Consider the following resource-allocation policy. Requests and releases for resources are allowed at any time. If a request for resources cannot be satisfied because the resources are not available, then we check any processes that are blocked, waiting for resources. If they have the desired resources, then these resources are taken away from them and are given to the requesting process. The vector of resources for which the waiting process is waiting is increased to include the resources that were taken away.
For example, consider a system with three resource types and the vector Available initialized to (4, 2, 2). If process P0 asks for (2, 2, 1), it gets them. If P1 asks for (1, 0, 1), it gets them. Then, if P0 asks for (0, 0, 1), it is blocked (resource not available). If P2 now asks for (2, 0, 0), it gets the available one (1, 0, 0) and one that was allocated to P0 (since P0 is blocked). P0’s Allocation vector goes down to (1, 2, 1), and its Need vector goes up to (1, 0, 1). a. Can deadlock occur? If so, give an example. If not, which necessary condition cannot occur?
b. Can indefinite blocking occur?