linux下关于多线程打印的问题

不得不说今天又遇到了一件坑爹的事情，linux下用多线程实现答应ABBABBABBABBABB....代码如下：红色部分为啃爹的部分！

#include
#include
#include
#include
#include
#include
#include
#include
sem_t sem;

void *thrd_fun1(void *arg)
{
int thrd_num=(int)arg;
while(1)
{
printf("A\n");//当驱动\n换行符会出现程序卡死现象，目前还不清楚为什么！
sem_post(&sem);
sleep(2);
}

pthread_exit(NULL);
}
void *thrd_fun2(void *arg)
{
int thrd_num=(int)arg;
int i;
while(1)
{
sem_wait(&sem);
printf("B\n");
sleep(1);
printf("B\n");
sleep(1);
}
pthread_exit(NULL);
}
int main(void)
{
pthread_t thread[2];
int no=0,res;
void *thrd_ret;
sem_init(&sem,0,0);
res=pthread_create(&thread[0],NULL,thrd_fun1,(void*)no);
if(res!=0)
{
printf("Create thread 1 failed\n");
exit(res);
}
res=pthread_create(&thread[1],NULL,thrd_fun2,(void*)no);
if(res!=0)
{
printf("Create thread 1 failed\n");
exit(res);
}
for(no=0;no<2;no++)
{
res =pthread_join(thread[no],&thrd_ret);
if(!res)
{
printf("Thread %d exit\n",no);
}
else
{
printf("Thread %d exit failed\n",no);
}
}
return 0;
}