Question

A system shares 9 tape drives. The current allocation and maximum requirement of tape drives for three processes are shown below:

Process	Current Allocation	Maximum Requirement
P1	3	7
P2	1	6
P3	3	5

 

Which of the following best describes current state of the system?

1. Safe, Deadlocked
2. Safe, Not Deadlocked
3. Note Safe, Deadlocked
4. Not Safe, Not Deadlocked

Answer 1

Correct Answer - Option 2 : Safe, Not Deadlocked

Resource allocation table:

Process	Current Allocation	Maximum Requirement	Need (Maximum-current)
P1	3	7	4
P2	1	6	5
P3	3	5	2

Available = 9 – ∑ (current allocation to process) = 9 – 7 = 2

Now, 2 resource will satisfy the need of P3.

After this available = 2 + 3 = 5

5 resource can satisfy need of P2 or P1

CASE 1:

If P2 is executed before P1, 

Available = 5 + 1 =6

6 resource can satisfy the need of P1 easily.

CASE 2:

If P1 is executed before P2

Available = 5 + 3 = 8

8 resource can satisfy the need of P1 easily.

Safe sequence will be P3, P1, P2 and P3, P2, P1

System is safe and there is no deadlock in the system.