IBPS IT SO-Operating system-Deadlock Avoidance

Deadlock Avoidance

1) Each request requires that the system consider the __________, _____________, ____________ to decide whether the current request can be satisfied or must wait to avoid a future possible deadlock. (choose three)
a) resources currently available
b) processes that have previously been in the system
c) resources currently allocated to each process
d) future requests and releases of each process

Answer: a, c and d
Explanation: None.

2) Given a priori information about the ________ number of resources of each type that maybe requested for each process, it is possible to construct an algorithm that ensures that the system will never enter a deadlock state.
a) minimum
b) average
c) maximum
d) approximate

Answer: c
Explanation: None.

3) A deadlock avoidance algorithm dynamically examines the __________, to ensure that a circular wait condition can never exist.
a) resource allocation state
b) system storage state
c) operating system
d) resources

Answer: a
Explanation: Resource allocation states are used to maintain the availability of the already and current available resources.

4) A state is safe, if :
a) the system does not crash due to deadlock occurrence
b) the system can allocate resources to each process in some order and still avoid a deadlock
c) the state keeps the system protected and safe
d) All of these

Answer: b
Explanation: None.

5) A system is in a safe state only if there exists a :
a) safe allocation
b) safe resource
c) safe sequence
d) All of these

Answer: c
Explanation: None.

6) All unsafe states are :
a) deadlocks
b) not deadlocks
c) fatal
d) None of these

Answer: b
Explanation: None.

7) A system has 12 magnetic tape drives and 3 processes : P0, P1, and P2. Process P0 requires 10 tape drives, P1 requires 4 and P2 requires 9 tape drives.

Process
P0
P1
P2

Maximum needs (process-wise : P0 through P2 top to bottom)
10
4
9

Currently allocated (process-wise)
5
2
2

Which of the following sequence is a safe sequence ?
a) P0, P1, P2
b) P1, P2, P0
c) P2, P0, P1
d) P1, P0, P2

Answer: d
Explanation: None.

8) If no cycle exists in the resource allocation graph :
a) then the system will not be in a safe state
b) then the system will be in a safe state
c) either a or b
d) None of these

Answer: b
Explanation: None.

9) The resource allocation graph is not applicable to a resource allocation system :
a) with multiple instances of each resource type
b) with a single instance of each resource type
c) Both a and b

Answer: a
Explanation: None.

10) The Banker’s algorithm is _____________ than the resource allocation graph algorithm.
a) less efficient
b) more efficient
c) None of these

Answer: a
Explanation: None.

11) The data structures available in the Banker’s algorithm are : (choose all that apply)
a) Available
b) Need
c) Allocation
d) Maximum
e) Minimum
f) All of these

Answer: a,b,c,d
Explanation: None.

12) The content of the matrix Need is :
a) Allocation – Available
b) Max – Available
c) Max – Allocation
d) Allocation – Max

Answer: c
Explanation: None.

13) A system with 5 processes P0 through P4 and three resource types A, B, C has A with 10 instances, B with 5 instances, and C with 7 instances. At time t0, the following snapshot has been taken :

Process
P0
P1
P2
P3
P4

Allocation (process-wise : P0 through P4 top to bottom)

A B C
0 1 0
2 0 0
3 0 2
2 1 1
0 0 2

Max (process-wise : P0 through P4 top to bottom)
A B C
7 5 3
3 2 2
9 0 2
2 2 2
4 3 3

Available
A B C
3 3 2
The sequence leads the system to :
a) an unsafe state
b) a safe state
c) a protected state
d) a deadlock

Answer: b
Explanation: None.