Merge pull request #3395 from vapor-keeb/main

executor/spin: introduce an architecture agnostic executor

3 files changed, 69 insertions, 1 deletions

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")]