// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
 * Ceph - scalable distributed file system
 *
 * Copyright (C) 2016 XSKY <haomai@xsky.com>
 *
 * Author: Haomai Wang <haomaiwang@gmail.com>
 *
 * This is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License version 2.1, as published by the Free Software
 * Foundation.  See file COPYING.
 *
 */

#include <poll.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/resource.h>

#include "include/str_list.h"
#include "include/compat.h"
#include "common/Cycles.h"
#include "common/deleter.h"
#include "common/Tub.h"
#include "RDMAStack.h"

#define dout_subsys ceph_subsys_ms
#undef dout_prefix
#define dout_prefix *_dout << "RDMAStack "

RDMADispatcher::~RDMADispatcher()
{
  ldout(cct, 20) << __func__ << " destructing rdma dispatcher" << dendl;
  polling_stop();

  ceph_assert(qp_conns.empty());
  ceph_assert(num_qp_conn == 0);
  ceph_assert(dead_queue_pairs.empty());
  ceph_assert(num_dead_queue_pair == 0);

  delete async_handler;
}

RDMADispatcher::RDMADispatcher(CephContext* c, RDMAStack* s)
  : cct(c), async_handler(new C_handle_cq_async(this)), lock("RDMADispatcher::lock"),
  w_lock("RDMADispatcher::for worker pending list"), stack(s)
{
  PerfCountersBuilder plb(cct, "AsyncMessenger::RDMADispatcher", l_msgr_rdma_dispatcher_first, l_msgr_rdma_dispatcher_last);

  plb.add_u64_counter(l_msgr_rdma_polling, "polling", "Whether dispatcher thread is polling");
  plb.add_u64_counter(l_msgr_rdma_inflight_tx_chunks, "inflight_tx_chunks", "The number of inflight tx chunks");
  plb.add_u64_counter(l_msgr_rdma_rx_bufs_in_use, "rx_bufs_in_use", "The number of rx buffers that are holding data and being processed");
  plb.add_u64_counter(l_msgr_rdma_rx_bufs_total, "rx_bufs_total", "The total number of rx buffers");

  plb.add_u64_counter(l_msgr_rdma_tx_total_wc, "tx_total_wc", "The number of tx work comletions");
  plb.add_u64_counter(l_msgr_rdma_tx_total_wc_errors, "tx_total_wc_errors", "The number of tx errors");
  plb.add_u64_counter(l_msgr_rdma_tx_wc_retry_errors, "tx_retry_errors", "The number of tx retry errors");
  plb.add_u64_counter(l_msgr_rdma_tx_wc_wr_flush_errors, "tx_wr_flush_errors", "The number of tx work request flush errors");

  plb.add_u64_counter(l_msgr_rdma_rx_total_wc, "rx_total_wc", "The number of total rx work completion");
  plb.add_u64_counter(l_msgr_rdma_rx_total_wc_errors, "rx_total_wc_errors", "The number of total rx error work completion");
  plb.add_u64_counter(l_msgr_rdma_rx_fin, "rx_fin", "The number of rx finish work request");

  plb.add_u64_counter(l_msgr_rdma_total_async_events, "total_async_events", "The number of async events");
  plb.add_u64_counter(l_msgr_rdma_async_last_wqe_events, "async_last_wqe_events", "The number of last wqe events");

  plb.add_u64_counter(l_msgr_rdma_handshake_errors, "handshake_errors", "The number of handshake errors");


  plb.add_u64_counter(l_msgr_rdma_created_queue_pair, "created_queue_pair", "Active queue pair number");
  plb.add_u64_counter(l_msgr_rdma_active_queue_pair, "active_queue_pair", "Created queue pair number");

  perf_logger = plb.create_perf_counters();
  cct->get_perfcounters_collection()->add(perf_logger);
  Cycles::init();
}

void RDMADispatcher::polling_start()
{
  // take lock because listen/connect can happen from different worker threads
  Mutex::Locker l(lock);

  if (t.joinable()) 
    return; // dispatcher thread already running 

  get_stack()->get_infiniband().get_memory_manager()->set_rx_stat_logger(perf_logger);

  tx_cc = get_stack()->get_infiniband().create_comp_channel(cct);
  ceph_assert(tx_cc);
  rx_cc = get_stack()->get_infiniband().create_comp_channel(cct);
  ceph_assert(rx_cc);
  tx_cq = get_stack()->get_infiniband().create_comp_queue(cct, tx_cc);
  ceph_assert(tx_cq);
  rx_cq = get_stack()->get_infiniband().create_comp_queue(cct, rx_cc);
  ceph_assert(rx_cq);

  t = std::thread(&RDMADispatcher::polling, this);
  ceph_pthread_setname(t.native_handle(), "rdma-polling");
}

void RDMADispatcher::polling_stop()
{
  {
    Mutex::Locker l(lock);
    done = true;
  }

  if (!t.joinable())
    return;

  t.join();

  tx_cc->ack_events();
  rx_cc->ack_events();
  delete tx_cq;
  delete rx_cq;
  delete tx_cc;
  delete rx_cc;
}

void RDMADispatcher::handle_async_event()
{
  ldout(cct, 30) << __func__ << dendl;
  while (1) {
    ibv_async_event async_event;
    if (ibv_get_async_event(get_stack()->get_infiniband().get_device()->ctxt, &async_event)) {
      if (errno != EAGAIN)
       lderr(cct) << __func__ << " ibv_get_async_event failed. (errno=" << errno
                  << " " << cpp_strerror(errno) << ")" << dendl;
      return;
    }
    perf_logger->inc(l_msgr_rdma_total_async_events);
    // FIXME: Currently we must ensure no other factor make QP in ERROR state,
    // otherwise this qp can't be deleted in current cleanup flow.
    if (async_event.event_type == IBV_EVENT_QP_LAST_WQE_REACHED) {
      perf_logger->inc(l_msgr_rdma_async_last_wqe_events);
      uint64_t qpn = async_event.element.qp->qp_num;
      ldout(cct, 10) << __func__ << " event associated qp=" << async_event.element.qp
                     << " evt: " << ibv_event_type_str(async_event.event_type) << dendl;
      Mutex::Locker l(lock);
      RDMAConnectedSocketImpl *conn = get_conn_lockless(qpn);
      if (!conn) {
        ldout(cct, 1) << __func__ << " missing qp_num=" << qpn << " discard event" << dendl;
      } else {
        ldout(cct, 1) << __func__ << " it's not forwardly stopped by us, reenable=" << conn << dendl;
        conn->fault();
        if (!cct->_conf->ms_async_rdma_cm)
          erase_qpn_lockless(qpn);
      }
    } else {
      ldout(cct, 1) << __func__ << " ibv_get_async_event: dev=" << get_stack()->get_infiniband().get_device()->ctxt
                    << " evt: " << ibv_event_type_str(async_event.event_type)
                    << dendl;
    }
    ibv_ack_async_event(&async_event);
  }
}

void RDMADispatcher::post_chunk_to_pool(Chunk* chunk)
{
  Mutex::Locker l(lock);
  get_stack()->get_infiniband().post_chunk_to_pool(chunk);
  perf_logger->dec(l_msgr_rdma_rx_bufs_in_use);
}

int RDMADispatcher::post_chunks_to_rq(int num, ibv_qp *qp)
{
  Mutex::Locker l(lock);
  return get_stack()->get_infiniband().post_chunks_to_rq(num, qp);
}

void RDMADispatcher::polling()
{
  static int MAX_COMPLETIONS = 32;
  ibv_wc wc[MAX_COMPLETIONS];

  std::map<RDMAConnectedSocketImpl*, std::vector<ibv_wc> > polled;
  std::vector<ibv_wc> tx_cqe;
  ldout(cct, 20) << __func__ << " going to poll tx cq: " << tx_cq << " rx cq: " << rx_cq << dendl;
  RDMAConnectedSocketImpl *conn = nullptr;
  uint64_t last_inactive = Cycles::rdtsc();
  bool rearmed = false;
  int r = 0;

  while (true) {
    int tx_ret = tx_cq->poll_cq(MAX_COMPLETIONS, wc);
    if (tx_ret > 0) {
      ldout(cct, 20) << __func__ << " tx completion queue got " << tx_ret
                     << " responses."<< dendl;
      handle_tx_event(wc, tx_ret);
    }

    int rx_ret = rx_cq->poll_cq(MAX_COMPLETIONS, wc);
    if (rx_ret > 0) {
      ldout(cct, 20) << __func__ << " rx completion queue got " << rx_ret
                     << " responses."<< dendl;
      perf_logger->inc(l_msgr_rdma_rx_total_wc, rx_ret);
      perf_logger->inc(l_msgr_rdma_rx_bufs_in_use, rx_ret);

      Mutex::Locker l(lock);//make sure connected socket alive when pass wc

      for (int i = 0; i < rx_ret; ++i) {
        ibv_wc* response = &wc[i];
        Chunk* chunk = reinterpret_cast<Chunk *>(response->wr_id);

        if (response->status == IBV_WC_SUCCESS) {
          ceph_assert(wc[i].opcode == IBV_WC_RECV);
          conn = get_conn_lockless(response->qp_num);
          if (!conn) {
            ldout(cct, 1) << __func__ << " csi with qpn " << response->qp_num << " may be dead. chunk " << chunk << " will be back ? " << r << dendl;
            get_stack()->get_infiniband().post_chunk_to_pool(chunk);
            perf_logger->dec(l_msgr_rdma_rx_bufs_in_use);
          } else {
            conn->post_chunks_to_rq(1);
            polled[conn].push_back(*response);
          }
        } else {
          perf_logger->inc(l_msgr_rdma_rx_total_wc_errors);
          ldout(cct, 1) << __func__ << " work request returned error for buffer(" << chunk
              << ") status(" << response->status << ":"
              << get_stack()->get_infiniband().wc_status_to_string(response->status) << ")" << dendl;
          if (response->status != IBV_WC_WR_FLUSH_ERR) {
            conn = get_conn_lockless(response->qp_num);
            if (conn && conn->is_connected())
              conn->fault();
          }
          get_stack()->get_infiniband().post_chunk_to_pool(chunk);
          perf_logger->dec(l_msgr_rdma_rx_bufs_in_use);
        }
      }
      for (auto &&i : polled)
        i.first->pass_wc(std::move(i.second));
      polled.clear();
    }

    if (!tx_ret && !rx_ret) {
      // NOTE: Has TX just transitioned to idle? We should do it when idle!
      // It's now safe to delete queue pairs (see comment by declaration
      // for dead_queue_pairs).
      // Additionally, don't delete qp while outstanding_buffers isn't empty,
      // because we need to check qp's state before sending
      perf_logger->set(l_msgr_rdma_inflight_tx_chunks, inflight);
      if (num_dead_queue_pair) {
        Mutex::Locker l(lock); // FIXME reuse dead qp because creating one qp costs 1 ms
        auto it = dead_queue_pairs.begin();
        while (it != dead_queue_pairs.end()) {
          auto i = *it;
          // Bypass QPs that do not collect all Tx completions yet.
          if (i->get_tx_wr()) {
            ldout(cct, 20) << __func__ << " bypass qp=" << i << " tx_wr=" << i->get_tx_wr() << dendl;
            ++it;
          } else {
            ldout(cct, 10) << __func__ << " finally delete qp=" << i << dendl;
            delete i;
            it = dead_queue_pairs.erase(it);
            perf_logger->dec(l_msgr_rdma_active_queue_pair);
            --num_dead_queue_pair;
          }
        }
      }
      if (!num_qp_conn && done && dead_queue_pairs.empty())
        break;

      uint64_t now = Cycles::rdtsc();
      if (Cycles::to_microseconds(now - last_inactive) > cct->_conf->ms_async_rdma_polling_us) {
        handle_async_event();
        if (!rearmed) {
          // Clean up cq events after rearm notify ensure no new incoming event
          // arrived between polling and rearm
          tx_cq->rearm_notify();
          rx_cq->rearm_notify();
          rearmed = true;
          continue;
        }

        struct pollfd channel_poll[2];
        channel_poll[0].fd = tx_cc->get_fd();
        channel_poll[0].events = POLLIN | POLLERR | POLLNVAL | POLLHUP;
        channel_poll[0].revents = 0;
        channel_poll[1].fd = rx_cc->get_fd();
        channel_poll[1].events = POLLIN | POLLERR | POLLNVAL | POLLHUP;
        channel_poll[1].revents = 0;
        r = 0;
        perf_logger->set(l_msgr_rdma_polling, 0);
        while (!done && r == 0) {
          r = TEMP_FAILURE_RETRY(poll(channel_poll, 2, 100));
          if (r < 0) {
            r = -errno;
            lderr(cct) << __func__ << " poll failed " << r << dendl;
            ceph_abort();
          }
        }
        if (r > 0 && tx_cc->get_cq_event())
          ldout(cct, 20) << __func__ << " got tx cq event." << dendl;
        if (r > 0 && rx_cc->get_cq_event())
          ldout(cct, 20) << __func__ << " got rx cq event." << dendl;
        last_inactive = Cycles::rdtsc();
        perf_logger->set(l_msgr_rdma_polling, 1);
        rearmed = false;
      }
    }
  }
}

void RDMADispatcher::notify_pending_workers() {
  if (num_pending_workers) {
    RDMAWorker *w = nullptr;
    {
      Mutex::Locker l(w_lock);
      if (!pending_workers.empty()) {
        w = pending_workers.front();
        pending_workers.pop_front();
        --num_pending_workers;
      }
    }
    if (w)
      w->notify_worker();
  }
}

void RDMADispatcher::register_qp(QueuePair *qp, RDMAConnectedSocketImpl* csi)
{
  Mutex::Locker l(lock);
  ceph_assert(!qp_conns.count(qp->get_local_qp_number()));
  qp_conns[qp->get_local_qp_number()] = std::make_pair(qp, csi);
  ++num_qp_conn;
}

RDMAConnectedSocketImpl* RDMADispatcher::get_conn_lockless(uint32_t qp)
{
  auto it = qp_conns.find(qp);
  if (it == qp_conns.end())
    return nullptr;
  if (it->second.first->is_dead())
    return nullptr;
  return it->second.second;
}

Infiniband::QueuePair* RDMADispatcher::get_qp(uint32_t qp)
{
  Mutex::Locker l(lock);
  // Try to find the QP in qp_conns firstly.
  auto it = qp_conns.find(qp);
  if (it != qp_conns.end())
    return it->second.first;

  // Try again in dead_queue_pairs.
  for (auto &i: dead_queue_pairs)
    if (i->get_local_qp_number() == qp)
      return i;

  return nullptr;
}

void RDMADispatcher::erase_qpn_lockless(uint32_t qpn)
{
  auto it = qp_conns.find(qpn);
  if (it == qp_conns.end())
    return ;
  ++num_dead_queue_pair;
  dead_queue_pairs.push_back(it->second.first);
  qp_conns.erase(it);
  --num_qp_conn;
}

void RDMADispatcher::erase_qpn(uint32_t qpn)
{
  Mutex::Locker l(lock);
  erase_qpn_lockless(qpn);
}

void RDMADispatcher::handle_tx_event(ibv_wc *cqe, int n)
{
  std::vector<Chunk*> tx_chunks;

  for (int i = 0; i < n; ++i) {
    ibv_wc* response = &cqe[i];
    Chunk* chunk = reinterpret_cast<Chunk *>(response->wr_id);
    ldout(cct, 25) << __func__ << " QP: " << response->qp_num
                   << " len: " << response->byte_len << " , addr:" << chunk
                   << " " << get_stack()->get_infiniband().wc_status_to_string(response->status) << dendl;

    QueuePair *qp = get_qp(response->qp_num);
    if (qp)
      qp->dec_tx_wr(1);

    if (response->status != IBV_WC_SUCCESS) {
      perf_logger->inc(l_msgr_rdma_tx_total_wc_errors);
      if (response->status == IBV_WC_RETRY_EXC_ERR) {
        ldout(cct, 1) << __func__ << " connection between server and client not working. Disconnect this now" << dendl;
        perf_logger->inc(l_msgr_rdma_tx_wc_retry_errors);
      } else if (response->status == IBV_WC_WR_FLUSH_ERR) {
        ldout(cct, 1) << __func__ << " Work Request Flushed Error: this connection's qp="
                      << response->qp_num << " should be down while this WR=" << response->wr_id
                      << " still in flight." << dendl;
        perf_logger->inc(l_msgr_rdma_tx_wc_wr_flush_errors);
      } else {
        ldout(cct, 1) << __func__ << " send work request returned error for buffer("
                      << response->wr_id << ") status(" << response->status << "): "
                      << get_stack()->get_infiniband().wc_status_to_string(response->status) << dendl;
        Mutex::Locker l(lock);//make sure connected socket alive when pass wc
        RDMAConnectedSocketImpl *conn = get_conn_lockless(response->qp_num);

        if (conn && conn->is_connected()) {
          ldout(cct, 25) << __func__ << " qp state is : " << conn->get_qp_state() << dendl;
          conn->fault();
        } else {
          ldout(cct, 1) << __func__ << " missing qp_num=" << response->qp_num << " discard event" << dendl;
        }
      }
    }

    //TX completion may come either from regular send message or from 'fin' message.
    //In the case of 'fin' wr_id points to the QueuePair.
    if (get_stack()->get_infiniband().get_memory_manager()->is_tx_buffer(chunk->buffer)) {
      tx_chunks.push_back(chunk);
    } else if (reinterpret_cast<QueuePair*>(response->wr_id)->get_local_qp_number() == response->qp_num ) {
      ldout(cct, 1) << __func__ << " sending of the disconnect msg completed" << dendl;
    } else {
      ldout(cct, 1) << __func__ << " not tx buffer, chunk " << chunk << dendl;
      ceph_abort();
    }
  }

  perf_logger->inc(l_msgr_rdma_tx_total_wc, n);
  post_tx_buffer(tx_chunks);
}

/**
 * Add the given Chunks to the given free queue.
 *
 * \param[in] chunks
 *      The Chunks to enqueue.
 * \return
 *      0 if success or -1 for failure
 */
void RDMADispatcher::post_tx_buffer(std::vector<Chunk*> &chunks)
{
  if (chunks.empty())
    return ;

  inflight -= chunks.size();
  get_stack()->get_infiniband().get_memory_manager()->return_tx(chunks);
  ldout(cct, 30) << __func__ << " release " << chunks.size()
                 << " chunks, inflight " << inflight << dendl;
  notify_pending_workers();
}


RDMAWorker::RDMAWorker(CephContext *c, unsigned i)
  : Worker(c, i), stack(nullptr),
    tx_handler(new C_handle_cq_tx(this)), lock("RDMAWorker::lock")
{
  // initialize perf_logger
  char name[128];
  sprintf(name, "AsyncMessenger::RDMAWorker-%u", id);
  PerfCountersBuilder plb(cct, name, l_msgr_rdma_first, l_msgr_rdma_last);

  plb.add_u64_counter(l_msgr_rdma_tx_no_mem, "tx_no_mem", "The count of no tx buffer");
  plb.add_u64_counter(l_msgr_rdma_tx_parital_mem, "tx_parital_mem", "The count of parital tx buffer");
  plb.add_u64_counter(l_msgr_rdma_tx_failed, "tx_failed_post", "The number of tx failed posted");

  plb.add_u64_counter(l_msgr_rdma_tx_chunks, "tx_chunks", "The number of tx chunks transmitted");
  plb.add_u64_counter(l_msgr_rdma_tx_bytes, "tx_bytes", "The bytes of tx chunks transmitted", NULL, 0, unit_t(UNIT_BYTES));
  plb.add_u64_counter(l_msgr_rdma_rx_chunks, "rx_chunks", "The number of rx chunks transmitted");
  plb.add_u64_counter(l_msgr_rdma_rx_bytes, "rx_bytes", "The bytes of rx chunks transmitted", NULL, 0, unit_t(UNIT_BYTES));
  plb.add_u64_counter(l_msgr_rdma_pending_sent_conns, "pending_sent_conns", "The count of pending sent conns");

  perf_logger = plb.create_perf_counters();
  cct->get_perfcounters_collection()->add(perf_logger);
}

RDMAWorker::~RDMAWorker()
{
  delete tx_handler;
}

void RDMAWorker::initialize()
{
  if (!dispatcher) {
    dispatcher = &stack->get_dispatcher();
  }
}

int RDMAWorker::listen(entity_addr_t &sa, unsigned addr_slot,
		       const SocketOptions &opt,ServerSocket *sock)
{
  get_stack()->get_infiniband().init();
  dispatcher->polling_start();
  RDMAServerSocketImpl *p;
  if (cct->_conf->ms_async_rdma_type == "iwarp") {
    p = new RDMAIWARPServerSocketImpl(
      cct, &get_stack()->get_infiniband(), &get_stack()->get_dispatcher(), this,
      sa, addr_slot);
  } else {
    p = new RDMAServerSocketImpl(cct, &get_stack()->get_infiniband(),
				 &get_stack()->get_dispatcher(), this, sa,
				 addr_slot);
  }
  int r = p->listen(sa, opt);
  if (r < 0) {
    delete p;
    return r;
  }

  *sock = ServerSocket(std::unique_ptr<ServerSocketImpl>(p));
  return 0;
}

int RDMAWorker::connect(const entity_addr_t &addr, const SocketOptions &opts, ConnectedSocket *socket)
{
  get_stack()->get_infiniband().init();
  dispatcher->polling_start();

  RDMAConnectedSocketImpl* p;
  if (cct->_conf->ms_async_rdma_type == "iwarp") {
    p = new RDMAIWARPConnectedSocketImpl(cct, &get_stack()->get_infiniband(), &get_stack()->get_dispatcher(), this);
  } else {
    p = new RDMAConnectedSocketImpl(cct, &get_stack()->get_infiniband(), &get_stack()->get_dispatcher(), this);
  }
  int r = p->try_connect(addr, opts);

  if (r < 0) {
    ldout(cct, 1) << __func__ << " try connecting failed." << dendl;
    delete p;
    return r;
  }
  std::unique_ptr<RDMAConnectedSocketImpl> csi(p);
  *socket = ConnectedSocket(std::move(csi));
  return 0;
}

int RDMAWorker::get_reged_mem(RDMAConnectedSocketImpl *o, std::vector<Chunk*> &c, size_t bytes)
{
  ceph_assert(center.in_thread());
  int r = get_stack()->get_infiniband().get_tx_buffers(c, bytes);
  ceph_assert(r >= 0);
  size_t got = get_stack()->get_infiniband().get_memory_manager()->get_tx_buffer_size() * r;
  ldout(cct, 30) << __func__ << " need " << bytes << " bytes, reserve " << got << " registered  bytes, inflight " << dispatcher->inflight << dendl;
  stack->get_dispatcher().inflight += r;
  if (got >= bytes)
    return r;

  if (o) {
    if (!o->is_pending()) {
      pending_sent_conns.push_back(o);
      perf_logger->inc(l_msgr_rdma_pending_sent_conns, 1);
      o->set_pending(1);
    }
    dispatcher->make_pending_worker(this);
  }
  return r;
}


void RDMAWorker::handle_pending_message()
{
  ldout(cct, 20) << __func__ << " pending conns " << pending_sent_conns.size() << dendl;
  while (!pending_sent_conns.empty()) {
    RDMAConnectedSocketImpl *o = pending_sent_conns.front();
    pending_sent_conns.pop_front();
    ssize_t r = o->submit(false);
    ldout(cct, 20) << __func__ << " sent pending bl socket=" << o << " r=" << r << dendl;
    if (r < 0) {
      if (r == -EAGAIN) {
        pending_sent_conns.push_back(o);
        dispatcher->make_pending_worker(this);
        return ;
      }
      o->fault();
    }
    o->set_pending(0);
    perf_logger->dec(l_msgr_rdma_pending_sent_conns, 1);
  }
  dispatcher->notify_pending_workers();
}

RDMAStack::RDMAStack(CephContext *cct, const string &t)
  : NetworkStack(cct, t), ib(cct), dispatcher(cct, this)
{
  ldout(cct, 20) << __func__ << " constructing RDMAStack..." << dendl;

  unsigned num = get_num_worker();
  for (unsigned i = 0; i < num; ++i) {
    RDMAWorker* w = dynamic_cast<RDMAWorker*>(get_worker(i));
    w->set_stack(this);
  }
  ldout(cct, 20) << " creating RDMAStack:" << this << " with dispatcher:" << &dispatcher << dendl;
}

RDMAStack::~RDMAStack()
{
  if (cct->_conf->ms_async_rdma_enable_hugepage) {
    unsetenv("RDMAV_HUGEPAGES_SAFE");	//remove env variable on destruction
  }
}

void RDMAStack::spawn_worker(unsigned i, std::function<void ()> &&func)
{
  threads.resize(i+1);
  threads[i] = std::thread(func);
}

void RDMAStack::join_worker(unsigned i)
{
  ceph_assert(threads.size() > i && threads[i].joinable());
  threads[i].join();
}