Register(taskId, cts) already refuses (and logs) a double-registration, but
both call sites discarded the bool and dispatched anyway under an
unregistered CTS. If the loser then unregistered the winner's CTS during
its own cleanup, TryCancel could silently no-op against a live process.
- OverrideSlotService.StartInSlot now fails RunNow/ContinueTask loudly
(throws) when it loses the registration race instead of registering
over — or silently proceeding despite losing to — the queue picker.
- QueueService's picker loop retries registration briefly (the loser's own
claim-attempt-then-unregister resolves fast) before dispatching; if
registration never resolves it marks the already-claimed row Failed
instead of running it unregistered.
- RunCancellationRegistry.Unregister already had compare-and-remove
semantics (TryRemove(KeyValuePair)), so a loser's cleanup could not have
removed the winner's CTS once registration correctly failed.
Added regression tests exercising the real registry through both dispatch
paths: RunNow losing the registration race throws without disturbing the
winner, the picker's retry succeeds and TryCancel reaches the live run when
the loser unregisters in time, and the picker fails the task instead of
running unregistered when it never does.
mika kuns
109e85da83