message: tweak correctness comment
diff: @@ -132,10 +132,10 @@ pub fn futex<'tcx>(
  // otherwise we will deadlock.
  //
  // There are two scenarios to consider:
  - // 1. If we (FUTEX_WAIT) executes first, we'll push ourselves into
  + // 1. If we (FUTEX_WAIT) execute first, we'll push ourselves into
  // the waiters queue and go to sleep. They (addr write & FUTEX_WAKE)
  // will see us in the queue and wake us up.
  - // 2. If they (addr write & FUTEX_WAKE) executes first, we must observe
  + // 2. If they (addr write & FUTEX_WAKE) execute first, we must observe
  // addr's new value. If we see an outdated value that happens to equal
  // the expected val, then we'll put ourselves to sleep with no one to wake us
  // up, so we end up with a deadlock. This is prevented by having a SeqCst
  @@ -157,7 +157,9 @@ pub fn futex<'tcx>(
  // right value. This is useless to us, since we need the read itself
  // to see an up-to-date value.
  //
  - // It is also critical that the fence, the atomic load, and the comparison
  + // The above case distinction is valid since both FUTEX_WAIT and FUTEX_WAKE
  + // contain a SeqCst fence, therefore inducting a total order between the operations.
  + // It is also critical that the fence, the atomic load, and the comparison in FUTEX_WAIT
  // altogether happen atomically. If the other thread's fence in FUTEX_WAKE
  // gets interleaved after our fence, then we lose the guarantee on the
  // atomic load being up-to-date; if the other thread's write on addr and FUTEX_WAKE
  