fix: Queue.LastSubmissionIndex deadlock — atomic instead of mutex - #289
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…R-056) onZero callbacks from Triage() called lastSubmissionIndex() which locked Queue.mu, already held by Submit(). Deadlock chain: Submit → postSubmit → Triage → onZero → lastSubmissionIndex → Queue.mu Fix: lastSubmissionIndex changed from mutex-protected uint64 to atomic.Uint64. Single writer (Submit under mu), lock-free readers (onZero callbacks). Safe because Store happens under mu (sequential) and Load is always-valid.
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Summary
Hotfix for v0.30.28 ADR-056 deadlock:
Submit() → Triage() → onZero → lastSubmissionIndex() → Queue.mu— mu already held by Submit.Fix:
lastSubmissionIndexchanged from mutex-protecteduint64toatomic.Uint64. Single writer (Submit), lock-free readers.Test plan
golangci-lint— 0 issues