Homework Assignment 7

Homework Assignment 7

• Silberschatz et al, Operating System Concepts, 9th edition, Chapter 7, Deadlock
  1. In a real computer system, neither the resources available nor the demands ofprocesses for resources are consistent over longperiods (months). Resources break or are replaced, new processes come and go, new resources are bought and added to the system. If deadlock is controlled by the banker's algorithm, which of the following changes can be made safely (without introducing the possibility of deadlock), and underwhat circumstances?
     1. Increase Available (new resources added)
     2. Decrease Available (resource permanently removed from system)
     3. Increase Max for one process (the process needs more resources than allowed, it may want more)
     4. Decrease Max for one process (the process decides it does not need that many resources)
     5. Increase the number of processes
     6. Decrease the number of processes

  2. Consider a system consisting of seven resources of the same type that are shared by three processes, each of which needs at most three resources. Show that the system is deadlock-free.

  3. Consider the following snapshot of a system:

     Process		Allocation					Max					Available
     		A	B	C	D		A	B	C	D		A	B	C	D
     P0		0	0	1	2		0	0	1	2		1	5	2	0
     P1		1	0	0	0		1	7	5	0
     P2		1	3	5	4		2	3	5	6
     P3		0	6	3	2		0	6	5	2
     P4		0	0	1	4		0	6	5	6

     Answer the following questions using the banker's algorithm:

     1. What is the content of the matrix Need?
     2. Is the system in a safe state?
     3. If a request from process P1 arrives for (0,4,2,0), can the request be granted immediately?