互斥量

 1 #include <stdio.h>
 2 #include <unistd.h>
 3 #include <pthread.h>
 4  
 5 int a = 200;
 6 int b = 100;
 7 pthread_mutex_t lock;
 8  
 9 void* ThreadA(void*)
10 {
11 pthread_mutex_lock(&lock);          //锁
12 a -= 50;
13 sleep(5);                                      //执行到一半 使用sleep 放弃cpu调度
14 b += 50;
15 pthread_mutex_unlock(&lock);
16 }
17  
18 void* ThreadB(void*)
19 {
20 sleep(1);                            //放弃CPU调度 目的先让A线程运行。
21 pthread_mutex_lock(&lock);
22 printf("%d\n", a + b);
23 pthread_mutex_unlock(&lock);
24 }
25  
26 int main()
27 {
28 pthread_t tida, tidb;
29 pthread_mutex_init(&lock, NULL);
30 pthread_create(&tida, NULL, ThreadA, NULL);
31 pthread_create(&tidb, NULL, ThreadB, NULL);
32 pthread_join(tida, NULL);
33 pthread_join(tidb, NULL);
34 return 1;
35 }

程序执行结果

300