Method StartCancel

tensorflow/core/framework/cancellation.cc:30–54

      next_cancellation_token_(0) {}

void CancellationManager::StartCancel() {
  gtl::FlatMap<CancellationToken, CancelCallback> callbacks_to_run;
  {
    mutex_lock l(mu_);
    if (is_cancelled_.load(std::memory_order_relaxed) || is_cancelling_) {
      return;
    }
    is_cancelling_ = true;
    std::swap(callbacks_, callbacks_to_run);
  }
  // We call these callbacks without holding mu_, so that concurrent
  // calls to DeregisterCallback, which can happen asynchronously, do
  // not block. The callbacks remain valid because any concurrent call
  // to DeregisterCallback will block until the
  // cancelled_notification_ is notified.
  for (auto key_and_value : callbacks_to_run) {
    key_and_value.second();
  }
  {
    mutex_lock l(mu_);
    is_cancelling_ = false;
    is_cancelled_.store(true, std::memory_order_release);
  }
  cancelled_notification_.Notify();
}

CancellationToken CancellationManager::get_cancellation_token() {
  mutex_lock l(mu_);