Applied Test Series

Question

In a system which has only 3 processes, there are 2 copies of R1 resource, 3 copies of R2 resource. Say, in the current snapshot of the system, Process P1 holds 2 copies of resource R1 and needs 1 copy of R2 to complete its execution. P2 holds 2 copies of R2 and needs 2 copies of R1. P3 needs 2 copies of R1 and holds 1 copy of R2. At this moment, P1 gives up and releases the resource copies that it holds, only to request them again at a much later point in time. The probability that the system will be in a deadlock again is ____ (up to 2 decimal places).

Answer 1

P1 holds 2 copies of R1. And P2 and P3 require 2 copies of R1 each. 

Now, allocation may happen in either of the following ways : 

1. P2 gets 1 copy of resource and P3 gets 1 copy of resource -- leads to deadlock
2. P2 gets both the resources -- deadlock-free
3. P3 gets both the resources -- deadlock-free


Therefore, 1 out of 3 possibilities leads to a deadlock. Therefore 1/3 = 0.33