OS Test -1

Question

A computer has 20 tape drivers, with n processes competing for them. Each process may need five drivers. What is the maximum value of n for the system to be deadlock free?

Answer 1

If we have 4 process than

process	p0	p1	p2	p3
drivers	5	5	5	5

so no deadlock will occur but if we have 5 processes

process	p0	p1	p2	p3	p4
drivers	4	4	4	4	4

 when their is 5 processes then this condition may occur so this will result in deadlock

so max 4 processes will always  ensure deadlock free operation of system.

Answer 2

Consider that all processes are deadlocked with 4 resources allocated to each. Now, if I allocate 1 resource to one of them, the system will be become deadlock free.

So, 4(n)+1 <= 20

i.e. n<= 4.xxxxx

i.e. n=4