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
 */

/*
 * 程序清单：信号量例程
 *
 * 该例程创建了一个动态信号量，初始化两个线程，线程1在count每计数10次时，
 * 发送一个信号量，线程2在接收信号量后，对number进行加1操作
 */
#include <rtthread.h>

#define THREAD_PRIORITY 25
#define THREAD_TIMESLICE 5

/* 指向信号量的指针 */
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每计数10次，就释放一次信号量 */
 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)
 {
 /* 永久方式等待信号量，获取到信号量，则执行number自加的操作 */
 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);
 }
 }
}

/* 信号量示例的初始化 */
int semaphore_sample()
{
 /* 创建一个动态信号量，初始值是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;
}

/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(semaphore_sample, semaphore sample);