5 files changed, 126 insertions, 2 deletions

diff --git a/embassy-executor-macros/src/lib.rs b/embassy-executor-macros/src/lib.rs
index 5461fe04c..61d388b9e 100644
--- a/embassy-executor-macros/src/lib.rs
+++ b/embassy-executor-macros/src/lib.rs
@@ -94,6 +94,35 @@ pub fn main_cortex_m(args: TokenStream, item: TokenStream) -> TokenStream {
     main::run(&args.meta, f, main::cortex_m()).unwrap_or_else(|x| x).into()
 }
 
+/// Creates a new `executor` instance and declares an architecture agnostic application entry point spawning
+/// the corresponding function body as an async task.
+///
+/// The following restrictions apply:
+///
+/// * The function must accept exactly 1 parameter, an `embassy_executor::Spawner` handle that it can use to spawn additional tasks.
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * Only a single `main` task may be declared.
+///
+/// A user-defined entry macro must provided via the `entry` argument
+///
+/// ## Examples
+/// Spawning a task:
+/// ``` rust
+/// #[embassy_executor::main(entry = "qingke_rt::entry")]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn main_spin(args: TokenStream, item: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as Args);
+    let f = syn::parse_macro_input!(item as syn::ItemFn);
+    main::run(&args.meta, f, main::spin(&args.meta))
+        .unwrap_or_else(|x| x)
+        .into()
+}
+
 /// Creates a new `executor` instance and declares an application entry point for RISC-V spawning the corresponding function body as an async task.
 ///
 /// The following restrictions apply:
diff --git a/embassy-executor-macros/src/macros/main.rs b/embassy-executor-macros/src/macros/main.rs
index 26dfa2397..66a3965d0 100644
--- a/embassy-executor-macros/src/macros/main.rs
+++ b/embassy-executor-macros/src/macros/main.rs
@@ -1,5 +1,5 @@
 use darling::export::NestedMeta;
-use darling::FromMeta;
+use darling::{Error, FromMeta};
 use proc_macro2::TokenStream;
 use quote::quote;
 use syn::{Expr, ReturnType, Type};
@@ -50,6 +50,33 @@ pub fn riscv(args: &[NestedMeta]) -> TokenStream {
     }
 }
 
+pub fn spin(args: &[NestedMeta]) -> TokenStream {
+    let maybe_entry = match Args::from_list(args) {
+        Ok(args) => args.entry,
+        Err(e) => return e.write_errors(),
+    };
+
+    let entry = match maybe_entry {
+        Some(str) => str,
+        None => return Error::missing_field("entry").write_errors(),
+    };
+    let entry = match Expr::from_string(&entry) {
+        Ok(expr) => expr,
+        Err(e) => return e.write_errors(),
+    };
+
+    quote! {
+        #[#entry]
+        fn main() -> ! {
+            let mut executor = ::embassy_executor::Executor::new();
+            let executor = unsafe { __make_static(&mut executor) };
+            executor.run(|spawner| {
+                spawner.must_spawn(__embassy_main(spawner));
+            })
+        }
+    }
+}
+
 pub fn cortex_m() -> TokenStream {
     quote! {
         #[cortex_m_rt::entry]
diff --git a/embassy-executor/Cargo.toml b/embassy-executor/Cargo.toml
index 01fa28b88..e2fedce3c 100644
--- a/embassy-executor/Cargo.toml
+++ b/embassy-executor/Cargo.toml
@@ -82,6 +82,8 @@ arch-riscv32 = ["_arch"]
 arch-wasm = ["_arch", "dep:wasm-bindgen", "dep:js-sys", "critical-section/std"]
 ## AVR
 arch-avr = ["_arch", "dep:portable-atomic", "dep:avr-device"]
+## spin (architecture agnostic; never sleeps)
+arch-spin = ["_arch"]
 
 #! ### Executor
 
diff --git a/embassy-executor/src/arch/spin.rs b/embassy-executor/src/arch/spin.rs
new file mode 100644
index 000000000..340023620
--- /dev/null
+++ b/embassy-executor/src/arch/spin.rs
@@ -0,0 +1,58 @@
+#[cfg(feature = "executor-interrupt")]
+compile_error!("`executor-interrupt` is not supported with `arch-spin`.");
+
+#[cfg(feature = "executor-thread")]
+pub use thread::*;
+#[cfg(feature = "executor-thread")]
+mod thread {
+    use core::marker::PhantomData;
+
+    pub use embassy_executor_macros::main_spin as main;
+
+    use crate::{raw, Spawner};
+
+    #[export_name = "__pender"]
+    fn __pender(_context: *mut ()) {}
+
+    /// Spin Executor
+    pub struct Executor {
+        inner: raw::Executor,
+        not_send: PhantomData<*mut ()>,
+    }
+
+    impl Executor {
+        /// Create a new Executor.
+        pub fn new() -> Self {
+            Self {
+                inner: raw::Executor::new(core::ptr::null_mut()),
+                not_send: PhantomData,
+            }
+        }
+
+        /// Run the executor.
+        ///
+        /// The `init` closure is called with a [`Spawner`] that spawns tasks on
+        /// this executor. Use it to spawn the initial task(s). After `init` returns,
+        /// the executor starts running the tasks.
+        ///
+        /// To spawn more tasks later, you may keep copies of the [`Spawner`] (it is `Copy`),
+        /// for example by passing it as an argument to the initial tasks.
+        ///
+        /// This function requires `&'static mut self`. This means you have to store the
+        /// Executor instance in a place where it'll live forever and grants you mutable
+        /// access. There's a few ways to do this:
+        ///
+        /// - a [StaticCell](https://docs.rs/static_cell/latest/static_cell/) (safe)
+        /// - a `static mut` (unsafe)
+        /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+        ///
+        /// This function never returns.
+        pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+            init(self.inner.spawner());
+
+            loop {
+                unsafe { self.inner.poll() };
+            }
+        }
+    }
+}
diff --git a/embassy-executor/src/lib.rs b/embassy-executor/src/lib.rs
index 6a2e493a2..d816539ac 100644
--- a/embassy-executor/src/lib.rs
+++ b/embassy-executor/src/lib.rs
@@ -23,7 +23,14 @@ macro_rules! check_at_most_one {
         check_at_most_one!(@amo [$($f)*] [$($f)*] []);
     };
 }
-check_at_most_one!("arch-avr", "arch-cortex-m", "arch-riscv32", "arch-std", "arch-wasm",);
+check_at_most_one!(
+    "arch-avr",
+    "arch-cortex-m",
+    "arch-riscv32",
+    "arch-std",
+    "arch-wasm",
+    "arch-spin",
+);
 
 #[cfg(feature = "_arch")]
 #[cfg_attr(feature = "arch-avr", path = "arch/avr.rs")]
@@ -31,6 +38,7 @@ check_at_most_one!("arch-avr", "arch-cortex-m", "arch-riscv32", "arch-std", "arc
 #[cfg_attr(feature = "arch-riscv32", path = "arch/riscv32.rs")]
 #[cfg_attr(feature = "arch-std", path = "arch/std.rs")]
 #[cfg_attr(feature = "arch-wasm", path = "arch/wasm.rs")]
+#[cfg_attr(feature = "arch-spin", path = "arch/spin.rs")]
 mod arch;
 
 #[cfg(feature = "_arch")]