Deadlock – Definition & Detailed Explanation – Operating Systems Glossary Terms

I. What is Deadlock?

Deadlock is a situation in computer science where two or more processes are unable to proceed because each is waiting for the other to release a resource. This can result in a standstill where none of the processes can make progress, leading to a system failure or a significant decrease in performance.

II. How Does Deadlock Occur?

Deadlock occurs when a set of processes are competing for resources and each process holds a resource that another process needs. If each process is waiting for a resource that is held by another process, a deadlock situation can arise. This can happen in systems where resources are limited and processes do not release resources in a timely manner.

III. What are the Conditions for Deadlock?

There are four necessary conditions for deadlock to occur:
1. Mutual Exclusion: Resources cannot be shared between processes and can only be used by one process at a time.
2. Hold and Wait: Processes hold resources while waiting for additional resources that are held by other processes.
3. No Preemption: Resources cannot be forcibly taken away from a process. A process must voluntarily release a resource.
4. Circular Wait: There is a circular chain of processes where each process is waiting for a resource held by the next process in the chain.

IV. How Can Deadlock be Prevented?

Deadlock prevention involves ensuring that one or more of the necessary conditions for deadlock are not met. Some strategies for preventing deadlock include:
1. Resource Allocation Graph: Use a resource allocation graph to track resource allocation and ensure that no circular wait condition exists.
2. Lock Ordering: Establish a global order for acquiring locks to prevent circular wait.
3. Timeout Mechanisms: Set timeouts for processes to wait for resources and release resources if the timeout expires.

V. What are the Different Deadlock Handling Strategies?

There are several strategies for handling deadlock once it occurs:
1. Deadlock Detection: Use algorithms to detect deadlock when it occurs.
2. Deadlock Avoidance: Use algorithms to prevent deadlock by carefully managing resource allocation.
3. Deadlock Recovery: Restart processes or release resources to recover from deadlock.
4. Deadlock Ignorance: Ignore deadlock and allow the system to continue running, potentially risking system failure.

VI. How Can Deadlock be Detected and Recovered from?

Deadlock detection involves periodically checking the system for deadlock using algorithms such as the Banker’s algorithm or the Wait-Die algorithm. Once deadlock is detected, recovery strategies can be implemented to resolve the deadlock situation. This may involve killing processes, releasing resources, or restarting processes to break the deadlock and allow the system to continue running smoothly.