Consider the following system snapshot using data structures in the Banker's algorithm, with resources A, B, C, and D, and process P0 to P4:
Max Allocation Need Available
|
P0
|
A
6
|
B
0
|
C
1
|
D
2
|
A
4
|
B
0
|
C
0
|
D
1
|
A B C D
|
A
|
B
|
C D
|
|
P1
|
1
|
7
|
5
|
0
|
1
|
1
|
0
|
0
|
|
|
|
|
|
P2
|
2
|
3
|
5
|
6
|
1
|
2
|
5
|
4
|
|
|
|
|
|
P3
|
1
|
6
|
5
|
3
|
0
|
6
|
3
|
3
|
|
|
|
|
|
P4
|
1
|
6
|
5
|
6
|
0
|
2
|
1
|
2
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
3
|
2
|
1 1
|
Using Banker's algorithm, answer the following questions.
(a) How many resources of type A, B, C, and D are there?
(b) What are the contents of the Need matrix?
(c) Is the system in a safe state? Why
(d) If a request from process P4 arrives for additional resources of (1,2,0,0,), can the Banker's algorithm grant the request immediately? Show the new system state and other criteria.
(a) Resources of type A, B, C, and D are as: A-9; B-13;C-10;D-11
(b) Need[i, j]=Max[i,j]-Allocation[i,j] therefore content of Need matrix is
A B C D
P0 2 0 1 1
P1 0 6 5 0
P2 1 1 0 2
P3 1 0 2 0
P4 1 4 4 4
(c) The system is in a safe state like the processes can be complete in the sequence P0, P2, P4, P1 and P3.
(d) If a request from process P4 attains for additional resources of (1,2,0,0,), and if such request is granted so the new system state would be in tabulated form asfollows.
Max Allocation Need Available
A B C D A B C D A B C D A B C D
P0 6 0 1 2 4 0 0 1 2 0 1 1
P1 1 7 5 0 1 1 0 0 0 6 5 0
P2 2 3 5 6 1 2 5 4 1 1 0 2
P3 1 6 5 3 0 6 3 3 1 0 2 0
P4 1 6 5 6 1 4 1 2 0 2 4 4
2 0 1 1
After PO finishes P3 can be assigned. 1020 from released 6012 and also available 2011(Total 80 23) and is a safe sequence.