executor: remove arch-xtensa.

It's been broken for months and nobody has noticed. The `esp*-hal` crates have
much better support.

Fixes #2234
Closes  #1912

4 files changed, 5 insertions, 93 deletions

diff --git a/embassy-executor/CHANGELOG.md b/embassy-executor/CHANGELOG.md
index 559717da6..c839981d6 100644
--- a/embassy-executor/CHANGELOG.md
+++ b/embassy-executor/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+- Removed `arch-xtensa`. Use the executor provided by the HAL crate (`esp-hal`, `esp32s3-hal`, etc...) instead. 
+
 ## 0.3.3 - 2023-11-15
 
 - Add `main` macro reexport for Xtensa arch.
diff --git a/embassy-executor/Cargo.toml b/embassy-executor/Cargo.toml
index ae46b17c6..bf58a2e1b 100644
--- a/embassy-executor/Cargo.toml
+++ b/embassy-executor/Cargo.toml
@@ -57,7 +57,6 @@ critical-section = { version = "1.1", features = ["std"] }
 _arch = [] # some arch was picked
 arch-std = ["_arch", "critical-section/std"]
 arch-cortex-m = ["_arch", "dep:cortex-m"]
-arch-xtensa = ["_arch"]
 arch-riscv32 = ["_arch", "dep:portable-atomic"]
 arch-wasm = ["_arch", "dep:wasm-bindgen", "dep:js-sys"]
 
diff --git a/embassy-executor/src/arch/xtensa.rs b/embassy-executor/src/arch/xtensa.rs
deleted file mode 100644
index 6ed9f9e72..000000000
--- a/embassy-executor/src/arch/xtensa.rs
+++ /dev/null
@@ -1,89 +0,0 @@
-#[cfg(feature = "executor-interrupt")]
-compile_error!("`executor-interrupt` is not supported with `arch-xtensa`.");
-
-#[cfg(feature = "executor-thread")]
-pub use thread::*;
-#[cfg(feature = "executor-thread")]
-mod thread {
-    use core::marker::PhantomData;
-    use core::sync::atomic::{AtomicBool, Ordering};
-
-    pub use embassy_macros::main_riscv as main;
-
-    use crate::{raw, Spawner};
-
-    /// global atomic used to keep track of whether there is work to do since sev() is not available on Xtensa
-    static SIGNAL_WORK_THREAD_MODE: AtomicBool = AtomicBool::new(false);
-
-    #[export_name = "__pender"]
-    fn __pender(_context: *mut ()) {
-        SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
-    }
-
-    /// Xtensa 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();
-
-                    // Manual critical section implementation that only masks interrupts handlers.
-                    // We must not acquire the cross-core on dual-core systems because that would
-                    // prevent the other core from doing useful work while this core is sleeping.
-                    let token: critical_section::RawRestoreState;
-                    core::arch::asm!("rsil {0}, 5", out(reg) token);
-
-                    // we do not care about race conditions between the load and store operations, interrupts
-                    // will only set this value to true.
-                    // if there is work to do, loop back to polling
-                    if SIGNAL_WORK_THREAD_MODE.load(Ordering::SeqCst) {
-                        SIGNAL_WORK_THREAD_MODE.store(false, Ordering::SeqCst);
-
-                        core::arch::asm!(
-                        "wsr.ps {0}",
-                        "rsync", in(reg) token)
-                    } else {
-                        // waiti sets the PS.INTLEVEL when slipping into sleep
-                        // because critical sections in Xtensa are implemented via increasing
-                        // PS.INTLEVEL the critical section ends here
-                        // take care not add code after `waiti` if it needs to be inside the CS
-                        core::arch::asm!("waiti 0"); // critical section ends here
-                    }
-                }
-            }
-        }
-    }
-}
diff --git a/embassy-executor/src/lib.rs b/embassy-executor/src/lib.rs
index d8ac4893b..897696150 100644
--- a/embassy-executor/src/lib.rs
+++ b/embassy-executor/src/lib.rs
@@ -1,5 +1,4 @@
 #![cfg_attr(not(any(feature = "arch-std", feature = "arch-wasm")), no_std)]
-#![cfg_attr(feature = "arch-xtensa", feature(asm_experimental_arch))]
 #![allow(clippy::new_without_default)]
 #![doc = include_str!("../README.md")]
 #![warn(missing_docs)]
@@ -21,12 +20,11 @@ macro_rules! check_at_most_one {
         check_at_most_one!(@amo [$($f)*] [$($f)*] []);
     };
 }
-check_at_most_one!("arch-cortex-m", "arch-riscv32", "arch-xtensa", "arch-std", "arch-wasm",);
+check_at_most_one!("arch-cortex-m", "arch-riscv32", "arch-std", "arch-wasm",);
 
 #[cfg(feature = "_arch")]
 #[cfg_attr(feature = "arch-cortex-m", path = "arch/cortex_m.rs")]
 #[cfg_attr(feature = "arch-riscv32", path = "arch/riscv32.rs")]
-#[cfg_attr(feature = "arch-xtensa", path = "arch/xtensa.rs")]
 #[cfg_attr(feature = "arch-std", path = "arch/std.rs")]
 #[cfg_attr(feature = "arch-wasm", path = "arch/wasm.rs")]
 mod arch;