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Deadlock issues in deadlock detection & resolution


  • Deadlock is a fundamental problem in distributed systems.
  • A process may request resources in any order, which may not be known a priori and a process can request resource while holding others.
  • If the sequence of the allocations of resources to the processes is not controlled.
  • A deadlock is a state where a set of processes request resources that are held by other processes in the set.

Deadlock Detection:

1. Resource Allocation Graph (RAG) Algorithm:

  • Deadlock detection typically involves constructing a resource allocation graph based on the current resource allocation and request status.
  • The RAG algorithm identifies cycles in the graph, indicating the presence of a potential deadlock.
  • However, the RAG algorithm suffers from scalability issues in large systems due to the overhead of maintaining the graph.

2. Resource-Requesting Algorithms:

  • Another approach is to periodically check the state of resource requests and allocations to identify potential deadlocks.
  • This approach involves tracking the resource allocation state and examining resource requests to detect circular waits.
  • However, this method may have high overhead and can only identify deadlocks when they occur during the detection phase.

Deadlock Resolution:

1. Deadlock Prevention:

  • Prevention involves ensuring that at least one of the necessary conditions for deadlock (mutual exclusion, hold and wait, no preemption, circular wait) is not satisfied.
  • By carefully managing resource allocation and enforcing certain policies, deadlocks can be avoided altogether.
  • However, prevention methods can be complex, restrictive, and may limit system performance or resource utilization.

2. Deadlock Avoidance:

  • Avoidance involves dynamically analyzing resource requests and allocations to ensure that the system avoids entering an unsafe state where a deadlock can occur.
  • Resource allocation is made based on resource requirement forecasts and resource availability to prevent circular waits.
  • Avoidance requires a safe state detection algorithm to determine if a resource allocation will lead to a deadlock.
  • However, avoidance techniques may suffer from increased overhead and may limit system responsiveness.

3. Deadlock Detection with Recovery:

  • Deadlock detection algorithms can be used to periodically check the system’s state for potential deadlocks.
  • Once a deadlock is detected, recovery mechanisms can be employed to resolve the deadlock.
  • Recovery may involve aborting one or more processes, rolling back their progress, and reallocating resources to allow the system to continue.
  • However, recovery mechanisms can be complex and may result in data loss or system instability.