prof.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;
  sema_init(NEW_QUESTION,0);
  sema_init(CAN_ASK,1);
  sema_init(CAN_LEAVE,0);
  
  while(1){
    sema_down(NEW_QUESTION);
    sleep(1);
    printf("prof:answer question\n");
    sema_up(CAN_LEAVE);
  }
  return 0;
}