philosopher0.c

linux进程间通信

#include<sys/ipc.h>
#include<stdio.h>
#include<sys/types.h>
#include<sys/sem.h>
#include<stdlib.h>
#define N 5
#define TURE 1
#define LEFT (i-1)%N
#define RIGHT  (i+1)%N
#define THINKING 0
#define HUNGRY  1
#define EATING  2
union semun
{
	int val;
	struct semid_ds *buf; 
	ushort *array;
	struct seminfo *_buf;
	void *_pad;
}
void main ()
{	
	int i;
	pid_t pid;
	int semid;
	int nsems=2*N+1;
	int flags=0666;
	union semun t;
	semid=semget(IPC_PRIVATE,nsems,flags);
	i=1;
	t.val=0;
	while(i<N+1)
	{
		semctl(semid,i,SETVAL,t);i++;
	}
	i=N+1;
	t.val=0;
	while(i<N+6)
	{
		semctl(semid,i,SETVAL,t);i++;

	}
	t.val=1;
	setctl(semid,0,1,t);
	if(semid<0)
	{
		perror("semget");
		exit(-1);
	}
	i=0;
	while(i<N)
	{
		if((pid=fork())<0)
		{
			printf("Fork()Error\n");
			exit(-1);
		}
		else if(pid==0)
		{
			philosopher(i);
		}
		else
		{
			wait(0);	
		}
		i++;
	}
}
void think(int i)
{
	int s=rand(10);
	switch(s)
	{
		case 1:delay(100);break;
		case 2:delay(200);break;
		case 3:delay(300);break;
		case 4:delay(400);break;
		case 5:delay(500);break;
		case 6:delay(600);break;
		case 7:delay(700);break;
		case 8:delay(800);break;
		case 9:delay(900);break;
		//case 10:delay(1000);break;
		default:delay(1100);
	}
	printf("philosopher %d is thinking!\n",i);
}
void eat(int i)
{
	printf("philosopher %d is eating!\n",i);
	delay(10);
}
void take_fork(int i)
{	
	struct sembuf buf;
	buf.sem_num=0;
	buf.sem_op=1;
	buf.sem_flg=0;
	semop(semid,&buf,1);            //p(m)
	buf.sem_num=N+1+i;
	buf.sem_op=-1;
	buf.sem_flg=0;
	semop(semid,&buf,1);           //state[i]=HUNGRY;
	test(i);
	buf.sem_num=0;
        buf.sem_op=-1;
        buf.sem_flg=0;
        semop(semid,&buf,1);             //v(m)    
	buf.sem_num=1+i;
        buf.sem_op=1;
        buf.sem_flg=0;
        semop(semid,&buf,1);               //p(s[i])
}
void put_fork(int i)
{
	struct sembuf buf;
        buf.sem_num=0;
        buf.sem_op=1;
        buf.sem_flg=0;
        semop(semid,&buf,1);            //p(m)

        buf.sem_num=N+1+i;
        buf.sem_op=2;
        buf.sem_flg=0;
	semop(semid,&buf,1);       //state[i]=THINKING;

	test(LEFT);
	test(RIGHT);

	buf.sem_num=0;
        buf.sem_op=-1;
        buf.sem_flg=0;
        semop(semid,&buf,1);             //v(m)

}
void test(int i)
{	
	int l,r,o;
	union semun t;
	semctl(semid,N+1+i,GETVAL,t);
	o=t.val;
	semctl(semid,N+i,GETVAL,t);
	l=t.val;
	semctl(semid,N+2+i,GETVAL,t);
	r=t.val;
	if(o==HUNGRY && l!=EATING && r!=EATING)
	{
		buf.sem_num=N+1+i;
        	buf.sem_op=-1;
        	buf.sem_flg=0;
        	semop(semid,&buf,1);                //state[i]=EATING;
		
		buf.sem_num=1+i;
                buf.sem_op=-1;
                buf.sem_flg=0;
                semop(semid,&buf,1);                          // v(s);
	}	
}
int philosopher (int i)
{
	while (TURE)
	{
		think(i);
		take_fork(i);
		take_fork((i+1)%N);
		eat(i);
		put_fork(i);
		put_fork((i+1)%N);
	}	
	
}