prepare trigger channel code for loom test

and ensure rest of code can still just run fine as-is

.github/workflows/CI.yml

@@ -98,6 +98,25 @@ jobs:
           command: test
           args: --all-features --examples
 
+  test-loom:
+    needs: check
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: ${{env.RUST_TOOLCHAIN}}
+          override: true
+          profile: minimal
+      - uses: Swatinem/rust-cache@v1
+      - name: Run tests
+        uses: actions-rs/cargo@v1
+        with:
+          command: test
+          args: test_loom --release
+        env:
+          RUSTFLAGS: --cfg loom
+
   cargo-hack:
     needs: check
     runs-on: ubuntu-latest

Cargo.toml

@@ -20,7 +20,9 @@ tokio = { version = "1", features = ["rt", "signal", "sync", "macros", "time"] }
 tracing = "0.1"
 
 [dev-dependencies]
-hyper = { version = "0.14", features = [ "server", "tcp", "http1", "http2" ] }
 rand = "0.8"
 tokio = { version = "1", features = ["net", "rt-multi-thread", "io-util", "test-util"] }
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+
+[target.'cfg(not(loom))'.dev-dependencies]
+hyper = { version = "0.14", features = [ "server", "tcp", "http1", "http2" ] }

src/lib.rs

@@ -40,7 +40,9 @@ mod guard;
 pub use guard::{ShutdownGuard, WeakShutdownGuard};
 
 mod shutdown;
-pub use shutdown::{default_signal, Shutdown};
+#[cfg(not(loom))]
+pub use shutdown::default_signal;
+pub use shutdown::Shutdown;
 
 pub(crate) mod sync;
 pub(crate) mod trigger;

src/shutdown.rs

@@ -1,7 +1,7 @@
 use std::{future::Future, time};
 
 use crate::{
-    sync::Arc,
+    sync::{Arc, JoinHandle},
     trigger::{trigger, Receiver},
     ShutdownGuard, WeakShutdownGuard,
 };
@@ -13,6 +13,8 @@ use crate::{
 /// create a [`Shutdown`] with [`Shutdown::default`], which uses the default
 /// signal handler to trigger shutdown. See [`default_signal`] for more info.
 ///
+/// > (NOTE: that these defaults are not available when compiling with --cfg loom)
+///
 /// See the [README] for more info on how to use this crate.
 ///
 /// [`Future`]: std::future::Future
@@ -85,7 +87,7 @@ impl Shutdown {
     /// to wait for the spawned task to complete. See
     /// [`crate::sync::spawn`] for more information.
     #[inline]
-    pub fn spawn_task<T>(&self, task: T) -> tokio::task::JoinHandle<T::Output>
+    pub fn spawn_task<T>(&self, task: T) -> JoinHandle<T::Output>
     where
         T: Future + Send + 'static,
         T::Output: Send + 'static,
@@ -97,7 +99,7 @@ impl Shutdown {
     /// to wait for the spawned task (fn) to complete. See
     /// [`crate::sync::spawn`] for more information.
     #[inline]
-    pub fn spawn_task_fn<T, F>(&self, task: F) -> tokio::task::JoinHandle<T::Output>
+    pub fn spawn_task_fn<T, F>(&self, task: F) -> JoinHandle<T::Output>
     where
         T: Future + Send + 'static,
         T::Output: Send + 'static,
@@ -182,6 +184,7 @@ impl Shutdown {
 ///
 /// [`Future`]: std::future::Future
 /// [`tokio::time::sleep`]: https://docs.rs/tokio/*/tokio/time/fn.sleep.html
+#[cfg(not(loom))]
 pub async fn default_signal() {
     let ctrl_c = tokio::signal::ctrl_c();
     let signal = async {
@@ -196,6 +199,7 @@ pub async fn default_signal() {
     }
 }
 
+#[cfg(not(loom))]
 impl Default for Shutdown {
     fn default() -> Self {
         Self::new(default_signal())

src/sync/default.rs

@@ -2,5 +2,3 @@ pub use std::sync::{
     atomic::{AtomicBool, AtomicUsize, Ordering},
     Arc, Mutex,
 };
-
-pub use tokio::task::{spawn, JoinHandle};

src/sync/loom.rs

@@ -1,6 +1,4 @@
 pub use loom::sync::{
     atomic::{AtomicBool, AtomicUsize, Ordering},
-    Arc, Mutex, Ordering,
+    Arc, Mutex,
 };
-
-pub use loom::task::{spawn, JoinHandle};

src/sync/mod.rs

@@ -1,9 +1,11 @@
 #[cfg(loom)]
 mod loom;
 #[cfg(loom)]
-pub use loom::*;
+pub use self::loom::*;
 
 #[cfg(not(loom))]
 mod default;
 #[cfg(not(loom))]
 pub use default::*;
+
+pub use tokio::task::{spawn, JoinHandle};

src/trigger.rs

@@ -213,3 +213,11 @@ pub fn trigger() -> (Sender, Receiver) {
 
     (sender, receiver)
 }
+
+#[cfg(all(test, loom))]
+mod loom_tests {
+    use super::*;
+
+    #[test]
+    fn test_loom_concurrent() {}
+}