线程调度问题，高低优先级线程不会一直占用CPU

发布于 2021-05-12 23:32:57 浏览：1349 订阅该版

用正点原子STM32F4探索者开发板，系统使用RT_THREAD V4.0.3，做DHT11温度采集实验时，定义read_temp_thread 线程为高优先级（初始编程线程未让出CPU），led_thread为低优先级，理论来说，read_temp_thread 线程会一直占用CPU，下载到板子之后发现led_thread线程会正常运行。求解答!!!
```c
/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2018-11-06     SummerGift   first version
 * 2018-11-19     flybreak     add stm32f407-atk-explorer bsp
 */

#include <rtthread.h>
#include <rtdevice.h>
#include <board.h>
#include <sensor.h>
#include <sensor_dallas_dht11.h>

#define LED0_PIN    GET_PIN(F, 9)
#define DHT11_DATA_PIN GET_PIN(G, 9)

#define THREAD_PRIORITY 15
//#define THREAD_STACK_SIZE 512
#define THREAD_TIMESLICE 5

ALIGN(RT_ALIGN_SIZE)
static char led_thread_stack[1024];
static struct rt_thread led_thread;

static char read_temp_stack[2048];
static struct rt_thread read_temp_thread;
static void led_thread_entry(void *param)
{
	 rt_pin_mode(LED0_PIN, PIN_MODE_OUTPUT);
	 while (1)
   {
        rt_pin_write(LED0_PIN, PIN_HIGH);
        rt_thread_mdelay(500);  
        rt_pin_write(LED0_PIN, PIN_LOW);
        rt_thread_mdelay(500);
	rt_kprintf("led_thread running!\n");
    }
}
static void read_temp_entry(void *param)
{
	rt_device_t dev = RT_NULL;
	struct rt_sensor_data sensor_data;
	rt_uint8_t get_data_freq = 1; /* 1Hz */
	rt_size_t res;
	
	dev = rt_device_find(param); 
	if(dev == RT_NULL)
	{
		rt_kprintf("can't find device:%s",param);
		return;
	}
	if(rt_device_open(dev,RT_DEVICE_FLAG_RDWR) != RT_EOK)
	{
		rt_kprintf("can't open the device:%c",param);
		return;
	}
	
	rt_device_control(dev,RT_SENSOR_CTRL_SET_ODR,(void *)(&get_data_freq));
	
	while(1)
	{
		res = rt_device_read(dev,1,&sensor_data,2);
		if(res != 1)
		{
			rt_kprintf("can't read the device:%c\n",param);
			return;
		}
		else
		{
			if(sensor_data.data.temp >= 0)
			{
				uint8_t temp = (sensor_data.data.temp&0xffff)>>0;
				uint8_t humi = (sensor_data.data.temp&0xffff0000)>>16;
				rt_kprintf("temp:%d,humi:%d\n",temp,humi);
			}
		}
		//rt_thread_mdelay(1000);
	}
	
}
int main(void)
{
	 rt_thread_init(&led_thread,
									"thread2",
									led_thread_entry,
									RT_NULL,
									&led_thread_stack[0],
									sizeof(led_thread_stack),
									THREAD_PRIORITY-1,THREAD_TIMESLICE);
	 rt_thread_startup(&led_thread);
  
	 rt_thread_init(&read_temp_thread,
									"read_temp",
									read_temp_entry,
									"temp_dht11",
									&read_temp_stack[0],
									sizeof(read_temp_stack),
									THREAD_PRIORITY-2,THREAD_TIMESLICE);
		rt_thread_startup(&read_temp_thread);
}

static int rt_hw_dht11_port(void)
{
    struct rt_sensor_config cfg;
    
    cfg.intf.user_data = (void *)DHT11_DATA_PIN;
    rt_hw_dht11_init("dht11", &cfg);

return RT_EOK;
}

INIT_COMPONENT_EXPORT(rt_hw_dht11_port);
```

![无标题.jpg](https://oss-club.rt-thread.org/uploads/20210512/9dbe2e74fc3c7e2511dc978538a9c526.jpg)