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Question

https://gateoverflow.in/2263/gate1997-6-7

1. They said at least 4 resource are required.

First p1 comes takes two system resource, then p2 comes takes 1 system resource, then p3 comes takes 1 system resource. Now P3 needs one more resource so it is waiting for P2 to leave that resource and later P2 also needs one resource so it waits for P3 to leave resource. There will be cycle between P2 and P3. There is a deadlock, After p1 gets completed will now operating system allocate available resource to each process? because this is the only way to avoid above deadlock. Is this implemented using semaphores?

2. Also when we say one process is waiting for some resources held by another process what exactly happens in between, how one process keeps track when the other process leaves resource, which part of the os performs this function? is it done by using semaphores?

Comments

I am unable to understand what you want to ask.Please ask your doubt in the comment section.

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I was getting deadlock with 4 resources, I have specified the reason in above question. The answer says there should be at least 4 resources present to avoid deadlock. I wanted to know how it is happening and where I am going wrong.

I could have posted comment over there but usually response time is very less also the question is very old so the normally people who were active are not there at present. Apart from that recent activity changes faster than the no. of questions that have been asked so there is a least chance of getting answer for the above question.