问题1:
Using only a single timer (either alarm or the higher precision setitimer) provide a set of functions that allows a process to set any number of timers.
问题2:
 重新编写sleep函数,使之避免消除对以前闹钟信号的影响.

这什么意思？是不是要code? 满足你。
int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
{
        register unsigned long i, j;
        int k;

        i = tvtojiffies(&value->it_interval);
        j = tvtojiffies(&value->it_value);
        if (ovalue && (k = do_getitimer(which, ovalue)) real_timer);
                        current->it_real_value = j;
                        current->it_real_incr = i;
                        if (!j)
                                break;
                        if (j > (unsigned long) LONG_MAX)
                                j = LONG_MAX;
                        i = j + jiffies;
                        current->real_timer.expires = i;
                        add_timer(¤t->real_timer);
                        break;
                case ITIMER_VIRTUAL:
                        if (j)
                                j++;
                        current->it_virt_value = j;
                        current->it_virt_incr = i;
                        break;
                case ITIMER_PROF:
                        if (j)
                                j++;
                        current->it_prof_value = j;
                        current->it_prof_incr = i;
                        break;
                default:
                        return -EINVAL;
        }
        return 0;
}

/* SMP: Again, only we play with our itimers, and signals are SMP safe
 *      now so that is not an issue at all anymore.
 */
asmlinkage long sys_setitimer(int which, struct itimerval *value,
                              struct itimerval *ovalue)
{
        struct itimerval set_buffer, get_buffer;
        int error;

        if (value) {
                if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
                        return -EFAULT;
        } else
                memset((char *) &set_buffer, 0, sizeof(set_buffer));

        error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : 0);
        if (error || !ovalue)
                return error;

        if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
                return -EFAULT;
        return 0;
}

不写程序
唯一一个计时器设定为最小时间间隔T
基本思路是使用一个timer链表，每个节点保存计时结果
每个T时间到，就给每一个节点的计数减一，如果出现0的，就必须
处理一次定时事件，然后删除这个节点