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I think it would be n*k-n+1....

Why its n*k-n+1 could the people commented explain, please.

I think its "None of the above".
* If there is only one resource there is no question of deadlock.
* If there are k instances of the resource and each instance need to be locked to access it then it is equivalent to having more than one resource.
* If there are more than one resource that each needs locking then, I don't think its number of resources or its need-to-be-locked instances dictates the deadlock scenario. The program should avoid the deadlock. For e.g. There are 2 processes and 2 resources process 1 locked resource 1 and waiting for resource 2, while process 2 has locked resource 2 and waiting for resource 1. How does the number of instances or resources avoid the deadlock scenario?

Wow they gave you multiple choice, just like a homework assignment. Coincidence huh?

i copied dis ques from someone's blog..
may b MS dint ask dis..bt i thot i shud share d question

even i think so..

@kannan its like n*k-n resources are required so that each process can have one less than the resource instance they require.. but still deadlock can occur as each process depend upon other process for one resource instance ..if we provide n*k-n+1 resource instances than the deadlock condition will never occur.

i also agree with that..

would depend upon whether they can be preempted or not. if can be preempted, then we just need only k instance of resources .if there is non preemption than we need n*(k-1) +1 ;

you can simply find out by putting the arbitrary small values of n & k. Suppose you take 2 & 2. You will find only 2 option gives the cirrect answer

Shouldn't ordering the resources fix the deadlock?
All processes lock the resources in one order that all of them agree upon.
Hence we require only k resources.

Comments/suggestions welcome!

well the deadlock can be avoided using banker's algorithm. Its scheduling algorithm, preemption and the number of resources that dictates the deadlock.
Cases will differ based on the discussion and requirements.

Answer will depend on language of question...if it is asked like find no. Of. Resources sothat deadlock should never occur...-> it will require n*(k-1)+1 nmber of resources..
Otherwise bankers algo will give the safe sequences and according to that only ' k' number of resources

what would be if we have three processes P(x), P(y), and P(z); and each one has maximum demands on a resource of single type 3,5 and 4 respectively. What is the minimum number of resources I need in order to ensure the system is deadlock free?

Correct Answer is : N*K -(N-1).

Correct Answer is : N*K - (N - 1) [or] (Total Number Process * Total Number of Resource ) - (Total Process -1 )

Let me prove my formulae

For Ex: There are 3 process and each require 2 resources to complete the task. So the Minimum number of resource which guarantee the dead lock free is 4.(Source : Tata McGraw Hill Book)

Formula: 3*2 - (3-1) = 6-2 = 4


For Ex: There are 5 process and each require 2 resources to complete the task. So the Minimum number of resource which guarantee the dead lock free is 6.(Source : Again Tata McGraw Hill Book)

Formula: 5*2 - (5-1) = 10-4 = 6

Hence the proof..!

what if there are 3 processes and each need 3 resources
in that case i think the answer should be 5
but the formula gives 7.....

((((Cant understand the logic of the first answer
can u explain again))))

minimum requiement scenario process deadlock

any one give answers