os_exp1

osexpp.c

SYSCALL_DEFINE3(setnice,pid_t,pid,int,flag,int,nicevalue)
{
        int errono = 0;
        struct pid * temp_pid=find_get_pid(pid);
        struct task_struct *p=pid_task(temp_pid,PIDTYPE_PID); 
        if(p->pid != pid)
        {
        errono=-EFAULT;
        return errono;  
        }
        switch(flag)
        {
         case(0):       // Read nice value
                {
                printk("the process's nice is : %d \n",task_nice(p));
                break;  
                }
         case(1):       // Set nice value
                {
                set_user_nice(p,nicevalue);
                printk("change nice to: %d \n",task_nice(p));
                 break;
                }
        default:       // wrong flag value
                {
                errono=-EFAULT;
                return errono;
                }
        }
         return errono;
}