Vibe codingHardvc-g184

Subject Ai code reviewLevel Senior–Staff~20 minCommon in Concurrency interviewsIndustries Software development, Technology

Question

An AI wrote this Rust rate-limiter counter and claims it's lock-free and correct because it uses atomics. Review the atomic logic.

rust

1use std::sync::atomic::{AtomicU64, Ordering};2 3struct Limiter { count: AtomicU64, max: u64 }4 5impl Limiter {6    fn try_acquire(&self) -> bool {7        let current = self.count.load(Ordering::Relaxed);8        if current >= self.max {9            return false;10        }11        self.count.store(current + 1, Ordering::Relaxed);12        true13    }14}

Under heavy concurrency it lets through more than `max`. Explain the race and fix it.

What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it — tests, edge cases, reading critically — and how you’d re-prompt or decompose to get it right.

Learn the concepts

Describe your solution

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.