COSC 4330                   QUIZ #2                  November 17, 1998

Closed Book.   You can have one sheet of notes.

1.   Complete the following sentences: (4*10 points)

     The initial value of a mutual exclusion semaphore should

     always be _ONE_.

     A missing _V()_ semaphore operation will often cause a

     deadlock.

     Disk blocks are said to be _REUSABLE________ resources.

     A situation where processes can keep some resources while

     waiting for other resources is called a

     HOLD AND WAIT______________________________________ condition.

2.   True or False: (4*10 points)

T  ____   F  _X__  Using a test and set instruction to solve the
                   critical section problem instead of Peterson’s
                   algorithm avoids busy waits.

T  _X__   F  ____  Monitor conditions do not need to be initialized.

T  ____   F  _X__  Starvation is always the result of a deadlock.

T  ____   F  _X__   Having a circular wait is a sufficient condition
                    for deadlock.

3.   What is wrong with the following monitor procedure debiting
     a bank account?  You may assume that balance is a private
     variable within the monitor handling a specific account and
     notonhold a monitor condition within the same monitor.  (20
     points)
  
         public void synchronized debit(double amount){
                 //check if funds are already on hold
                 notonhold.wait;
                 // do the debit operation
                 balance = balance - amount;
         } // debit

	 THE  PROCEDURE DOES A WAIT ON A MONITOR CONDITION WITHOUT
	 CHECKING BEFOREHAND THAT THE WAIT IS NEEDED.  IT COULD
	 THUS WAIT FOREVER.


--IMPORTANT----IMPORTANT----IMPORTANT----IMPORTANT----IMPORTANT--
Please do not try to answer these questions by yourself BEFORE
having a clear idea of what's on the test for which you are
studying.

Materials covered in each test DO VARY from semester to semester
because the pace of the course can change, some materials are be
added and other deleted almost every semester.
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