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Standardized System Software for Automotive Applications
Published in Richard Zurawski, Networked Embedded Systems, 2017
Hereby, Figure 18.3a illustrates the task states for the extended task model (which exhibits an additional Waiting state), whereas Figure 18.3b depicts the tasks states for basic task model. Synchronization between extended tasks in OSEK OS is performed via “events.” In case extended tasks can wait for an event, they remain in a Waiting task state until the event is set by some other extended task. Mutual exclusion between extended tasks is performed by means of “resources.” To prevent deadlocks and priority inversion, OSEK OS implements the “priority ceiling protocol” [13] for resources. Communication between tasks in OSEK OS is performed by means of “messages.” A detailed description of the OSEK communication primitives is provided in the section on OSEK COM (Section 18.3.3). For cyclic operations, OSEK OS provides the OS entities “counters” and “alarms.” Counters are represented by a counter value. Hereby, OSEK OS takes care of periodically incrementing this counter value. In case the counter value reaches a defined threshold, an alarm, which is linked to the counter, can be triggered. This alarm can, for example, set an event or activate a suspended task. To account for different modes of operations of an automotive real-time system, OSEK OS provides different “application modes.” Each application mode owns its own subset of operating system entities (e.g., tasks, ISRs, etc.). During operation, a switch between these application modes is possible.
Vehicle Functional Domains and Their Requirements
Published in Nicolas Navet, Françoise Simonot-Lion, Automotive Embedded Systems Handbook, 2017
Françoise Simonot-Lion, Yvon Trinquet
OSEK/VDX OS provides services on objects like tasks (“basic tasks,” without blocking point, and “extended tasks,” that can include blocking points), events, resources, and alarms. It proposes a fixed priority (FP) scheduling policy that is applied to tasks that can be preemptive or non-preemptive, and combined with a reduced version of the priority ceiling protocol (PCP) [28,29] in order to avoid priority inversion or deadlock due to exclusive resource access. Intertask synchronization is achieved through private events and alarms. The implementation of an OSEK/VDX specification has to be compliant to one of the four conformance classes—BCC1, BCC2, ECCI, ECC2—that are specified according to the supported tasks (basic only or basic and extended), the number of tasks on each priority level (only one or possibly several), and the constraints of the reactivation counter (only one or possibly several). BCC1 defines a restricted implementation that aims to minimize the size of the corresponding memory footprint, the size of the data structures, and the complexity of the management algorithms. ECC2 specifies the implementation of all the services. The MODISTARC project (Methods and tools for the validation of OSEK/VDX based DISTributed ARChitectures) [30] provided the relevant test methods and tools to assess the compliance of OSEK/VDX implementations.
Introduction
Published in Joseph Y.-T. Leung, Handbook of SCHEDULING, 2004
Priority ceiling protocol is the basic priority inheritance protocol with an additional priority ceiling rule. Under the priority ceiling protocol, the priority ceiling of a semaphore S is defined as the maximum priority of all the jobs that may ever use this semaphore. That is, ceil(S)=maxiπi∣τimay lockS
Modeling, analysis and verification of real-time resource access control protocols: a formal approach
Published in International Journal of Computers and Applications, 2018
Rumpa Hazra, Shouvik Dey, Jayashree Singha
This paper is an extension of the research work proposed in [19]. The fundamental commitment of that work was to consider the occurrence of deadlock using priority inheritance protocol and focused on stack-based priority ceiling protocol, a better approach to overcome the deadlock occurrence. But the work did not provide any formal specification to verify the correctness of the design. In this work, we further enhance that concept and model both the above-mentioned protocols in a formal way using CFG notation with respect to UML 2.0 sequence diagram and further analyze it.
Stack-Based Dynamic Resource Access Control Protocol for Real-Time Systems
Published in IETE Journal of Research, 2022
Rumpa Hazra, Shouvik Dey, Ananya Kanjilal, Swapan Bhattacharya
Wang et al. [7] have carried out a research based on the layered scheduling algorithm which is a refinement of priority inheritance and PCPs. The Layered Priority Inheritance Protocol and the Layered Priority Ceiling Protocol are proposed in a layered scheduling environment where priority inversion and the occurrence of deadlock are prevented.