Implement Design B from local/docs/INITNSMGR-CONCURRENCY-DESIGN.md:
initnsmgr now uses O_NONBLOCK on openat to provider daemons and
parks requests when the provider is not ready, instead of
blocking the entire request loop.
Previously: open_scheme_resource did a blocking syscall::openat
to the provider. If the provider was briefly not servicing its
socket (descheduled under load, mid-tick, in a one-shot startup
window), the openat blocked, the loop stopped, and every other
request queued behind it. The wedge surfaced at whatever boot
stage was in flight (e.g. 'ahcid' in the logs) - that stage was
the symptom location, not the cause.
Now:
- openat to a provider is called with O_NONBLOCK.
- On Ok(fd), return the fd immediately.
- On EAGAIN, park the request in a bounded PendingOpens queue
(tag, cap_fd, reference, flags, fcntl_flags).
- On any other error, return the error to the caller (preserves
existing behavior).
- After each next_request cycle, retry ALL parked opens with
O_NONBLOCK. Any that succeed are written back to the original
request via the deferred Response API.
- The park queue is bounded (64 entries). On overflow, the
request falls back to the synchronous path (same as before) -
never unbounded growth.
This implements the traffic-driven retry model: as long as new
requests arrive (e.g. processes starting), parked opens are
re-attempted frequently. When the slow provider finally responds,
all parked opens succeed in the next retry sweep.
The kernel change (commit f5baa05d on submodule/kernel) is the
prerequisite: it implements O_NONBLOCK on OpenAt so the openat
syscall returns EAGAIN when the provider hasn't immediately
answered instead of blocking.
Preserves all existing handlers (dup, unlinkat, on_close,
on_sendfd, getdents, fstat, namespace:/"" branches) unchanged.
Only the openat -> open_scheme_resource path is changed.
Per local/AGENTS.md:
- No new branches (work on submodule/base)
- No stubs, no todo!/unimplemented!
- Cat 2 fork - changes committed to submodule/base branch
Closes v5.3 Design B (base side). Kernel side is the companion
commit on submodule/kernel.
kellito
8c7f6172a2