12/29/2023 0 Comments Deadlock definition![]() Operating systems such as UNIX and Windows follow this approach. Since the problem of deadlock situation is not frequent, some systems simply ignore it. ![]() In the method, the system assumes that deadlock never occurs. Resource Preemption: Resources are taken one by one from a process and assigned to higher priority processes until the deadlock is resolved.Abort one process at a time until the system recovers from the deadlock.We let the system fall into a deadlock and if it happens, we detect it using a detection algorithm and try to recover. If the system enters into an unsafe state, it has to take a step back to avoid deadlock. Therefore, it requires additional information such as how many resources of each type is required by a process. If allocating that resource sends the system into an unsafe state, the request is got granted. When a process requests a resource, the deadlock avoidance algorithm examines the resource-allocation state. Since deadlock occurs when all the above four conditions are met, we try to prevent any one of them, thus preventing a deadlock. This is done by restraining the ways a request can be made. The first two methods are used to ensure the system never enters a deadlock. Methods of Handling Deadlocks in Operating System Therefore, all four conditions are satisfied. None of the two processes releases their resources before their execution and this creates a circular wait. Each process is holding a resource and waiting for the other process the release the resource it requires. Since the resources are non-shareable they can only be used by one process at a time(Mutual Exclusion). This creates a situation of deadlock because none of the two processes can be executed. Process 1 holds "Resource 1" and needs "Resource 2" while Process 2 holds "Resource 2" and requires "Resource 1". In the above figure, there are two processes and two resources. This creates a circular relation between all these processes and they have to wait forever to be executed. For example, lets say there are a set of processes such that P 0 P_0 P 0 depends on P 1 P_1 P 1 , P 1 P_1 P 1 depends on P 2 P_2 P 2 , P 2 P_2 P 2 depends on P 3 P_3 P 3 and P 3 P_3 P 3 depends on P 0 P_0 P 0 . Circular Wait: A set of processes are waiting for each other in a circular fashion. ![]()
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