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Deadlock System Model
In a computer system a deadlock is where two or more processes are unable to proceed because each process is waiting for the other to release a resource that it needs to continue execution. In other words, a deadlock occurs when two or more processes are in a circular wait state, and none of them can release the resources they hold until they receive the resources they are waiting for.
Deadlock System Model − The Deadlock System model is a way to describe and analyze systems that may be prone to deadlocks, which occur when two or more processes are unable to proceed because they are each waiting for the other to release a resource. Below are the components of this model −
Resources − The system has a set of resources that are shared among processes. These resources can be hardware or software components, such as memory, files, printers, or network connections. Each resource is identified by a unique name or identifier.
Processes − The system has a set of processes that request and release resources. Processes are units of execution that can be started, suspended, resumed, and terminated. Each process is identified by a unique process ID.
Resource Allocation − Each resource can be in one of two states , allocated or available. A resource that is allocated to a process cannot be used by any other process until it is released.
Request and Release − A process can request a resource by sending a request to the system. If the resource is available, it will be allocated to the process. When a process is finished using a resource, it must release it so that it can be used by other processes.
Resource Dependency − Some processes may require multiple resources to complete their tasks. A resource dependency graph can be used to represent the relationships between processes and resources and to detect potential deadlocks.
Deadlock Detection − A deadlock can occur when two or more processes are waiting for resources that are being held by other processes, creating a circular dependency. Deadlock detection algorithms can be used to detect when a deadlock has occurred, so that corrective action can be taken.
Deadlock Resolution − Once a deadlock has been detected, it can be resolved by breaking the circular dependency between the processes. This can be done by releasing one or more resources that are being held by a process, or by preempting one or more processes that are holding resources. The Working of some of the techniques are given below −
Resource preemption is a technique used to break the circular wait condition of a deadlock. The operating system can preempt resources from one or more processes involved in the deadlock and allocate them to the processes that need them. Preemption can be done either selectively or globally. In selective preemption, only the resources that are required to resolve the deadlock are preempted, while in global preemption, all the resources held by the deadlocked processes are preempted.
When a process is terminated, all the resources held by the process are released, and other processes can proceed. However, this approach can lead to data loss and inconsistency if the terminated process was in the middle of a critical task.
Deadlock Avoidance − Deadlock avoidance is a technique used to prevent the occurrence of deadlocks in a computer system. The goal of deadlock avoidance is to ensure that all resources required by a process are available before the process starts execution, thereby avoiding the possibility of deadlock.
There are several algorithms that can be used for deadlock avoidance, including the banker's algorithm and the resource allocation graph. These algorithms use a mathematical model to analyze resource allocation and to determine whether a process should be allowed to start or wait for resources.
The banker's algorithm is a widely used method for deadlock avoidance. It is a resource allocation algorithm that checks whether a requested resource can be granted to a process without causing a deadlock. The algorithm works by simulating the allocation of resources and checking whether a safe state can be reached. A safe state is a state where all processes can complete their execution without causing a deadlock.
The resource allocation graph is another method for deadlock avoidance. It represents the allocation of resources as a directed graph. Each process is represented by a node, and each resource is represented by an edge. The algorithm checks for cycles in the graph to determine whether a deadlock has occurred. If a cycle is detected, the process requesting the resource is blocked until the required resource becomes available.
Conclusion
In summary, the deadlock system model is a crucial idea in the design and management of operating systems. It outlines the potential causes of deadlocks as well as strategies for avoiding and resolving them. It is crucial to put into practice efficient prevention measures for deadlocks since they might result in substantial performance degradation and data loss.
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