Substrate for fork-per-accept pattern in gpu-worker.lsp — enables
async bend dispatch with internal load balancing.
c-tier (builtins.c):
- bi_fork_self: fork() wrapper, returns 0 in child / pid in parent / #f on fail
- bi_waitpid_nonblock: waitpid(-1, WNOHANG), returns reaped pid or 0
- bi_exit_immediate: _exit() wrapper — REQUIRED in fork-self children,
regular exit() runs atexit handlers against shared parent state and
hangs the child (observed empirically 2026-06-11 via vm-runner.sh).
- bi_sleep: real wall-clock sleep(3) — yields CPU. Replaces busy-loop
patterns that would (a) burn CPU and (b) SIGKILL in cgroup-limited
VMs (observed: 100M iter let-loop SIGKILL'd after 5s in qemu vm).
python-tier (lumbda.py): _fork_self / _waitpid_nonblock / _exit_immediate
/ _sleep mirrors via os.fork / os.waitpid / os._exit / time.sleep.
Tested in vm-runner.sh VM (Ubuntu 2G/2vCPU): 3-child fork-cycle test
spawns + reaps cleanly 3/3 in both c-tier + python-tier. The exact
test pattern that crashed neoblanka host pre-fix now works fine.
Asm tier: deferred. Lock retained at chmod a-x ~/git/lumbda/asm/lumbda*
per CLAUDE.md threat model.
russell@unturf.com
81ac49ece0