Operating Systemsmedium

What causes deadlocks and how can you prevent them?

Tags

#deadlock#locks#concurrency

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Answer

Deadlocks require four conditions: mutual exclusion, hold-and-wait, no preemption, and circular wait. Prevention breaks at least one condition (e.g., ordering locks or using timeouts).

Advanced answer

Deep dive

Strategies:

Lock ordering to prevent cycles.
Try-lock + backoff to avoid hold-and-wait.
Timeouts and deadlock detection for recovery.
Reduce shared resources to minimize contention.

Examples

Lock ordering rule:

Always acquire locks in order: A -> B -> C

Common pitfalls

Inconsistent lock ordering across code paths.
Long critical sections increasing contention.
Ignoring deadlocks in rare error paths.

Interview follow-ups

When would you prefer detection vs prevention?
How do you debug a deadlock in production?
What is livelock and how is it different?

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