1 #include
     
       2 #include
      
        3 #include
       
         4 #include
        
          5 #include
         
           6 pthread_mutex_t mutex_x = PTHREAD_MUTEX_INITIALIZER; 7 int total_ticket_num = 20; 8 void *sell_ticket(void *arg) { 9     for (int i = 0; i < 20; i++) {10         pthread_mutex_lock(&mutex_x);11         if (total_ticket_num > 0) {12             sleep(1);13             printf("sell the %dth ticket\n", 21 - total_ticket_num);14             total_ticket_num--;15         }16         pthread_mutex_unlock(&mutex_x);17     }18     return 0;19 }20 int main() {21     int iRet;22     pthread_t tids[4];23     int i = 0; for (i = 0; i < 4; i++) {24         int iRet = pthread_create(&tids[i], NULL, &sell_ticket, NULL);25         if (iRet) {26             printf("pthread_create error, iRet=%d\n", iRet);27             return iRet;28         }29     }30     sleep(30);31     void *retval;32     for (i = 0; i < 4; i++) {33         iRet = pthread_join(tids[i], &retval);34         if (iRet) {35             printf("tid = %d,join error, iRet=%d\n",tids[i], iRet);36             return iRet;37         }38         printf("retval = %ld\n", (long*)retval);39     }40     return 0;41 }