Linux进程间的通信，信号量的使用，生产者消费者

这是简单的生产者消费者问题，只有一个缓冲区

#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<linux/sem.h>
struct sembuf buf;
int Psem(int sem_id);
int Vsem(int sem_id);
int cache;
int main()
{
	union semun arg;
	int mutexid;
	int full_sem;
	int empty_sem;
	mutexid=semget(IPC_PRIVATE,1,0666|IPC_CREAT);
	full_sem=semget(IPC_PRIVATE,1,0666|IPC_CREAT);
	empty_sem=semget(IPC_PRIVATE,1,0666|IPC_CREAT);
	arg.val=1;
	if(semctl(mutexid,0,SETVAL,arg)==-1)
	{
		perror("set the mutex error/n");
		return -1;
	}
	arg.val=0;
	if(semctl(full_sem,0,SETVAL,arg)==-1)
	{
		perror("set the full_sem error/n");
		return -1;
	}
	arg.val=1;
	if(semctl(empty_sem,0,SETVAL,arg)==-1)
	{
		perror("set the empty_sem error/n");
	}
	pid_t pid;
	pid=fork();
	//the father process
	while(1)
	{
		if(pid>0)//the producer
		{
			Psem(mutexid);
			Psem(empty_sem);
			printf("The producer are producing a product......waiting.....");
			sleep(1);
			printf("Done!/n");
			Vsem(full_sem);
			Vsem(mutexid);
		}
		else//the consumer
		{
			Psem(mutexid);
			Psem(full_sem);
			printf("The consumer are consuming a product......waiting......");
			sleep(1);
			printf("Done!/n");
			Vsem(empty_sem);
			Vsem(mutexid);
		}
	}
	return 0;
}

int Psem(int sem_id)
{
	buf.sem_num=0;
	buf.sem_op=-1;
	buf.sem_flg=SEM_UNDO;
	if(semop(sem_id,&buf,1)==-1)
	{
		perror("P failed!/n");
		return 0;
	}
	return 1;
}
int Vsem(int sem_id)
{
	buf.sem_num=0;
	buf.sem_op=1;
	buf.sem_flg=SEM_UNDO;
	if(semop(sem_id,&buf,1)==-1)
	{
		perror("V failed!/n");
		return 0;
	}
	return 1;
}