1. 31 Oct, 2018 2 commits
    • Robbert Krebbers's avatar
    • Robbert Krebbers's avatar
      Fine-grained post-conditions for forked-off threads. · ebf06f91
      Robbert Krebbers authored
      This commit extends the state interpretation with an additional parameter to
      talk about the number of forked-off threads, and a fixed postcondition for each
      forked-off thread:
          state_interp : Λstate → list Λobservation → nat → iProp Σ;
          fork_post : iProp Σ;
      This way, instead of having `True` as the post-condition of `Fork`, one can
      have any post-condition, which is then recorded in the state interpretation.
      The point of keeping track of the postconditions of forked-off threads, is that
      we get an (additional) stronger adequacy theorem:
          Theorem wp_strong_all_adequacy Σ Λ `{invPreG Σ} s e σ1 v vs σ2 φ :
             (∀ `{Hinv : invG Σ} κs,
               (|={⊤}=> ∃
                   (stateI : state Λ → list (observation Λ) → nat → iProp Σ)
                   (fork_post : iProp Σ),
                 let _ : irisG Λ Σ := IrisG _ _ _ Hinv stateI fork_post in
                 stateI σ1 κs 0 ∗ WP e @ s; ⊤ {{ v,
                   let m := length vs in
                   stateI σ2 [] m -∗ [∗] replicate m fork_post ={⊤,∅}=∗ ⌜ φ v ⌝ }})%I) →
            rtc erased_step ([e], σ1) (of_val <$> v :: vs, σ2) →
            φ v.
      The difference with the ordinary adequacy theorem is that this one only applies
      once all threads terminated. In this case, one gets back the post-conditions
      `[∗] replicate m fork_post` of all forked-off threads.
      In Iron we showed that we can use this mechanism to make sure that all
      resources are disposed of properly in the presence of fork-based concurrency.
  2. 18 Oct, 2018 3 commits
  3. 05 Oct, 2018 3 commits
  4. 13 Jan, 2018 1 commit