AT组件

AT组件中at_recvfrom（）函数设置errno = EIO错误的问题

发布于 2023-07-21 13:50:40 浏览：772 订阅该版

我使用AT组件驱动N720模块，在测试数据收发的时候at_recvfrom（）函数偶尔会返回-1，同时errno被设置为了EIO，分析以后发现当接收到了信号，但是没有数据时，会设置errno为EIO，就是下面这段代码:
```c
    while (1)
    {
        /* wait the receive semaphore */
        if (rt_sem_take(sock->recv_notice, timeout) < 0)
        {
            LOG_D("AT socket (%d) receive timeout (%d)!", socket, timeout);
            errno = EAGAIN;
            result = -1;
            goto __exit;
        }
        else
        {

/* get receive buffer to receiver ring buffer */
            rt_mutex_take(sock->recv_lock, RT_WAITING_FOREVER);
            recv_len = at_recvpkt_get(&(sock->recvpkt_list), (char *) mem, len);
            rt_mutex_release(sock->recv_lock);
            if (recv_len > 0)
            {
                break;
            }
            else
            {
                /* we have no data to receive but are woken up,
                    which means the socket have been closed. */
                errno = EIO;
                result = -1;
                goto __exit;
            }
        }
    }
```
但看这段没什么问题，但是在这段之前，还有一段：
```c
    /* receive packet list last transmission of remaining data */
    rt_mutex_take(sock->recv_lock, RT_WAITING_FOREVER);
    if((recv_len = at_recvpkt_get(&(sock->recvpkt_list), (char *)mem, len)) > 0)
    {
        rt_mutex_release(sock->recv_lock);
        goto __exit;
    }
    rt_mutex_release(sock->recv_lock);
```
先检查了链表里是否有数据，如果有数据，就直接返回了，没有重置信号，这会导致下一次进入的时候，获得了信号，但是数据早就被取走了