1. Final Review David Ferry, Chris Gill
CSE 522S - Advanced Operating Systems
Washington University in St. Louis
St. Louis, MO 63130

2. CSE 522S – Advanced Operating Systems
Exam Scope
Questions derived from slides
Split between comprehension and analysis
Studios useful for analysis & concepts
8 questions
80 minutes
10 minutes per question
Does not cover “details” slides (i.e. device drivers)
CSE 522S – Advanced Operating Systems

3. Major Concepts Pre-Midterm
Kernel execution:
Scheduling:
System calls
CFS Scheduler
Interrupt handlers
Real-Time Scheduler
Kernel threads
Kernel modules
Processes:
Process creation
Process address space
CSE 522S – Advanced Operating Systems

4. CSE 522S – Advanced Operating Systems
Exam Concepts
Signals:
Sockets:
Generation & delivery
Communication endpoint abstraction
Similarity to interrupt
Bind, listen, accept
Pipes/FIFOs:
Shared memory:
Anonymous & named
Does not use kernel
Atomicity
Same physical memory
Capacity
How to impose order?
CSE 522S – Advanced Operating Systems

5. CSE 522S – Advanced Operating Systems
Example Question #1
Imagine you are writing two programs that communicate small quantities of data: If neither process is a direct descendent of each other, is the pipe() system call or the mkfifo() system call more appropriate? Why? (4 points) Give one advantage and one disadvantage of using a shared memory region. (4 points) Suppose you initially write your programs with FIFOs, but then want to switch to sockets. What aspect of these interfaces minimizes the amount of re-writing you need to do? (2 points)
CSE 522S – Advanced Operating Systems

6. CSE 522S – Advanced Operating Systems
Example Question #2
Recall that some functions are unsafe to be used inside a signal handler. Explain why the function below is unsafe to be used in a main program as well as a signal handler: (2 pts)
int temp;
void swap( int *a, int *b){
temp = &a;
&a = &b;
&b = temp; }
Suppose you really need to call the above function as a result of a signal and cannot modify it. Give two approaches for doing so. (8 pts)
CSE 522S – Advanced Operating Systems

7. CSE 522S – Advanced Operating Systems
Example Question #3
Suppose you have one producer process passing work to multiple consumer processes through a single FIFO. The consumers try to read the FIFO continuously. What is the maximum size of each unit of work, in bytes, on a typical system? Why? (4 pts) Give an example of what might go wrong if the unit of work exceeds your limit given above. (2 pts) Propose a FIFO-based communications scheme for a single-producer, multiple-consumers scenario that supports individual units of work that is greater than this limit. (6 pts)
CSE 522S – Advanced Operating Systems