1
GATE CSE 2021 Set 2
MCQ (More than One Correct Answer)
+2
-0

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 OWNRESOURCES(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?

A
The scheme may lead to starvation.
B
The scheme may lead to live-lock.
C
The scheme ensures that deadlocks will not occur.
D
The scheme violates the mutual exclusion property.
2
GATE CSE 2021 Set 2
MCQ (More than One Correct Answer)
+2
-0

Consider the following multi-threaded code segment (in a mix of C and pseudocode), 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 ?

A
Both T1 and T2, in both the processes, will print the value of y as 1.
B
At least one of P1 and P2 will print the value of x as 4
C
Both P1 and P2 will print the value of x as 2.
D
At least one of the threads will print the value of y as 2.
3
GATE CSE 2020
MCQ (Single Correct Answer)
+2
-0.67
Each of a set of n processes executes the following code using two semaphores a and b initialized to 1 and 0, respectively. Assume that count is a shared variable GATE CSE 2020 Operating Systems - Synchronization and Concurrency Question 7 English
What does the code achieve?
A
It ensures that all processes execute CODE SECTION P mutually exclusively.
B
It ensures that at most two processes are in CODE SECTION Q at any time.
C
It ensures that no process executes CODE SECTION Q before every process has finished CODE SECTION P.
D
It ensures that at most n-1 processes are in CODE SECTION P at any time.
4
GATE CSE 2013
MCQ (Single Correct Answer)
+2
-0.6
A shared variable x, initialized to zero, is operated on by four concurrent processes W, X, Y, Z as follows. Each of the processes W and X reads x from memory, increments by one, stores it to memory, and then terminates. Each of the processes Y and Z reads x from memory, decrements by two, stores it to memory, and then terminates. Each process before reading x invokes the P operation (i.e., wait) on a counting semaphore S and invokes the V operation (i.e., signal) on the semaphore S after storing x to memory. Semaphore S is initialized to two. What is the maximum possible value of x after all processes complete execution?
A
-2
B
-1
C
1
D
2
GATE CSE Subjects
Software Engineering
Web Technologies
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