【练习】条件变量：创建三个线程 id号为ABC，三个线程循环打印自己的ID号，运行顺序为 ABCABC

题目：

• 创建三个线程 id号为ABC，三个线程循环打印自己的ID号，运行顺序为 ABCABC......
• 要求使用条件变量

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>//创建互斥锁
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
//条件变量创建
pthread_cond_t cond1 =PTHREAD_COND_INITIALIZER;
pthread_cond_t cond2 =PTHREAD_COND_INITIALIZER;
pthread_cond_t cond3 =PTHREAD_COND_INITIALIZER;
//限制访问机制
int flag=1;void* callback1(void* arg)
{while(1){/*************临界区**************///上锁pthread_mutex_lock(&mutex);if(flag != 1){//休眠 解锁pthread_cond_wait(&cond1,&mutex);}printf("A");flag=2;//唤醒pthread_cond_signal(&cond2);//解锁pthread_mutex_unlock(&mutex);/*************临界区**************/}pthread_exit(NULL);
}
void* callback2(void* arg)
{while(1){/*************临界区**************///上锁pthread_mutex_lock(&mutex);if(flag != 2){//休眠 解锁pthread_cond_wait(&cond2,&mutex);}printf("B");flag=3;//唤醒pthread_cond_signal(&cond3);//解锁pthread_mutex_unlock(&mutex);/*************临界区**************/}pthread_exit(NULL);}
void* callback3(void* arg)
{while(1){/*************临界区**************///上锁pthread_mutex_lock(&mutex);if(flag != 3){//休眠 解锁pthread_cond_wait(&cond3,&mutex);}printf("C\n");flag=1;//唤醒pthread_cond_signal(&cond1);//解锁pthread_mutex_unlock(&mutex);/*************临界区**************/}pthread_exit(NULL);}int main(int argc, const char *argv[])
{//练习1.创建三个线程id号为ABC,要求三个线程循环打印自己的ID号， 运行顺序为ABCAB.....pthread_t A,B,C;if(pthread_create(&A,NULL,callback1,NULL)!=0){fprintf(stderr,"pthread_create faild __%d__\n",__LINE__);return -1;}if(pthread_create(&B,NULL,callback2,NULL)!=0){fprintf(stderr,"pthread_create faild __%d__\n",__LINE__);return -1;}if(pthread_create(&C,NULL,callback3,NULL)!=0){fprintf(stderr,"pthread_create faild __%d__\n",__LINE__);                             return -1;}pthread_join(A,NULL);pthread_join(B,NULL);pthread_join(C,NULL);//销毁互斥锁pthread_mutex_destroy(&mutex);//销毁条件变量pthread_cond_destroy(&cond1);pthread_cond_destroy(&cond2);pthread_cond_destroy(&cond3);return 0;
}

运行结果：死循环输出ABC\n

ubuntu@ubuntu:04_pthread$ gcc t3.3pthread.c -pthread
ubuntu@ubuntu:04_pthread$ ./a.out 
ABC
ABC
ABC
ABC
ABC