kernel-sample/zh/mutex_sample.c

/*
 * Copyright (c) 2006-2022, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2018-08-24     yangjie      the first version
 */

/*
 * 程序清单：互斥锁例程
 *
 * 互斥锁是一种保护共享资源的方法。当一个线程拥有互斥锁的时候，
 * 可以保护共享资源不被其他线程破坏。线程1对2个number分别进行加1操作
 * 线程2也会对2个number分别进行加1操作。使用互斥量保证2个number值保持一致
 */
#include <rtthread.h>

#define THREAD_PRIORITY         8
#define THREAD_TIMESLICE        5

/* 指向互斥量的指针 */
static rt_mutex_t dynamic_mutex = RT_NULL;
static rt_uint8_t number1, number2 = 0;

ALIGN(RT_ALIGN_SIZE)
static char thread1_stack[1024];
static struct rt_thread thread1;
static void rt_thread_entry1(void *parameter)
{
    while (1)
    {
        /* 线程1获取到互斥量后，先后对number1、number2进行加1操作，然后释放互斥量 */
        rt_mutex_take(dynamic_mutex, RT_WAITING_FOREVER);
        number1++;
        rt_thread_mdelay(10);
        number2++;
        rt_mutex_release(dynamic_mutex);
    }
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;
static void rt_thread_entry2(void *parameter)
{
    while (1)
    {
        /* 线程2获取到互斥量后，检查number1、number2的值是否相同，相同则表示mutex起到了锁的作用 */
        rt_mutex_take(dynamic_mutex, RT_WAITING_FOREVER);
        if (number1 != number2)
        {
            rt_kprintf("not protect.number1 = %d, mumber2 = %d \n", number1, number2);
        }
        else
        {
            rt_kprintf("mutex protect ,number1 = mumber2 is %d\n", number1);
        }

        number1++;
        number2++;
        rt_mutex_release(dynamic_mutex);

        if (number1 >= 50)
            return;
    }
}

/* 互斥量示例的初始化 */
int mutex_sample(void)
{
    /* 创建一个动态互斥量 */
    dynamic_mutex = rt_mutex_create("dmutex", RT_IPC_FLAG_PRIO);
    if (dynamic_mutex == RT_NULL)
    {
        rt_kprintf("create dynamic mutex failed.\n");
        return -1;
    }

    rt_thread_init(&thread1,
                   "thread1",
                   rt_thread_entry1,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack),
                   THREAD_PRIORITY, THREAD_TIMESLICE);
    rt_thread_startup(&thread1);

    rt_thread_init(&thread2,
                   "thread2",
                   rt_thread_entry2,
                   RT_NULL,
                   &thread2_stack[0],
                   sizeof(thread2_stack),
                   THREAD_PRIORITY - 1, THREAD_TIMESLICE);
    rt_thread_startup(&thread2);
    return 0;
}

/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(mutex_sample, mutex sample);