---
title: "parking_lot"
description: "1 posts about parking_lot, summarised, each linking to the original."
---

# parking\_lot
> 1 posts about parking\_lot, summarised, each linking to the original.

## Articles

### [parking\_lot: ffffffffffffffff...](https://yomu.fyi/post/parking-lot-ffffffffffffffff.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: May 28, 2025
- Type: Incident / postmortem

Fly.io’s fly-proxy, a Rust-based Anycast router, suffered lockups while managing rapidly changing routing state across thousands of servers. An earlier outage came from an if let expression that kept a read lock through both branches, while later regionalization and lazy loading increased write contention in the Catalog. The investigation traced the new failures to parking\_lot’s try\_write\_for wakeup path: after a waiting writer timed out, it attempted to clear WRITER and WRITER\_PARKED together even though one bit had already been cleared, and wrapping arithmetic produced the corrupted lock value 0xFFFFFFFFFFFFFFFE. The parking\_lot team fixed the defect, after which the lockups did not recur; the team also audited Catalog locking, removed if let patterns and RAII lock guards, and added lock-timing metrics, labeled slow-write logs, and holder tracking.