Stack takes an explicit (reserve, guard) shape, both page-rounded and
stored; usable_base derives from the stored guard. Guard default raised
4 KiB -> 64 KiB (DEFAULT_STACK_GUARD): probestack makes one page enough
for Rust frames, but an unprobed C frame can leap a page in one sub rsp
— the motivating SQLite segfault. Reserve default stays 64 KiB
(DEFAULT_STACK_RESERVE); ACTOR_STACK_SIZE retired.
Config::{stack_reserve, stack_guard} thread the runtime defaults into
RuntimeInner pre-rounded. All acquisition/recycling now goes through
acquire_stack/recycle_stack carrying the pool rule: only default-shaped
stacks are pooled (pooled ⇒ default-shaped by induction); custom shapes
mmap fresh and munmap at death. Pool lock still dropped before any mmap.
No public spawn API change (SpawnOpts is the next commit).
Tests: shape rounding + accessors, wide-guard faults at both ends
(subprocess), Config::stack_reserve permits >64 KiB recursion that
previously could only segfault.
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-agent