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課程名稱︰作業系統
課程性質︰必修
課程教師︰薛智文
開課學院：電資學院
開課系所︰資工系
考試日期（年月日）︰2010.12.2
考試時限（分鐘）：180
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
Operating System
Name:_____ 902 36700 01, Fall 2010 Score:_______/110
ID:______ Midterm, December 2th, 9:10-12:10
This is an open-book and open-own-note exam. Please do answer with your own
SUCCINCT words in the order of question number in EXACTLY one given answer
sheet. You can write in Chinese and keep this paper. If you would like to
design your own project 3, send me a one-page proposal as soon as possible.
Good luck.
1.For an OS A running on a single-core machine and an OS B running on a
multicore machine, what are the main differences between A and B in terms of
OS design for synchronization?[10%]
2.For a system call issued in a virualized platform, what problem might occur?
[5%] How to solve it? [5%]
3.Describe 2 examples where OS and Architecture help each other to improve
performance.[10%]
4.Explain what race condition is.[5%] How to avoid it? [5%]
5.For some OS, there is an extra state, ZOMBIE, between RUNNING and TERMINATED.
Why do we need it? [5%] What to do with the need if we do not have it? [5%]
6.Explain why multithreading might improve performance even in a single
processor system [5%] and why it might degrade performance in a multicore
platform. [5%]
7.In class, when we show slides from notebook, it will display on the screen of
the notebook and project to the big screen. When wwe close the screen of the
notebook, the 2 screens will be off and black. In what situation, when the
screen of the notebook is close, the 2 screens are still on? [5%] Why?[5%]
8.Describe the problem for the following implementation of a critical section.
[10%] Initial: flag[i] = FALSE, flag[j] = FALSE
do{
turn = j;
flag[i] = TRUE;
while(flag[j] && turn == j);
critical section
flag[i] = false;
remainder section
}while(1);
9.Find a save sequence if any.[5%] Can request (1,1,0) by P4 be granted? [5%]
Find the maximal request of P4 that can be granted at current stage. [5%]
Allocation Need Available
ABC ABC ABC
P0 221 120 231
P1 301 500
P2 010 743
P3 302 040
P4 002 341
10.The following program uses two semaphores, mutex and delay, implementing a
critical region. What problem might occur? [5%] How to fix it with still the
same semaphores or other assumption? [10%] Initially, mutex = 1, delay = 0,
count = 0.
wait(mutex);
while(!B){
count++;
if(count > 0) signal(delay);
else signal(mutex);
wait(delay);
count--;
}
S;
if(count > 0) signal(delay);
else signal(mutex);
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