Instrument queue for loom

Cargo.toml

@@ -16,6 +16,9 @@ edition = "2021"
 metrics = "0.22.0"
 tracing = "0.1.40"
 
-[dev-dependencies]
+[target.'cfg(loom)'.dependencies]
+loom = { version = "0.7", features = ["futures"] }
+
+[target.'cfg(not(loom))'.dev-dependencies]
 smol = "2.0.0"
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }

examples/demo.rs

@@ -1,6 +1,9 @@
+#[cfg(not(loom))]
 use std::time::Duration;
+#[cfg(not(loom))]
 use tracing_subscriber::{fmt, prelude::*, EnvFilter};
 
+#[cfg(not(loom))]
 fn main() -> Result<(), Box<dyn std::error::Error>> {
     tracing_subscriber::registry()
         .with(fmt::layer())
@@ -52,3 +55,6 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
         Ok(())
     })
 }
+
+#[cfg(loom)]
+fn main() {}

flake.nix

@@ -20,6 +20,8 @@
           nativeBuildInputs = [ cargo cargo-outdated clippy rust-analyzer rustc rustfmt ];
 
           RUST_SRC_PATH = "${pkgs.rust.packages.stable.rustPlatform.rustLibSrc}";
+
+          LOOM_MAX_PREEMPTIONS = "2";
         };
       });
 }

src/drop_notifier.rs

@@ -1,4 +1,4 @@
-use std::sync::Arc;
+use crate::sync::Arc;
 
 use crate::notify::Notify;
 

src/lib.rs

@@ -7,6 +7,7 @@ mod notify;
 mod queue;
 mod selector;
 mod spsc;
+mod sync;
 
 use std::{
     future::Future,
@@ -21,6 +22,15 @@ use executor::block_on;
 use queue::Queue;
 use selector::select;
 
+#[cfg(any(loom, test))]
+#[doc(hidden)]
+pub mod tests {
+    #[doc(hidden)]
+    pub mod queue {
+        pub use crate::queue::{bounded, queue_count, Queue};
+    }
+}
+
 /// Configuration builder for the CpuPool
 #[derive(Debug)]
 pub struct Config {

src/notify.rs

@@ -1,13 +1,11 @@
 use std::{
     collections::VecDeque,
     future::{poll_fn, Future},
-    sync::{
-        atomic::{AtomicU8, Ordering},
-        Arc, Mutex,
-    },
     task::{Poll, Waker},
 };
 
+use crate::sync::{Arc, AtomicU8, Mutex, Ordering};
+
 const UNNOTIFIED: u8 = 0b0000;
 const NOTIFIED_ONE: u8 = 0b0001;
 const RESOLVED: u8 = 0b0010;
@@ -210,3 +208,213 @@ impl Future for Listener<'_> {
         Poll::Pending
     }
 }
+
+#[cfg(all(test, loom))]
+mod tests {
+    use super::Notify;
+    use std::future::Future;
+
+    struct NoopWaker;
+
+    impl std::task::Wake for NoopWaker {
+        fn wake(self: std::sync::Arc<Self>) {}
+        fn wake_by_ref(self: &std::sync::Arc<Self>) {}
+    }
+
+    fn noop_waker() -> std::task::Waker {
+        std::sync::Arc::new(NoopWaker).into()
+    }
+
+    #[test]
+    fn dropped_notified_listener() {
+        loom::model(|| {
+            loom::future::block_on(async {
+                let notify = Notify::new();
+
+                let listener = notify.listen().await;
+
+                notify.notify_one();
+                drop(listener);
+
+                assert_eq!(
+                    notify.state.lock().unwrap().token,
+                    1,
+                    "Dropped notify should not have consumed token"
+                );
+            });
+        });
+    }
+
+    #[test]
+    fn threaded_dropped_notified_listener() {
+        loom::model(|| {
+            let notify = loom::sync::Arc::new(Notify::new());
+
+            let notify2 = notify.clone();
+            let handle = loom::thread::spawn(move || {
+                loom::future::block_on(async move {
+                    drop(notify2.listen().await);
+                });
+            });
+
+            notify.notify_one();
+
+            handle.join().unwrap();
+
+            assert_eq!(
+                notify.state.lock().unwrap().token,
+                1,
+                "Dropped notify should not have consumed token"
+            );
+        });
+    }
+
+    #[test]
+    fn notified_listener() {
+        loom::model(|| {
+            loom::future::block_on(async {
+                let notify = Notify::new();
+
+                let mut listener = notify.listen().await;
+
+                notify.notify_one();
+
+                let waker = noop_waker();
+                let mut cx = std::task::Context::from_waker(&waker);
+
+                assert_eq!(
+                    std::pin::Pin::new(&mut listener).poll(&mut cx),
+                    std::task::Poll::Ready(()),
+                    "Polled listen should be notified"
+                );
+                assert_eq!(
+                    notify.state.lock().unwrap().token,
+                    0,
+                    "Dropped notify should have consumed token"
+                );
+            })
+        });
+    }
+
+    #[test]
+    fn threaded_notified_listener() {
+        loom::model(|| {
+            let notify = loom::sync::Arc::new(Notify::new());
+
+            let notify2 = notify.clone();
+            let handle = loom::thread::spawn(move || {
+                loom::future::block_on(async move {
+                    notify2.listen().await.await;
+                });
+            });
+
+            notify.notify_one();
+
+            handle.join().unwrap();
+
+            assert_eq!(
+                notify.state.lock().unwrap().token,
+                0,
+                "Dropped notify should have consumed token"
+            );
+        });
+    }
+
+    #[test]
+    fn multiple_listeners() {
+        loom::model(|| {
+            loom::future::block_on(async {
+                let notify = Notify::new();
+
+                let mut listener_1 = notify.listen().await;
+                let mut listener_2 = notify.listen().await;
+
+                notify.notify_one();
+
+                let waker = noop_waker();
+                let mut cx = std::task::Context::from_waker(&waker);
+
+                assert_eq!(
+                    std::pin::Pin::new(&mut listener_1).poll(&mut cx),
+                    std::task::Poll::Ready(()),
+                    "Polled listen_1 should be notified"
+                );
+
+                assert_eq!(
+                    std::pin::Pin::new(&mut listener_2).poll(&mut cx),
+                    std::task::Poll::Pending,
+                    "Polled listen_2 should not be notified"
+                );
+            });
+        });
+    }
+
+    #[test]
+    fn multiple_notifies() {
+        loom::model(|| {
+            loom::future::block_on(async {
+                let notify = Notify::new();
+
+                let mut listener_1 = notify.listen().await;
+                let mut listener_2 = notify.listen().await;
+
+                notify.notify_one();
+                notify.notify_one();
+
+                let waker = noop_waker();
+                let mut cx = std::task::Context::from_waker(&waker);
+
+                assert_eq!(
+                    std::pin::Pin::new(&mut listener_1).poll(&mut cx),
+                    std::task::Poll::Ready(()),
+                    "Polled listen_1 should be notified"
+                );
+
+                assert_eq!(
+                    std::pin::Pin::new(&mut listener_2).poll(&mut cx),
+                    std::task::Poll::Ready(()),
+                    "Polled listen_2 should be notified"
+                );
+
+                assert_eq!(
+                    notify.state.lock().unwrap().token,
+                    0,
+                    "notifies should have consumed tokens"
+                );
+            });
+        });
+    }
+
+    #[test]
+    fn threaded_multiple_notifies() {
+        loom::model(|| {
+            let notify = loom::sync::Arc::new(Notify::new());
+
+            let notify2 = notify.clone();
+            let handle1 = loom::thread::spawn(move || {
+                loom::future::block_on(async move {
+                    notify2.listen().await.await;
+                })
+            });
+
+            let notify2 = notify.clone();
+            let handle2 = loom::thread::spawn(move || {
+                loom::future::block_on(async move {
+                    notify2.listen().await.await;
+                })
+            });
+
+            notify.notify_one();
+            notify.notify_one();
+
+            handle1.join().unwrap();
+            handle2.join().unwrap();
+
+            assert_eq!(
+                notify.state.lock().unwrap().token,
+                0,
+                "threaded notifies should have consumed tokens"
+            );
+        });
+    }
+}

src/queue.rs

@@ -1,15 +1,38 @@
-use std::{
-    collections::VecDeque,
-    sync::{Arc, Mutex},
-};
+use std::collections::VecDeque;
 
 use crate::notify::Notify;
+use crate::sync::{Arc, Mutex};
 
-pub(super) fn bounded<T>(capacity: usize) -> Queue<T> {
+thread_local! {
+    #[cfg(any(loom, test))]
+    static QUEUE_COUNT: std::cell::RefCell<std::num::Wrapping<u64>> = std::cell::RefCell::new(std::num::Wrapping(0));
+}
+
+#[inline(always)]
+fn increment_queue_count() {
+    #[cfg(any(loom, test))]
+    QUEUE_COUNT.with_borrow_mut(|v| *v += 1);
+}
+
+#[inline(always)]
+fn decrement_queue_count() {
+    #[cfg(any(loom, test))]
+    QUEUE_COUNT.with_borrow_mut(|v| *v -= 1);
+}
+
+#[cfg(any(test, loom))]
+#[doc(hidden)]
+pub fn queue_count() -> u64 {
+    QUEUE_COUNT.with_borrow(|v| v.0)
+}
+
+#[doc(hidden)]
+pub fn bounded<T>(capacity: usize) -> Queue<T> {
     Queue::bounded(capacity)
 }
 
-pub(crate) struct Queue<T> {
+#[doc(hidden)]
+pub struct Queue<T> {
     inner: Arc<QueueState<T>>,
     capacity: usize,
 }
@@ -21,8 +44,11 @@ struct QueueState<T> {
 }
 
 impl<T> Queue<T> {
-    pub(super) fn bounded(capacity: usize) -> Self {
+    #[doc(hidden)]
+    pub fn bounded(capacity: usize) -> Self {
+        increment_queue_count();
         metrics::counter!("async-cpupool.queue.created").increment(1);
+
         Self {
             inner: Arc::new(QueueState {
                 queue: Mutex::new(VecDeque::new()),
@@ -33,7 +59,8 @@ impl<T> Queue<T> {
         }
     }
 
-    pub(super) fn len(&self) -> usize {
+    #[doc(hidden)]
+    pub fn len(&self) -> usize {
         self.inner.queue.lock().expect("not poisoned").len()
     }
 
@@ -47,21 +74,23 @@ impl<T> Queue<T> {
         }
     }
 
-    pub(super) async fn push(&self, mut item: T) {
+    #[doc(hidden)]
+    pub async fn push(&self, mut item: T) {
         loop {
             let listener = self.inner.push_notify.listen().await;
 
-            if let Some(returned_item) = self.try_push(item) {
-                item = returned_item;
-
-                listener.await;
-            } else {
+            let Some(returned_item) = self.try_push(item) else {
                 return;
-            }
+            };
+
+            item = returned_item;
+
+            listener.await;
         }
     }
 
-    pub(super) fn try_push(&self, item: T) -> Option<T> {
+    #[doc(hidden)]
+    pub fn try_push(&self, item: T) -> Option<T> {
         match self.try_push_impl(item) {
             Some(item) => Some(item),
             None => {
@@ -83,13 +112,12 @@ impl<T> Queue<T> {
         }
     }
 
-    pub(super) async fn pop(&self) -> T {
+    #[doc(hidden)]
+    pub async fn pop(&self) -> T {
         loop {
             let listener = self.inner.pop_notify.listen().await;
 
             if let Some(item) = self.try_pop() {
-                self.inner.push_notify.notify_one();
-                metrics::counter!("async-cpupool.queue.popped").increment(1);
                 return item;
             }
 
@@ -97,7 +125,16 @@ impl<T> Queue<T> {
         }
     }
 
-    fn try_pop(&self) -> Option<T> {
+    #[doc(hidden)]
+    pub fn try_pop(&self) -> Option<T> {
+        let item = self.try_pop_impl()?;
+        self.inner.push_notify.notify_one();
+        metrics::counter!("async-cpupool.queue.popped").increment(1);
+
+        Some(item)
+    }
+
+    fn try_pop_impl(&self) -> Option<T> {
         self.inner.queue.lock().expect("not poisoned").pop_front()
     }
 }
@@ -111,8 +148,9 @@ impl<T> Clone for Queue<T> {
     }
 }
 
-impl<T> Drop for Queue<T> {
+impl<T> Drop for QueueState<T> {
     fn drop(&mut self) {
+        decrement_queue_count();
         metrics::counter!("async-cpupool.queue.dropped").increment(1);
     }
 }

src/selector.rs

@@ -1,13 +1,11 @@
 use std::{
     future::Future,
     pin::Pin,
-    sync::{
-        atomic::{AtomicBool, Ordering},
-        Arc,
-    },
     task::{Context, Poll, Wake, Waker},
 };
 
+use crate::sync::{Arc, AtomicBool, Ordering};
+
 pub(super) enum Either<L, R> {
     Left(L),
     Right(R),
@@ -27,16 +25,16 @@ struct SelectWaker {
 }
 
 impl Wake for SelectWaker {
-    fn wake_by_ref(self: &Arc<Self>) {
+    fn wake_by_ref(self: &std::sync::Arc<Self>) {
         self.flag.store(true, Ordering::Release);
 
         self.inner.wake_by_ref();
     }
 
-    fn wake(self: Arc<Self>) {
+    fn wake(self: std::sync::Arc<Self>) {
         self.flag.store(true, Ordering::Release);
 
-        match Arc::try_unwrap(self) {
+        match std::sync::Arc::try_unwrap(self) {
             Ok(this) => this.inner.wake(),
             Err(this) => this.inner.wake_by_ref(),
         }
@@ -51,7 +49,7 @@ where
     type Output = Either<F1::Output, F2::Output>;
 
     fn poll(mut self: std::pin::Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let left_waker = Arc::new(SelectWaker {
+        let left_waker = std::sync::Arc::new(SelectWaker {
             inner: cx.waker().clone(),
             flag: self.left_woken.clone(),
         })
@@ -63,7 +61,7 @@ where
             return Poll::Ready(Either::Left(left_out));
         }
 
-        let right_waker = Arc::new(SelectWaker {
+        let right_waker = std::sync::Arc::new(SelectWaker {
             inner: cx.waker().clone(),
             flag: self.right_woken.clone(),
         })

src/sync.rs

@@ -0,0 +1,11 @@
+#[cfg(not(loom))]
+pub(crate) use std::sync::{
+    atomic::{AtomicBool, AtomicU8, Ordering},
+    Arc, Mutex,
+};
+
+#[cfg(loom)]
+pub(crate) use loom::sync::{
+    atomic::{AtomicBool, AtomicU8, Ordering},
+    Arc, Mutex,
+};

tests/queue.rs

@@ -0,0 +1,244 @@
+#![cfg(loom)]
+
+#[test]
+fn push_pop() {
+    loom::model(|| {
+        let queue = async_cpupool::tests::queue::bounded(1);
+
+        assert!(queue.try_push(()).is_none(), "Failed to push item");
+
+        assert!(queue.try_push(()).is_some(), "Shouldn't have pushed item");
+
+        assert!(queue.try_pop().is_some(), "Failed to pop item");
+
+        assert!(queue.try_pop().is_none(), "Shoudln't have popped item");
+
+        assert_eq!(queue.len(), 0, "Should have popped pushed item");
+
+        assert!(queue.try_push(()).is_none(), "Failed to push item");
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            1,
+            "Should have created one queue"
+        );
+
+        drop(queue);
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            0,
+            "Should have dropped queue"
+        );
+    });
+}
+
+#[test]
+fn async_push_pop() {
+    loom::model(|| {
+        let queue = async_cpupool::tests::queue::bounded(1);
+
+        loom::future::block_on(async {
+            queue.push(()).await;
+            queue.pop().await;
+        });
+
+        assert_eq!(queue.len(), 0, "Should have popped pushed item");
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            1,
+            "Should have created one queue"
+        );
+
+        drop(queue);
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            0,
+            "Should have dropped queue"
+        );
+    });
+}
+
+#[test]
+fn threaded_push_pop() {
+    loom::model(|| {
+        let queue = async_cpupool::tests::queue::bounded(1);
+
+        let q2 = queue.clone();
+        let handle = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.pop().await;
+            });
+
+            drop(q2);
+        });
+
+        assert!(queue.try_push(()).is_none(), "failed to push item");
+        handle.join().unwrap();
+
+        assert_eq!(queue.len(), 0, "Should have popped pushed item");
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            1,
+            "Should have created one queue"
+        );
+
+        drop(queue);
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            0,
+            "Should have dropped queue"
+        );
+    });
+}
+
+#[test]
+fn multiple_threaded_push_pop() {
+    loom::model(move || {
+        let queue = async_cpupool::tests::queue::bounded(1);
+
+        let q2 = queue.clone();
+        let h1 = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.pop().await;
+                q2.pop().await;
+            });
+
+            drop(q2);
+        });
+
+        loom::future::block_on(async {
+            queue.push(()).await;
+            queue.push(()).await;
+        });
+
+        h1.join().unwrap();
+
+        assert_eq!(queue.len(), 0, "Should have popped both pushed items");
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            1,
+            "Should have created one queue"
+        );
+
+        drop(queue);
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            0,
+            "Should have dropped queue"
+        );
+    });
+}
+
+#[test]
+fn multiple_threaded_push_pop_2() {
+    loom::model(|| {
+        let queue = async_cpupool::tests::queue::bounded(1);
+
+        let q2 = queue.clone();
+        let h1 = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.push(()).await;
+            });
+
+            drop(q2);
+        });
+
+        let q2 = queue.clone();
+        let h2 = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.push(()).await;
+            });
+
+            drop(q2);
+        });
+
+        loom::future::block_on(async {
+            queue.pop().await;
+            queue.pop().await;
+        });
+
+        h1.join().unwrap();
+        h2.join().unwrap();
+
+        assert_eq!(queue.len(), 0, "Should have popped both pushed items");
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            1,
+            "Should have created one queue"
+        );
+
+        drop(queue);
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            0,
+            "Should have dropped queue"
+        );
+    });
+}
+
+#[test]
+fn multiple_threaded_push_pop_3() {
+    loom::model(|| {
+        let queue = async_cpupool::tests::queue::bounded(1);
+
+        let q2 = queue.clone();
+        let h1 = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.push(()).await;
+            });
+
+            drop(q2);
+        });
+
+        let q2 = queue.clone();
+        let h2 = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.push(()).await;
+            });
+
+            drop(q2);
+        });
+
+        let q2 = queue.clone();
+        let h3 = loom::thread::spawn(move || {
+            loom::future::block_on(async {
+                q2.pop().await;
+            });
+
+            drop(q2);
+        });
+
+        loom::future::block_on(async {
+            queue.pop().await;
+        });
+
+        h1.join().unwrap();
+        h2.join().unwrap();
+        h3.join().unwrap();
+
+        assert_eq!(queue.len(), 0, "Should have popped both pushed items");
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            1,
+            "Should have created one queue"
+        );
+
+        drop(queue);
+
+        assert_eq!(
+            async_cpupool::tests::queue::queue_count(),
+            0,
+            "Should have dropped queue"
+        );
+    });
+}