These puzzles model real bench hangs where nothing crashes but progress stops. The key skill is drawing wait-for graphs across semaphore tokens and mailbox blocking behavior, including `try_*` APIs and bounded queues.
1. Lock Held Across Blocking Response Wait [Medium]
2. Bounded Mailbox put Deadlock [Hard]
3. try_get Busy Spin at Time 0 [Easy]
4. Leaked Semaphore Token on Error Path [Medium]
5. Two Consumers Waiting on One Mailbox [Hard]
6. Deadlock-Free Request Loop with try_put/try_get [Medium]Work each puzzle before reading the solution: predict the exact output or answer, name the rule that governs it, then check yourself.
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?"