Gate2018 cs Q53
53In a system, there are three types of resources: E, F and G. Four processes P0, P1, P2 and P3 execute concurrently. At the outset, the processes have declared their maximum resource requirements using a matrix named Max as given below. For example, Max[P2, F] is the maximum number of instances of F that P2 would require. The number of instances of the resources allocated to the various processes at any given state is given by a matrix named Allocation. Consider a state of the system with the Allocation matrix as shown below, and in which 3 instances of E and 3 instances of F are the only resources available.
| Allocation | Max | |||||||
| E | F | G | E | F | G | |||
| P0 | 1 | 0 | 1 | P0 | 4 | 3 | 1 | |
| P1 | 1 | 1 | 2 | P1 | 2 | 1 | 4 | |
| P2 | 1 | 0 | 3 | P2 | 1 | 3 | 3 | |
| P3 | 2 | 0 | 0 | P3 | 5 | 4 | 1 | |
From the perspective of deadlock avoidance, which one of the following is true?
- A
The system is in safe state
- B
The system is not in safe state, but would be safe if one more instance of E were available
- C
The system is not in safe state, but would be safe if one more instance of F were available
- D
The system is not in safe state, but would be safe if one more instance of G were available
- Option : A
- Explanation :
Safe sequence : P0, P2, P1, P3 Safe stateMax need Current allocation Current available Remaining need E F G E F G E(3) F(3) G(0) E F G P0 4 3 1 1 0 1 4 3 1 3 3 0 P1 2 1 4 1 1 2 5 3 4 1 0 2 P2 1 3 3 1 0 3 6 4 6 0 3 0 P3 5 4 1 2 0 0 8 4 6 3 4 1
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