《操作系统教学资料》Operating System Review Problems.docVIP

Operating System Review Problems What is a process？ Please draw a process state transition diagram with nine states in Unix SVR4? Illustrated some scenarios where process switch occur? Suppose there are three processes running in an operating system with multithreading as following: Process ID Threads A T11, T12 B T21, T22 C T31, T32 If the multithreading is supported by user-level implementation and thread T11 is blocked, which thread may be scheduled to run next? If the multithreading is supported by kernel-level implementation, which thread may be scheduled to run next? What is race condition? Give a program implementation to demonstrate the mutual exclusion enforced by Test and Set (or exchange) instruction or by semaphore? Consider the following program: boolean blocked[2]; int turn; void P(int id) { while (true) { blocked[id] = true; while (turn != id){ while (blocked[1-id]) /* do nothing */; turn = id; } /* critical section */ blocked[id] = false; /* remainder */ } } void main() { blocked[0] = false; blocked[1] = false; turn = 0; parbegin(P(0), P(1)); } This software segment is the solution to the mutual exclusion problem for two processes. Find a counterexample(反例) that demonstrates that this solution is incorrect. 考虑进程0执行到blocked[id] = true这个语句是发生了进程切换，操作系统调度进程1运行。这种情况下会导致进程0和进程1同时进入临界区。 Give a solution to bounded producer-consumer problem with semaphore. What is deadlock? Banker algorithms? Safe state/unsafe state Address mapping in paging system: What is TLB? Page replacement algorithms (Optimal/LRU/FIFO/CLOCK) in paging system. LRU: Replaces the page that has not been referenced for the longest time By the principle of locality, this should be the page least likely to be referenced in the near future Each page could be tagged with the time of last reference. This would require a great deal of overhead CLOCK: Additional bit called a use bit When a page is first loaded in memory, the use bit is