The iterate-2.BE host-driven synchronous ISR dispatcher relies on
something queueing v-syncs. In lockstep that's `tick_vsync_instr`,
called from `coord_pre_round` per round. If the scheduler stalls into
`coord_idle_advance` (no Ready threads), the instruction counter
freezes — the accumulator stops incrementing, the ticker stops
queueing, and the dispatcher is left starved for the duration of the
idle wait.
Tick `tick_vsync_wallclock` at the top of `coord_idle_advance` so
v-syncs keep firing on host time even when the guest scheduler is
parked. The dispatcher in the outer loop drains whatever we queue on
the next iteration. Same MMIO `D1MODE_VBLANK_VLINE_STATUS` bit-set as
the production path.
Note: empirically in Sylpheed at 50M/500M instruction horizons,
`coord_idle_advance` is never reached (tids 9/10/12 stay Ready through
the early-boot deadlock), so this commit doesn't move
`gpu.interrupt.delivered{source=0}` off 54 for this title at these
horizons. It is the correct fix for the documented starvation pattern
and will activate as soon as the kernel reaches a state where Ready
threads drop to zero with timers/waits pending.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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