Process Synchronization Questions

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31.

What are the two kinds of semaphores?

A

mutex

B

binary

C

counting

D

decimal

Correct Answer: B

None.

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32.

What is a mutex?

A

is a binary mutex

B

must be accessed from only one process

C

can be accessed from multiple processes

D

none of the mentioned

Correct Answer: B

None.

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33.

At a particular time of computation the value of a counting semaphore is 7.Then 20 P operations and 15 V operations were completed on this semaphore. The resulting value of the semaphore is? (GATE 1987)

A

42

B

2

C

7

D

12

Correct Answer: B

P represents Wait and V represents Signal. P operation will decrease the value by 1 every time and V operation will increase the value by 1 every time.

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34.

A binary semaphore is a semaphore with integer values ____________

A

1

B

-1

C

0.8

D

0.5

Correct Answer: A

None.

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35.

The following pair of processes share a common variable X.

Process A
int Y;
A1: Y = X*2;
A2: X = Y;   
 
Process B
int Z;
B1: Z = X+1;
B2: X = Z;

X is set to 5 before either process begins execution. As usual, statements within a process are executed sequentially, but statements in process A may execute in any order with respect to statements in process B. How many different values of X are possible after both processes finish executing?

A

two

B

three

C

four

D

eight

Correct Answer: C

Here are the possible ways in which statements from A and B can be interleaved.

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36.

The program follows to use a shared binary semaphore T.

Process A  
int Y;            
A1: Y = X*2;      
A2: X = Y;        
signal(T);        
 
Process B
int Z;
B1: wait(T);
B2: Z = X+1;
X = Z;

T is set to 0 before either process begins execution and, as before, X is set to 5. Now, how many different values of X are possible after both processes finish executing?

A

one

B

two

C

three

D

four

Correct Answer: A

The semaphore T ensures that all the statements from A finish execution before B begins. So now there is only one way in which statements from A and B can be interleaved:

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37.

Semaphores are mostly used to implement ____________

A

System calls

B

IPC mechanisms

C

System protection

D

None of the mentioned

Correct Answer: B

None.

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38.

Spinlocks are intended to provide __________ only.

A

Mutual Exclusion

B

Bounded Waiting

C

Aging

D

Progress

Correct Answer: B

None.

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39.

The bounded buffer problem is also known as ____________

A

Readers-Writers Problem

B

Dining- Philosophers Problem

C

Producer- Consumer Problem

D

None of the mentioned

Correct Answer: C

None.

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40.

In the bounded buffer problem, there are the empty and full semaphores that ____________

A

count the number of empty and full buffers

B

count the number of empty and full memory spaces

C

count the number of empty and full queues

D

none of the mentioned

Correct Answer: A

None.

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