Follow-up to the salvaged #93200 commit. Factors the portable
_cross_process_repair_lock ownership pattern (msvcrt on Windows, flock on
POSIX, bounded 120s wait) into a cycle-safe shared primitive,
fts_rebuild_admission() in hermes_state_common, and routes EVERY full
structural FTS rebuild entry point through it:
- SessionSearchMixin.rebuild_fts() (replaces the POSIX-only, fail-open
30s flock from the original commit)
- _init_schema's trigger-repair rebuilds (_rebuild_fts_indexes /
_rebuild_legacy_fts_indexes) via _run_admitted_startup_rebuild
- _recover_stale_fts()
Fail closed: a caller that cannot acquire the authority DEFERS the rebuild
(FTS detached + durable stale breadcrumb, retried at next startup) instead
of proceeding into the exact concurrent-rebuild interleaving that
structurally corrupted state.db in production. Chunked deferred backfill
(fts_rebuild_step) intentionally stays outside the authority.
Adds spawned-process regression tests (real child process holding the real
lock file): holder blocks contender, deferral fails closed on both the
runtime and schema paths, release/holder-death permits the next owner, and
stale recovery completes after contention clears. Sabotage-verified: 4/6
tests fail with the admission forced open.
Teknium
9d0727d49b