GATE 2026 · CS2 - Afternoon
Consider three processes P1, P2, and P3 running identical code, as shown in the pseudocode below. A and B are two binary semaphores initialized to 1 and 0, respectively. X is a shared variable initialized to 0. Each line in the pseudocode is executed atomically.
Pseudocode of P1, P2, and P3:
Wait(A);
Print(*);
X = X+1;
If (X == 2)
{
Print($);
Signal(B);
}
Signal(A);
Wait(B);
Print(#);
Signal(B);
Assume that any of the three processes can start to execute first and context switching can happen between these processes at any arbitrary time and in any arbitrary order.
Which of the following patterns is/are possible to be generated as an outcome of the execution of these three processes?