Method read_lock

include/process/rwlock.hpp:109–124

TODO(bmahler): Consider returning a 'Locked' object in the future as the mechanism for unlocking, rather than exposing unlocking functions for all to call.

  // future as the mechanism for unlocking, rather than exposing
  // unlocking functions for all to call.
  Future<Nothing> read_lock()
  {
    Future<Nothing> future = Nothing();

    synchronized (data->lock) {
      if (!data->write_locked && data->waiters.empty()) {
        data->read_locked++;
      } else {
        Waiter w{Waiter::READ};
        future = w.promise.future();
        data->waiters.push(std::move(w));
      }
    }

    return future;
  }

  void read_unlock()
  {