Every EditorState leaked its entire worker pool (cores-1 threads, each
waking every 100ms): the Rc<AsyncRuntime> is cloned into dozens of Lua
closures, and registries those closures capture store mlua::Function
values -- reference cycles through the Lua VM that keep the Rc from
ever reaching zero, so WorkerPool::Drop never ran. Harmless for one
editor per process; in the m4 acceptance suite (54 editor-building
tests) it accumulated 1000+ live threads (observed: 60 complete
pmacs-worker-0..14 pools at once) plus ~9k spurious wakeups/second.
Fix: WorkerPool::signal_shutdown() -- set the shutdown flag + wake the
parkers from a shared reference; parked workers exit within their
100ms park timeout. Exposed as AsyncRuntime::shutdown_workers(), called
from a new impl Drop for EditorState. Deliberately signal-only, NO
join on the drop path: a worker can be blocked publishing its reply
onto the bus only the main thread drains, and a first cut that joined
in Drop deadlocked the m4 suite at teardown (fake-LSP tests wedged
2h+). WorkerPool::shutdown() (signal + join) remains for owners with
no bus consumer to deadlock against; Drop delegates to it as before.
Measured on the m4 suite: peak live threads 1026 -> 122.
Regression: tests/worker_shutdown_acceptance.rs (thread-count probe is
/proc-based, Linux-gated; the idempotence test runs everywhere).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Levi Neuwirth
a1f5b1ffd7