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Two shared resources $R_1$ and $R_2$ are used by processes $P_1$ and $P_2$. Each process has a certain priority for accessing each resource. Let $T_{ij}$ denote the priority of $P_i$ for accessing  $R_j$. A process $P_i$ can snatch a resource $R_k$ from process $P_j$ if $T_{ik}$ is greater than $T_{jk}$.
Given the following :

1. $T_{11} > T_{21}$
2. $T_{12} > T_{22}$
3. $T_{11} < T_{21}$
4. $T_{12} < T_{22}$

Which of the following conditions ensures that $P_1$ and $P_2$ can never deadlock?

1. (I) and (IV)
2. (II) and (III)
3. (I) and (II)
4. None of the above

edited | 2.3k views
+4

I think in question it should be R instead of Rh

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first given R1 and R2 to P1 and complete it then given to again R1,R2 to P2 ..

ans should be 1 and 2  or 3 and 4   can ensure no deadlock

If any process has highest priority over all the resources then it can snatch any resource from any other process and so no deadlock can occur with another process as this highest priority process will eventually finish and release all the resources for the other less priority process.

In case of (I) and (II) process $1$ has given highest priority over all the resources and hence deadlock cannot occur.

Similarly, in the case of (III) and (IV) process $2$ has given highest priority over all the resources and hence deadlock cannot occur.

If we consider option (A) (I) and (IV)

•  $T_{11} > T_{21}$     // for resource 1, process 1 has the highest priority
•  $T_{22} > T_{12}$     // for resource 2 , process 2 has highest priority

Let $P_1$ be holding $R_1$ and waiting for $R_2.$

Let $P_2$ be holding $R_2$ and waiting for $R_1.$

This is deadlock as neither is releasing its held resources. Similarly in option B also deadlock can occur.

by Active (3.6k points)
edited by

If $R_1$ and $R_2$ are allocated to the Process $P_1$ , then it will complete it's job and release it . After that process $P_2$  will get both the resources and complete it's Job .

by (91 points)
edited by
+30
Yes. Both I and II as well as III and IV can ensure no deadlock.
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@Arjun Sir : If u can please elaborately explain ,can't understand the above solution
+33
1.  T11 > T21 :  Allocate R1 to process P1.

2.  T12 > T22 : Allocate R2 to process P1.

3.  T11 < T21 :  Allocate R1 to process P2.

4.  T12 < T22 : Allocate R2 to process P2.

Allocation of all resources to one process never cause deadlock. Once that process complete execution resources will be free and are available to allocate some other process. Deadlock never happen..

That will be given by 1 & 2 As well as 3 & 4..
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Thanks :)
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Thqq soo much...