Direction: Suppose we want to synchronize two concurrent processes P and Q using binary semaphores S and T. The code for the processes P and Q is shown below:
| Process P | Process Q |
| while (1) { | while (1) { |
| W: | Y: |
| print ‘0’; | print ‘1’ |
| print ‘0’; | print ‘1’ |
| X: | Z: |
| } |
Synchronization statement can be inserted only at point W, X, Y and Z
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Which of the following will ensure that the output string never contains a substring of the form 01n 0 or 10n1 where n is odd?
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- P(S) at W, V(S) at X, P(T) at Y, V(T) at Z, S and T initially 1
- P(S) at W, V(T) at X, P(T) at Y, V(S) at Z, S and T initially 1
- P(S) at W, V(S) at X, P(S) at Y, V(S) at Z, S initially 1
- V(S) at W, V(T) at X, P(S) at Y, P(T) at Z, S and T initially 1
- P(S) at W, V(S) at X, P(T) at Y, V(T) at Z, S and T initially 1
Correct Option: C
To ensure this condition that substring of form 01n0 or 10n1, where n is odd S should be initially 1, we will case only 1 semaphore S.
So at W P(s), at X V(s) whereas at Y P(s), at Z V(s) Hence (c) is correct option.
