thread.c

liunx下的shell实现；进程、线程同步的实现；I/O系统调用的比较（mmap）——操作系统的课程设计

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <semaphore.h>
#define N 6

sem_t t[6];
int tindex=0;
void
update_msg (int index)
{
	int sval;
	switch (index)
	{
	case 0:
		printf ("I am process p%d\n", index + 1);
		sem_post (&t[0]);
		sem_post (&t[0]);
		break;
	case 1:
		sem_wait (&t[0]);
		printf ("I am process p%d\n", index + 1);
		sem_post (&t[1]);
		sem_post (&t[1]);
		break;
	case 2:
		sem_wait (&t[0]);
		printf ("I am process p%d\n", index + 1);
		sem_post (&t[2]);
		break;
	case 3:
		sem_wait (&t[1]);
		printf ("I am process p%d\n", index + 1);
		sem_post (&t[3]);
		break;
	case 4:
		sem_wait (&t[1]);
		sem_wait (&t[2]);
		printf ("I am process p%d\n", index + 1);
		sem_post (&t[4]);
		break;
	case 5:
		sem_wait (&t[3]);
		sem_wait (&t[4]);
		printf ("I am process p%d\n", index + 1);
		break;
	default:
		break;
	}
}
void *printmsg (void* data)
{
	int index=*((int*)data);
	int i;
	long j;
	
	for(i=0;i<3;i++)
	{
		update_msg (index);
		for(j=0;j<1000000;j++);
	}
}

int
main (int argc, char *argv[])
{
	int i;
	int num[N];
	pthread_t thres[N];
	for (i = 0; i < N; i++)
	{
		sem_init (&t[i], 0, 0);
		num[i]=i;
	}
	for (i = 0; i < N; i++)
		pthread_create (&thres[i], NULL,printmsg,(void *)&num[i]);
	for (i = 0; i < N; i++)
		pthread_join(thres[i],NULL);
	printf ("main: we're done\n");
	return 0;
}