- acquireWriterLock now CLAIMS with an atomic create-exclusive write (O_EXCL)
inside a bounded retry loop: two processes racing an absent lock can never
both succeed (the old read-then-tmp-rename flow let the loser keep running
unlocked, silently). An EEXIST loser re-evaluates and either throws loudly
with the winner's details or performs a verified stale-takeover (re-read
before unlink so a lock that changed hands mid-deliberation is never
clobbered). Exhausted contention fails loudly instead of degrading into a
lockless open.
- BRAINY_WRITER_LOCKED passes through init() unwrapped: the error documents a
machine-readable contract (err.code + err.lockInfo with the holder's
pid/host/heartbeat), but init's blanket error wrapping stripped both,
leaving consumers a message to regex against.
- Two contract tests added: stale-foreign takeover installs OUR lock via the
atomic claim; the conflict error carries code + lockInfo at the public
init() surface.
David Snelling
01a3b46ade