#include<stdio.h>#include<pthread.h>#include<unistd.h>pthread_mutex_t mutex;pthread_cond_t cond;void *child (void *arg){pthread_cleanup_push(pthread_mutex_unlock,&mutex); while(1) {printf("thread1 get running \n");  printf("thread1 pthread_mutex_lock returns %d\n",pthread_mutex_lock(&mutex));  pthread_cond_wait(&cond,&mutex);  printf("thread1 condition applied\n");  pthread_mutex_unlock(&mutex);  sleep(5);  } pthread_cleanup_pop(0);}void *child (void *arg){ while(1) {sleep(3);//注释1  printf("thread2 get running \n");  printf("thread2 pthread_mutex_lock returns %d\n",pthread_mutex_lock(&mutex));  pthread_cond_wait(&cond,&mutex);  printf("thread2 condition applied\n");  pthread_mutex_unlock(&mutex);  sleep(1);  }}int main(){int tid1,tid2; printf("hello condition variable test\n"); pthread_mutex_init(&mutex,NULL); pthread_cond_init(&cond,NULL); pthread_create(&tid1,NULL,child1,NULL); pthread_create(&tid2,NULL,child1,NULL); do{    sleep(2);//此语句（注释2）和注释1的作用是使tid1有时间完成取消动作！    pthread_cancle(tid1);//没有此语句程序照样可以执行的。    sleep(2);    pthread_cond_signal(&cond);    }while(1);    sleep(100);    pthread_exit(0);}//没有回调函数 pthread_cleanup_push(pthread_mutex_unlock,&mutex);和pthread_cleanup_pop(0);//则系统将挂起在在tid2请求锁的地方.//如把注释1和注释2这两行代码不执行则child2能在child1完成取消动作前得到控制，从而顺利执行//申请锁的操作，但可能在pthread_cond_wait(&cond,&mutex);中挂起，因为其中也有申请mutex的操作//(因为在条件满足而离开pthread_cond_wait()前，mutex将重新被加锁，以和进入pthread_cond_wait()前的加锁动作对应！)
//child1给出的是标准条件变量的使用方式：回调函数保护，等待条件前解锁， pthread_cond_wait(&cond,&mutex);返回后解锁。