bool IbvNic::pollOnce()

in tensorpipe/channel/cuda_gdr/context_impl.cc [285:347]
53 lines of code
10 McCabe index (conditional complexity)

bool IbvNic::pollOnce() {
  std::array<IbvLib::wc, kNumPolledWorkCompletions> wcs;
  auto rv = ibvLib_.poll_cq(cq_.get(), wcs.size(), wcs.data());

  if (rv == 0) {
    return false;
  }
  TP_THROW_SYSTEM_IF(rv < 0, errno);

  int numSends = 0;
  int numRecvs = 0;
  for (int wcIdx = 0; wcIdx < rv; wcIdx++) {
    IbvLib::wc& wc = wcs[wcIdx];

    TP_VLOG(6) << "Channel context " << id_ << " got work completion on device "
               << name_ << " for request " << wc.wr_id << " for QP "
               << wc.qp_num << " with status "
               << ibvLib_.wc_status_str(wc.status) << " and opcode "
               << ibvWorkCompletionOpcodeToStr(wc.opcode)
               << " (byte length: " << wc.byte_len << ")";

    auto iter = requestsInFlight_.find(wc.wr_id);
    TP_THROW_ASSERT_IF(iter == requestsInFlight_.end())
        << "Got work completion with unknown ID " << wc.wr_id;

    IbvLib::wc_opcode opcode = std::move(std::get<0>(iter->second));
    std::function<void(const Error&)> cb = std::move(std::get<1>(iter->second));
    requestsInFlight_.erase(iter);

    if (wc.status != IbvLib::WC_SUCCESS) {
      cb(TP_CREATE_ERROR(IbvError, ibvLib_.wc_status_str(wc.status)));
    } else {
      cb(Error::kSuccess);
    }

    switch (opcode) {
      case IbvLib::WC_RECV:
        numRecvs++;
        break;
      case IbvLib::WC_SEND:
        numSends++;
        break;
      default:
        TP_THROW_ASSERT() << "Unknown opcode: " << opcode;
    }
  }

  numAvailableSendSlots_ += numSends;
  while (!sendsWaitingForSlots_.empty() && numAvailableSendSlots_ > 0) {
    applyFunc(
        *this, &IbvNic::postSend, std::move(sendsWaitingForSlots_.front()));
    sendsWaitingForSlots_.pop_front();
  }

  numAvailableRecvSlots_ += numRecvs;
  while (!recvsWaitingForSlots_.empty() && numAvailableRecvSlots_ > 0) {
    applyFunc(
        *this, &IbvNic::postRecv, std::move(recvsWaitingForSlots_.front()));
    recvsWaitingForSlots_.pop_front();
  }

  return true;
}