1
GATE CSE 2021 Set 1
MCQ (More than One Correct Answer)
+2
-0.67

Consider the following pseudocode, where S is a semaphore intialized to 5 in line#2 an counter is a shared variable intialized to 0 in line#1. Assume that the increment operation in line#7 is not atomic.

1. int counter = 0;

2. Semaphore S = init(5);

3. void parop(void)

4. {

5. wait (S);

6. wait (S);

7. counter++;

8. signal (S);

9. signal (S);

10. }

If five threads execute the function parop concurrently, which of the following program behavior (s) is/are possible?

A

There is a deadlock involving all the threads.

B
The value of counter is 5 after all the threads successfully complete the execution of parop.
C
The value of counter is 1 after all the threads successfully complete the execution of parop.
D
The value of counter is 0 after all the threads successfully complete the execution of parop.
2
GATE CSE 2018
MCQ (Single Correct Answer)
+2
-0.6
In a system, there are three types of resources: $$E, F$$ and $$G.$$ Four processes $${P_0},$$ $${P_1},$$ $${P_2}$$ and $${P_3}$$ execute concurrently. At the outset, the processes have declared their maximum resource requirements using a matrix named Max as given below. For example, Max$$\left[ {{P_{2,}}F} \right]$$ is the maximum number of instances of $$F$$ that $${{P_{2,}}}$$ 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
E F G
P0 1 0 1
P1 1 1 2
P2 1 0 3
P3 2 0 0

Max
E F G
P0 4 3 1
P1 2 1 4
P2 1 3 3
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
3
GATE CSE 2016 Set 2
Numerical
+2
-0
Consider a non-negative counting semaphore $$S.$$ The operation $$P(S)$$ decrements $$S,$$ and $$V(S)$$ increments $$S.$$ During an execution, $$20$$ $$P(S)$$ operations and $$12$$ $$V(S)$$ operations are issued in some order. The largest initial value of $$S$$ for which at least one $$P(S)$$ operation will remain blocked is _____________ .
Your input ____
4
GATE CSE 2015 Set 3
MCQ (Single Correct Answer)
+2
-0.6
Consider the following policies for preventing deadlock in a system with mutually exclusive resources.

$$\,\,\,\,\,\,\,{\rm I}.$$ $$\,\,\,\,\,\,$$ Processes should acquire all their resources at the beginning of execution. If
$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ any resource is not available, all resources acquired so far are released
$$\,\,\,\,\,{\rm II}.$$ $$\,\,\,\,\,\,$$ The resources are numbered uniquely, and processes are allowed to request
$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ for resources only in increasing resource numbers
$$\,\,\,{\rm III}.$$ $$\,\,\,\,\,\,$$ The resources are numbered uniquely, and processes are allowed to request
$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ for resources only in decreasing resource numbers
$$\,\,\,{\rm IV}.$$ $$\,\,\,\,\,\,$$ The resources are numbered uniquely. A process is allowed to request only
$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ for a resource with resource number larger than its currently held resources

Which of the above policies can be used for preventing deadlock?

A
Any one of $${\rm I}$$ and $${\rm III}$$ but not $${\rm II}$$ or $${\rm IV}$$
B
Any one of $${\rm I},$$ $${\rm III},$$ and $${\rm IV}$$ but not $${\rm II}$$
C
Any one of $${\rm II}$$ and $${\rm III}$$ but not $${\rm I}$$ or $${\rm IV}$$
D
Any one of $${\rm I},$$ $${\rm II},$$ $${\rm III},$$ and $${\rm IV}$$
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