求助：如何在串口接收线程中调度其他线程？

#include <rtthread.h>
#include <rtdevice.h>
#include <board.h>
#define THREAD_PRIORITY         25
#define THREAD_STACK_SIZE       512
#define THREAD_TIMESLICE        10
/* 配置 LED 灯引脚 */
#define LED_PIN            PIN_LED_R
#define LED_PIN1        PIN_LED_B
#define UART_NAME       "uart2"      /* 串口设备名称 */
/* 邮箱控制块 */
static struct rt_mailbox mb;
/* 用于放邮件的内存池 */
static char mb_pool[128];
static char mb_str1[] = "open";
static char mb_str2[] = "close";
static char mb_str3[] = "over";
/* 用于接收消息的信号量 */
static struct rt_semaphore rx_sem;
static rt_device_t serial;
/* 互斥量控制块 */
static struct rt_mutex static_mutex;
/* 接收数据回调函数 */
static rt_err_t uart_input(rt_device_t dev, rt_size_t size)
{
    /* 串口接收到数据后产生中断，调用此回调函数，然后发送接收信号量 */
    rt_sem_release(&rx_sem);
    return RT_EOK;
}
static void serial_thread_entry(void *parameter)
{
    //rt_uint8_t result = 2;
    //rt_uint32_t count = 0;
     /* 设置 LED 引脚为输出模式 */
    rt_pin_mode(LED_PIN, PIN_MODE_OUTPUT);
    rt_pin_mode(LED_PIN1, PIN_MODE_OUTPUT);
    rt_pin_write(LED_PIN, PIN_HIGH);
    rt_pin_write(LED_PIN1, PIN_HIGH);
    char ch = 0;
    while (1)
    {
        /* 阻塞等待接收信号量，等到信号量后再次读取数据 */
        rt_sem_take(&rx_sem, RT_WAITING_FOREVER);
        /* 从串口读取一个字节的数据，没有读取到则等待接收信号量 */
        if (rt_device_read(serial, -1, &ch, 1) != 1) //pos用不到，无效参数，所以就把他赋个-1，方便代码理解，成功返回1
        {
            continue;
        }
        //rt_device_write(serial, 0, &ch, 1); //从第0位开始发（其实只有一个，无妨）
        if(ch == '0')
        {
            /* 发送mb_str1地址到邮箱中 */
            rt_mb_send(&mb, (rt_uint32_t)&mb_str1);
            rt_pin_write(LED_PIN1, PIN_LOW);
            //rt_kprintf("result = %d\n", result);
            //rt_thread_mdelay(10000);
        }
        else if(ch == '1')
        {
            /* 发送mb_str2地址到邮箱中 */
            rt_mb_send(&mb, (rt_uint32_t)&mb_str2);
            rt_pin_write(LED_PIN1, PIN_HIGH);
            //rt_thread_mdelay(10000);
        }
    }
}
ALIGN(RT_ALIGN_SIZE) // 4个字节对齐
static char thread1_stack[1024];
static struct rt_thread thread1;
/* 线程1入口 */
static void thread1_entry(void *param)
{
    char *str;
    rt_uint32_t count = 0;
     /* 设置 LED 引脚为输出模式 */
    rt_pin_mode(LED_PIN, PIN_MODE_OUTPUT);
    while (1)
    {
        //rt_mutex_take(&static_mutex, RT_WAITING_FOREVER);
        rt_mb_recv(&mb, (rt_ubase_t *)&str, RT_WAITING_FOREVER);
        if(str == mb_str1)
        {
            /* LED 灯亮 */
            rt_pin_write(LED_PIN, PIN_LOW);
        }
        else if(str == mb_str2)
        {
            rt_pin_write(LED_PIN, PIN_HIGH);
        }
    }
}
static int uart_sample()
{
    rt_err_t result;
    /* 初始化一个mailbox */
    result = rt_mb_init(&mb,
                        "mbt",                      /* 名称是mbt */
                        &mb_pool[0],                /* 邮箱用到的内存池是mb_pool */
                        sizeof(mb_pool) / sizeof(rt_ubase_t), /* 邮箱中的邮件数目,sizeof(rt_ubase_t)表示指针大小 */
                        RT_IPC_FLAG_PRIO);          /* 采用PRIO方式进行线程等待 */
    if (result != RT_EOK)
    {
        rt_kprintf("init mailbox failed.\n");
        return -1;
    }
    rt_err_t ret = RT_EOK;
    /* 查找串口设备 */
    serial = rt_device_find(UART_NAME);
    if (!serial)
    {
        rt_kprintf("find %s failed!\n", UART_NAME);
        return RT_ERROR;
    }
    /* 初始化信号量 */
    rt_sem_init(&rx_sem, "rx_sem", 0, RT_IPC_FLAG_FIFO);
    /* 以读写及中断接收方式打开串口设备 */
    rt_device_open(serial, RT_DEVICE_OFLAG_RDWR | RT_DEVICE_FLAG_INT_RX);
    /* 设置接收回调函数 */
    rt_device_set_rx_indicate(serial, uart_input);
    /* 创建 serial 线程 */
    rt_thread_t thread = rt_thread_create("serial", serial_thread_entry, RT_NULL, 1024, 25, 10);
    /* 创建成功则启动线程 */
    if (thread != RT_NULL)
    {
        rt_thread_startup(thread);
    }
    else
    {
        ret = RT_ERROR;
    }
    return ret;
    /* 初始化线程1，名称是thread1，入口是thread1_entry */
    rt_thread_init(&thread1,
                   "thread1",
                   thread1_entry,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack),
                   5, THREAD_TIMESLICE);
    rt_thread_startup(&thread1);
    return 0;
}
/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(uart_sample, uart device sample);