互斥锁

 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 #include<string.h>
 4 #include<unistd.h>
 5 #include<pthread.h>
 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
", 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
", 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
",tids[i], iRet);
36             return iRet;
37         }
38         printf("retval = %ld
", (long*)retval);
39     }
40     return 0;
41 }