linux 互斥锁应用实例

/*这是一个使用互斥锁实现两个线程之间同步实例，一个线程负责从标准输入设备中读取数据，而另一个线程则负责将读入的数据输出到标准输出设备上*/

#include <stdio.h>

#include <unistd.h>

#include <stdlib.h>

#include <pthread.h>

#include <semaphore.h>

#include <string.h>

void *thread_function(void *arg);

pthread_mutex_t work_mutex; //全局互斥锁对象，首先应该定义一个这样的互斥锁

#define WORK_SIZE 1024 //全局共享数据去

char work_area[WORK_SIZE];

int time_to_exit = 0;

int main(int argc,char *argv[])

{

int res;

pthread_t a_thread;

void *thread_result;

res = pthread_mutex_init(&work_mutex, NULL); //init mutex 初始化互斥锁

if (res != 0)

{

perror("Mutex initialization failed");

exit(EXIT_FAILURE);

}

res = pthread_create(&a_thread, NULL, thread_function, NULL);//create new thread创建新线程

if (res != 0)

{

perror("Thread creation failed");

exit(EXIT_FAILURE);

}

pthread_mutex_lock(&work_mutex); //lock the mutex 互斥锁上锁

printf("Input some text. Enter 'end' to finish\n");

while(!time_to_exit) //标志

{

fgets(work_area, WORK_SIZE, stdin); //get a string from stdin读取一行信息 pthread_mutex_unlock(&work_mutex); //unlock the mutex解锁

while(1)

{

pthread_mutex_lock(&work_mutex); //lock the mutex

if (work_area[0] != '\0') //检查读入的内容输出没有

{

pthread_mutex_unlock(&work_mutex); //unlock the mutex如果没有输出，解锁

sleep(1);

}

else

{

break;

}

}

}

pthread_mutex_unlock(&work_mutex);//解锁

printf("\nWaiting for thread to finish...\n");

res = pthread_join(a_thread, &thread_result);//等待另一个线程结束

if (res != 0)

{

perror("Thread join failed");

exit(EXIT_FAILURE);

}

printf("Thread joined\n");

pthread_mutex_destroy(&work_mutex);//销毁互斥锁

exit(EXIT_SUCCESS);

}

void *thread_function(void *arg)

{

sleep(1);

pthread_mutex_lock(&work_mutex);//上锁，抢占资源

while(strncmp("end", work_area, 3) != 0) //判断是不是结束信息end

{

printf("You input %d characters\n", strlen(work_area) -1);//时结束信心的话，就输出输入的字符个数

printf("the characters is %s",work_area);//输出输入的字符内容

work_area[0] = '\0';//设置最后以为为“\0”

pthread_mutex_unlock(&work_mutex);// 输出完成以后就解锁

sleep(1);

pthread_mutex_lock(&work_mutex);//上锁

while (work_area[0] == '\0' ) //判断第一位是不是为\0

{

pthread_mutex_unlock(&work_mutex);//解锁等待

sleep(1);

pthread_mutex_lock(&work_mutex);//上锁再次循环

}

}

time_to_exit = 1;//设置结束标志 work_area[0] = '\0';

pthread_mutex_unlock(&work_mutex); pthread_exit(0);

}

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