Linux进程间的通信，信号量的使用，生产者消费者

#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;
}