kernel-sample/en/semaphore_sample.c

/*
 * 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
 * 2020-10-17     Meco Man     translate to English comment
 */

/*
 * Demo: semaphore
 * This demo creates one semaphore and two threads:
 *    1) thread #1: release the semaphore
 *    2) thread #2: receive the semaphore
 *
 * read more:
 *    https://www.rt-thread.io/document/site/thread-sync/thread-sync/#semaphores
 */
 
#include <rtthread.h>

#define THREAD_PRIORITY         25
#define THREAD_TIMESLICE        5

/* semaphore handler */
static rt_sem_t dynamic_sem = RT_NULL;

ALIGN(RT_ALIGN_SIZE)
static char thread1_stack[1024];
static struct rt_thread thread1;
static void rt_thread1_entry(void *parameter)
{
    static rt_uint8_t count = 0;

    while (1)
    {
        if (count <= 100)
        {
            count++;
        }
        else
            return;

        /* count release semaphore every 10 counts */
        if (0 == (count % 10))
        {
            rt_kprintf("thread1 release a dynamic semaphore.\n");
            rt_sem_release(dynamic_sem);
        }
    }
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;
static void rt_thread2_entry(void *parameter)
{
    static rt_err_t result;
    static rt_uint8_t number = 0;
    while (1)
    {
        /* permanently wait for the semaphore; once obtain the semaphore, perform the number self-add operation */
        result = rt_sem_take(dynamic_sem, RT_WAITING_FOREVER);
        if (result != RT_EOK)
        {
            rt_kprintf("thread2 take a dynamic semaphore, failed.\n");
            rt_sem_delete(dynamic_sem);
            return;
        }
        else
        {
            number++;
            rt_kprintf("thread2 take a dynamic semaphore. number = %d\n", number);
        }
    }
}

int semaphore_sample()
{
    /* create semaphtore and its initial value is 0 */
    dynamic_sem = rt_sem_create("dsem", 0, RT_IPC_FLAG_FIFO);
    if (dynamic_sem == RT_NULL)
    {
        rt_kprintf("create dynamic semaphore failed.\n");
        return -1;
    }
    else
    {
        rt_kprintf("create done. dynamic semaphore value = 0.\n");
    }

    rt_thread_init(&thread1,
                   "thread1",
                   rt_thread1_entry,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack),
                   THREAD_PRIORITY, THREAD_TIMESLICE);
    rt_thread_startup(&thread1);

    rt_thread_init(&thread2,
                   "thread2",
                   rt_thread2_entry,
                   RT_NULL,
                   &thread2_stack[0],
                   sizeof(thread2_stack),
                   THREAD_PRIORITY - 1, THREAD_TIMESLICE);
    rt_thread_startup(&thread2);

    return 0;
}

/* export the msh command */
MSH_CMD_EXPORT(semaphore_sample, semaphore sample);