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unix 互斥锁与信号量应用例子

发表于：2025-02-08 作者：千家信息网编辑

千家信息网最后更新 2025年02月08日，#include#include #include #include #include #include #define SIZE 3#define STR_SIZE 20pthread_mutex_

千家信息网最后更新 2025年02月08日unix 互斥锁与信号量应用例子

#include<pthread.h>
#include<semaphore.h>
#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<unistd.h>
#define SIZE 3
#define STR_SIZE 20
pthread_mutex_t mutex; //全局变量对main 及线程函数都可见
sem_t read_sem, write_sem; //全局变量对main 及线程函数都可见
struct _buf_
{
char* buf[SIZE];
int front, rear;
}buffer; //循环队列结构体
void thread(void)
{
while(1)
{
if(0 != sem_wait(&read_sem))
{
perror("sem_wait_0");
exit(1);
}
if(0 != pthread_mutex_lock(&mutex))
{
perror("pthread_mutex_lock_0");
exit(1);
}
fputs("output characters:\n",stdout);
fputs(buffer.buf[buffer.front],stdout);
buffer.front = (buffer.front + 1) % SIZE;
if(0 != pthread_mutex_unlock(&mutex))
{
perror("pthread_mutex_lock_0");
exit(1);
}
if(0 != sem_post(&write_sem))
{
perror("sem_wait_0");
exit(1);
}
sleep(10);
}
}
int main(void)
{
//初始化循环队列结构体
int i;
bufferbuffer.front = buffer.rear = 0;
for(i=0; i < SIZE; i++)
{
buffer.buf[i] =(char*) malloc(STR_SIZE);
}
//初始化互斥锁
//存在警告 pthread_mutexattr_t mutex_attr = PTHREAD_MUTEX_INITIALIZER;
if(0 != pthread_mutex_init(&mutex, NULL))
{
perror("pthread_mutex_init\n");
exit(1);
}
//初始化信号量
if(0 != sem_init(&read_sem, 0, 0))//linux进程间的信号共享还未能实现，参数PSHARE为0，而且还没有进行写操作没有数据可读，将参数vaule设置为0，进行阻塞
{
perror("sem_init_0\n");
exit(1);
}
if(0 != sem_init(&write_sem, 0, 2))
{
perror("sem_init_1\n");
exit(1);
}
//创建两个子线程
pthread_t thd0,thd1;
if(0 != pthread_create(&thd0,NULL,(void*)thread,NULL))
{
perror("pthread_create_0\n");
exit(1);
}
if(0 != pthread_create(&thd1,NULL,(void*)thread,NULL))
{
perror("pthread_create_1\n");
exit(1);
}
//进行写入字符操作
while(1)
{
//写信号量阻塞
if(0 != sem_wait(&write_sem))
{
perror("sem_wait_1");
exit(1);
}
//上互斥锁所进行写入操作
if(0 != pthread_mutex_lock(&mutex))
{
perror("pthread_mutex_lock_1");
exit(1);
}
fputs("pls enter 20 character:\n",stdout);
//读标准输入文件
if(NULL == fgets(buffer.buf[buffer.rear],STR_SIZE,stdin))
{
perror("fgets\n");
exit(1);
}
if(0 == strncmp("end\n",buffer.buf[buffer.rear],3))
{
printf("manual exit successfully\n");
exit(1);
}
buffer.rear = (buffer.rear+1)% SIZE;
//解互斥锁
if(0 != pthread_mutex_unlock(&mutex))
{
perror("pthread_mutex_lock_1");
exit(1);
}
if(0 != sem_post(&read_sem))
{
perror("sem_wait_1");
exit(1);
}
sleep(1);
}
return 0;
}

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