smarm/tests/cross_thread_wake.rs

//! Cross-thread wake: a thread that is *not* a smarm scheduler thread must be
//! able to wake (and stop) a parked actor.
//!
//! The gap this pins down: every off-runtime wake primitive (`unpark`,
//! `unpark_at`, `request_stop`) reaches the runtime through the `RUNTIME`
//! thread-local, which is `None` on any non-scheduler thread — so a wake
//! issued from a foreign OS thread is a silent no-op and the parked actor
//! sleeps forever. Both failure modes below manifest as `Runtime::run` never
//! returning, so each test is wrapped in a watchdog: a timeout is the failure.
//!
//! The fix mirrors RFC 018's IO backend — the waker reaches the runtime
//! through a `Weak<RuntimeInner>` it already holds (the receiver captures one
//! when it parks; `Runtime::handle()` hands one to an app thread).

use std::sync::mpsc;
use std::thread;
use std::time::Duration;

const WATCHDOG: Duration = Duration::from_secs(10);
/// Give the target actor time to actually park before the foreign thread pokes
/// it, so we exercise the *wake* of a parked actor rather than the entry-side
/// stop check.
const SETTLE: Duration = Duration::from_millis(200);

fn assert_send_sync<T: Send + Sync>() {}

/// A cross-thread `send` from a plain OS thread must wake a receiver parked in
/// `recv`. Under the thread-local-only wake path the send enqueues the message
/// but never wakes the receiver, so `recv` — and therefore `run` — hangs.
#[test]
fn foreign_thread_send_wakes_parked_receiver() {
    let (done_tx, done_rx) = mpsc::channel();
    thread::spawn(move || {
        let rt = smarm::init(smarm::Config::exact(2));
        rt.run(|| {
            let (tx, rx) = smarm::channel::<u32>();
            // Receiver actor: parks on recv until the foreign thread sends.
            let h = smarm::spawn(move || {
                assert_eq!(rx.recv().expect("recv"), 42);
            });
            // Foreign (non-scheduler) OS thread owns the Sender and sends
            // after the receiver has parked.
            let sender = thread::spawn(move || {
                thread::sleep(SETTLE);
                tx.send(42).expect("send");
            });
            let _ = h.join();
            sender.join().expect("sender thread");
        });
        let _ = done_tx.send(());
    });
    done_rx
        .recv_timeout(WATCHDOG)
        .expect("run did not return: a foreign-thread send never woke the parked receiver");
}

/// A cross-thread `request_stop` through a `RuntimeHandle` must wake and stop a
/// parked actor. The actor parks on a long sleep (only a stop can end it); the
/// handle is grabbed before `run` and driven from a foreign thread.
#[test]
fn foreign_thread_request_stop_wakes_parked_actor() {
    assert_send_sync::<smarm::RuntimeHandle>();

    let rt = smarm::init(smarm::Config::exact(2));
    let handle = rt.handle();

    // Foreign thread: learn the target pid from inside the run, let it park,
    // then stop it through the handle.
    let (pid_tx, pid_rx) = mpsc::channel::<smarm::Pid>();
    let stopper = thread::spawn(move || {
        let pid = pid_rx.recv().expect("pid");
        thread::sleep(SETTLE);
        handle.request_stop(pid);
    });

    let (done_tx, done_rx) = mpsc::channel();
    thread::spawn(move || {
        rt.run(move || {
            let h = smarm::spawn(|| {
                // Parks indefinitely; only a cooperative stop unwinds it.
                smarm::sleep(Duration::from_secs(3600));
            });
            pid_tx.send(h.pid()).expect("send pid");
            let _ = h.join();
        });
        let _ = done_tx.send(());
    });

    done_rx
        .recv_timeout(WATCHDOG)
        .expect("run did not return: a foreign-thread request_stop never woke the parked actor");
    stopper.join().expect("stopper thread");
}

/// A `RuntimeHandle` held across (and beyond) a run must not keep the runtime
/// alive or block all-done: `run` still returns, and once the `Runtime` is
/// dropped the handle degrades to a harmless no-op (Weak lifecycle) rather than
/// panicking or touching freed memory.
#[test]
fn lingering_handle_does_not_block_all_done() {
    let rt = smarm::init(smarm::Config::exact(1));
    let handle = rt.handle(); // outlives the run below

    let (pid_tx, pid_rx) = mpsc::channel::<smarm::Pid>();
    let (done_tx, done_rx) = mpsc::channel();
    let runner = thread::spawn(move || {
        rt.run(move || {
            let h = smarm::spawn(|| {});
            pid_tx.send(h.pid()).expect("send pid");
            let _ = h.join();
        });
        // `rt` is dropped here, at the end of this thread.
        let _ = done_tx.send(());
    });

    done_rx
        .recv_timeout(WATCHDOG)
        .expect("run did not return while a RuntimeHandle was held live");
    runner.join().expect("runner thread");

    // Runtime is now dropped. A stop through the lingering handle must be a
    // silent no-op, not a panic or use-after-free.
    let dead_pid = pid_rx.recv().expect("pid");
    handle.request_stop(dead_pid);
}