ISRO-2013-58

Question

Consider the following process and resource requirement of each process.

Predict the state of this system, assuming that there are a total of $5$ instances of resource type $1$ and $4$ instances of resource type $2$.

• A. Can go to safe or unsafe state based on sequence
• B. Safe state
• C. Unsafe state
• D. Deadlock state

Comments

when they gives u total instance  of resources like here typ1 and type 2 ur aim is to compute available  resources of both type 1 and type then u apply banker algorithm on it then u get safe or unsafe state . and remember one thing if u got avaliable  resources of type1 and type2 is (0,0) thats means deadlock is occured

Answer 1

This is definitely in unsafe state. The state is not a deadlock state, since every process is not waiting for other processes to release the resources (we have some resources available to fulfill some need). This violates the condition for deadlock : 

Circular Wait - A set of processes ${ P0, P1, P2, . . ., PN }$ must exist such that every $P[ i ]$ is waiting for P[ ( i + 1 ) % ( N + 1 ) ].

However, after allocating the remaining resources, the system may go to deadlock, but currently we can only say that it is in unsafe state.

So, the answer is (C).

Comments

Here p1 use 2 resources and wait for 3(waiting for completion of either p2 or p3  ).

similarly,

 p2 use 2 resources and wait for 3(waiting for completion of either p1 or p3  ).

 p3 use 3 resources and wait for 5(waiting for completion of either p1 or p2  ).

that is the waiting is like

p1->p2->p3->p1 or p1->p3->p2->p1 or p1->p2->p1->p3 or p2->p3->p2->p1 in all this situations we can find that there is a minimum circular wait of between 2 process.so actually is this satisfy the 4 necessary conditions of deadlock??.please clarify me in this part ...please....

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The circular wait condition states that there exists a chain of processes where each process is waiting for a resource that is being held by another process.

Since we have 1 resource available each of $R1$ (Total $5$, allocated $4$) and $R2$ (Total $4$, allocated $3$), any of the process is not currently waiting for other processes to release any resource. If we allocate the remaining resource, then only we can say it is in deadlock. That is why the current state of the system is Unsafe.

 

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@Shijith M You may have confused with the 'Predict' term there. No, I think they are asking about the current state of the system. There is still no deadlock there. But there is no way to avoid it, so we can say the system is in Unsafe state. Hope it is clear now.

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Ok now i got it sir. Tnx a lot.

Answer 2

There does not exist any safe sequence so the system is in unsafe state. It may or may not be in dead lock state

Answer 3

Answer is A because it can go to safe or unsafe according to sequence

Comments

I think C is the right answer.