GATE Computer Science (CS) 2020 Solved Papers

Question : 57 of 65

Marks: +1, -0

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 initialized to 0 and not used in CODE SECTION P.
CODE SECTION P
wait (a); count=count+1;
If (count==n) signal (b);
signal (a); wait (b); signal (b);
CODE SECTION Q
What does the code achieve?

It ensures that all processes execute CODE SECTION P mutually exclusively.
It ensures that at most n–1 processes are in CODE SECTION P at any time.
It ensures that no process executes CODE SECTION Q before every process has finishedCODE SECTION P.
It ensures that at most two processes are in CODE SECTION Q at any time.

Validate

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