pred.next = succ;
          if (pred.thread == null) { // We raced with another node that unlinked pred. Restart.
            continue restart;
          }
        } else if (!ATOMIC_HELPER.casWaiters(this, curr, succ)) { // We are unlinking head
          continue restart; // We raced with an add or complete
        }
        curr = succ;
      }
      break;
    }
  }

   *       applies only to the task that was running at the point of interruption.
   *   <li>if the thread was interrupted before the SequentialExecutor's worker begins execution,
   *       the interrupt will be restored to the thread after it completes so that its {@code
   *       delegate} Executor may process the interrupt.
   *   <li>subtasks are run with the thread uninterrupted and interrupts received during execution

   *       ExecutionError} (if the cause is an {@code Error}).
   *   <li>Any {@link InterruptedException} causes a retry of the {@code get} call. The interrupt is
   *       restored before {@code getUnchecked} returns.
   *   <li>Any {@link CancellationException} is propagated untouched. So is any other {@link
   *       RuntimeException} ({@code get} implementations are discouraged from throwing such