多线程 同步

/*thread_mutex.c*/
#include  <stdio.h>
#include <stdlib.h>
#include <pthread.h>

#define THREAD_NUMBER   3
#define REPEAT_NUMBER   3
#define DELAY_TIME_LEVELS   10.0

pthread_mutex_t mutex;

void *thrd_func(void *arg)
{
    int thrd_num = (int )arg;
    int delay_time = 0,count =0;
    int res;
    /**互斥上锁*/
    res = pthread_mutex_lock(&mutex);
    if(res){
        printf("Thread %d lock failed\n",thrd_num);
        pthread_exit(NULL);
    }
    printf("Thread %d is starting \n",thrd_num);
    for(count = 0; count <REPEAT_NUMBER;count++)
    {
        delay_time = (int)(rand()*DELAY_TIME_LEVELS/(RAND_MAX))+1;
        sleep(delay_time);
        printf("\tThread %d :job %d delay = %d \n",thrd_num,count,delay_time);
    }
    pthread_mutex_unlock(&mutex); // 解开互斥锁
    printf("Thread %d finished \n",thrd_num);
    pthread_exit(NULL);
}


int main(void)
{
    pthread_t thread[THREAD_NUMBER];
    int no = 0,res;
    void * thrd_ret;

    srand(time(0));
    /*互斥锁初始化*/
    pthread_mutex_init(&mutex,NULL);
    for(no =0;no < THREAD_NUMBER; no++)
    {
        /*创建多线程*/
        res = pthread_create(&thread[no],NULL,thrd_func,(void*)no);
        if(res != 0)
        {
            printf("Create thread %d failed \n",no);
            exit(res);
        }
    }

    printf("Create tread success\n Waiting for threads to finish...\n");
    for(no = 0;no <THREAD_NUMBER;no++)
    {
        /*等待线程结束*/
        res = pthread_join(thread[no],&thrd_ret);
        if(!res)
        {
            printf("Thread %d joined \n",no);
        }
        else
        {
            printf("Thread %d join failed \n",no);
        }
        /* 互斥锁解锁*/
       // pthread_mutex_unlock(&mutex);
    }
    pthread_mutex_destroy(&mutex);
    return 0;
}

使用是实验的源程序，我发现会报错，因为线程在创建的时候已经在执行了，不一定是线程0抢到了进程锁，我试了一下发现是进程2拿到了进程锁，而下面就是一直在等带进程0结束，而进程0又在等待进程2释放进程锁，所以，实验程序跑不下去了。我把释放进程锁放到了，子程序中，实验完成。