smarm-dev
594392a5ae
A minimal Config::exact(1) program with two actors doing a fixed number of yield_now() calls. No I/O/timers/channels, so the instruction stream stays centered on the naked-asm switch. Frame-pointer-friendly. Intended for single-threaded inspection under a debugger (e.g. llmdbg).
48 lines
1.8 KiB
Rust
48 lines
1.8 KiB
Rust
//! A deliberately small, deterministic smarm program for inspecting the
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//! naked-asm context switch under a debugger (llmdbg).
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//!
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//! Design goals that make it debugger-friendly:
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//! - Exactly one scheduler thread (`Config::exact(1)`) so the whole run is
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//! single-OS-threaded — llmdbg is single-threaded-debuggee only today.
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//! - A known, small number of voluntary yields, so the number of
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//! `switch_to_actor` / `switch_to_scheduler` transitions is predictable.
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//! - Frame pointers preserved (see the [profile] note in how we build it),
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//! so llmdbg's `finish()` and frame-pointer assumptions hold.
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//! - No I/O, no timers, no channels — just the scheduler and the context
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//! switch, to keep the instruction stream centered on the asm we care
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//! about.
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//!
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//! Two actors each yield `N_YIELDS` times, printing a counter. Run normally
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//! it just prints an interleaving. Run under llmdbg with breakpoints on
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//! `smarm::context::switch_to_actor_asm` and
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//! `smarm::context::switch_to_scheduler` to watch the stack pointer hand off
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//! between the scheduler stack and each actor's mmap'd stack.
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use smarm::{init, Config};
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const N_YIELDS: usize = 3;
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fn main() {
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// Single scheduler thread: one OS thread, cooperative only.
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let rt = init(Config::exact(1));
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rt.run(|| {
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let a = smarm::spawn(|| {
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for i in 0..N_YIELDS {
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println!("actor A tick {i}");
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smarm::yield_now();
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}
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println!("actor A done");
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});
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let b = smarm::spawn(|| {
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for i in 0..N_YIELDS {
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println!("actor B tick {i}");
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smarm::yield_now();
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}
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println!("actor B done");
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});
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a.join().expect("A joined");
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b.join().expect("B joined");
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println!("root done");
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});
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}
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