Operating Systems · Concurrency and Synchronization
Official IIT answer key · IIT Bombay · Audited Aug 2026
GATE CSE 2013 Q39 · MCQ · 2 marks
a and b such that a[i]=f(i) for 0≤i<n and b[i]=g(a[i]) for 0≤i<n. Suppose this computation is decomposed into two concurrent processes X and Y such that X computes the array a and Y computes the array b. The processes employ two binary semaphores R and S, both initialized to zero. The array a is shared by the two processes. The structures of the processes are shown below.
Process X:
private i;
for (i=0; i<n; i++) {
a[i] = f(i);
ExitX(R, S);
}Process Y:
private i;
for (i=0; i<n; i++) {
EntryY(R, S);
b[i] = g(a[i]);
}
Which one of the following represents the CORRECT implementations of ExitX and EntryY?Key concept
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Topic notes
Concurrency and Synchronization is consistently evaluated through rigorous interleaving analysis, semaphore tracing, and correctness verification of mutual exclusion algorithms. Over the years, GATE tests whether candidates can systematically trace race conditions, identify potential deadlocks from mismatched semaphore wait/signal orders, and compute the bounds or exact sets of possible shared variable values under non-atomic operations. Recent papers heavily favor Multi-Select Questions (MSQs) requiring complete enumeration of all valid execution traces and program outcomes.
Full Concurrency and Synchronization guide →A certain computation generates two arrays a and b such that a[i] = f(i) for 0 i a and Y computes the array b . The processes employ two binary semaphores R and S, both initialized to zero. The array a is shared by the two processes. The structures of the processes are shown below. Process X: private i; for (i=0; i Process Y: private i; for (i=0; i Which one of the following represents the CORRECT implementations of ExitX and EntryY ?
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