message: Reset the session before save op is run.
diff: @@ -92,6 +92,8 @@ Status SingleMachine::Provision() {
  VLOG(1) << "Adding GPU device " << device_name;
  devices_[device_name] = GetLocalGPUInfo(i);
  }
  + mutex_lock l(this->last_graph_mu_);
  + last_graph_ = nullptr;
  return Status::OK();
  }
  @@ -230,7 +232,7 @@ Status SingleMachine::RunWithTimeout(
  }
  Status SingleMachine::CloseSession(bool use_timeout) {
  - if (!session_) {
  + if (!session_ || !thread_pool_) {
  return Status::OK();
  }
  