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Course contents

  • How to Use This Puzzle Bank
  • SystemVerilog Language Puzzles25
    • Datatype and Bit Puzzles
    • Fork Join Puzzles
      • join vs join_any vs join_none
      • Loop Variable Capture in Detached Threads
      • wait fork Synchronization Point
      • disable Named Fork Scope
      • join_any Without Cleanup
      • Inner disable fork Does Not Kill Outer Sibling
    • Queue and Array Puzzles
    • String and Casting Puzzles
    • SystemVerilog Language Puzzles: Tricky Q&A
  • Difficulty Guide
  • Full Topic Map
  • Interview-Day Tips
  • Study Route: One Week Before the Interview
  • Study Route: Two Weeks
  • Study Route: Four Weeks (Full Course)4
  • OOP & Testbench Puzzles25
  • Concurrency & Timing Puzzles25
  • Randomization & Constraint Puzzles25
  • SVA Assertion Puzzles25
  • Functional Coverage Puzzles25
  • Logic & Aptitude Puzzles25
  • Scenario & Debug Puzzles25
  • UVM Testbench Puzzles25
  • Clock, Reset & CDC Puzzles25
  • Bus and Interface Protocol Puzzles25
  • Interview Prep: Puzzle Rounds7
  • DV Puzzle Cheatsheet
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←SystemVerilog Language Puzzles
  1. Topics
  2. DV Interview Puzzles
  3. SystemVerilog Language Puzzles
  4. Fork Join Puzzles
On this page

    VLSI DV Interview PuzzlesAll levels

    Fork Join Puzzles

    These puzzles test process-lifetime reasoning under real simulator scheduling. You need to predict when parent code resumes, which child threads keep running, and exactly what scope `disable fork` can terminate.

    • 6topics
    • 6lessons

    Topics in this section

    1. 1join vs join_any vs join_none1 lesson
    2. 2Loop Variable Capture in Detached Threads1 lesson
    3. 3wait fork Synchronization Point1 lesson
    4. 4disable Named Fork Scope1 lesson
    5. 5join_any Without Cleanup1 lesson
    6. 6Inner disable fork Does Not Kill Outer Sibling1 lesson

    About this puzzle set

    These puzzles test process-lifetime reasoning under real simulator scheduling. You need to predict when parent code resumes, which child threads keep running, and exactly what scope `disable fork` can terminate.

    Puzzles in this topic

    Diagram
    1. join vs join_any vs join_none  [Easy]
    2. Loop Variable Capture in Detached Threads  [Medium]
    3. wait fork Synchronization Point  [Easy]
    4. disable Named Fork Scope  [Medium]
    5. join_any Without Cleanup  [Medium]
    6. Inner disable fork Does Not Kill Outer Sibling  [Medium]

    Work each puzzle before reading the solution: predict the exact output or answer, name the rule that governs it, then check yourself.

    SV scheduling regions at puzzle scale

    Diagram
    SYSTEMVERILOG EVENT REGIONS (SIMPLIFIED ORDER)
    
    time slot T
       |
       +--> ACTIVE   : blocking statements, RHS sampling
       +--> INACTIVE : #0 queued work
       +--> NBA      : non-blocking LHS updates commit
       +--> OBSERVED : assertions sample stable design values
       +--> REACTIVE : testbench/program reaction code
    
    If behavior looks impossible, ask: "Which region saw which value?"

    Related topics

    • SystemVerilog Language Puzzles section

    • VLSI DV Interview Puzzles hub

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    See also

    • Datatype and Bit Puzzles
    • Queue and Array Puzzles
    • String and Casting Puzzles