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Open Source / Free Software

In the following, you can find open source and free software authored by our research staff. The related publications are also provided in PDF format. If you use our contributions in your work, please refer to the corresponding publication. Note that the copyrights of the paper publications are associated with organizations like IEEE, ACM, etc. Please contact Kuan-Hsun Chen or the relevant authors if you have any further questions.

Contact Please contact Kuan-Hsun Chen or the relevant authors if you have any further questions.

 

Overrun Handling in RTEMS

Real-time operating systems are not only used in embedded real-time systems but also useful for the simulation and validation of those systems. During the evaluation of our paper about Systems with Dynamic Real-Time Guarantees that appears in RTSS 2016 we discovered certain unexpected system behavior in the open-source real-time operating system RTEMS. In the current implementation of RTEMS (version 4.11), overruns of an implicit-deadline task, i.e., deadline misses, result in unexpected system behavior as they may lead to a shift of the release pattern of the task. This also has the consequence that some task instances are not released as they should be. In the paper we explain the reason why such problems occur in RTEMS and our solutions. The proposed solution now is adopted into the current implementation of RTEMS (version 4.12).

Citation:
Kuan-Hsun Chen, Georg von der Brüggen and Jian-Jia Chen, Overrun Handling for Mixed-Criticality Support in RTEMS, In 4th International Workshop on Mixed-Criticality Systems (WMC), Porto, Portugal, November 2016.

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Efficient Probabilistic Schedulability Test

Due to rising integrations, low voltage operations, and environmental influences such as electromagnetic interference and radiation, transient faults may cause soft errors and corrupt the execution state. Such soft errors can be recovered by applying fault-tolerant techniques. Therefore, the execution time of a job of a sporadic/periodic task may differ, depending upon the occurrence of soft errors and the applied error detection and recovery mechanisms. We model a periodic/sporadic real-time task under such a scenario by using two different worst-case execution times (WCETs), in which one is with the occurrence of soft errors and another is not. Based on a probabilistic soft-error model, the WCETs are hence with different probabilities. In this paper, we present efficient probabilistic schedulability tests that can be applied to verify the schedulability based on probabilistic arguments under fixed-priority scheduling on a uniprocessor system. We demonstrate how the Chernoff bounds can be used to calculate the task workloads based on their probabilistic WCETs. In addition, we further consider how to calculate the probability of -consecutive deadline misses of a task.

Citation:
Kuan-Hsun Chen and Jian-Jia Chen, Probabilistic Schedulability Tests for Uniprocessor Fixed-Priority Scheduling under Soft Errors, In 12th IEEE International Symposium on Industrial Embedded Systems, Toulouse, France, June 2017.

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Implementation and Evaluation of Multiprocessor Resource Synchronization Protocol (MrsP) on LITMUSRT

Preventing race conditions or data corruptions for concurrent shared resource accesses of real-time tasks is a challenging problem. By adopting the resource synchronization protocols, such a problem has been studied in the literature, but there are not enough evaluations that consider the overhead from the implementations of different protocols. In this paper, we discuss our implementation of the Multiprocessor Resource Sharing Protocol (MrsP) and the Distributed Non-Preemptive Protocol (DNPP) on LITMUS RT . Both of them are released in open source under GNU General Public License (GPL2). To study the impact of the implementation overhead, we deploy different synchronization scenarios with generated task sets and measure the performance with respect to the worst-case response time. The results illustrate that generally the implementation overhead is acceptable, whereas some unexpected system overhead may happen under distributed synchronization protocols on LITMUSRT.

Citation:
Junjie Shi, Kuan-Hsun Chen, Shuai Zhao, Wen-Hung Huang, Jian-Jia Chen, and Andy Wellings, Implementation and Evaluation of Multiprocessor Resource Synchronization Protocol (MrsP) on LITMUSRT, 13th Workshop on Operating Systems Platforms for Embedded Real-Time Applications, Dubrovnik, Kroatia, June 2017.

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