpoints possible areas of improvement of the kernel, useful for regression testing. This article also presents an extension of the Linux tracing framework that enables the tracing of kernel events to verify the consistency of the kernel execution compared to the event sequences that are legal according to the formal model. This article proposes an automata-based model for describing and validating sequences of kernel events in Linux PREEMPT RT and how they influence the timeline of threads’ execution, comprising preemption control, interrupt handling and control, scheduling and locking.
0 kommentar(er)
