Feedback from Reviewers

Properly implement `portable-atomic` and `critical-section` features to enable compilation on `thumbv6m-none-eabi` (as an example platform)

Co-Authored-By: Mike <[email protected]>

crates/bevy_tasks/Cargo.toml

@@ -10,12 +10,28 @@ keywords = ["bevy"]
 
 [features]
 default = ["std", "async_executor"]
-std = ["futures-lite/std", "async-task/std", "spin/std", "edge-executor?/std"]
+std = [
+  "futures-lite/std",
+  "async-task/std",
+  "spin/std",
+  "edge-executor?/std",
+  "portable-atomic-util?/std",
+]
 multi_threaded = ["std", "dep:async-channel", "dep:concurrent-queue"]
 async_executor = ["std", "dep:async-executor"]
 edge_executor = ["dep:edge-executor"]
-critical-section = ["edge-executor/critical-section"]
-portable-atomic = ["edge-executor/portable-atomic"]
+critical-section = [
+  "dep:critical-section",
+  "edge-executor?/critical-section",
+  "portable-atomic?/critical-section",
+]
+portable-atomic = [
+  "dep:portable-atomic",
+  "dep:portable-atomic-util",
+  "edge-executor?/portable-atomic",
+  "async-task/portable-atomic",
+  "spin/portable_atomic",
+]
 
 [dependencies]
 futures-lite = { version = "2.0.1", default-features = false, features = [
@@ -37,6 +53,13 @@ edge-executor = { version = "0.4.1", default-features = false, optional = true }
 async-channel = { version = "2.3.0", optional = true }
 async-io = { version = "2.0.0", optional = true }
 concurrent-queue = { version = "2.0.0", optional = true }
+critical-section = { version = "1.2.0", optional = true }
+portable-atomic = { version = "1", default-features = false, features = [
+  "fallback",
+], optional = true }
+portable-atomic-util = { version = "0.2.4", features = [
+  "alloc",
+], optional = true }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 wasm-bindgen-futures = "0.4"

crates/bevy_tasks/README.md

@@ -34,6 +34,10 @@ The determining factor for what kind of work should go in each pool is latency r
   await receiving data from somewhere (i.e. disk) and signal other systems when the data is ready
   for consumption. (likely via channels)
 
+## `no_std` Support
+
+To enable `no_std` support in this crate, you will need to disable default features, and enable the `edge_executor` and `critical-section` features. For platforms without full support for Rust atomics, you may also need to enable the `portable-atomic` feature.
+
 [bevy]: https://bevyengine.org
 [rayon]: https://github.com/rayon-rs/rayon
 [async-executor]: https://github.com/stjepang/async-executor

crates/bevy_tasks/src/single_threaded_task_pool.rs

@@ -1,8 +1,14 @@
-use alloc::{string::String, sync::Arc, vec::Vec};
+use alloc::{string::String, vec::Vec};
 use core::{cell::RefCell, future::Future, marker::PhantomData, mem};
 
 use crate::Task;
 
+#[cfg(feature = "portable-atomic")]
+use portable_atomic_util::Arc;
+
+#[cfg(not(feature = "portable-atomic"))]
+use alloc::sync::Arc;
+
 #[cfg(feature = "std")]
 use crate::executor::LocalExecutor;
 

tools/ci/src/commands/compile_check_no_std.rs

@@ -73,7 +73,7 @@ impl Prepare for CompileCheckNoStdCommand {
         commands.push(PreparedCommand::new::<Self>(
             cmd!(
                 sh,
-                "cargo check -p bevy_tasks --no-default-features --features edge_executor --features critical-section --target {target}"
+                "cargo check -p bevy_tasks --no-default-features --features edge_executor,critical-section --target {target}"
             ),
             "Please fix compiler errors in output above for bevy_tasks no_std compatibility.",
         ));