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Tokio's multi-thread scheduler has an unfixed vulnerability where all worker threads can end up parked on condvars with no worker driving the I/O reactor. Condvar-parked workers have no timeout and sleep indefinitely, so once in this state the runtime never recovers. This was observed on a box migrating from 0.3.5.1: after heavy task churn (package reinstalls, container operations, logging) all 16 workers ended up on futex_wait with no thread on epoll_wait. The web server listened on both HTTP and HTTPS but never replied. The box was stuck for 7+ hours with 0% CPU. Two mitigations: 1. Watchdog OS thread (startd.rs): a plain std::thread that every 30s injects a no-op task via Handle::spawn. This forces a condvar-parked worker to wake, cycle through park, and grab the driver TryLock — breaking the stall regardless of what triggered it. 2. block_in_place in the logger (logger.rs): the TeeWriter holds a std::sync::Mutex across blocking file + stderr writes on worker threads. Wrapping in block_in_place tells tokio to hand off driver duties before the worker blocks, reducing the window for starvation. Guarded by runtime_flavor() to avoid panicking on current-thread runtimes used by the CLI.
StartOS Backend
- Requirements:
- Install Rust
- Recommended: rust-analyzer
- Docker
Structure
startos: This contains the core library for StartOS that supports buildingstartbox.helpers: This contains utility functions used across bothstartosandjs-enginemodels: This contains types that are shared acrossstartos,js-engine, andhelpers
Artifacts
The StartOS backend is packed into a single binary startbox that is symlinked under
several different names for different behavior:
startd: This is the main daemon of StartOSstart-cli: This is a CLI tool that will allow you to issue commands tostartdand control it similarly to the UIstart-sdk: This is a CLI tool that aids in building and packaging services you wish to deploy to StartOS
Documentation
- ARCHITECTURE.md — Backend architecture, modules, and patterns
- CONTRIBUTING.md — How to contribute to core