On ARCHIVE (replay-heavy) startup the restore counters could drift:
numberofracesrestoreddoneloading short and numberofracesstillloading
negative (observed -1). The negative count traced to a single race whose
stillLoading-- callback fired twice against one matching raceAdded +1.
Every restored race arms runWhenDoneLoading twice, from two independent
sites with two distinct runnables (restore path -> doneLoading++, and
RaceAdditionListener.raceAdded -> stillLoading--), each meant to fire
once. The old runWhenDoneLoading removed its listener inside
statusChanged with no one-shot guard. Because notifyListeners snapshots
the listener set under lock and then iterates the snapshot outside the
lock, a removeListener happening during dispatch does not shorten an
already-in-flight iteration. When a race crossed past-LOADING twice
back-to-back under concurrent status pushes (loader finish plus the
stopTracking teardown), a second dispatch snapshotted the listener array
before the first dispatch's removeListener landed, so the callback fired
on both transitions -> two decrements vs one increment -> net -1 (and a
symmetric +1 over-count on doneLoading).
Rewrite runWhenDoneLoading to mirror runWhenPastLoading: a settled
AtomicBoolean CAS makes firing strictly one-shot per registration no
matter how many times or along how many concurrent paths the transition
is delivered, plus a cooperating regatta raceRemoved listener that tears
down and settles-without-firing if the race is removed while still
PREPARED/LOADING/ERROR (closing the companion bug6241 listener-leak
class).
Add TrackedRaceRunWhenDoneLoadingTest as contract tests for the
single-fire / already-done / removed-before-done / fire-then-remove
behaviours. Note these do not reproduce the production concurrency
interleaving: setStatus dispatches statusChanged synchronously and
sequentially, so single-threaded JUnit cannot deterministically recreate
the snapshot/remove race; the fix rests on the settled CAS.
Assisted-By: Claude (Anthropic claude-4.8-opus)
Axel Uhl
15dbbc03a1