Skip to content

Liveness failure

Category: Hazards · Status: stub · Lessons: chapter 03, When locks go wrong (planned)

One line: A task that should make progress never does, though nothing has crashed: it waits for ever, spins for ever, or never gets its turn.

How it connects

flowchart LR
  n_deadlock["Deadlock"]
  n_task_leak["Leaked tasks"]
  n_livelock["Livelock"]
  n_liveness_failure["Liveness failure"]
  n_priority_inversion["Priority inversion"]
  n_scoped_lock["Scoped locking"]
  n_starvation["Starvation"]
  n_deadlock -->|is a| n_liveness_failure
  n_livelock -->|is a| n_liveness_failure
  n_priority_inversion -->|is a| n_liveness_failure
  n_scoped_lock -->|prevents| n_liveness_failure
  n_starvation -->|is a| n_liveness_failure
  n_task_leak -->|is a| n_liveness_failure
  classDef center stroke-width:3px
  class n_liveness_failure center
  classDef outside stroke-dasharray: 4 3
  class n_deadlock,n_task_leak,n_livelock,n_priority_inversion,n_scoped_lock,n_starvation outside

In each language
Rust The Rustonomicon ↗ counts getting deadlocked as safe: the compiler checks memory safety, not progress
Java JLS §17.1 ↗: the language neither prevents nor requires detection of deadlock
Haskell BlockedIndefinitelyOnMVar ↗ is the exception for a thread blocked on an MVar that nothing else references, so it can never continue