> A system has 6 identical resources and $N$ processes competing for
> them. Each process can request at most two requests. Which one of the
> following values of $N$ could lead to a deadlock?
>
>  1. 1
>  2. 2
>  3. 3
>  4. 4

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My attempt:

Deadlock free condition is:

$R  \geq P(N-1)+1 ,$

Where R is total number of resources,

P is the number of processes, and

N is the max need of resources by each process.

$6 \geq P(2-1) + 1$

$6 \geq P + 1$

$5 \geq P$

So, the number of processes should be less than $5$ for the deadlock free condition.

Hence, all options can not be deadlocked.


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In this exercise problem the answer given option (4).

> Can you explain it in a formal way, please?