This is in reference to the video made on CS-Gate 2006 question

Thank you for the nice explanation Sir. I am having problem in posting my doubt there under the video and hence i am asking it here.

As you said, if the initial value of S is 1 and a process P1 tries to enter, it will go into a loop until some other process executes V(). So we can assume that there is some process that may first invoke V instead of P() before entering into critical section?