RT_ Use of thread message queue

One 、 The working mechanism of message queue

The message queue is RT_thread Another commonly used way of communication between threads , Message queuing is an extension of the mailbox .
Message queues can receive messages of varying length from threads or interrupt service routines , And cache messages in your own memory space , Other threads can read messages from the message queue and process them accordingly .

Two 、 Control block of message queue

Through the operation of message queue

The basic content is similar to that of email , I won't explain it in detail ！！！

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

/* *  Program listing ： Message queuing routines  * *  This program will create 2 A dynamic thread , A thread will receive messages from the message queue ; A thread will cancel regularly  *  Message queue sending   General and emergency messages . */
#include <rtthread.h>

/*  Message queuing control block  */
static struct rt_messagequeue mq;
/*  The memory pool used in the message queue to place messages  */
static rt_uint8_t msg_pool[2048];

ALIGN(RT_ALIGN_SIZE)
static char thread1_stack[1024];
static struct rt_thread thread1;
/*  Threads 1 Entry function  */
static void thread1_entry(void *parameter)
{
    
    char buf = 0;
    rt_uint8_t cnt = 0;

    while (1)
    {
    
        /*  Receive messages from the message queue  */
        if (rt_mq_recv(&mq, &buf, sizeof(buf), RT_WAITING_FOREVER) == RT_EOK)
        {
    
            rt_kprintf("thread1: recv msg from msg queue, the content:%c\n", buf);
            if (cnt == 19)
            {
    
                break;
            }
        }
        /*  Time delay 50ms */
        cnt++;
        rt_thread_mdelay(50);
    }
    rt_kprintf("thread1: detach mq \n");
    rt_mq_detach(&mq);
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;
/*  Threads 2 entrance  */
static void thread2_entry(void *parameter)
{
    
    int result;
    char buf = 'A';    
    rt_uint8_t cnt = 0;
    
    while (1)
    {
    
        if (cnt == 8)
        {
    
            /*  Send an emergency message to the message queue  */
            result = rt_mq_urgent(&mq, &buf, 1);
            if (result != RT_EOK)
            {
    
                rt_kprintf("rt_mq_urgent ERR\n");
            }
            else
            {
    
                rt_kprintf("thread2: send urgent message - %c\n", buf);
            }
        }
        else if (cnt >= 20)/*  send out 20 Exit after message  */
        {
    
            rt_kprintf("message queue stop send, thread2 quit\n");
            break;
        }
        else
        {
    
            /*  Send a message to the message queue  */
            result = rt_mq_send(&mq, &buf, 1);
            if (result != RT_EOK)
            {
    
                rt_kprintf("rt_mq_send ERR\n");
            }

            rt_kprintf("thread2: send message - %c\n", buf);
        }
        buf++;
        cnt++;
        /*  Time delay 5ms */
        rt_thread_mdelay(5);
    }
}

/*  Initialization of the message queue example  */
int msgq_sample(void)
{
    
    rt_err_t result;

    /*  Initialize message queue  */
    result = rt_mq_init(&mq,
                        "mqt",
                        &msg_pool[0],               /*  The memory pool points to msg_pool */
                        1,                          /*  The size of each message is  1  byte  */
                        sizeof(msg_pool),           /*  The size of the memory pool is msg_pool Size  */
                        RT_IPC_FLAG_FIFO);          /*  If there are multiple threads waiting , Allocate messages on a first come, first served basis  */

    if (result != RT_EOK)
    {
    
        rt_kprintf("init message queue failed.\n");
        return -1;
    }

    rt_thread_init(&thread1,
                   "thread1",
                   thread1_entry,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack), 25, 5);
    rt_thread_startup(&thread1);

    rt_thread_init(&thread2,
                   "thread2",
                   thread2_entry,
                   RT_NULL,
                   &thread2_stack[0],
                   sizeof(thread2_stack), 25, 5);
    rt_thread_startup(&thread2);

    return 0;
}

/*  Export to  msh  In the command list  */
MSH_CMD_EXPORT(msgq_sample, msgq sample);