The stall classifier's present witness never worked: the consumer was opened
without PROCESS_TRACE_MODE_RAW_TIMESTAMP, so ProcessTrace converted every
event's TimeStamp to FILETIME regardless of the session's ClientContext=1 —
FILETIME ticks (100 ns since 1601) are ~4 orders of magnitude above QPC, so
every ts <= to_q comparison was false. summary() always printed etw=none,
window_counts() always returned presents=0/queue_adds=0 while present_history
was still true (satisfied by the unfiltered ring), and classify() therefore
convicted EVERY compose-silence hole as CONTENT-SILENCE; FRAME-GENERATION —
the class the program exists to catch — was unreachable. Two comments
asserted the wrong contract ("TimeStamp IS a QPC value"); both now state the
real one: ClientContext selects the session clock, RAW_TIMESTAMP is what
stops the FILETIME conversion on delivery.
Three adjacent defects fixed with it:
- summary() and window_counts() each took their own ring lock and their own
(Instant::now(), qpc_now()) anchor, with OpenProcess syscalls between the
two calls — the prose and the verdict could disagree about the same hole.
Merged into window_report(): one snapshot, one anchor, both halves; the
summary keeps its 300 ms lead-in, the counts keep the gap-only window, and
the etw=/etw_presents=/etw_queue_adds= log fields are unchanged.
- present_history/queue_history meant "an event EVER sat in the ring" —
satisfied by events arriving after the hole, or by a previous session's
leftovers in the never-cleared static RING. Both flags now mean witness
LIVENESS: at least one event inside a 5 s LOOKBACK ending at the hole's
start, i.e. the witness demonstrably worked before the hole opened. The
ring is cleared when a new session starts, so a dead session's events can
never pose as the next one's history.
- window_counts() accepted only BltQueueAddEntry (1071) as queue history
while summary() also took BltQueueCompleteIndirectPresent (1068); either
proves the queue witness works, so the merged reader takes both.
The windowing math is factored into a pure count_window() (plain i64 tick
arithmetic) with unit tests, and the classify() matrix gains the live-witness
zero-presents case. Conviction thresholds are untouched.
Verified: scripts/xcheck.sh windows clippy (-D warnings, --all-targets) green
for pf-frame/pf-win-display/pf-capture/pf-vdisplay; native cargo check green.
The new Windows-gated tests type-check but need a Windows box to run.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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