nx_registry_txn.nx

nx_registry_txn.nx -- the RACE-FREE registry-write COORDINATOR (operator 2026-06-14: "fix this race callout from the hardware rung up to be S-class exceed"). THE RACE: nx_reconcile / nx_mark_migrate / nx_express_lane all do read-modify-write on assignment_queue.tsv / row_markers.tsv with NO lock. Atomic-rename saves them from a TORN file (corruption) but NOT from a LOST UPDATE: if two run concurrently both read the same base, both rewrite, the second clobbers the first. (Confirmed: el_apply_mark renames, reconcile/mark_migrate truncate-write; none lock.) HARDWARE RUNG: the lock primitive flock was silently broken -- rv64 syscall 32 had NO entry in the rv64->x86_64 map (nx_x86_64_ctx.nx) so it fell through to x86_64 32 = dup2 (a no-op "lock"). FIXED (32->73). And flock is anyway dead on /mnt/c drvfs. So the drvfs-safe mutual-exclusion primitive is an O_CREAT|O_EXCL lockfile (kernel guarantees ONE creator wins, no TOCTOU) + atomic renameat. S-CLASS EXCEED over the incumbent ad_acquire_lock (which HARD-FAILS on contention with NO staleness recovery): this coordinator SPIN-SERIALIZES contenders AND self-heals a stale lock left by a crashed holder (the lockfile stamps its acquire-epoch; a lock older than RT_STALE_SEC is stolen) -- so it is serializable + crash-safe + drvfs-portable, exceeding flock (drvfs-dead), atomic-rename-alone (loses updates), and ad_acquire_lock (deadlocks on a crashed holder). SELF-GATE (no-args): fork 2 writers, each does N lock-guarded increments of a counter file. GUARDED -> final == 2N (no lost update). UNGUARDED control -> final < 2N (the race is real, the lock necessary). GREEN iff guarded==2N AND unguarded<2N. license_tier: ORIGINAL LOCK PRIMITIVE EXTRACTED 2026-06-14: rt_lock/rt_unlock (+ rt_now/rt_unlink/rt_readint/ rt_writeint_fd and the RT_OEXCL/RT_MODE/RT_STALE_SEC consts) now live in the shared mainless lib nx_registry_lock.nx so the queue writers + daemons can share ONE serializable lock (DRY, rule 15). This organ now imports the lib ONLY (NOT nx_syscalls directly -- the lib pulls it in transitively; the nx_assign_core<-nx_dep_audit convention that dodges the double-import rc=6). This file stays the GATE that proves the lib (RTXN-GATE = fork-2-writers losslessness).