Deadlock Avoidance - TarisMajor/5143-OpSystems GitHub Wiki

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Deadlock avoidance is a dynamic strategy employed by operating systems to ensure that deadlocks do not occur. It involves carefully allocating resources based on the current state and the potential future states to avoid any circular wait conditions that could lead to deadlocks. Unlike deadlock prevention, which uses fixed rules to prevent deadlocks, deadlock avoidance takes a more flexible approach by examining each resource allocation request and making decisions based on the system’s current state.

Key Characteristics of Deadlock Avoidance

  1. Dynamic Allocation: Resource allocation decisions are made dynamically based on the current state of resource usage and the requested resources.
  2. Safe State: The system constantly checks whether it is in a safe state, meaning it can allocate resources to each process in some order and still avoid deadlock. If a request could lead to an unsafe state, it is denied.
  3. Resource Allocation Graph (RAG): Deadlock avoidance algorithms often use a resource allocation graph to track the allocation of resources to processes and ensure no cycles form.

Advantages of Deadlock Avoidance

  1. Resource Utilization: Deadlock avoidance typically allows for better resource utilization than deadlock prevention because it does not impose strict rules on resource allocation.
  2. Flexibility: The dynamic nature of deadlock avoidance provides more flexibility in handling resource requests, adapting to the system's state.
  3. Reduced Deadlocks: By ensuring the system remains in a safe state, deadlock avoidance effectively reduces the chances of deadlocks occurring.

Disadvantages of Deadlock Avoidance

  1. Complexity: Implementing deadlock avoidance algorithms is complex and requires constant monitoring of the system's state and potential future states.
  2. Overhead: The continuous checking of safe states and resource allocation conditions introduces computational overhead.
  3. Decision Making: The system must make quick and accurate decisions about resource allocation, which can be challenging in highly dynamic environments.

Common Deadlock Avoidance Algorithms

  1. Banker’s Algorithm: This algorithm simulates the allocation of resources and checks if the system will remain in a safe state after the allocation. It grants the resource only if the system remains safe.
  2. Resource Allocation Graph Reduction: Involves removing processes and their allocated resources from the graph if they can complete without causing a deadlock, ensuring no cycles form.

Use Cases for Deadlock Avoidance

  1. Operating Systems: Used in operating systems to manage multiple processes and resources efficiently, preventing deadlocks in dynamic environments.
  2. Database Systems: Crucial for database management systems where transactions frequently lock resources and deadlock risks are high.
  3. Real-Time Systems: Important in real-time systems where resource availability is critical, and deadlocks can lead to missed deadlines and system failures.

Sources for Further Reading