revoke_commit_admission() used to invoke the holder-qualified lease
release unconditionally — including while an admitted commit was still
mutating SessionDB — letting a second compressor acquire the durable
lock mid-commit and interleave with the first commit's writes.
The admission_revoked flag store stays lock-free, but the lease-release
decision now coordinates with the fence lock:
- revoke acquires the fence lock non-blocking; on success no commit can
be in flight (an admitted commit retains the lock until finish_commit)
and the release runs immediately, still under the lock so a racing
begin_commit cannot slip between the check and the release.
- on failure the release is deferred: finish_commit() re-checks
_admission_revoked and performs it AFTER the commit completes (prompt
even if the worker thread is later parked), and the begin_commit
refusal path does the same for a revoke that lost the race to a
transient lock-setup/cancel boundary. All paths are idempotent with
the worker's own outer cleanup (DB release is holder-qualified).
Invariant encoded + tested: no second compressor can acquire the durable
lock while an admitted commit is still mutating; after a post-revoke
commit finishes the lease is released promptly. Both regressions
(revoke-during-commit deferral, revoke-before-commit immediate release +
refused begin_commit) are sabotage-verified.
Teknium
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