Galvin Edition 9 Exercise 7 Question 22 (Page No. 343)

Question

Consider the following snapshot of a system:

                               $Allocation$                                         $Max$

                               $A$ $B$ $C$ $D$                                         $A$ $B$ $C$ $D$

                 $P_0$         $3$  $0$  $1$  $4$                                             $5$  $1$  $1$  $7$ 

                 $P_1$         $2$  $2$  $1$  $0$                                             $3$  $2$  $1$  $1$ 

                 $P_2$         $3$  $1$  $2$  $1$                                             $3$  $3$  $2$  $1$ 

                 $P_3$         $0$  $5$  $1$  $0$                                             $4$  $6$  $1$  $2$   

                 $P_4$         $4$  $2$  $1$  $2$                                             $6$  $3$  $2$  $5$ 

Using the banker’s algorithm, determine whether or not each of the following states is unsafe. If the state is safe, illustrate the order in which the processes may complete.Otherwise, illustrate why the state is unsafe.

$a$. $Available$ $=$ $(0, 3, 0, 1)$
$b$. $Available$ $=$ $(1, 0, 0, 2)$

Comments

a) Not safe:Processes P2 , P1 , and P3 are able to finish, but no remaining processes can finish.
b) Safe:Processes P1 , P2 , and P3 are able to finish. Following this, processes P0 and P4 are also able to finish.

Answer 1

(a) P0 and P4 are not satisfied and both lead to a Unsafe State.

(b) All the process are Satisfied And Safe Seqence Is Also Present , which lead to a system into Safe State.