C语言三个线程轮流打印数字（顺序打印）

题目：三个线程轮流打印数字，从0开始，其中：
线程1打印：0,3,6----
线程2打印：1,4,7----
线程3打印：2,5,8----
以此类推

在博客看到很多都是用Java和c++实现的，我想用c+来实现一下。
下面看代码；

#include 
#include 
#include 
#include 
#include 
#include 
#include 


int g_num;
pthread_mutex_t mutex;
pthread_cond_t cond1,cond2,cond3;

void* Func_p1(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		pthread_cond_wait(&cond1,&mutex);
		printf("---thread id: %lu , p1 num: %d \n",pthread_self(),g_num);
		pthread_mutex_unlock(&mutex);
		sleep(1);
	}
	return NULL;
}

void* Func_p2(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		pthread_cond_wait(&cond2,&mutex);
		printf("---thread id: %lu , p2 num: %d \n",pthread_self(),g_num);
		pthread_mutex_unlock(&mutex);
		sleep(1);
	}
	return NULL;
}

void* Func_p3(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		pthread_cond_wait(&cond3,&mutex);
		printf("---thread id: %lu , p3 num: %d \n",pthread_self(),g_num);
		pthread_mutex_unlock(&mutex);
		sleep(1);
	}
	return NULL;
}

void* Func_p4(void* arg)
{
	while(1)
	{
		pthread_mutex_lock(&mutex);
		++g_num;
		pthread_mutex_unlock(&mutex);
		if((g_num % 3) == 0)
			pthread_cond_signal(&cond3);
		else if((g_num % 3) == 1)
			pthread_cond_signal(&cond1);
		else if((g_num % 3) == 2)
			pthread_cond_signal(&cond2);
		sleep(1);
	}
	return NULL;
}

int main()
{
	pthread_t p1,p2,p3,p4;
	
	pthread_mutex_init(&mutex,NULL);
	pthread_cond_init(&cond1,NULL);
	pthread_cond_init(&cond2,NULL);
	pthread_cond_init(&cond3,NULL);	
	
	pthread_create(&p1,NULL,Func_p1,NULL);
	pthread_create(&p2,NULL,Func_p2,NULL);
	pthread_create(&p3,NULL,Func_p3,NULL);
	pthread_create(&p4,NULL,Func_p4,NULL);

	pthread_join(p1,NULL);
	pthread_join(p2,NULL);
	pthread_join(p3,NULL);
	pthread_join(p4,NULL);

	pthread_mutex_destroy(&mutex);
	pthread_cond_destroy(&cond1);
	pthread_cond_destroy(&cond2);
	pthread_cond_destroy(&cond3);

	return 0;
}

下面是运行结果