Deadlock Detection and Recovery in Operating Systems: Handling Deadlock Situations

Explore deadlock detection and recovery techniques in operating systems. This guide explains how deadlock detection algorithms (using resource allocation graphs) identify deadlocks and how recovery strategies (process termination, resource preemption) resolve them.

Deadlock Detection and Recovery in Operating Systems

Deadlock Detection and Recovery

Deadlock detection and recovery is a strategy for handling deadlocks in an operating system. Unlike deadlock prevention or avoidance, this approach allows deadlocks to occur. The operating system periodically checks for deadlocks, and if one is detected, it takes steps to resolve the situation. This approach is often used in systems where completely preventing deadlocks is difficult or overly restrictive.

Deadlock Detection

Deadlock detection usually involves constructing a resource allocation graph (RAG), a diagram showing which processes hold which resources and which processes are waiting for resources. In systems with only one instance of each resource type, a cycle in the RAG indicates a deadlock. For systems with multiple instances of each resource type, a more sophisticated algorithm (like the Banker's algorithm) is needed.

Deadlock Recovery Strategies

Deadlock recovery involves breaking the deadlock cycle. There are two main approaches:

Recovery Methods Focusing on Resources

  1. Resource Preemption: Forcibly taking a resource from a process and giving it to a waiting process. Choosing which resource to preempt can be challenging.
  2. Rollback: Restoring the system to a previous safe state. This requires saving checkpoints periodically; however, this method is not very practical as it requires significant additional overhead.

Recovery Methods Focusing on Processes

  1. Process Termination: Killing one or more deadlocked processes. Choosing which process(es) to terminate might require considering factors such as which process has completed the least amount of work.
  2. Terminating All Processes: A drastic measure, resulting in significant performance loss because all processes must restart.