@inproceedings { OSPERT17,
  author = {Shi, Junjie and Chen, Kuan-Hsun and Zhao, Shuai and Huang, Wen-Hung and Chen, Jian-Jia and Wellings, Andy},
  title = {Implementation and Evaluation of Multiprocessor Resource Synchronization Protocol (MrsP) on LITMUSRT},
  booktitle = {13th Workshop on Operating Systems Platforms for Embedded Real-Time Applications},
  year = {2017},
  keywords = {kuan, junjie},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017-junjie-ospert.pdf},
  confidential = {n},
  abstract = {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.},
}

@inproceedings { DBLP:conf/ecrts/ChenBHD17,
  author = {Chen, Jian-Jia and Br\"uggen, Georg von der and Huang, Wen-Hung and Davis, Robert I.},
  title = {On the Pitfalls of Resource Augmentation Factors and Utilization Bounds in Real-Time Scheduling},
  booktitle = {29th Euromicro Conference on Real-Time Systems, ECRTS},
  year = {2017},
  pages = {9:1--9:25},
  address = {Dubrovnik, Croatia},
  month = {June 27-30},
  url = {https://doi.org/10.4230/LIPIcs.ECRTS.2017.9},
  keywords = {Georg},
  file = {http://drops.dagstuhl.de/opus/volltexte/2017/7161/pdf/LIPIcs-ECRTS-2017-9.pdf},
  confidential = {n},
  abstract = {In this paper, we take a careful look at speedup factors, utilization bounds, and capacity augmentation bounds. These three metrics have been widely adopted in real-time scheduling research as the de facto standard theoretical tools for assessing scheduling algorithms and schedulability tests. Despite that, it is not always clear how researchers and designers should interpret or use these metrics. In studying this area, we found a number of surprising results, and related to them, ways in which the metrics may be misinterpreted or misunderstood. In this paper, we provide a perspective on the use of these metrics, guiding researchers on their meaning and interpretation, and helping to avoid pitfalls in their use. Finally, we propose and demonstrate the use of parametric augmentation functions as a means of providing nuanced information that may be more relevant in practical settings.},
}

@inproceedings { DBLP:conf/rtcsa/ChenBH017,
  author = {Chen, Jian-Jia and Br\"uggen, Georg von der and Huang, Wen-Hung and Liu, Cong},
  title = {State of the art for scheduling and analyzing self-suspending sporadic real-time tasks},
  booktitle = {23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications RTCSA},
  year = {2017},
  pages = {1--10},
  address = {Hsinchu, Taiwan},
  month = {August 16-18},
  note = {Invited paper},
  url = {http://doi.ieeecomputersociety.org/10.1109/RTCSA.2017.8046321},
  keywords = {Georg},
  file = {media/documents/publications/downloads/2017-chen-rtcsa.suspension-review.pdf},
  confidential = {n},
  abstract = {In computing systems, a job/process/task/thread may suspend itself when it has to wait for some other internal or external activities, such as computation offloading or memory accesses, to finish before it can continue its execution. In the literature, there are two commonly adopted self-suspending sporadic task models in real-time systems: 1) the dynamic self-suspension model and 2) the segmented self-suspension sporadic task model. A dynamic self-suspending sporadic task is specified with an upper bound on the maximum suspension time for a job (task instance), which allows a job to dynamically suspend itself arbitrary often as long as the suspension time upper bound is not violated. By contrast, a segmented self-suspending sporadic task has a predefined execution and suspension pattern in an interleaving manner. The dynamic self-suspension model is very flexible but inaccurate, whilst the segmented self-suspension model is very restrictive but very accurate. The gap between these two widely-adopted self-suspension task models can be potentially filled by the hybrid self-suspension task model. 

The investigation of the impact of self-suspension on timing predictability has been started in 1988. This survey paper
provides a short summary of the state of the art in the design and analysis of scheduling algorithms and schedulability tests for self-suspending tasks in real-time systems.},
}

@inproceedings { DBLP:conf/rtcsa/ChenHD017,
  author = {Chen, Jian-Jia and Huang, Wen-Hung and Dong, Zheng and Liu, Cong},
  title = {Fixed-priority scheduling of mixed soft and hare real-time tasks on multiprocessors},
  booktitle = {23rd {IEEE} International Conference on Embedded and Real-Time Computing Systems and Applications, {RTCSA} },
  year = {2017},
  pages = {1--10},
  address = {Hsinchu, Taiwan},
  month = {August 16-18},
  url = {http://doi.ieeecomputersociety.org/10.1109/RTCSA.2017.8046312},
  file = {media/documents/publications/downloads/2017-chen-RTCSA-SRT.pdf},
  confidential = {n},
}

@inproceedings { DBLP:conf/rtcsa/BruggenHC17,
  author = {Br\"uggen, Georg von der and Huang, Wen-Hung and Chen, Jian-Jia},
  title = {Hybrid self-suspension models in real-time embedded systems},
  booktitle = {23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA},
  year = {2017},
  pages = {1--9},
  address = {Hsinchu, Taiwan},
  month = {August 16-18},
  url = {http://doi.ieeecomputersociety.org/10.1109/RTCSA.2017.8046328},
  keywords = {Georg, kevin},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017-rtcsa-georg.pdf},
  confidential = {n},
  abstract = {To tackle the unavoidable self-suspension behavior due to I/O-intensive interactions, multi-core processors, computation offloading systems with coprocessors, etc., the dynamic and the segmented self-suspension sporadic task models have been widely used in the literature. We propose new self-suspension models that are hybrids of the dynamic and the segmented models. Those hybrid models are capable of exploiting knowledge about execution paths, potentially reducing modelling pessimism. In addition, we provide the corresponding schedulability analysis under fixed-relative-deadline (FRD) scheduling and explain how the state-of-the-art FRD scheduling strategy can be applied. Empirically, these hybrid approaches are shown to be effective with regards to the number of schedulable task sets.},
}

@inproceedings { DBLP:conf/rtns/Bruggen17rop,
  author = {Br\"uggen, Georg von der and Chen, Jian-Jia and Huang, Wen-Hung and Yang, Maolin},
  title = {Release Enforcement in Resource-Oriented Partitioned Scheduling for Multiprocessor Systems},
  booktitle = {25th International Conference on Real-Time Networks and Systems (RTNS)},
  year = {2017},
  address = {Grenoble, France},
  month = {October 04 - 06},
  url = {https://dl.acm.org/citation.cfm?id=3139287},
  keywords = {Georg, kevin},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017_rtns_brueggen_rop.pdf},
  confidential = {n},
  abstract = {When partitioned scheduling is used in real-time multiprocessor systems, access to shared resources can jeopardize the
schedulability if the task partition is not done carefully. To tackle this problem we change our view angle from focusing
on the computing tasks to focusing on the shared resources by applying resource-oriented partitioned scheduling. We use a release enforcement technique to shape the interference from the higher-priority jobs to be sporadic, analyze the
schedulability, and provide strategies for partitioning both the critical and the non-critical sections of tasks onto processors individually. Our approaches are shown to be effective, both in the evaluations and from a theoretical point of view by providing a speedup factor of 6, improving previously known results. },
}

@inproceedings { DBLP:conf/rtns/Bruggen17automotive,
  author = {Br\"uggen, Georg von der and Ueter, Niklas and Chen, Jian-Jia and Freier, Matthias},
  title = {Parametric Utilization Bounds for Implicit-Deadline Periodic Tasks in Automotive Systems},
  booktitle = {25th International Conference on Real-Time Networks and Systems (RTNS)},
  year = {2017},
  address = {Grenoble, France},
  url = {https://dl.acm.org/citation.cfm?id=3139273},
  keywords = {georg},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017_brueggen_rtns_automotive.pdf},
  confidential = {n},
  abstract = {Fixed-priority scheduling has been widely used in safety-critical applications. This paper explores the parametric utilization bounds for implicit-deadline periodic tasks in automotive uniprocessor systems, where the period of a task is either 1, 2, 5, 10, 20, 50, 100, 200, or 1000 milliseconds. We prove a parametric utilization bound of 90%+z for such automotive task systems under rate-monotonic preemptive scheduling (RM-P), where z is a parameter defined by the input task set with 0 ≤ z ≤ 10%. Moreover, we explain how to perform an exact schedulability test for an automotive task set under RM-P by validating only three conditions. Furthermore, we extend our analyses to rate-monotonic non-preemptive scheduling (RM-NP). We show that very reasonable utilization values can still be achieved under RM-NP if the execution time of all tasks is below 1 millisecond. The analyses presented here are compatible with angle- synchronous tasks by applying the related arrival curves. It is shown in the evaluations that scheduling those angle-synchronous tasks according to their minimum inter-arrival time instead of assigning them to the highest priority can drastically increase the acceptance ratio in some settings.},
}

@inproceedings { SIES2017,
  author = {Chen, Kuan-Hsun and Chen, Jian-Jia},
  title = {Probabilistic Schedulability Tests for Uniprocessor Fixed-Priority Scheduling under Soft Errors},
  booktitle = {IEEE International Symposium on Industrial Embedded Systems (SIES)},
  year = {2017},
  pages = {1--8},
  keywords = {kuan},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017-kuan-epst.pdf},
  confidential = {n},
  abstract = {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. The pessimism and the efficiency of our approaches are evaluated against the tighter and approximated convolution-based approaches, by running extensive evaluations under different soft-error rates. The evaluation results show that our approaches are effective to derive the probability of deadline misses and efficient with respect to the needed calculation time.},
}

@article { IPL2017-speedup,
  author = {Br\"uggen, Georg von der and Chen, Jian-Jia and Davis, Robert I. and Huang, Wen-Hung Kevin},
  title = {Exact Speedup Factors for Linear-Time Schedulability Tests for Fixed-Priority Preemptive and Non-preemptive Scheduling},
  journal = {Information Processing Letters (IPL)},
  year = {2017},
  volume = {117},
  pages = {1-5},
  month = {Jan},
  url = {http://dx.doi.org/10.1016/j.ipl.2016.08.001},
  keywords = {kevin, Georg},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017-ipl-georg.pdf},
  confidential = {n},
  abstract = {In this paper, we investigate the quality of several linear-time schedulability tests for preemptive and non-preemptive fixed-priority scheduling of uniprocessor systems. The metric used to assess the quality of these tests is the resource augmentation bound commonly known as the processor speedup factor. The speedup factor of a schedulability test corresponds to the smallest factor by which the processing speed of a uniprocessor needs to be increased such that any task set that is feasible under an optimal preemptive (non-preemptive) work-conserving scheduling algorithm is guaranteed to be schedulable with preemptive (non-preemptive) fixed priority scheduling if this scheduling test is used, assuming an appropriate priority assignment. We show the surprising result that the exact speedup factors for Deadline Monotonic (DM) priority assignment combined with sufficient linear-time schedulability tests for implicit-, constrained-, and arbitrary-deadline task sets are the same as those obtained for optimal priority assignment policies combined with exact schedulability tests. Thus in terms of the speedup-factors required, there is no penalty in using DM priority assignment and simple linear schedulability tests.
},
}

@article { DBLP:journals/rts/YangCH17,
  author = {Yang, Maolin and Chen, Jian-Jia and Huang, Wen-Hung},
  title = {A misconception in blocking time analyses under multiprocessor synchronization protocols},
  journal = {Real-Time Systems},
  year = {2017},
  volume = {53},
  number = {2},
  pages = {187--195},
  url = {https://doi.org/10.1007/s11241-016-9261-4},
  confidential = {n},
}

@article { DBLP:journals/tpds/PaganiPSCH17,
  author = {Pagani, Santiago and Pathania, Anuj and Shafique, Muhammad and Chen, Jian-Jia and Henkel, J{\"{o}}rg},
  title = {Energy Efficiency for Clustered Heterogeneous Multicores},
  journal = {{IEEE} Trans. Parallel Distrib. Syst.},
  year = {2017},
  volume = {28},
  number = {5},
  pages = {1315--1330},
  url = {https://doi.org/10.1109/TPDS.2016.2623616},
  confidential = {n},
}

@article { DBLP:journals/tc/PaganiKCSLH17,
  author = {Pagani, Santiago and Khdr, Heba and Chen, Jian-Jia and Shafique, Muhammad and Li, Minming and Henkel, J{\"{o}}rg},
  title = {Thermal Safe Power {(TSP):} Efficient Power Budgeting for Heterogeneous Manycore Systems in Dark Silicon},
  journal = {{IEEE} Trans. Computers},
  year = {2017},
  bdsk-url-1 = {http://doi.ieeecomputersociety.org/10.1109/TC.2016.2564969},
  bdsk-url-2 = {http://dx.doi.org/10.1109/TC.2016.2564969},
  volume = {66},
  number = {1},
  pages = {147--162},
  url = {http://doi.ieeecomputersociety.org/10.1109/TC.2016.2564969},
  confidential = {n},
}

@article { DavisTGDPC17-RTS,
  author = {Davis, Robert I. and Thekkilakattil, Abhilash and Gettings, Oliver and Dobrin, Radu and Punnekkat, Sasikumar and Chen, Jian-Jia},
  title = {Exact speedup factors and sub-optimality fornon-preemptive scheduling},
  journal = {Real-Time Systems},
  year = {2017},
  volume = {??},
  number = {??},
  pages = {??-??},
  month = {??},
  note = {preprint },
  url = {http://link.springer.com/article/10.1007/s11241-017-9294-3},
  file = {http://link.springer.com/article/10.1007/s11241-017-9294-3},
  confidential = {n},
  abstract = {Fixed priority scheduling is used in many real-time systems; however,both preemptive and non-preemptive variants (FP-P and FP-NP) are known to besub-optimal when compared to an optimal uniprocessor scheduling algorithm suchas preemptive earliest deadline first (EDF-P). In this paper, we investigate the sub-optimality of fixed priority non-preemptive scheduling. Specifically, we derive theexact processor speed-up factor required to guarantee the feasibility under FP-NP (i.e. schedulability assuming an optimal priority assignment) of any task set that is feasi-ble under EDF-P. As a consequence of this work, we also derive a lower bound onthe sub-optimality of non-preemptive EDF (EDF-NP). As this lower bound matches arecently published upper bound for the same quantity, it closes the exact sub-optimalityfor EDF-NP. It is known that neither preemptive, nor non-preemptive fixed priorityscheduling dominates the other, in other words, there are task sets that are feasibleon a processor of unit speed under FP-P that are not feasible under FP-NP and vice-versa. Hence comparing these two algorithms, there are non-trivial speedup factors inboth directions. We derive the exact speed-up factor required to guarantee the FP-NPfeasibility of any FP-P feasible task set. Further, we derive the exact speed-up factorrequired to guarantee FP-P feasibility of any constrained-deadline FP-NP feasible task set.},
}

@techreport { ChenReport854-2016,
  author = {Chen, Jian-Jia and Nelissen, Geoffrey and Huang, Wen-Hung and Yang, Maolin and Brandenburg, Bj\"orn and Bletsas, Konstantinos and Liu, Cong and Richard, Pascal and Ridouard, Fr\'ed\'eric and Audsley, Neil and Rajkumar, Raj and Niz, Dionisio and Br\"uggen, Georg von der},
  title = {Many Suspensions, Many Problems: A Review of Self-Suspending Tasks in Real-Time Systems},
  institution = {Department of Computer Science, TU Dortmund},
  year = {2017},
  number = {854},
  month = {March},
  note = { (Status: Preprint, 2nd Version)   The  first version  was published in May 2016.},
  keywords = {kevin, Georg},
  file = {http://ls12-www.cs.tu-dortmund.de/daes/media/documents/publications/downloads/2017-chen-techreport-854-v2.pdf},
  confidential = {n},
  abstract = {In general computing systems, a job (process/task) may suspend itself whilst it is waiting for some activity to complete, e.g., an accelerator to return data. % or results from offloaded computation. In real-time systems, such self-suspension can cause substantial performance/schedulability degradation. This observation, first made in 1988, has led to the investigation of the impact of self-suspension on timing predictability, and many relevant results have been published since. Unfortunately, as it has recently come to light, a number of the existing results are flawed.

To provide a correct platform on which future research can be built, this paper reviews the state of the art in the design and analysis of scheduling algorithms and schedulability tests for self-suspending tasks in real-time systems.  We provide (1)~a systematic description of how self-suspending tasks can be handled in both soft and hard real-time systems; (2)~an explanation of the existing misconceptions  and their potential remedies; (3)~an assessment of the influence of  such flawed analyses on partitioned multiprocessor fixed-priority scheduling when tasks synchronize access to shared resources; and (4)~a discussion of the computational complexity of analyses for different self-suspension task models.
},
}