Gate previous Years

Question

Suppose we want to synchronize two concurrent processes P and Q using binary semaphores S, T and U:

                    Process P:                                           Process Q:

                        P(S)                                                     W:

                        P(T)                                                     X:

                        P(U)                                                    Y:

                      Print ‘a’                                             Print ‘a’;

                      Print ‘b’                                            Print ‘b’;

                        V(S)                                                    A:

                        V(T)                                                    B:

                        V(U)                                                    C:

What should be written at W to avoid deadlock?

(a) P(T)                                                                       (b) P(U)

(c) P(S)                                                                       (d) Not possible to avoid deadlock

Comments

Add the Gate year.

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Sorry but I don't know the gate year. I found it in a practice book and year wasn't mentioned.

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If W= P(S)

Y=P(T)

Z=P(U)

Then no deadlock

If W= P(S)
   Y=P(U)
   Z=P(T)

then also no deadlock will occur.

So for this particular question C is the correct answer.