832cbcdf91Doc 19: status DIAGNOSED -> DIAGNOSED + PINNED RED; the repro section leads with the automated deterministic spec (the manual Leonardo flow stays as the field repro). Doc 20: D0 work-log entry; status D-1 + D0 done; next = D1. Doc 21: red-spec section updated to "landed", with the staging test's anti-vacuity role. Carried finding: the strand reproduces on a 2-OBJECT fixture schematic, so warm-load byte volume (the 68/1 dice-loader) is not an ingredient — two concurrent parks suffice. That is why D3 closes this class and D5 is not required for it. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01TEHGiiXMShNXbBr7gSJ7iz
106 lines
6.2 KiB
Markdown
106 lines
6.2 KiB
Markdown
# 19 — Symbol Properties dialog hangs: a stranded tool fiber (live investigation)
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> **Status: DIAGNOSED + PINNED RED, NOT FIXED (2026-08-05).** Reproduced end-to-end in a
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> real browser against the dev platform on the scheduler build, and since D0 also
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> **deterministically in e2e**: `tests/kicad/quasimodal-strand.spec.ts` (6/6 identical —
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> `closed=false dialogs=1 refused-resumes=1`). The fix lands at doc 20 **D3**, where that
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> spec's `test.fail()` marker comes off. Regression-vs-pre-existing is **not yet
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> determined** — see §5. Related: [`17`](17-mailbox-scheduler-plan.md) S4 (waits),
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> [`16`](16-fiber-resume-guard.md) (the quarantine guard), the 8/4 three-UI-bugs triage
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> (which blamed the interlock drain — that is the *symptom layer*, not the proximate cause).
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## 1. Repro
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**Automated (D0, ~30 s, deterministic):**
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`npx playwright test --project=kicad-firefox kicad/quasimodal-strand.spec.ts`. The
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"staging" test proves the window is real (dialog open + timer fired + concurrent-park
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beacons); the "doc-19 red" test clicks OK and records the hang. The overlap is
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structural, not a race: the parking timer (`wasm/bindings/timer_park.h`) is armed
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*after* the dialog is confirmed open, so it necessarily parks on top of the opener's
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open-ended fiber park. Note the strand reproduces on a **2-object fixture schematic** —
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Leonardo's byte volume is not an ingredient, only concurrent parks are.
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**Manual (100%, ~40 s):** dev platform (`npm run dev`), editor at `:3048`, Arduino
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Leonardo schematic:
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1. Open the project URL, wait for load (~30 s).
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2. Double-click the USB receptacle (J1) → **Symbol Properties** opens.
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3. Click OK / Cancel / any control → **nothing happens**. Only the titlebar × closes it.
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## 2. Frozen state (captured live)
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```
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Fibers.__internallyParked = [607191040] // tool fiber, quarantined
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Fibers.__parkSleepBuf = {607191040 → 607977472}
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Asyncify.__pendingSleepContexts= [{buf 607977472, rootOwned:false, cleaned:false},
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{buf 205586432, rootOwned:true, cleaned:false}]
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Asyncify.currData = 205586432, state = 0
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Fibers.__validSuspensions ∌ 607191040 // no resumable suspension
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scheduler: mailbox=3 enqueued=655 delivered=652 // FROZEN (0 progress in 4 s)
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waits=1 waitsBegun=1 waitsResolved=0 // the quasi-modal wait, unresolved
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```
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Console beacons, in order:
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```
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[wx-asyncify] overlapped-wake × 10 (benign: restore over null)
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[wx-asyncify] aliased-wake-live: restoring currData=205586432 over 607977472
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[wx-asyncify] fiber-resume-refused: fiber=607191040 is asyncify-parked mid-body (sleep in flight)
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```
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## 3. What is NOT the cause
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- **Not clicks failing to reach wx.** The OK click produced exactly one
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`wx_dom_event(domId 81, kind 1)` ccall; the button is enabled and hit-testable.
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(Rules out the `WINDOW_DISABLER`/`IsEnabled()` hypothesis.)
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- **Not slow I/O.** The last library network resource completed at t=5 s; the hang was
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inspected at t=277 s with nothing in flight. The fiber's park is waiting on a promise
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that will never settle — a **lost wake**, not pending work.
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- **Not the mailbox/embind/wait bookkeeping.** `strayWrites=0`, `mutQ=0`, no deferred
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wakes, no stranded messages beyond the 3 blocked by the interlock.
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## 4. Mechanism
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The tool fiber running the dialog parks mid-body (the quasi-modal wait). The stale-fiber
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guard correctly marks it `__internallyParked` — its slice ended with a sleep in flight.
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Its resume then arrives and is **refused** (`fiber-resume-refused`), because a quarantined
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fiber has no valid suspension; the guard's contract is "the parked body completes via its
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own wake." Here that wake *is* the refused resume, so nothing ever completes:
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- the fiber never resumes → the dispatch guard it holds is never released →
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- `wxWasmDispatchParked()` stays true forever → `ProcessEvents` is Paint-only and
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`wxWasmMailboxDeliver` bails → **every** subsequent click is deferred and never drained,
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and timer delivery stops (the frozen 652).
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- The × works because `wx_window_close` (`toplevel.cpp`) is ungated and synchronous.
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The 8/4 triage saw the *outer* ring of this (deferred clicks + a drain gated on the same
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predicate) and proposed flushing the queue at depth 0 — that cannot help: the depth never
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returns to 0 because the holder is stranded.
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## 5. Open: regression or pre-existing?
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Undetermined. The quarantine guard and the aliasing repair are pre-existing (ported
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verbatim into the scheduler at S2), but S4 changed *how* a quasi-modal parks
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(`wxWasmRunNestedLoop` pump → `wxWasmBeginWait`/`wxWasmYieldUntil`). Both shapes park the
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fiber mid-body, so the quarantine interaction plausibly predates S4 — but that must be
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proven, not assumed. **A hand-edited legacy glue is not a valid comparison** (attempted
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2026-08-05: stripping the scheduler and re-injecting `handlesleep.js` into a C-lane build
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booted to a fatal `TypeError: … reading 'mode'`). The differential needs a real
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`WX_SCHEDULER=0` docker build of `kicad_editor`, same flow.
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## 6. Fix directions (ranked, none implemented)
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1. **Don't drop a refused resume — defer it.** When `__refuseFiber` fires for a fiber in
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`__internallyParked`, record the pending resume and retry it when that fiber's park
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resolves (`__parkSleepBuf` already maps fiber → its sleep buffer, and the sleep's
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context leaving `__pendingSleepContexts` is the exact "now safe" signal). This is the
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same drop→deliver flip the whole mailbox migration is built on, applied one layer down.
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Caveat: doc 16 closed the *deferral family* for the root-hot case (a suspension broken
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at write time). This is a different case — a healthy fiber quarantined mid-body — so the
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closure does not automatically apply, but the round-6 evidence must be re-read first.
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2. **Make a permanently-held interlock loud** (watchdog beacon after N seconds with a
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parked holder). Diagnostic only, but it turns this class from "UI mysteriously dead"
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into a one-line console verdict.
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3. **Handler fibers** (the ledgered Design-B step): if parkable handlers own scheduler
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contexts, "a parked chain holds the global interlock" stops being representable. This is
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the structural cure and the S5 ledger's unlock for deleting the interlock entirely.
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