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Suspension-Aware Design and Analysis

In computing systems, a job may suspend itself, due to the interactions with external I/O devices or accelerators, multicore systems with shared resources, suspension-aware multiprocessor synchronization protocols, etc. For real-time embedded systems, self-suspension behavior negatively impact the schedulability of real-time tasks and typically cause substantial performance/schedulability degradation.

Fig: Two tasks τ1 (higher priority, period 5, relative deadline 5, computation time 3) and τ2 (lower priority, period 7, relative deadline 7, computation time 2) meet their deadlines in (a). Conventional schedulability analysis predicts maximum response times of 3 and 5 respectively. In (b), task τ1 suspends itself, with the result that task τ2 misses its deadline at time 14.  (Source: Many suspensions many problems by Chen et al. in RTSJ 2019)

Even though some seemingly positive results have been reported for tackling self-suspending task systems in the past, the recent investigation by Prof. Dr. Jian-Jia Chen and his colleagues indicates that a significant portion of the literature (and also the majority of these results) before 2013 has been seriously flawed. Since most results before 2013 were in fact flawed (or with incomplete proofs), the investigation of self-suspending task models in real-time embedded systems has been restarted since 2015.

This project intends to investigate robust and solid fundamental algorithms and analyses to carefully mitigate (via safe and sound execution/suspension enforcements) and analyze (via tight schedulability tests) the impact of self-suspending behavior in modern real-time embedded systems. The targeting systems are safety-critical systems with real-time requirements. Since the self-suspending behavior can introduce a high degree of complexity, new scheduling strategies or revisions of existing scheduling strategies are required. This project intends to provide fundamental breakthrough in the scheduling theory and the corresponding schedulability analysis to flexibly accommodate the self-suspension behavior without introducing much pessimism when considering the worst-case timing behavior.

With the scheduling strategies and schedulability tests provided in this project, we aim to offer tools for real-time system designers so that further optimizations by considering the perspectives of controllers, communications, and computation are possible.

(Source: DFG)

Project Information

Duration: Nov. 2019 - Oct. 2022 (3 years)
  • Jian-Jia Chen, Geoffrey Nelissen, Wen-Hung Huang, Maolin Yang, Björn B. Brandenburg, Konstantinos Bletsas, Cong Liu, Pascal Richard, Frédéric Ridouard, Neil C. Audsley, Raj Rajkumar, Dionisio de Niz, Georg von der Brüggen: Many suspensions, many problems: a review of self-suspending tasks in real-time systems. Real-Time Systems 55(1): 144-207 (2019). Open Access Download
  • Jian-Jia Chen, Georg von der Brüggen, Wen-Hung Huang, Cong Liu:State of the art for scheduling and analyzing self-suspending sporadic real-time tasks. RTCSA 2017: 1-10. IEEE Xplore Link
Hired: M.Sc. Mario Günzel




  • Correspodning paper can be found in "Work-in-Progress: Evaluation Framework for Self-Suspending Schedulability Tests" by Mario Günzel, Harun Teper, Kuan-Hsun Chen, Georg von der Brüggen, and Jian-Jia Chen, IEEE Real-Time Sys­tems Symposium (RTSS),  pp 532-535, 2021


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Location & approach

The campus of TU Dort­mund University is located close to interstate junction Dort­mund West, where the Sauerlandlinie A 45 (Frankfurt-Dort­mund) crosses the Ruhrschnellweg B 1 / A 40. The best interstate exit to take from A 45 is "Dort­mund-Eichlinghofen" (closer to Campus Süd), and from B 1 / A 40 "Dort­mund-Dorstfeld" (closer to Campus Nord). Signs for the uni­ver­si­ty are located at both exits. Also, there is a new exit before you pass over the B 1-bridge leading into Dort­mund.

To get from Campus Nord to Campus Süd by car, there is the connection via Vogelpothsweg/Baroper Straße. We recommend you leave your car on one of the parking lots at Campus Nord and use the H-Bahn (suspended monorail system), which conveniently connects the two campuses.

TU Dort­mund University has its own train station ("Dort­mund Uni­ver­si­tät"). From there, suburban trains (S-Bahn) leave for Dort­mund main station ("Dort­mund Hauptbahnhof") and Düsseldorf main station via the "Düsseldorf Airport Train Station" (take S-Bahn number 1, which leaves every 20 or 30 minutes). The uni­ver­si­ty is easily reached from Bochum, Essen, Mülheim an der Ruhr and Duisburg.

You can also take the bus or subway train from Dort­mund city to the uni­ver­si­ty: From Dort­mund main station, you can take any train bound for the Station "Stadtgarten", usually lines U41, U45, U 47 and U49. At "Stadtgarten" you switch trains and get on line U42 towards "Hombruch". Look out for the Station "An der Palmweide". From the bus stop just across the road, busses bound for TU Dort­mund University leave every ten minutes (445, 447 and 462). Another option is to take the subway routes U41, U45, U47 and U49 from Dort­mund main station to the stop "Dort­mund Kampstraße". From there, take U43 or U44 to the stop "Dort­mund Wittener Straße". Switch to bus line 447 and get off at "Dort­mund Uni­ver­si­tät S".

The AirportExpress is a fast and convenient means of transport from Dortmund Airport (DTM) to Dortmund Central Station, taking you there in little more than 20 minutes. From Dortmund Central Station, you can continue to the university campus by interurban railway (S-Bahn). A larger range of international flight connections is offered at Düsseldorf Airport (DUS), which is about 60 kilometres away and can be directly reached by S-Bahn from the university station.

The H-Bahn is one of the hallmarks of TU Dort­mund University. There are two stations on Campus Nord. One ("Dort­mund Uni­ver­si­tät S") is directly located at the suburban train stop, which connects the uni­ver­si­ty directly with the city of Dort­mund and the rest of the Ruhr Area. Also from this station, there are connections to the "Technologiepark" and (via Campus Süd) Eichlinghofen. The other station is located at the dining hall at Campus Nord and offers a direct connection to Campus Süd every five minutes.

The facilities of TU Dortmund University are spread over two campuses, the larger Campus North and the smaller Campus South. Additionally, some areas of the university are located in the adjacent "Technologiepark".

Site Map of TU Dort­mund University (Second Page in English).