CS 3733 Operating Systems, Fall 2008 Exam 2 Comments

Grade distribution:

• 90-99: 0
• 80-89: 4
• 70-79: 4
• 60-69: 6
• 50-59: 6
• below 50: 2
• Average: 67

• Problem 1c:
  This is not asking about the value of the mask at a particular point in the program.
• Problem 2:
  The point here is that you can get a deadlock because the signal hander is not scheduled independently from the main program. Using a semaphore will not help. The action of the mutex is undefined if the same thread tries to lock the mutex a second time.
• Problem 4c:
  The disk access time completely swamps anything else that goes on when a page fault occurs. More than half the class used 0.01 instead of .0001. The percent sign in the problem is meaningful.
• Problem 5:
  This is the problem that gave people the most trouble. You need to explain why you agree or disagree, not just state that you do. If a statement is of the form: It is never correct and you disagree, you need to give a specific case in which it is not true.
  Part a) does not ask if there is a better way, only if this way is correct.
  If you disagree with part b), you need to say why, not just that one is better.
  For part e) you needed to show you understood what the question meant.
• Problem 5:
  Most people did fine on this through part e). After that the results varied.