Linux下用pthread实现“生产者---消费者”的同步与互斥

最新推荐文章于 2024-05-21 15:53:52 发布

原创最新推荐文章于 2024-05-21 15:53:52 发布 · 960 阅读

2 ·

CC 4.0 BY-SA版权

文章标签：

#linux #运维 #服务器

linux 专栏收录该内容

67 篇文章

订阅专栏

本文档详细介绍了使用C++实现的生产者消费者模型，通过互斥和信号量控制，实现在缓冲区有名管道（FIFO）中的数据同步。生产者随机延迟写入，消费者随机延迟读取，展示了并发编程的基本原理。


#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <pthread.h>
#include <errno.h>
#include <semaphore.h>
#include <sys/ipc.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

#define	MYFIFO				"myfifo"	//缓冲区有名管道的名字
#define BUFFER_SIZE			3
#define UNIT_SIZE			5
#define RUN_TIME			30
#define DELAY_TIME_LEVELS	5.0


int fd;
time_t end_time;
sem_t mutex,full,avail;

void *producer(void *arg)
{
	int real_write;
	int delay_time = 0;
	
	while(time(NULL) < end_time)
	{
		delay_time = (int)(rand() * DELAY_TIME_LEVELS / (RAND_MAX) / 2.0) + 1;
		sleep(delay_time);
		//p操作信号量avail和mutex
		sem_wait(&avail);
		sem_wait(&mutex);
		printf("\n Producer: delay = %d \n",delay_time);
		
		//生产者写入数据
		if((real_write = write(fd, "hello", UNIT_SIZE)) == -1)
		{
			if(errno == EAGAIN)
			{
				printf("The FIFO has not been read yet.Please try later\n");
			}
		}
		else
		{
			printf("Write %d to the FIFO\n",real_write);
		}
		
		//V操作信号量full和mutex
		sem_post(&full);
		sem_post(&mutex);
	}
	pthread_exit(NULL);
}

void *customer(void *arg)
{
	unsigned char read_buffer[UNIT_SIZE];
	int real_read;
	int delay_time;
	
	while(time(NULL) < end_time)
	{
		delay_time = (int)(rand() * DELAY_TIME_LEVELS / (RAND_MAX)) + 1;
		sleep(delay_time);
		//P操作信号量full和mutex
		sem_wait(&full);
		sem_wait(&mutex);
		memset(read_buffer, 0, UNIT_SIZE);
		printf("\n Customer: delay = %d\n",delay_time);
		
		if((real_read = read(fd,read_buffer,UNIT_SIZE)) == -1)
		{
			if(errno == EAGAIN)
			{
				printf("No data yet \n");
			}
		}
		printf("Read %s from FIFO\n", read_buffer);
		//V操作信号量avail和mutex
		sem_post(&avail);
		sem_post(&mutex);
	}
	pthread_exit(NULL);
}

int main()
{
	pthread_t thrd_prd_id,thrd_cst_id;
	pthread_t mon_th_id;
	int ret;
	srand(time(NULL));
	end_time = time(NULL) + RUN_TIME;
	//创建有名管道
	if(access(MYFIFO,F_OK) == -1)
	{
		if((mkfifo(MYFIFO, O_CREAT | O_EXCL) < 0) && (errno != EEXIST))
		{
			printf("Cannot creat fifo\n");
			return errno;
		}
	}
	//打开
	fd = open(MYFIFO,O_RDWR);
	if(fd == -1)
	{
		printf("Open fifo error %d\n", fd);
		return fd;
	}
	//初始化信号量为1
	ret = sem_init(&mutex, 0, 1);
	//初始化avail信号量为 N
	ret +=sem_init(&avail, 0, BUFFER_SIZE);
	//初始化full信号量为 0
	ret +=sem_init(&full, 0, 0);
	
	if(ret != 0)
	{
		printf("Any semaphore initialion failed\n");
		return ret;
	}
	//创建两个线程
	ret = pthread_create(&thrd_prd_id, NULL, producer, NULL);
	if(ret != 0)
	{
		printf("Create producer thread error\n");
		return ret;
	}
	ret = pthread_create(&thrd_cst_id, NULL, customer, NULL);
	if(ret != 0)
	{
		printf("Create customer thread error\n");
		return ret;
	}
	pthread_join(thrd_prd_id,NULL);
	pthread_join(thrd_cst_id,NULL);
	close(fd);
	unlink(MYFIFO);
	return 0;
}