Fall back to a portable lock when flock is unavailable#931
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set-port.sh serialized concurrent port allocation with flock(1) (util-linux), which stock macOS does not ship, so `make dev` aborted on first run with `flock: command not found` on a supported platform. Keep flock where present -- its kernel-managed lock auto-releases on process death -- and fall back to an atomic, per-user directory mutex where it is absent (e.g. macOS). The fallback recovers a lock orphaned by a crashed run via the holder PID's liveness, stealing through an atomic rename so a concurrent run cannot delete a freshly taken lock. test-set-port.sh exercises both paths: existing cases run under real flock, while two new cases force the fallback (allocation works without flock; a stale lock from a dead holder is recovered). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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set-port.shserialized concurrent port allocation withflock(1)(util-linux), which stock macOS does not ship, somake devaborted on first run withflock: command not foundon a supported platform.Keep flock where present — its kernel-managed lock auto-releases on process death, even on SIGKILL — and fall back to an atomic, per-user directory mutex where it is absent (e.g. macOS). The fallback recovers a lock orphaned by a crashed run via the holder PID's liveness, stealing through an atomic rename so a concurrent run cannot delete a freshly taken lock.
test-set-port.shexercises both paths: the existing cases run under real flock, while two new cases force the fallback (allocation works without flock; a stale lock from a dead holder is recovered).