Ettore Di Giacinto 24f2d2a4c6 backend(audio-cpp): make the B10 test able to fail, and document LaneEntry ...

Review of the previous commit found the B10 test could not fail for the reason
it was named. It aged the in-flight run to about 120 ms and then tried two
budgets, 30 ms and 60 ms, both under that age, so both callers took the
fail-fast path. "The two failure modes do not share one message" was comparing
two fail-fast messages that differ only in the budget they print, and the
timeout path was never reached. The second budget is now 400 ms, well over the
run's age, so that caller queues and times out, and a new check asserts which
path each caller took instead of inferring it from inequality. A mutant that
makes the fail-fast path emit the timeout message previously died only on B4 and
B8 checks; it now also dies on B10.

Comment-only changes elsewhere. LaneEntry now says it is not reentrant and does
not detect reentrancy: a second entry on a thread that already holds the lane
surfaces as LaneUnavailable with a positive budget, but parks silently in
unbounded mode, which matters because a handler may hold one across a whole
stream. The immovability note now names the shapes that work, an optional
emplaced in place or a unique_ptr, rather than saying to hold the entry
indirectly without saying how; all three documented forms were compiled before
being written down, which is how the note came to say that an optional of an
immovable type cannot itself be returned.

The header's explanation of why fail-fast exists is reworded. Two clauses traced
back to a specification written after reading the Apache-2.0 upstream header,
and while that was judged de minimis, this unit was rewritten precisely to carry
no upstream expression at all.

The margin table in the report was also wrong about which wall-clock margins are
load-sensitive: there are four, not one, and the tightest is the B3 arrival
check, which is now flagged at the call site. No margin value changed and none
moved across 65 runs.

Assisted-by: Claude:claude-opus-5 [Claude Code]
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

2026-07-29 19:03:32 +00:00

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