Feasibility of fork-join real-time task graph models: Hardness and algorithms

Jinghao Sun, Nan Guan, Yang Wang, Qingxu Deng, Peng Zeng, Wang Yi

Research output: Journal article publicationJournal articleAcademic researchpeer-review

12 Citations (Scopus)


In the formal analysis of real-time systems, modeling of branching codes and modeling of intratask parallelism structures are two of the most important research topics. These two real-time properties are combined, resulting in the fork-join real-time task (FJRT) model, which extends the digraph-based task model with forking and joining semantics. We prove that the EDF schedulability problem on a preemptive uniprocessor for the FJRT model is coNP-hard in the strong sense, even if the utilization of the task system is bounded by a constant strictly less than 1. Then, we show that the problem becomes tractable with some slight structural restrictions on parallel sections, for which we propose an exact schedulability test with pseudo-polynomial time complexity. Our results thus establish a borderline between the tractable and intractable FJRT models.
Original languageEnglish
Article number14
JournalACM Transactions on Embedded Computing Systems
Issue number1
Publication statusPublished - 1 Feb 2016
Externally publishedYes


  • Digraph-based task
  • EDF-schedulability
  • Fork-join
  • Tractability

ASJC Scopus subject areas

  • Software
  • Hardware and Architecture


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