Consider a computer system with multiple shared resource types, with one instance per resource type. Each instance can be owned by only one process at a time. Owning and freeing of resources are done by holding a global lock (L). The following scheme is used to own a resource instance :function OWNRESOURCE(Resource R) Acquire lock L // a global lock if R is available then Acquire R Release lock L else if R is owned by another process P then Terminate P, after releasing all resources owned by P Acquire R Restart P Release lock L end if end if end functionWhich of the following choice(s) about the above scheme is/are correct?

Let us analyze the given resource allocation scheme against each statement:

1. Deadlock Freedom (Option A):

   • Deadlock requires four necessary conditions: Mutual Exclusion, Hold and Wait, No Preemption, and Circular Wait.

   • In this scheme, if a requested resource $R$ is currently held by process $P$, $P$ is immediately terminated and all its held resources are forcibly released (preempted). Because preemption is enforced, circular wait cannot persist, ensuring that deadlocks will not occur. Hence, (A) is correct.

2. Livelock (Option B):

   • Consider two processes, $P_1$ and $P_2$, competing for resources $R_1$ and $R_2$. Suppose $P_1$ holds $R_1$ and requests $R_2$ (held by $P_2$), causing $P_2$ to be terminated and restarted. Then restarted $P_2$ requests $R_1$, terminating and restarting $P_1$. This cycle of mutual preemption and restarting can repeat indefinitely with processes actively executing without making any forward progress, which is a classic live-lock condition. Hence, (B) is correct.

3. Starvation (Option C):

   • Since a process holding a resource can be repeatedly preempted, terminated, and restarted whenever another process requests its resource, an unlucky process may never finish execution, leading to starvation. Hence, (C) is correct.

4. Mutual Exclusion (Option D):

   • The global lock $L$ ensures atomic check-and-acquisition. If a resource is not available, the current owner is terminated and all its resources are released before the requesting process acquires it. At any moment, at most one process owns an instance of a resource. Thus, mutual exclusion is strictly preserved and not violated. Hence, (D) is incorrect.

Therefore, the correct options are A, B, and C.