maillon: a concurrent intrusive list for building faster synchronization primitives
maillon is a Rust crate for intrusive waiter lists and synchronization primitives such as Semaphore and Notify. Its design uses stack-pinned nodes, lock-free insertion by default, and configurable ordering/linking strategies; removal still takes a mutex because futures can invalidate stack storage immediately, making ordinary deferred-reclamation techniques unsuitable.
The author says the project has been in development since early this year, is used in a channel crate, and passes Miri, Loom, and Tokio’s Loom tests. The claimed semaphore speedups are from the author’s benchmarks, not independent validation. Reddit commenters questioned the high-contention benchmark and suggested backoff; the author explained why backoff is not the default but can be configured. Others probed the pinning and drop-safety model, prompting details about pinned nodes and the mutex-protected removal path.