Lockstep vsync delivery was capped at 54/run despite the ticker firing
333 periods and dispatcher being called 1.2M times. Root cause: the
blanket `is_in_callback()` gate skipped dispatch entirely whenever the
async audio path held `interrupts.saved`, which is essentially the
entire boot (audio worker rarely hits its LR_HALT_SENTINEL between
back-to-back callbacks). 5.85M dispatch_skip_in_callback events drowned
out the 55 with-pending windows.
Graphics dispatch (iterate-2.BE) runs the ISR synchronously and
restores the borrowed context before returning — it doesn't touch
`interrupts.saved`. The only real conflict is if graphics picks the
*same* thread audio borrowed (which would stomp audio's
SavedCallbackCtx). Replace the blanket gate with per-thread exclusion:
when audio is mid-flight, exclude only its `injected_ref` from
victim selection. Falls through to the existing no-victim drop if
that's the only candidate.
Lockstep (50M instr): gpu.interrupt.delivered{source=0} 54 → 295
(5.5×), all 333 ticker periods either delivered or unarmed (no more
queue_full_drops). Wallclock unchanged ~3 s.
Parallel (30M instr): 1193 → 3458 baseline lift (2.9×), no regression.
Tests: xenia-kernel 127/127, xenia-app 5/5 non-ignored. Lockstep
goldens will drift (interrupts.delivered is in the digest); deferred
to next iterate.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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