linux 多线程生产者和消费者问题

最新推荐文章于 2024-06-05 14:41:14 发布

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最新推荐文章于 2024-06-05 14:41:14 发布

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分类专栏： linux

本文链接：https://blog.youkuaiyun.com/wangyulinyy/article/details/22652919

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本文介绍了一个使用条件变量实现的多线程生产者-消费者问题的实例。通过C语言编程，展示了如何利用pthread库中的条件变量进行线程间的同步控制。

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最近实习学习了点多线程的课程，老师让写个多线程的应用，本来自己想码一个银行排队请求服务的问题，奈何调试了下无果，贴下这个用条件变量实现的多线程问题吧。

用到的条件变量的函数：

条件变量数据结构： pthread_cond_t

初始化条件变量： pthread_con_init(pthread_cond_t *)

阻塞等待条件变量: pthread_con_wait

通知等待该条件变量的第一个线程： pthread_cond_sigal

通知等待该条件变量的所有线程： pthread_cond_broadcast

销毁条件变量状态： pthread_cond_destroy

the result screenshot

下面贴下书中码的代码：

/*
 * =====================================================================================
 *
 *       Filename:  pthread_cond_exmaple.c
 *
 *    Description:  the product and the consumer 
 *
 *        Version:  1.0
 *        Created:  03/30/2014 06:47:52 PM
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  wyl (), 1510178628@qq.com
 *   Organization:  
 *
 * =====================================================================================
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>

#define BUFFER_SIZE 2

struct prodcons
{
	int buffer[BUFFER_SIZE];
	pthread_mutex_t lock;
	int readpos, writepos;
	pthread_cond_t notempty;
	pthread_cond_t notfull;
};

void init(struct prodcons* prod)
{
	pthread_mutex_init(&prod->lock, NULL);
	pthread_cond_init(&prod->notempty, NULL);
	pthread_cond_init(&prod->notfull, NULL);
	prod->readpos = 0;
	prod->writepos = 0;
}

void put(struct prodcons* prod, int data)
{

	pthread_mutex_lock(&prod->lock);
	
	while((prod->writepos+1) % BUFFER_SIZE == prod->readpos)
	{
		printf("producter wait for not full\n");
		pthread_cond_wait(&prod->notfull, &prod->lock);
	}

	prod->buffer[prod->writepos] = data;
	prod->writepos++;
	if(prod->writepos >= BUFFER_SIZE)
		prod->writepos = 0;

	pthread_cond_signal(&prod->notempty);
	pthread_mutex_unlock(&prod->lock);
}

int get(struct prodcons* prod)
{
	int data;
	pthread_mutex_lock(&prod->lock);

	while(prod->writepos == prod->readpos)
	{
		printf("consumer wait for not empty\n");
		pthread_cond_wait(&prod->notempty, &prod->lock);
	}

	data = prod->buffer[prod->readpos];
	prod->readpos++;
	if(prod->readpos >= BUFFER_SIZE)
		prod->readpos = 0;

	pthread_cond_signal(&prod->notfull);
	pthread_mutex_unlock(&prod->lock);
	return data;
}

#define OVER (-1)

struct prodcons buffer;

void* producer(void* arg)
{
	int n;
	for(n=1; n<=5; ++n)
	{
		printf("producer sleep 1 second ....\n");
		sleep(1);
		printf("put the %d product\n", n);
		put(&buffer, n);
	}

	for(n=6; n<=10; ++n)
	{
		printf("producer sleep 1 second ....\n");
		sleep(3);
		printf("put the %d product\n", n);
		put(&buffer, n);
	}

	put(&buffer, OVER);
	printf("product stoped\n");
	return NULL;
}

void* consumer(void* arg)
{
	int d = 0;
	while(1)
	{
		printf("consumer sleep 2 second ....\n");
		sleep(2);
		d = get(&buffer);
		printf("get the %d product\n", d);
		if(d == OVER)
			break;
	}
	printf("consumer stopped\n");
	return NULL;
}

int main(int argc, char* argv[])
{
	pthread_t th_a, th_b;
	void* retval;
	init(&buffer);
	pthread_create(&th_a, NULL, producer, 0);
	pthread_create(&th_b, NULL, consumer, 0);

	pthread_join(th_a, &retval);
	pthread_join(th_b, &retval);
	printf("the retval %d\n", (int*)retval);
	return 0;

}