GATE CSE 2015 Set 3 | Question: 52 OS Doubt

Question

In this question:- https://gateoverflow.in/8561/gate2015-3-52

In options II III and IV i am not understanding how its violating the rule of circular wait. Rather i feel its creating a circular wait condition. Please Explain….

Any Example would be appreciated.

Answer 1

suppose there are two processes P1 and P2 then  there are resourses named R1 and R2 which are unordered then the following allocation is done:

A:P1-R1;P2-R2;P1-R2;P2-R1  then we observe that there is  a deadlock condition  and it is having circular wait .

NOW,

R1 IS ASSIGNED NO.=1;

R2 IS ASSIGNED NO.=2;

<II>

Here P2 will not be able to access R1 after accessing R2 as R1<R2;

<III>

Here P1 will not be able to access R2 after accessing R1 as R1<R2;

IV  also has the same explanation.