[理工] 一些OS題目

看板Grad-ProbAsk作者leonchoco (choco)時間12年前 (2013/11/11 22:43)推噓2(2推 0噓 15→)

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一些題目不會寫也不知從何找解答只好來請教大家 1. List four situations in which CPU scheduling decisions may take place. 2. What is the reason, from the perspective of system security that OS should not allow a process to simply disable/enable interrupt to achieve the mutual exclusion of the critical section problem? 3. 3.1 Why a non-preemptive OS cannot assign the CPU occupied by a busy-waiting process to another process? 3.2 Please use atomic operation Swap() to implement binary semaphore’s two operations (Busy-waiting is fine). 3.3 Please use block() and wakeup() to implement semaphore’s two operations with no busy waiting. 4. Use multilevel queue to design a scheduler which can distinguish I/O-bound programs from CPU-bound program. Please explain how it can achieve the goal. 5. The following code guarantees bounded-waiting mutual exclusion which is done by adding the highlighted code. Please explain how these highlighted codes may achieve bounded-waiting mutual exclusion. do{ waiting[i] = TRUE; key=TRUE; while( waiting[i] && key ) key = TestAndSet( &lock ); waiting[i] = FALSE; // critical section j = ( i+1 ) % n; While( ( j!=i ) && !waiting[j] ) j = ( j+1 ) % n; if( j == i ) lock = FALSE; else waiting[j] = FALSE; // remainder section } while( TRUE ); 6. Illustrate the priority inversion problem and its solution. 7. Write down a code in which a parent process (P0) will create two child process ( P1 and P2 ) such that P0 can send data to P1 via a pipe, P1 can send data to P2 via a pipe, P2 can send data to P0 via a pipe. -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 218.161.96.202

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