Concurrent Programming (19530-V)

Dr. Richard S. Hall WS 01/02

- Übung 6 -

Assigned: 4.12.2001
Due: 11.12.2001

1. Exercise

a) How do you create a mutual exclusion lock with a semaphore?
b) In the Java Semaphore class from the lecture, why is it okay to call notify() instead of notifyAll() in up()?
c) What causes the nested monitor problem?
d) What causes deadlock?
e) How does ordering the acquisition of resource types avoid deadlock?

2.  Exercise

Using the Java code for Counter and Semaphore from Lecture 6, implement a StrictCounter (a counter that does not ignore increments/decrements) using semaphores rather than condition synchronization.


      
 



     
3.  Exercise                      
      


      
      
      
The figure below depicts a maze. Write a description of the
 maze in FSP and then use the deadlock analysis of LTSA to find the shortest
 path out of the maze starting from any position.

      
maze  
(Hint: At each number in the maze, a directional
action (i.e., north, south, east, west) can be used to indicate an allowed path to another number.)