线程同步

最新推荐文章于 2025-04-21 07:00:00 发布

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最新推荐文章于 2025-04-21 07:00:00 发布

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分类专栏： Linux 文章标签： Linux

本文链接：https://blog.youkuaiyun.com/Dthinking/article/details/86513402

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本文深入探讨了线程同步机制，包括信号量、互斥锁、条件变量和读写锁的使用方法。通过具体示例代码，展示了如何利用这些机制确保多线程环境下数据的一致性和安全性。

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线程同步：信号量互斥锁条件变量读写锁

线程安全：

1、同步

2、线程安全的函数

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<assert.h>
#include<pthread.h>
#include<semaphore.h>
//strtok_r 可重入的函数
void* thread_fun(void *arg)
{

    char str[]={"a b c d e f g h k l"};
    char *ss=NULL;
    char *s=strtok_r(str," ",&ss);
    //char *s=strtok(str," ");//不安全的线程函数
    while(s !=NULL)
    {
	printf("s=%s\n",s);
	sleep(1);
	s=strtok_r(NULL," ",&ss);
	//s=strtok(NULL," ");
    }
    
}


int main()
{
    pthread_t id;
    
    
	pthread_create(&id,NULL,thread_fun,NULL);//创建线程,已经被创建出来的线程和主线程并发
	char arr[]={"1 2 3 4 5 6 7 8 9"};
	char *dd=NULL;
	char *p=strtok_r(arr," ",&dd);
	//char *p=strtok(arr," ");

	while(p!=NULL)
	{
	    printf("p=%s\n",p);
	    sleep(1);
	    p=strtok_r(NULL," ",&dd);
	    //p=strtok(NULL," ");
	}
    

    

	pthread_join(id,NULL);
    
    

    exit(0);

}

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<assert.h>
#include<pthread.h>



pthread_mutex_t mutex;//定义互斥锁
//sem_t sem;//定义信号量

void *thread_fun(void* arg)

{
    int i=0;
    for(;i<5;i++)
    {
	//sem_wait(&sem);//p操作 获取资源
	pthread_mutex_lock(&mutex);//上锁
	write(1,"B",1);
	int n =rand()%3;
	sleep(n);
	write(1,"B",1);
	//sem_post(&sem);//v操作 释放资源
	pthread_mutex_unlock(&mutex);//解锁
	n=rand()%3;
	sleep(n);
    }
}
int main()
{
    pthread_t id;//
    //sem_init(&sem,0,1);初始化信号量
    pthread_mutex_init(&mutex,NULL);//初始化互斥锁
    pthread_create(&id,NULL,thread_fun,NULL);//

    int i=0;
    for(;i<5;i++)
    {
	//sem_wait(&sem);
	pthread_mutex_lock(&mutex);
	write(1,"A",1);
	int n =rand()%3;
	sleep(n);
	write(1,"A",1);
	//sem_post(&sem);
	pthread_mutex_unlock(&mutex);
	n=rand()%3;
	sleep(n);
    }
    pthread_mutex_destroy(&mutex);
    pthread_join(id,NULL); //等待子线程结束，否则主线程结束后 直接结束程序
    exit(0);
}

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<assert.h>
#include<pthread.h>
#include<semaphore.h>

pthread_mutex_t mutex;
pthread_cond_t cond;//条件变量

void *fun1(void *arg)
{
    char *s=(char*)arg;
    while(1)
    {
	pthread_mutex_lock(&mutex);
	pthread_cond_wait(&cond,&mutex);
	pthread_mutex_unlock(&mutex);

	printf("fun1 read:%s\n",s);
	if(strncmp(s,"end",3)==0)
	{
	    break;
	}
    }
}
void *fun2(void *arg)
{
    char *s=(char*)arg;
    while(1)
    {
	pthread_mutex_lock(&mutex);
	pthread_cond_wait(&cond,&mutex);
	pthread_mutex_unlock(&mutex);

	printf("fun2 read:%s\n",s);
	if(strncmp(s,"end",3)==0)
	{
	    break;
	}
    }
}
int main()
{
    pthread_t id[2];
    char buff[128]={0};
    pthread_cond_init(&cond,NULL);
    pthread_mutex_init(&mutex,NULL);
    pthread_create(&id[0],NULL,fun1,(void *)buff);
    pthread_create(&id[1],NULL,fun2,(void *)buff);
    while(1)
    {
	fgets(buff,128,stdin);
	if(strncmp(buff,"end",3)==0)
	{
	    pthread_mutex_lock(&mutex);
	    pthread_cond_broadcast(&cond);//广播式唤醒
	    pthread_mutex_unlock(&mutex);

	    break;
	}
	else
	{

	    pthread_mutex_lock(&mutex);
	    pthread_cond_signal(&cond);//一次只能有一个线程被唤醒
	    pthread_mutex_unlock(&mutex);
	}
    }

    pthread_join(id[0],NULL);
    pthread_join(id[1],NULL);
    exit(0);



}