5 Search Results for "Ahmed, Shareef"

Document
DOI: 10.4230/LITES.11.1.1
A Survey of Real-Time Support, Analysis, and Advancements in ROS 2

Authors: Daniel Casini, Jian-Jia Chen, Jing Li, Federico Reghenzani, and Harun Teper

Published in: LITES, Volume 11, Issue 1 (2026). Leibniz Transactions on Embedded Systems, Volume 11, Issue 1

Abstract
The Robot Operating System 2 (ROS 2) has emerged as a relevant middleware framework for robotic applications, offering modularity, distributed execution, and communication. In the last six years, ROS 2 has drawn increasing attention from the real-time systems community and industry. This survey presents a comprehensive overview of research efforts that analyze, enhance, and extend ROS 2 to support real-time execution. We first provide a detailed description of the internal scheduling mechanisms of ROS 2 and its layered architecture, including the interaction with DDS-based communication and other communication middleware. We then review key contributions from the literature, covering timing analysis for both single- and multi-threaded executors, metrics such as response time, reaction time, and data age, and different communication modes. The survey also discusses community-driven enhancements to the ROS 2 runtime, including new executor algorithm designs, real-time GPU management, and microcontroller support via micro-ROS. Furthermore, we summarize techniques for bounding DDS communication delays, message filters, and profiling tools that have been developed to support analysis and experimentation. To help systematize this growing body of work, we introduce taxonomies that classify the surveyed contributions based on different criteria. This survey aims to guide both researchers and practitioners in understanding and improving the real-time capabilities of ROS 2.
Cite as

Daniel Casini, Jian-Jia Chen, Jing Li, Federico Reghenzani, and Harun Teper. A Survey of Real-Time Support, Analysis, and Advancements in ROS 2. In LITES, Volume 11, Issue 1 (2026). Leibniz Transactions on Embedded Systems, Volume 11, Issue 1, pp. 1:1-1:37, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

Copy BibTex To Clipboard

@Article{casini_et_al:LITES.11.1.1,
  author =	{Casini, Daniel and Chen, Jian-Jia and Li, Jing and Reghenzani, Federico and Teper, Harun},
  title =	{{A Survey of Real-Time Support, Analysis, and Advancements in ROS 2}},
  journal =	{Leibniz Transactions on Embedded Systems},
  pages =	{1:1--1:37},
  ISSN =	{2199-2002},
  year =	{2026},
  volume =	{11},
  number =	{1},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LITES.11.1.1},
  URN =		{urn:nbn:de:0030-drops-257914},
  doi =		{10.4230/LITES.11.1.1},
  annote =	{Keywords: ROS 2, middleware, real-time, timing predictability, publish-subscribe}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2024.11
Open Problem Resolved: The "Two" in Existing Multiprocessor PI-Blocking Bounds Is Fundamental

Authors: Shareef Ahmed and James H. Anderson

Published in: LIPIcs, Volume 298, 36th Euromicro Conference on Real-Time Systems (ECRTS 2024)

Abstract
The goal of a real-time locking protocol is to reduce any priority-inversion blocking (pi-blocking) a task may incur while waiting to access a shared resource. For mutual-exclusion sharing on an m-processor platform, the best existing lower bound on per-task pi-blocking under suspension-oblivious analysis is a (trivial) lower bound of (m-1) request lengths under any job-level fixed-priority (JLFP) scheduler. Surprisingly, most asymptotically optimal locking protocols achieve a per-task pi-blocking upper bound of (2m-1) request lengths under JLFP scheduling, even though a range of very different mechanisms are used in these protocols. This paper closes the gap between these existing lower and upper bounds by establishing a lower bound of (2m-2) request lengths under global fixed-priority (G-FP) and global earliest-deadline-first (G-EDF) scheduling. This paper also shows that worst-case per-task pi-blocking can be arbitrarily close to (2m-1) request lengths for locking protocols that satisfy a certain property that is met by most (if not all) existing locking protocols. These results imply that most known asymptotically optimal locking protocols are almost truly optimal (not just asymptotic) under G-FP and G-EDF scheduling.
Cite as

Shareef Ahmed and James H. Anderson. Open Problem Resolved: The "Two" in Existing Multiprocessor PI-Blocking Bounds Is Fundamental. In 36th Euromicro Conference on Real-Time Systems (ECRTS 2024). Leibniz International Proceedings in Informatics (LIPIcs), Volume 298, pp. 11:1-11:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2024)

Copy BibTex To Clipboard

@InProceedings{ahmed_et_al:LIPIcs.ECRTS.2024.11,
  author =	{Ahmed, Shareef and Anderson, James H.},
  title =	{{Open Problem Resolved: The "Two" in Existing Multiprocessor PI-Blocking Bounds Is Fundamental}},
  booktitle =	{36th Euromicro Conference on Real-Time Systems (ECRTS 2024)},
  pages =	{11:1--11:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-324-9},
  ISSN =	{1868-8969},
  year =	{2024},
  volume =	{298},
  editor =	{Pellizzoni, Rodolfo},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2024.11},
  URN =		{urn:nbn:de:0030-drops-203145},
  doi =		{10.4230/LIPIcs.ECRTS.2024.11},
  annote =	{Keywords: Real-Time Systems, Real-Time Synchronization, Multiprocessors}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2023.16
Optimal Multiprocessor Locking Protocols Under FIFO Scheduling

Authors: Shareef Ahmed and James H. Anderson

Published in: LIPIcs, Volume 262, 35th Euromicro Conference on Real-Time Systems (ECRTS 2023)

Abstract
Real-time locking protocols are typically designed to reduce any priority-inversion blocking (pi-blocking) a task may incur while waiting to access a shared resource. For the multiprocessor case, a number of such protocols have been developed that ensure asymptotically optimal pi-blocking bounds under job-level fixed-priority scheduling. Unfortunately, no optimal multiprocessor real-time locking protocols are known that ensure tight pi-blocking bounds under any scheduler. This paper presents the first such protocols. Specifically, protocols are presented for mutual exclusion, reader-writer synchronization, and k-exclusion that are optimal under first-in-first-out (FIFO) scheduling when schedulability analysis treats suspension times as computation. Experiments are presented that demonstrate the effectiveness of these protocols.
Cite as

Shareef Ahmed and James H. Anderson. Optimal Multiprocessor Locking Protocols Under FIFO Scheduling. In 35th Euromicro Conference on Real-Time Systems (ECRTS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 262, pp. 16:1-16:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

Copy BibTex To Clipboard

@InProceedings{ahmed_et_al:LIPIcs.ECRTS.2023.16,
  author =	{Ahmed, Shareef and Anderson, James H.},
  title =	{{Optimal Multiprocessor Locking Protocols Under FIFO Scheduling}},
  booktitle =	{35th Euromicro Conference on Real-Time Systems (ECRTS 2023)},
  pages =	{16:1--16:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-280-8},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{262},
  editor =	{Papadopoulos, Alessandro V.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2023.16},
  URN =		{urn:nbn:de:0030-drops-180451},
  doi =		{10.4230/LIPIcs.ECRTS.2023.16},
  annote =	{Keywords: Real-Time Systems, Real-Time Synchronization, Multiprocessors}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2022.10
Overrun-Resilient Multiprocessor Real-Time Locking

Authors: Zelin Tong, Shareef Ahmed, and James H. Anderson

Published in: LIPIcs, Volume 231, 34th Euromicro Conference on Real-Time Systems (ECRTS 2022)

Abstract
Existing real-time locking protocols require accurate worst-case execution time (WCET) estimates for both tasks and critical sections (CSs) in order to function correctly. On multicore platforms, however, the only seemingly viable strategy for obtaining such estimates is via measurements, which cannot produce a true WCET with certainty. The absence of correct WCETs can be partially ameliorated by enforcing execution budgets at both the task and CS levels and by using a locking protocol that is resilient to budget overruns, i.e., that ensures that the schedulability of non-overrunning tasks is not compromised by tasks that do overrun their budgets. Unfortunately, no fully overrun-resilient locking protocol has been proposed to date for multiprocessor systems. To remedy this situation, this paper presents two such protocols, the OR-FMLP and the OR-OMLP , which introduce overrun-resiliency mechanisms to two existing multiprocessor protocols, the spin-based FMLP and suspension-based global OMLP, respectively. In devising such mechanisms, undo code can be problematic. For the important locking use case of protecting shared data structures, it is shown that such code can be avoided entirely by using abortable critical sections, a concept proposed herein that leverages obstruction-free synchronization techniques. Experiments are presented that demonstrate both the effectiveness of the mechanisms introduced in this paper and their cost.
Cite as

Zelin Tong, Shareef Ahmed, and James H. Anderson. Overrun-Resilient Multiprocessor Real-Time Locking. In 34th Euromicro Conference on Real-Time Systems (ECRTS 2022). Leibniz International Proceedings in Informatics (LIPIcs), Volume 231, pp. 10:1-10:25, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2022)

Copy BibTex To Clipboard

@InProceedings{tong_et_al:LIPIcs.ECRTS.2022.10,
  author =	{Tong, Zelin and Ahmed, Shareef and Anderson, James H.},
  title =	{{Overrun-Resilient Multiprocessor Real-Time Locking}},
  booktitle =	{34th Euromicro Conference on Real-Time Systems (ECRTS 2022)},
  pages =	{10:1--10:25},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-239-6},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{231},
  editor =	{Maggio, Martina},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2022.10},
  URN =		{urn:nbn:de:0030-drops-163272},
  doi =		{10.4230/LIPIcs.ECRTS.2022.10},
  annote =	{Keywords: Real-Time Systems, Real-Time Synchronization, Budget Enforcement}
}
Document
DOI: 10.4230/LIPIcs.ECRTS.2021.11
Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers

Authors: Shareef Ahmed and James H. Anderson

Published in: LIPIcs, Volume 196, 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)

Abstract
The global earliest-deadline-first (GEDF) scheduler and its variants are soft-real-time (SRT) optimal for periodic/sporadic tasks, meaning they provide bounded tardiness so long as the underlying platform is not over-utilized. Although their SRT-optimality has long been known, tight tardiness bounds for these schedulers have remained elusive. In this paper, a tardiness bound, that does not depend on the processor or task count, is derived for pseudo-harmonic periodic tasks, which are commonly used in practice, under global-EDF-like (GEL) schedulers. This class of schedulers includes both GEDF and first-in-first-out (FIFO). This bound is shown to be generally tight via an example. Furthermore, it is shown that exact tardiness bounds for GEL-scheduled pseudo-harmonic periodic tasks can be computed in pseudo-polynomial time.
Cite as

Shareef Ahmed and James H. Anderson. Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers. In 33rd Euromicro Conference on Real-Time Systems (ECRTS 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 196, pp. 11:1-11:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

Copy BibTex To Clipboard

@InProceedings{ahmed_et_al:LIPIcs.ECRTS.2021.11,
  author =	{Ahmed, Shareef and Anderson, James H.},
  title =	{{Tight Tardiness Bounds for Pseudo-Harmonic Tasks Under Global-EDF-Like Schedulers}},
  booktitle =	{33rd Euromicro Conference on Real-Time Systems (ECRTS 2021)},
  pages =	{11:1--11:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-192-4},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{196},
  editor =	{Brandenburg, Bj\"{o}rn B.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ECRTS.2021.11},
  URN =		{urn:nbn:de:0030-drops-139428},
  doi =		{10.4230/LIPIcs.ECRTS.2021.11},
  annote =	{Keywords: soft real-time systems, multicore, tardiness bounds}
}
  • Refine by Type
  • 5 Document/PDF

  • Refine by Publication Year
  • 1 2026
  • 1 2024
  • 1 2023
  • 1 2022
  • 1 2021

  • Refine by Author
  • 4 Ahmed, Shareef
  • 4 Anderson, James H.
  • 1 Casini, Daniel
  • 1 Chen, Jian-Jia
  • 1 Li, Jing
  • Show More...

  • Refine by Series/Journal
  • 4 LIPIcs
  • 1 LITES

  • Refine by Classification
  • 4 Computer systems organization → Real-time systems
  • 1 Computer systems organization → Real-time operating systems
  • 1 Computer systems organization → Robotics
  • 1 Software and its engineering → Real-time schedulability
  • 1 Software and its engineering → Real-time systems software

  • Refine by Keyword
  • 3 Real-Time Synchronization
  • 3 Real-Time Systems
  • 2 Multiprocessors
  • 1 Budget Enforcement
  • 1 ROS 2
  • Show More...

Any Issues?
X

Feedback on the Current Page

CAPTCHA

Thanks for your feedback!

Feedback submitted to Dagstuhl Publishing

Could not send message

Please try again later or send an E-mail
© 2023-2026 Schloss Dagstuhl – LZI GmbH Schloss Dagstuhl – LZI GmbH About DROPS Imprint Privacy Contact