7e2603a9e5
Lockstep livelocked the scheduler the same way --parallel did before
0332d19: the kernel deadline-arithmetic (`now_basis_at`) read per-thread
`ctx(hw_id).timebase`, but a parked/poll thread has `running_idx == None`
so `Scheduler::ctx()` returns `idle_ctx` (timebase 0). A poll thread (tid=7,
a `KeWaitForSingleObject` loop with a 30ms relative timeout) computing its
deadline via `parse_timeout` therefore read `now = 0` and registered
`deadline = 0 + 3000 = 3000` — a constant ~7.78M units in the past.
`coord_idle_advance` then re-armed that same constant 3000 deadline forever,
pinning virtual time and starving every other thread's real future deadline.
Render-gate impact: the submitter (tid=6) re-enters a 16ms-timeout
WaitForMultiple after its first jobs; that timeout never fired because vtime
was pinned at 3000, so virtual time never reached real future deadlines.
Fix (Option A — mirror the parallel fix): drive the existing deterministic
`Scheduler::global_clock` in lockstep too (floored up once per outer round
to `stats.instruction_count`, a pure function of retired guest instructions —
no wall-clock), and route `KernelState::now_basis_at` through `global_clock()`
in BOTH modes. New `Scheduler::advance_global_clock_to(now)` floor-up keeps it
monotone alongside `advance_all_timebases_to`. Parallel behavior unchanged
(it already read `global_clock()`).
Verified (lockstep, 50M):
- DETERMINISM: two cold `check -n 5M` and two cold `-n 50M` runs byte-identical.
- LIVELOCK GONE: "advanced to deadline" went from 592,679 fires / 2 unique
values / 562,084 pinned at 3000 -> 18,586 fires / 18,567 unique /
0 pinned, strictly increasing 5.4M -> 50M. Poll thread tid=7 now ends
Blocked with a real future deadline Some(60002824) instead of spin-Ready
on the past 3000.
- imports 1,790,936 -> 92,317 at 50M (the spin no longer burns import calls).
Cascade (lockstep, XENIA_CACHE_PERSIST=1, -n 200M): engine now runs to budget
instead of hard-deadlocking. Hub enqueue (sub_82458068) 4x; submitter dequeue
(sub_82458508) still 3x — the lost 4th-job HANDOFF (count/notify between
sub_82458068's tail and the submitter queue) is a SEPARATE downstream gate,
not the timebase. New gate: tid=5 (hub) Blocked INFINITE on event 0x1080
(job-4 completion); tid=6 (submitter) Ready, parked in WaitForMultiple
(sub_824AB214), loop-top stops at cycle 6.23M. draws still 0, VdSwap 1.
Golden re-baseline (same commit): sylpheed_n50m
instructions 50000004 -> 50000007, imports 1790936 -> 92317
(swaps/draws/RTs/shaders/textures unchanged). sylpheed_n2m unchanged
(livelock onsets after 2M). Suite 665/665 + oracle green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Sylpheed regression goldens
These JSON files anchor xenia-rs check digest output for Project Sylpheed.
Files
| File | -n | Mode | Captures |
|---|---|---|---|
sylpheed_n2m.json |
2_000_000 | full digest | early boot (swaps=0, no rendering) |
sylpheed_n50m.json |
50_000_000 | stable-digest | first VdSwap pair (swaps=2 post-Phase-A) |
Stable-digest mode
sylpheed_n50m.json is captured with --stable-digest, which omits
timing-sensitive counters: packets (±2–8% lockstep noise from a GPU thread
race), resolves, interrupts_delivered, interrupts_dropped,
texture_decodes. The remaining fields are byte-identical across repeated
lockstep runs at a fixed -n.
sylpheed_n2m.json predates the stable-digest flag and uses full-digest
compare. It still works because at -n 2M the GPU pipeline has not produced any
packets yet — packets=0 is trivially deterministic.
Circularity hazard
Per ORACBUG-001/002/003, these goldens were captured by running the same code
they validate. They detect regression from a known-good snapshot, not
correctness. When a planned fix intentionally moves the digest (e.g. a
shader fix landing draws > 0 for the first time), re-baseline the golden as
a separate commit and reference the audit ID in the message.
Re-baselining
cargo build --release -p xenia-app
target/release/xenia-rs check \
"$SYLPHEED_ISO" \
-n 50000000 \
--stable-digest \
--out crates/xenia-app/tests/golden/sylpheed_n50m.json
Running the goldens
cargo test --release -p xenia-app --test sylpheed_oracles -- --ignored --nocapture
The tests are #[ignore]-gated because each run takes a few seconds, which is
unacceptable in the default cargo test cycle. The ISO path defaults to the
contributor's local ~/RE Project Sylpheed/Project Sylpheed*.iso and can be
overridden via SYLPHEED_ISO=/path/to/sylpheed.iso.
n4b canonical-invocation regression anchor (deferred)
The audit's recommended next sprint also called for a sylpheed_n4b.json
golden capturing the canonical reference invocation
xenia-rs check sylpheed.iso -n 4_000_000_000 --parallel --reservations-table.
This is deferred because:
- The
--parallel --reservations-tablecombination is empirically pathologically slow at -n 100M (>32 min per run per the audit memory). At -n 4B the run cost is many hours, not the single-session-friendly 5–15 min the original plan estimated. - Each phase that intentionally moves rendering counters (C, D, E, F) would need a re-baseline of n4b — a significant time cost compounding over the sprint.
Once the renderer-unblock phases (C+D+E) land and draws > 0 is confirmed at
-n 100M lockstep, an n4b artifact may be captured one-shot and stored under
audit-runs/post-fix/ (not as a test golden) as a manual regression anchor for
the canonical invocation.