GATE CSE 2021 Paper 2 — page 18

Questions 52–54 of 65. Imported answers require review unless explicitly marked reviewed.

Consider the following multi-threaded code segment (in a mix of C and pseudo-code), invoked by two processes P1 and P2, and each of the processes spawns two threads T1 and T2:

int x = 0; // global

Lock L1; // global

main() {

create a thread to execute foo(); // Thread T1

create a thread to execute foo(); // Thread T2

wait for the two threads to finish execution;

print (x);

}

foo() {

int y = 0;

Acquire L1;

x = x + 1;

y = y + 1;

Release L1;

print (y);

}

Which of the following statement(s) is/are correct?

Your answerSelect all correct options. You can choose more than one.

Both P1 and P2 will print the value of x as 2.

At least one of P1 and P2 will print the value of x as 4.

At least one of the threads will print the value of y as 2.

Both T1 and T2, in both the processes, will print the value of y as 1.

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Consider a computer system with multiple shared resource types, with one instance per resource type. Each instance can be owned by only one process at a time. Owning and freeing of resources are done by holding a global lock (L). The following scheme is used to own a resource instance:

function OwnResource(Resource R) Acquire lock L // a global lock if R is available then Acquire R Release lock L else if R is owned by another process P then Terminate P, after releasing all resources owned by P Acquire R Restart P Release lock L end if end if end function

Which of the following choice(s) about the above scheme is/are correct?

Your answerSelect all correct options. You can choose more than one.

The scheme ensures that deadlocks will not occur.

The scheme may lead to live-lock.

The scheme may lead to starvation.

The scheme violates the mutual exclusion property.

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If the numerical value of a 2-byte signed integer on a little endian computer is 255 more than that on a big endian computer, which of the following choices represent(s) the unsigned integer on a little endian computer?

Your answerSelect all correct options. You can choose more than one.

0x665

0x001

0x423

0x100

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2021 · Paper 2

Question 42

Question 43

Question 44