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let S and Q to be initialized to 1

process p0:          process p1:

wait(S);             wait(Q);
wait(Q);             wait(S); 

..                    ..
..                    ..
Signal(S);           Signal(Q);
Signal(Q);           Signal(S);

I know there is a deadlock , where both the process will be going into the sleep , so what about starvation and bounded waiting?

My approach:

as only p0 can be executed any number of times i think there will be starvation and no bounded waiting.But answer is given that there is No Starvation.

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  • $\begingroup$ I don't understand why "the answer" is "no starvation". Note that starvation freedom implies deadlock freedom. Since it suffers from deadlocks, it must also suffer from starvations. $\endgroup$ – hengxin Dec 15 '16 at 7:16
  • $\begingroup$ @hengxin you meant to say that if there is deadlock then that implies starvation? $\endgroup$ – Pavan Kumar Munnam Dec 15 '16 at 7:27
  • $\begingroup$ No starvation $\implies$ No deadlock. So deadlock $\implies$ starvation. $\endgroup$ – hengxin Dec 15 '16 at 7:31
  • $\begingroup$ i was thinking this way cs.stackexchange.com/questions/67406/… $\endgroup$ – Pavan Kumar Munnam Dec 15 '16 at 7:34
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The answer is wrong.

Deadlock implies starvation, and the given code suffers from deadlock, here's how.

Say p0 executes wait(S); and then p1 executes wait(Q);. Now both the semaphores S and Q have value = 0.Now p0 will keep on waiting due to statement wait(Q); and p1 will keep on waiting due to statement wait(S);.

Freedom from starvation means that:

if a thread tries to acquire a lock , it will eventually succeed.

This does not happen here, so the answer is wrong.

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