1 files changed, 313 insertions, 0 deletions
diff --git a/rtic-time/tests/delay_precision_subtick.rs b/rtic-time/tests/delay_precision_subtick.rs
new file mode 100644
index 0000000..4db889c
--- /dev/null
+++ b/rtic-time/tests/delay_precision_subtick.rs
@@ -0,0 +1,313 @@
+//! A test that verifies the sub-tick correctness of the [`TimerQueue`]'s `delay` functionality.
+//!
+//! To run this test, you need to activate the `critical-section/std` feature.
+
+use std::{
+    fmt::Debug,
+    future::Future,
+    pin::Pin,
+    sync::{
+        atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering},
+        Arc,
+    },
+    task::Context,
+    thread::sleep,
+    time::Duration,
+};
+
+use ::fugit::ExtU64Ceil;
+use cooked_waker::{IntoWaker, WakeRef};
+use parking_lot::Mutex;
+use rtic_time::{Monotonic, TimeoutError, TimerQueue};
+
+const SUBTICKS_PER_TICK: u32 = 10;
+struct SubtickTestTimer;
+static TIMER_QUEUE: TimerQueue<SubtickTestTimer> = TimerQueue::new();
+static NOW_SUBTICKS: AtomicU64 = AtomicU64::new(0);
+static COMPARE_TICKS: Mutex<Option<u64>> = Mutex::new(None);
+
+impl Monotonic for SubtickTestTimer {
+    const ZERO: Self::Instant = Self::Instant::from_ticks(0);
+    const TICK_PERIOD: Self::Duration = Self::Duration::from_ticks(1);
+
+    type Instant = fugit::Instant<u64, SUBTICKS_PER_TICK, 1000>;
+    type Duration = fugit::Duration<u64, SUBTICKS_PER_TICK, 1000>;
+
+    fn now() -> Self::Instant {
+        Self::Instant::from_ticks(
+            NOW_SUBTICKS.load(Ordering::Relaxed) / u64::from(SUBTICKS_PER_TICK),
+        )
+    }
+
+    fn set_compare(instant: Self::Instant) {
+        *COMPARE_TICKS.lock() = Some(instant.ticks());
+    }
+
+    fn clear_compare_flag() {}
+
+    fn pend_interrupt() {
+        unsafe {
+            Self::__tq().on_monotonic_interrupt();
+        }
+    }
+}
+
+impl SubtickTestTimer {
+    pub fn init() {
+        Self::__tq().initialize(Self)
+    }
+
+    pub fn tick() -> u64 {
+        let now = NOW_SUBTICKS.fetch_add(1, Ordering::Relaxed) + 1;
+        let ticks = now / u64::from(SUBTICKS_PER_TICK);
+        let subticks = now % u64::from(SUBTICKS_PER_TICK);
+
+        let compare = COMPARE_TICKS.lock();
+
+        // println!(
+        //     "ticks: {ticks}, subticks: {subticks}, compare: {:?}",
+        //     *compare
+        // );
+        if subticks == 0 && Some(ticks) == *compare {
+            unsafe {
+                Self::__tq().on_monotonic_interrupt();
+            }
+        }
+
+        subticks
+    }
+
+    pub fn forward_to_subtick(subtick: u64) {
+        assert!(subtick < u64::from(SUBTICKS_PER_TICK));
+        while Self::tick() != subtick {}
+    }
+
+    pub fn now_subticks() -> u64 {
+        NOW_SUBTICKS.load(Ordering::Relaxed)
+    }
+
+    fn __tq() -> &'static TimerQueue<Self> {
+        &TIMER_QUEUE
+    }
+
+    /// Delay for some duration of time.
+    #[inline]
+    pub async fn delay(duration: <Self as Monotonic>::Duration) {
+        Self::__tq().delay(duration).await;
+    }
+
+    /// Timeout after a specific duration.
+    #[inline]
+    pub async fn timeout_after<F: core::future::Future>(
+        duration: <Self as Monotonic>::Duration,
+        future: F,
+    ) -> Result<F::Output, TimeoutError> {
+        Self::__tq().timeout_after(duration, future).await
+    }
+}
+
+rtic_time::embedded_hal_delay_impl_fugit64!(SubtickTestTimer);
+rtic_time::embedded_hal_async_delay_impl_fugit64!(SubtickTestTimer);
+
+// A simple struct that counts the number of times it is awoken. Can't
+// be awoken by value (because that would discard the counter), so we
+// must instead wrap it in an Arc.
+#[derive(Debug, Default)]
+struct WakeCounter {
+    count: AtomicUsize,
+}
+
+impl WakeCounter {
+    fn get(&self) -> usize {
+        self.count.load(Ordering::SeqCst)
+    }
+}
+
+impl WakeRef for WakeCounter {
+    fn wake_by_ref(&self) {
+        let _prev = self.count.fetch_add(1, Ordering::SeqCst);
+    }
+}
+
+struct OnDrop<F: FnOnce()>(Option<F>);
+impl<F: FnOnce()> OnDrop<F> {
+    pub fn new(f: F) -> Self {
+        Self(Some(f))
+    }
+}
+impl<F: FnOnce()> Drop for OnDrop<F> {
+    fn drop(&mut self) {
+        (self.0.take().unwrap())();
+    }
+}
+
+macro_rules! subtick_test {
+    (@run $start:expr, $actual_duration:expr, $delay_fn:expr) => {{
+        // forward clock to $start
+        SubtickTestTimer::forward_to_subtick($start);
+
+        // call wait function
+        let delay_fn = $delay_fn;
+        let mut future = std::pin::pin!(delay_fn);
+
+        let wakecounter = Arc::new(WakeCounter::default());
+        let waker = Arc::clone(&wakecounter).into_waker();
+        let mut context = Context::from_waker(&waker);
+
+        let mut finished_after: Option<u64> = None;
+        for i in 0..10 * u64::from(SUBTICKS_PER_TICK) {
+            if Future::poll(Pin::new(&mut future), &mut context).is_ready() {
+                if finished_after.is_none() {
+                    finished_after = Some(i);
+                }
+                break;
+            };
+
+            assert_eq!(wakecounter.get(), 0);
+            SubtickTestTimer::tick();
+        }
+
+        let expected_wakeups = {
+            if $actual_duration == 0 {
+                0
+            } else {
+                1
+            }
+        };
+        assert_eq!(wakecounter.get(), expected_wakeups);
+
+        // Tick again to test that we don't get a second wake
+        SubtickTestTimer::tick();
+        assert_eq!(wakecounter.get(), expected_wakeups);
+
+        assert_eq!(
+            Some($actual_duration),
+            finished_after,
+            "Expected to wait {} ticks, but waited {:?} ticks.",
+            $actual_duration,
+            finished_after,
+        );
+    }};
+
+    (@run_blocking $start:expr, $actual_duration:expr, $delay_fn:expr) => {{
+        // forward clock to $start
+        SubtickTestTimer::forward_to_subtick($start);
+
+        let t_start = SubtickTestTimer::now_subticks();
+
+        let finished = AtomicBool::new(false);
+        std::thread::scope(|s|{
+            s.spawn(||{
+                let _finished_guard = OnDrop::new(|| finished.store(true, Ordering::Relaxed));
+                ($delay_fn)();
+            });
+            s.spawn(||{
+                sleep(Duration::from_millis(10));
+                while !finished.load(Ordering::Relaxed) {
+                    SubtickTestTimer::tick();
+                    sleep(Duration::from_millis(10));
+                }
+            });
+        });
+
+        let t_end = SubtickTestTimer::now_subticks();
+        let measured_duration = t_end - t_start;
+        assert_eq!(
+            $actual_duration,
+            measured_duration,
+            "Expected to wait {} ticks, but waited {:?} ticks.",
+            $actual_duration,
+            measured_duration,
+        );
+    }};
+
+
+
+
+    ($start:expr, $min_duration:expr, $actual_duration:expr) => {{
+        subtick_test!(@run $start, $actual_duration, async {
+            let mut timer = SubtickTestTimer;
+            embedded_hal_async::delay::DelayNs::delay_ms(&mut timer, $min_duration).await;
+        });
+        subtick_test!(@run $start, $actual_duration, async {
+            let mut timer = SubtickTestTimer;
+            embedded_hal_async::delay::DelayNs::delay_us(&mut timer, 1_000 * $min_duration).await;
+        });
+        subtick_test!(@run $start, $actual_duration, async {
+            let mut timer = SubtickTestTimer;
+            embedded_hal_async::delay::DelayNs::delay_ns(&mut timer, 1_000_000 * $min_duration).await;
+        });
+        subtick_test!(@run $start, $actual_duration, async {
+            SubtickTestTimer::delay($min_duration.millis_at_least()).await;
+        });
+        subtick_test!(@run $start, $actual_duration, async {
+            let _ = SubtickTestTimer::timeout_after($min_duration.millis_at_least(), std::future::pending::<()>()).await;
+        });
+
+        // Those are slow and unreliable; enable them when needed.
+        const ENABLE_BLOCKING_TESTS: bool = false;
+        if ENABLE_BLOCKING_TESTS {
+            subtick_test!(@run_blocking $start, $actual_duration, || {
+                let mut timer = SubtickTestTimer;
+                embedded_hal::delay::DelayNs::delay_ms(&mut timer, $min_duration);
+            });
+            subtick_test!(@run_blocking $start, $actual_duration, || {
+                let mut timer = SubtickTestTimer;
+                embedded_hal::delay::DelayNs::delay_us(&mut timer, 1_000 * $min_duration);
+            });
+            subtick_test!(@run_blocking $start, $actual_duration, || {
+                let mut timer = SubtickTestTimer;
+                embedded_hal::delay::DelayNs::delay_ns(&mut timer, 1_000_000 * $min_duration);
+            });
+        }
+    }};
+}
+
+#[test]
+fn timer_queue_subtick_precision() {
+    SubtickTestTimer::init();
+
+    // subtick_test!(a, b, c) tests the following thing:
+    //
+    // If we start at subtick a and we need to wait b subticks,
+    // then we will actually wait c subticks.
+    // The important part is that c is never smaller than b,
+    // in all cases, as that would violate the contract of
+    // embedded-hal's DelayUs.
+
+    subtick_test!(0, 0, 0);
+    subtick_test!(0, 1, 20);
+    subtick_test!(0, 10, 20);
+    subtick_test!(0, 11, 30);
+    subtick_test!(0, 12, 30);
+
+    subtick_test!(1, 0, 0);
+    subtick_test!(1, 1, 19);
+    subtick_test!(1, 10, 19);
+    subtick_test!(1, 11, 29);
+    subtick_test!(1, 12, 29);
+
+    subtick_test!(2, 0, 0);
+    subtick_test!(2, 1, 18);
+    subtick_test!(2, 10, 18);
+    subtick_test!(2, 11, 28);
+    subtick_test!(2, 12, 28);
+
+    subtick_test!(3, 0, 0);
+    subtick_test!(3, 1, 17);
+    subtick_test!(3, 10, 17);
+    subtick_test!(3, 11, 27);
+    subtick_test!(3, 12, 27);
+
+    subtick_test!(8, 0, 0);
+    subtick_test!(8, 1, 12);
+    subtick_test!(8, 10, 12);
+    subtick_test!(8, 11, 22);
+    subtick_test!(8, 12, 22);
+
+    subtick_test!(9, 0, 0);
+    subtick_test!(9, 1, 11);
+    subtick_test!(9, 10, 11);
+    subtick_test!(9, 11, 21);
+    subtick_test!(9, 12, 21);
+}