Robert Allan JamesandClaude Opus 5.5
4440faf352
VM.running_on claimed by compare-and-swap on switch-in and released once the context is saved (release_after, sk_vm_switch_finish); a lost claim returns 1 and the caller re-decides; double claims counted. Per-core entry_vm and decision_due. g_lock_physics over capsule_vm_physics.c (rank between switch and registry). KILL refuses a VM running anywhere. Probe: 15737 claims, 0 lost, 0 double; a core-1 claim of Hera refused. 3-ISA acceptance with a 28-VM churn clean, 0 order violations. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
103 lines
4.5 KiB
C
103 lines
4.5 KiB
C
/*
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* switch.h - Cooperative VM context switch (FABRIC-3.md §XXVIII, Stage 2,
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* 2026-09-13).
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*
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* sk_vm_context_switch() suspends `from`'s execution exactly where it is
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* (mid-C-call-stack, on from's own native stack -- Stage 1) and resumes
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* `to` -- either for the first time ever (a synthesized initial frame,
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* entering sk_vm_switch_entry()) or exactly where `to` was itself last
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* switched out. Returns to the caller only once something later switches
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* back to `from` -- from from's own point of view, this call simply
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* takes a while to return, like any blocking call.
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*
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* Cooperative only: nothing here is interrupt-driven yet (that's Stage
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* 3), so this is safe to call only from ordinary FORTH word dispatch,
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* never from ISR context.
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*/
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#ifndef STARKERNEL_VM_SWITCH_H
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#define STARKERNEL_VM_SWITCH_H
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#ifdef __STARKERNEL__
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#include <stdint.h>
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struct VM;
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int sk_vm_context_switch(struct VM *from, struct VM *to);
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/* FABRIC-3.10.8 MC-2: how many switches were refused because they would
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* have entered an observer on a core other than core 0 (a guard; 0). */
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uint64_t sk_vm_switch_observer_refusals(void);
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/* FABRIC-3.10.8 MC-3a: the claim. sk_vm_try_claim() takes `vm` for this
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* core (running_on 0 -> core_id + 1) by compare-and-swap: 1 if taken, 0 if
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* another core holds it (counted as lost). sk_vm_context_switch() returns
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* 1 when that happens to `to` -- nothing switched; the caller re-decides.
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* The stats: claims taken, claims lost, and double claims (a switch-in that
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* found its VM held by another core -- must stay 0). */
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int sk_vm_try_claim(struct VM *vm);
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void sk_vm_switch_claim_stats(uint64_t *claims, uint64_t *lost, uint64_t *doubles);
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/* FABRIC-3.md §XXVIII Stage 3 follow-on (2026-09-14): which VM is
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* currently physically running, tracked by the switch mechanism itself --
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* see switch.c's own doc comment on g_switch_current_vm for why this
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* exists instead of reusing vm_log_attributed_vm(). sk_vm_switch_set_
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* current() seeds the initial value (whoever is running before any
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* switch has ever happened) -- call once, at Stage 3 registration time. */
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struct VM *sk_vm_switch_current_vm(void);
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void sk_vm_switch_set_current(struct VM *vm);
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/* FABRIC-3.8.md §3.13.3 (Stage C-b): the word checkpoint's switch point.
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* Call only where `vm` owns its outermost frame (vm_core.c gates this with
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* sk_vm_owns_outermost_frame()). Re-decides only if something physical
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* changed since the last decision (a beat of the running VM, or mail);
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* switches to a strictly cooler VM with work, if there is one. */
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void sk_vm_switch_checkpoint(struct VM *vm);
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/* FABRIC-3.8.md §3.13.5 (Stage C-b, ruling C-5): the idle point. Called
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* from the console's input poll loops (repl.c) each pass with no input.
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* Acts only when Hera is running with no frame live (between lines); then
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* switches to the coolest VM with work, if any.
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*
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* FABRIC-3.9.8 Stage O-B (FABRIC-3.9.0.md §2.5): Hera's own mail is drained
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* here first, one message per call, instead of on the timer-paced idle beat
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* -- she is an observer that acts on events, promptly. may_drain_self is
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* the caller's gate: readline passes (n == 0), so a drained payload never
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* prints into a line being typed. */
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void sk_vm_idle_point(int may_drain_self);
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/* FABRIC-3.8.md §3.5 (Stage D): 1 if `vm` is parked at its own trampoline
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* with nothing in progress -- its frame stack holds exactly one frame, its
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* own VM_FRAME_IDLE. Its saved context is the bare trampoline loop; no
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* payload, no borrowed frame, nothing that would ever need resuming. This
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* is what makes a SWITCHED_OUT VM killable. (Hera parked at her idle point
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* also has one IDLE frame, but she can never be killed anyway.) */
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int sk_vm_parked_idle(const struct VM *vm);
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#endif /* __STARKERNEL__ */
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#endif /* STARKERNEL_VM_SWITCH_H */
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