GATE 2023 · CS - Forenoon
Consider the two functions `incr` and `decr` shown below.
c
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?
incr() {
wait(s);
X = X + 1;
signal(s);
}
decr() {
wait(s);
X = X - 1;
signal(s);
}