linux多线程编程之互斥锁

　　多线程并行运行，共享同一种互斥资源时，需要上互斥锁来运行，主要是用到pthread_mutex_lock函数和pthread_mutex_unlock函数对线程进行上锁和解锁

　　下面是一个例子：

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

#define THREAD_NUMBER        3            /* 线程数 */
#define REPEAT_NUMBER        3            /* 每个线程的小任务数 */
#define DELAY_TIME_LEVELS 10.0         /*小任务之间的最大时间间隔*/
pthread_mutex_t mutex;

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

int main(void)
{
     pthread_t thread[THREAD_NUMBER];
     int no = 0, res;
     void * thrd_ret;
    
     srand(time(NULL));
     /* 互斥锁初始化 */
     pthread_mutex_init(&mutex, NULL);
     for (no = 0; no < THREAD_NUMBER; no++)
     {
          res = pthread_create(&thread[no], NULL, thrd_func, (void*)no);//创建多个线程
          if (res != 0)
          {
              printf("Create thread %d failed ", no);
              exit(res);
          }
     }    
     printf("Create treads success Waiting for threads to finish... ");
     for (no = 0; no < THREAD_NUMBER; no++)
     {
          res = pthread_join(thread[no], &thrd_ret);
          if (!res)
          {
          printf("Thread %d joined ", no);
          }
          else
          {
              printf("Thread %d join failed ", no);
          }
          /* 互斥锁解锁 */
          pthread_mutex_unlock(&mutex);
     }    
     pthread_mutex_destroy(&mutex);         
     return 0;       
}

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