self doubt(deadlock)

Question

there are total 100 resources and each process require 3 instance of resources then find maximum and minimum number of process so that deadlock will not occur.

i am confused for the answer i.e(it is 49 or 98??)

Answer 1

Let the no.of processes = N

Let each process requires r resources and Total Resources = R

for avoiding deadlock:-

N*(r-1) + 1 ≤ R

N  * 2 + 1 ≤ 100 ===> 2 N ≤ 99 ===> N ≤ 49.5

Now the doubt arises... we have take 49 or 50?

take 50 processes ===> allocate 2 resources for P₁,...P₄₉, ===> 49*2=98 resources consumed

now allocate remaining resources P₅₀ ===> Lead to DEADLOCK

take 49 processes ===> allocate 2 resources for P₁,...P₄₉, ===> 49*2=98 resources consumed

now allocate remaining resources to any process it will never Lead to DEADLOCK

Therefore Maximum no.of processes, never lead to deadlock = 49

 

Comments

yes it is general approach i agree with you. if i allocate one resource to  p1 to p98 it is still remain in deadlock i.e( p1->p2->p3->p4-................p98->p1) and i keep two resource to allocate any of the process to avoid deadlock why this approach is wrong????

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Brother you are getting into wrong concept....

the question is 

 find maximum number of process so that deadlock will not occur.

it means at any case deadlock never happens with the no.of processes

 

i agree, the case which you are taken doesn't lead to deadlock... but there is a case which leads to deadlock with the 98 processes... right?

So n can't be 98..... take n=49 ===> at any case it doesn't lead to deadlock....