pthread_mutex

#include "stdio.h"
#include "string.h"
#include "pthread.h"
#include "unistd.h"

int counter;
pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;/*定义并初始化互斥锁*/

void *update(void *vptr)
{
    int i,val;

    while(1)
    {
        pthread_mutex_lock(&counter_mutex);/*上锁*/
        val = counter;
        printf("%x: %d\n",(unsigned int)pthread_self(),val+1);
        counter = val + 1;
        pthread_mutex_unlock(&counter_mutex);/*开锁*/
        sleep(1);
    }

    return NULL;
}

int main(int argc, char *argv[])
{
    pthread_t tha,thb;

    pthread_create(&tha,NULL,&update,NULL);/*创建两个线程，调用同一个函数*/
    pthread_create(&thb,NULL,&update,NULL);

    pthread_join(tha,NULL);
    pthread_join(thb,NULL);

    return 0;
}

编      译：gcc -o mutex  pthread_mutex.c -l pthread
运行结果：
b7f42b90: 1
b7541b90: 2
b7f42b90: 3
b7541b90: 4
b7f42b90: 5
b7541b90: 6
b7f42b90: 7
b7541b90: 8
。
。
。

Tips:
可以将lock和unlock两句注释掉，对比看下运行结果--