ntp_sync时间同步问题

发布于 2021-05-28 16:54:00 浏览：1613 订阅该版

[tocm]

# RT-Thread ntp_sync时钟同步问题

## 硬件

> RT-THREAD ART-PI开发板，使用4G模块EC200进行时钟同步。

## 现象

```
msh />ntp_sync
[I/ntp] Get local time from NTP server: Fri May 28 23:02:58 2021

[I/ntp] 1622214178
[I/ntp] year:2000, month:3, day:4
[I/ntp] hour:23, min:2, sec:58
[I/ntp] Get local time from NTP server: Fri May 28 23:02:58 2021
```

使用`ntp_sync`进行网络时钟同步。年月日时间没有同步，时分秒时间同步了。

## 解决

修改`packages\netutils\ntp\ntp.c`文件中代码。

```c
struct tm *cur_tm;
cur_tm = localtime(&cur_time);
set_time(cur_tm->tm_hour, cur_tm->tm_min, cur_tm->tm_sec);
set_date(cur_tm->tm_year + 1900, cur_tm->tm_mon + 1, cur_tm->tm_mday);
```

更改为

```c
struct tm *cur_tm;
struct tm cur_tm_t;
cur_tm = &cur_tm_t;
localtime_r(&cur_time, cur_tm);
set_time(cur_tm->tm_hour, cur_tm->tm_min, cur_tm->tm_sec);
set_date(cur_tm->tm_year + 1900, cur_tm->tm_mon + 1, cur_tm->tm_mday);
```

或者使用设备操作替换

```c
rt_device_control(rt_device_find("rtc"), RT_DEVICE_CTRL_RTC_SET_TIME, &cur_time);
```

## 问题分析

函数`localtime`调用流程。

```
graph LR
A[localtime] --> B[localtime_r]
B --> C[gmtime_r]
```

其中它返回的地址是`localtime`函数中声明的静态变量`static struct tm tmp`。

其中`cur_tm`指针指向`struct tm tmp`的地址。而后面的函数`set_time(cur_tm->tm_hour, cur_tm->tm_min, cur_tm->tm_sec);`会调用`localtime`函数，同时更改静态变量的值，同步更新`cur_tm->tm_year`等值。造成set_date函数中参数变化，影响年月日的设置。

使用`localtime_r`函数，将值保存在声明的局部变量，可修复bug。

`set_time`中包含`localtime()`,影响`cur_tm`指针指向的变量。
```c
rt_err_t set_time(rt_uint32_t hour, rt_uint32_t minute, rt_uint32_t second)
{
    time_t now;
    struct tm *p_tm;
    struct tm tm_new;
    rt_device_t device;
    rt_err_t ret = -RT_ERROR;

/* get current time */
    now = time(RT_NULL);

/* lock scheduler. */
    rt_enter_critical();
    /* converts calendar time into local time. */
    p_tm = localtime(&now);
    /* copy the statically located variable */
    rt_memcpy(&tm_new, p_tm, sizeof(struct tm));
    /* unlock scheduler. */
    rt_exit_critical();

/* update time. */
    tm_new.tm_hour = hour;
    tm_new.tm_min  = minute;
    tm_new.tm_sec  = second;

/* converts the local time into the calendar time. */
    now = mktime(&tm_new);

device = rt_device_find("rtc");
    if (device == RT_NULL)
    {
        return -RT_ERROR;
    }

/* update to RTC device. */
    ret = rt_device_control(device, RT_DEVICE_CTRL_RTC_SET_TIME, &now);

return ret;
}
```