shoney.arickathil
ab8ef64cd9
- five stories under docs/stories/runtime-v2/: 1 streaming subprocess (42's follow-up; five forks incl. the mailbox-cap collision), 2 PTY, 3 signals-as-events (signalfd lean), 4 termios adoption, 5 SCM_RIGHTS fd passing; 00-story states the arc — the plane learned sockets in 8/11/35, files in 6, this adds processes/terminals/signals - build order 1 -> 2 -> 3; 4 and 5 startable alone; all readiness: refine, brainstormed on demand - board: Five tracks; "▸ runtime-v2" pending section; wmux section now points at it; graph section 6 nodes carry runtime-v2 numbers + links - wmux stories re-reference the track; prefix `rt2` claimed - linkcheck: 0 broken Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> (cherry picked from commit e0451cb4889bb3d03429c0276d03c090269a5ced)
57 lines
2.5 KiB
Markdown
57 lines
2.5 KiB
Markdown
---
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track: runtime-v2
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iteration: "3"
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status: pending
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readiness: refine
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---
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# runtime-v2 3 — signals as events: SIGWINCH into a mailbox
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> Part of [Story — runtime-v2: the runtime beyond sockets](00-story.md).
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> The seam iteration
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> [42](../language-runtime-database/42-bounded-subprocess.md)
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> deliberately deferred "to its real consumer" — this is that consumer
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> arriving. A terminal application's resize IS a signal (SIGWINCH), and
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> nothing today can turn a signal into anything a program observes
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> except the SIGTERM/SIGINT stop latch.
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>
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> **The problem.** Signals are process-global, delivered on an arbitrary
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> thread, and allowed to do almost nothing — the exact opposite of a
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> shard-owned mailbox message. The runtime already crossed this bridge
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> once: the stop flag is a signal made safe by latching. This iteration
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> generalizes that shape without handing user code a signal handler.
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## Info — the forks (open)
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1. **Registration surface.** `signal.on(SIGWINCH, addr, msg)` in the
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`time.after` mould (the msg MOVES to the runtime, delivered on
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arrival) versus a process-level subscription table in `wo.toml`.
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Lean: the builtin — dynamic, one consumer today.
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2. **Delivery mechanics.** `signalfd` on shard 0's plane (a signal
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becomes an fd event — no async-signal-safety questions at all, the
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kernel-primitive taste) versus a latch array swept like deadlines.
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Lean: signalfd; the runtime is Linux-first and the plane already
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multiplexes fds.
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3. **Which signals are offerable.** SIGWINCH and SIGCHLD certainly;
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SIGTERM/SIGINT stay the ENGINE's (the stop latch is load-bearing —
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iteration 40's drain). The fork is whether user registration for the
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stop signals is refused by name or layered before the latch.
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4. **Coalescing.** Signals coalesce in the kernel; a mailbox message per
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delivery can't promise one-per-resize. Disclose coalescing (lean —
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it is what SIGWINCH consumers expect anyway) versus sequence-number
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them.
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## Acceptance sketch
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- Resize the controlling terminal of a test child: the registered actor
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receives the message; the grid-owning code calls
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[2](02-pty.md)'s resize onward — the wmux wiring, proven in miniature.
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- SIGCHLD registration does not disturb 42's pidfd machinery (they
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coexist; the pidfd stays the reap path).
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- SIGTERM still stops the engine with the full drain — the iteration 40
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battery unchanged.
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## Consumers
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wmux 1 (SIGWINCH fan-out to panes). Everything else can wait — this
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iteration exists exactly once a real consumer does, per 42's deferral.
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