rtic-sync: reorganize channel code for improved maintainability.

.github/workflows/build.yml

@@ -491,6 +491,16 @@ jobs:
       - name: Run cargo test
         run: cargo xtask --deny-warnings --backend ${{ matrix.backend }} test ${{ matrix.package }}
 
+  loom-tests:
+    name: rtic-sync loom tests
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run cargo test
+        run: RUSTFLAGS="--cfg loom" cargo test -p rtic-sync --release --lib 
+
   # Build documentation, check links
   docs:
     name: build docs

rtic-sync/CHANGELOG.md

@@ -7,6 +7,10 @@ For each category, _Added_, _Changed_, _Fixed_ add new entries at the top!
 
 ## [Unreleased]
 
+### Changed
+
+- Add `loom` support.
+
 ## v1.3.2 - 2025-03-16
 
 ### Fixed

rtic-sync/Cargo.toml

@@ -25,15 +25,23 @@ portable-atomic = { version = "1", default-features = false }
 embedded-hal = { version = "1.0.0" }
 embedded-hal-async = { version = "1.0.0" }
 embedded-hal-bus = { version = "0.2.0", features = ["async"] }
-
 defmt-03 = { package = "defmt", version = "0.3", optional = true }
 
 [dev-dependencies]
 cassette = "0.3.0"
 static_cell = "2.1.0"
-tokio = { version = "1", features = ["rt", "macros", "time"] }
+
+[target.'cfg(not(loom))'.dev-dependencies]
+tokio = { version = "1", features = ["rt", "macros", "time"], default-features = false }
 
 [features]
 default = []
-testing = ["critical-section/std", "rtic-common/testing"]
+testing = ["rtic-common/testing"]
 defmt-03 = ["dep:defmt-03", "embedded-hal/defmt-03", "embedded-hal-async/defmt-03", "embedded-hal-bus/defmt-03"]
+
+[lints.rust]
+unexpected_cfgs = { level = "allow", check-cfg = ['cfg(loom)'] }
+
+[target.'cfg(loom)'.dependencies]
+loom = { version = "0.7.2", features = [ "futures" ] }
+critical-section = { version = "1", features = [ "restore-state-bool" ] }

rtic-sync/src/arbiter.rs

@@ -381,6 +381,7 @@ pub mod i2c {
     }
 }
 
+#[cfg(not(loom))]
 #[cfg(test)]
 mod tests {
     use super::*;