request_stop(pid) sets a per-actor flag and wakes a parked target. The
actor realizes the stop as a controlled unwind at its next observation
point (check!()/alloc via maybe_preempt, or the wakeup side of any
blocking park): a StopSentinel panic tears the stack down via the
trampoline's existing catch_unwind, running Drop, and is reported as the
new Outcome::Stopped (distinct from a user Panic).
Death surface kept distinct from Exit: Signal::Stopped(pid) +
DownReason::Stopped, so the supervisor await logic to come can tell a
requested stop apart from a self-termination.
Flag lives on Actor behind Arc<AtomicBool>; the scheduler resume path
takes a raw pointer into it (no per-resume refcount traffic), keeping
yield throughput at baseline.
Builds on the existing supervisor_channel funnel (one mailbox per
supervisor; better than N monitor channels given there is no select).
- supervisor.rs: Restart{Permanent,Transient,Temporary}, ChildSpec (an
Fn factory so children can be re-instantiated), and OneForOne with a
builder (child/intensity) and run() supervision loop. Restart decision
keys off whether the Signal was a panic; a sliding-window intensity cap
stops crash loops and returns instead of spinning.
- Does NOT forcibly terminate children: shared-heap + Drop make async
teardown of a peer unsound, so one_for_all/rest_for_one and true links
wait on a cooperative-cancellation primitive. Cap-trip just stops
restarting; live children are left as-is.
tests/supervisor.rs: transient restart-then-settle, transient/temporary
no-restart, permanent crash-loop hitting the cap, and one-for-one
isolation across two children. Full suite green.
`monitor(pid) -> Receiver<Down>` lets any actor watch any other and
receive a single Down{pid, reason} when it terminates. Generalizes the
existing single supervisor_channel (which is just a hard-wired monitor
the parent installs at spawn).
- src/monitor.rs: Down / DownReason{Exit,Panic,NoProc} + monitor().
Payload-free: a panic payload has one owner and goes to the joiner via
JoinError, so monitors learn only that it panicked. Monitoring an
already-gone pid yields NoProc immediately.
- runtime: Slot grows `monitors: Vec<Sender<Down>>`; finalize_actor
drains and notifies them outside the shared lock (send can unpark a
receiver, which re-takes the non-reentrant mutex). Cleared in
reclaim_slot and on slot reuse at spawn.
- Registration and finalize both serialize on the shared mutex, so a
target alive at registration always delivers a real Down (no race
between liveness check and registration).
tests/monitor.rs: Exit, Panic, NoProc-on-dead-target, and fan-out to
multiple monitors. Full suite green.
Stable Rust emits stack probes inline (subq/movq/jne loop) rather than
calling __rust_probestack, so there's no transparent hook for stack-
frame preemption. Override of __rust_probestack links cleanly but never
runs. Falling back to an explicit check!() that users drop into hot
compute loops.
check!() decrements the same ALLOC_COUNT counter as the heap path, so
both event sources fire timeslice checks at the same rate. Documents
the prep-to-park invariant on maybe_preempt — library code that
registers a wakeup and then parks must keep that window alloc-free and
check-free, or a preemption-driven yield in the middle would lose the
wakeup.
Adds a BinaryHeap of timer entries on SchedulerState. sleep() inserts
an entry and parks; schedule_loop pops due entries each iteration and
unparks them. When the run queue is empty but timers are pending, the
OS thread sleeps until the soonest deadline.
Single-threaded only; thread::sleep is fine because no other thread
can wake us. The IO thread coming next will need a Condvar or pipe
wakeup to break this OS-sleep early.
Hand-rolled context switching on mmap'd stacks with guard pages,
allocator-driven RDTSC preemption, unbounded MPSC channels, supervision
via per-slot Signal mailboxes, root supervisor as sentinel PID.
Lib + tests + benches clean check/clippy. All 29 tests pass.
Bench: smarm 3.4% over serial baseline, within 160us of tokio
current-thread on prime-counting fan-out.
smarm-dev