Question

Deadlock Avoidance using Banker’s Algorithm

Q1: Use the following information and complete the Table, also write down the safe sequence if exist?

Three Resources (R1=4, R2=9, R3=11)

Processes	Allocated Resources R1   R2    R3	Maximum Required Resources R1   R2    R3	Currently Available Resources R1   R2    R3	Remaining Need R1   R2    R3	Safe Sequence
P1	1      4      2	2      4      6
P2	2      1      1	3      2      8
P3	0      0      1	1      2      3
P4	0      0      0	4      4      2

Answer 1

Equations involved in bankers algorithm are

Need Matrix = max resources - allocated resources

Available Resources = Total resources - sum of allocated resources for each process.

If need <=available Resources , then process can be executed . After execution allocated resources are added to available Resources.

Max Matrix

Process	R1	R2	R3
P1	1	0	4
P2	1	1	7
P3	1	2	2
P4	4	4	2

Available Resources.

R1 = 4-(1+2)= 1

R2=9-(4+1)=4

R3=11-(2+1+1)=7

Checking availability for P1,

1,0,4 <= 1,4,7

So P1 executes, after completion

Available Resources = 2,8,9

Checking availability for P2,

1,1,7<=2,8,9

P2 executes,

After execution available Resources = 4,9,10

Checking availability for P3,

1,2,2 <= 4,9,10

P3 executes,

After execution, available Resources = 4,9,11

Checking availability for P4,

4,4,2 <= 4,9,11

P4 executes.

Safe cycle = P1,P2,P3,p4