How does an operating system handle deadlocks?

An operating system handles deadlocks through prevention, avoidance, detection, and recovery strategies.

Deadlocks are a common issue in operating systems, where two or more processes are unable to proceed because each is waiting for the other to release a resource. To manage this, operating systems employ several strategies. The first is deadlock prevention, which aims to ensure that at least one of the necessary conditions for a deadlock does not hold. This can be achieved by implementing a policy that prevents mutual exclusion, hold and wait, no preemption, or circular wait.

Deadlock avoidance is another strategy, which requires the operating system to have prior knowledge about which and when resources will be requested and released. The system then makes decisions based on this information to avoid potential deadlocks. This is often implemented using the Banker's algorithm, which simulates the allocation of resources for each process and checks if it would lead to a safe state (no deadlock) or an unsafe state (potential deadlock).

Deadlock detection is a more reactive approach, where the operating system regularly checks for deadlocks, typically using a resource allocation graph. If a cycle is detected in the graph, a deadlock exists. However, this method can be costly in terms of system performance, especially in large systems with many processes and resources.

Finally, if a deadlock is detected, the system must recover from it. This can be done by terminating one or more processes to break the deadlock, or by preempting resources from some processes and giving them to others. Both methods have their drawbacks: terminating a process can result in lost work, while preempting resources can lead to other issues such as starvation, where a process is perpetually denied the resources it needs.

In conclusion, handling deadlocks is a complex task that requires careful management by the operating system. The chosen strategy will depend on the specific requirements and constraints of the system, and often a combination of strategies is used to effectively manage deadlocks.