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AGC: retain label producers and report failed release writes (#719)
* AGC: retain active label producer records
Ported from the archived silent-hill-minimal branch (274ccfdf).
RegisterLabelProducer bounded its history with RemoveRange(0, 1024) once it
reached 4096 entries, which evicts the oldest records regardless of whether
their label write has completed. Those records are not a diagnostic cache:
a suspended DCB resolves its wait_reg_mem by finding the producer that will
write the watched label. Dropping an active record hides an earlier
same-submission label write, so a legitimate in-stream fence suspends
forever and the graphics queue stops.
Compact only completed history, and let the list exceed the soft bound when
every record is still active — correctness over a diagnostic limit.
Two hardening changes over the ported version, because a suspended queue is
exactly when every record is active:
- compaction is a single order-preserving pass instead of repeated RemoveAt,
which would shift the tail per eviction (quadratic) while the label gate is
held;
- when a pass frees nothing the bound is raised to twice the current count, so
registration does not rescan the whole list on every subsequent add, and it
is reset once compaction can make progress again.
Tests: 664 pass, 0 fail (SharpEmu.Libs.Tests 598 -> 600).
* AGC: keep produced label values a suspended wait still needs
GpuWaitRegistry.RecordProduced dropped the entire produced-value table once it
reached 8192 entries:
if (_lastProduced.Count >= 8192) { _lastProduced.Clear(); }
Those entries are release state, not a cache. CollectDeadlockBroken is the only
way out for a DCB suspended on a WAIT_REG_MEM whose label the guest has since
recycled for other data: it replays the value a real producer already wrote to
that label. Clearing the table wholesale erases exactly the records live waiters
depend on, so every such waiter is stranded permanently — the suspended graphics
queue never resumes, and with it the render thread and the whole engine thread
graph park.
That is what Silent Hill (PPSA10112) hits. Its final unsatisfied waits watch
labels holding guest allocator metadata (each reads a pointer into its own
region rather than the expected 1), i.e. recycled memory, which is precisely
the case the deadlock breaker exists to handle — yet agc.deadlock_break fires 0
times across a run with 490 wait suspensions and 1068 successful release_mem
writes, because the producing values had already been cleared.
Prune only values no registered waiter is watching, and let the table exceed the
soft bound while they are all watched. Same reasoning as the label-producer
history in the preceding commit: correctness of synchronization state takes
precedence over a diagnostic bound.
Tests: 666 pass, 0 fail. The regression test fails against the previous
wholesale Clear() and passes with the prune, verified by reverting the fix.
* AGC: report release-label writes that never reach guest memory
Both release_mem handlers recorded the produced label value only on success:
if (wroteData && dataSelection is 1 or 2) GpuWaitRegistry.RecordProduced(...)
with no else. A failed write is not benign here. That packet is the producer a
suspended WAIT_REG_MEM is waiting for, so when it fails the label is neither
written nor recorded, CollectDeadlockBroken has no value to replay, and the
graphics queue stays suspended forever — the render thread and the engine
thread graph park behind it with nothing in the log to say why.
Measured on Silent Hill (PPSA10112): the fatal AccessViolation lands exactly
here, on the presenter thread, in ApplySubmittedReleaseMem's label write into a
protected guest page. The faulting variant kills the process; the
returns-false variant wedges the GPU silently. Only the first was ever visible.
Report the failure (rate-limited: first 16, then powers of two) instead of
dropping it. This does not fix the underlying write failure — it makes a
permanently suspended queue diagnosable rather than silent.
Tests: 666 pass, 0 fail.
This commit is contained in:
kuba