课程名称︰作业系统 课程性质︰必修 课程教师︰薛智文 开课学院：电资学院 开课系所︰资工系 考试日期（年月日）︰2010.12.2 考试时限（分钟）：180 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 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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