student.c

MINIX操作系统的内核修改补丁

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

extern int sema_init(int semaphore_number, int start_value);
extern int sema_down(int semaphore_number);
extern int sema_up(int semaphore_number);
extern int sema_release(int semaphore_number);

#define NEW_QUESTION 0
#define CAN_ASK      1
#define CAN_LEAVE    2


int main(void)
{
	int i;
  while(1){
    sema_down(CAN_ASK);
    printf("student %d: ask question\n",getpid());
    sema_up(NEW_QUESTION);

    sema_down(CAN_LEAVE);
    printf("student %d: leave room\n",getpid());
    sema_up(CAN_ASK);
  }
	sema_release(0);
	sema_release(1);
	sema_release(2);
  return 0;
}