1
GATE CSE 2024 Set 1
Numerical
+2
-0.66

Consider the following code snippet using the fork() and wait() system calls. Assume that the code compiles and runs correctly, and that the system calls run successfully without any errors.

int x = 3;
while(x > 0) {
  fork();
  printf("hello");
  wait(NULL);
  x--;
}

The total number of times the printf statement is executed is _______

Your input ____
2
GATE CSE 2023
MCQ (Single Correct Answer)
+2
-0.67

Consider the two functions incr and decr shown below.


incr() {
  wait(s);
  X = X+1;
  signal(s);
}

decr() {
   wait(s);
   X = X-1;
   signal(s);
}

There are 5 threads each invoking incr once, and 3 threads each invoking decr once, on the same shared variable X. The initial value of X is 10.

Suppose there are two implementations of the semaphore s, as follows:

I-1: s is a binary semaphore initialized to 1.

I-2: s is a counting semaphore initialized to 2.

Let V1, V2 be the values of X at the end of execution of all the threads with implementations I-1, I-2, respectively.

Which one of the following choices corresponds to the minimum possible values of V1, V2, respectively?

A
15, 7
B
7, 7
C
12, 7
D
12, 8
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 6 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
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