请帮忙看一下，为什么Linux下 select 总返回 0，windows下就正常。

void sock_manager_t::poll()
{
    vector::iterator it;
    for (it = m_socks.begin(); it != m_socks.end(); )
    {
        if ((*it)->m_sock == -1 || (*it)->m_destroyed)
        {
            m_socks.erase(it);
            sys_msg("sock_manager_t sock num : %d", m_socks.size());
            continue;
        }
        ++it;
    }
    if (m_socks.empty()) 
    {
        THREAD_SLEEP(1);
        return;
    }

    int cnt = m_socks.size();

    int tick = sys_tick();

    struct timeval tv;

    fd_set fdRead, fdWrite, fdExcept;

    int i, j, index, temp, max_fd;
    index = temp  = 0;

    int reader_num = 0;

    for (i = 0; i m_listening || p->m_connected)
            {
                FD_SET(p->m_sock, &fdRead);
            }
            if (p->m_connected || p->m_connectting)
            {
                FD_SET(p->m_sock, &fdWrite);
            }
            FD_SET(p->m_sock, &fdExcept);

            if (++index >= cnt) break;
        }

        int result = 0;
        result = select(max_fd + 1, &fdRead, &fdWrite, &fdExcept, &tv);
        if (result == 0) continue;
        if (result == SOCKET_ERROR)
        {
            //sys_msg("result == 0 ||result == SOCKET_ERROR");
            continue;
        }

        index = temp;

        for (j = 0; j m_sock, &fdRead))
            {
                if (p->m_listening)
                {
                    if (p->m_on_accept) p->m_on_accept(p, 0, p->m_param);
                }
                else if (p->m_connected)
                {
                    if (p->m_on_recv) p->m_on_recv(p, 0, p->m_param);
                }
                reader_num++;
            }

            // on_connect(ok)
            if (FD_ISSET(p->m_sock, &fdWrite))
            {
                if (p->m_connectting)
                {
                    bool is_ok = true;
/*
#ifdef LINUX 
                    // in linux should check again
                    int err, len, ret;
                    len = sizeof(err);
                    ret = getsockopt(p->m_sock, SOL_SOCKET, SO_ERROR, (char*)&err, (socklen_t*)&len);
                    if (ret != SOCKET_ERROR) 
                    {
                        if (err != 0) is_ok = false;
                    }
                    else
                    {
                        is_ok = false;
                    }
#endif    
*/                    
                    if (is_ok)
                    {
                        p->m_connectting = false;
                        p->m_connected = true;
                        if (p->m_on_connect) p->m_on_connect(p, 0, p->m_param);
                    }
                    else
                    {
                        p->m_connectting = false;
                        p->m_connected = false;
                        if (p->m_on_connect) p->m_on_connect(p, -1, p->m_param);
                    }
                }
                else if (p->m_connected)
                {
                    if (p->m_on_send) p->m_on_send(p, 0, p->m_param);
                }
            }

            // on_connect(error)
            if (FD_ISSET(p->m_sock, &fdExcept))
            {
                if (p->m_connectting)
                {
                    p->m_connectting = false;
                    p->m_connected = false;
                    if (p->m_on_connect) p->m_on_connect(p, -1, p->m_param);
                }
                else if (p->m_connected || p->m_listening)
                {
                    p->close();
                    if (p->m_on_close) p->m_on_close(p, -1, p->m_param);
                }
            }

            if (++index >= cnt) break;
        }

        if (index >= cnt) break;
    }

    if (reader_num == 0 && sys_tick() - tick m_listening || p->m_connected)
            {
                FD_SET(p->m_sock, &fdRead);  //它执行了吗?
            }
            if (p->m_connected || p->m_connectting)
            {
                FD_SET(p->m_sock, &fdWrite); //它执行了吗?
            }