cortex-m/executor: don't use the owned interrupts system.

Preparation for #1224.

embassy-cortex-m/src/executor.rs

@@ -1,18 +1,22 @@
 //! Executor specific to cortex-m devices.
-use core::marker::PhantomData;
 
+use core::cell::UnsafeCell;
+use core::mem::MaybeUninit;
+
+use atomic_polyfill::{AtomicBool, Ordering};
+use cortex_m::interrupt::InterruptNumber;
+use cortex_m::peripheral::NVIC;
 pub use embassy_executor::*;
 
-use crate::interrupt::{Interrupt, InterruptExt};
+#[derive(Clone, Copy)]
+struct N(u16);
+unsafe impl cortex_m::interrupt::InterruptNumber for N {
+    fn number(self) -> u16 {
+        self.0
+    }
+}
 
 fn pend_by_number(n: u16) {
-    #[derive(Clone, Copy)]
-    struct N(u16);
-    unsafe impl cortex_m::interrupt::InterruptNumber for N {
-        fn number(self) -> u16 {
-            self.0
-        }
-    }
     cortex_m::peripheral::NVIC::pend(N(n))
 }
 
@@ -37,26 +41,37 @@ fn pend_by_number(n: u16) {
 ///
 /// It is somewhat more complex to use, it's recommended to use the thread-mode
 /// [`Executor`] instead, if it works for your use case.
-pub struct InterruptExecutor<I: Interrupt> {
+pub struct InterruptExecutor {
-    irq: I,
+    started: AtomicBool,
-    inner: raw::Executor,
+    executor: UnsafeCell<MaybeUninit<raw::Executor>>,
-    not_send: PhantomData<*mut ()>,
 }
 
-impl<I: Interrupt> InterruptExecutor<I> {
+unsafe impl Send for InterruptExecutor {}
-    /// Create a new Executor.
+unsafe impl Sync for InterruptExecutor {}
-    pub fn new(irq: I) -> Self {
+
-        let ctx = irq.number() as *mut ();
+impl InterruptExecutor {
+    /// Create a new, not started `InterruptExecutor`.
+    #[inline]
+    pub const fn new() -> Self {
         Self {
-            irq,
+            started: AtomicBool::new(false),
-            inner: raw::Executor::new(|ctx| pend_by_number(ctx as u16), ctx),
+            executor: UnsafeCell::new(MaybeUninit::uninit()),
-            not_send: PhantomData,
         }
     }
 
+    /// Executor interrupt callback.
+    ///
+    /// # Safety
+    ///
+    /// You MUST call this from the interrupt handler, and from nowhere else.
+    pub unsafe fn on_interrupt(&'static self) {
+        let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
+        executor.poll();
+    }
+
     /// Start the executor.
     ///
-    /// This initializes the executor, configures and enables the interrupt, and returns.
+    /// This initializes the executor, enables the interrupt, and returns.
     /// The executor keeps running in the background through the interrupt.
     ///
     /// This returns a [`SendSpawner`] you can use to spawn tasks on it. A [`SendSpawner`]
@@ -67,23 +82,35 @@ impl<I: Interrupt> InterruptExecutor<I> {
     /// To obtain a [`Spawner`](embassy_executor::Spawner) for this executor, use [`Spawner::for_current_executor()`](embassy_executor::Spawner::for_current_executor()) from
     /// a task running in it.
     ///
-    /// This function requires `&'static mut self`. This means you have to store the
+    /// # Interrupt requirements
-    /// 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)
+    /// You must write the interrupt handler yourself, and make it call [`on_interrupt()`](Self::on_interrupt).
-    /// - a `static mut` (unsafe)
+    ///
-    /// - a local variable in a function you know never returns (like `fn main() -> !`), upgrading its lifetime with `transmute`. (unsafe)
+    /// This method already enables (unmasks) the interrupt, you must NOT do it yourself.
-    pub fn start(&'static mut self) -> SendSpawner {
+    ///
-        self.irq.disable();
+    /// You must set the interrupt priority before calling this method. You MUST NOT
+    /// do it after.
+    ///
+    pub fn start(&'static self, irq: impl InterruptNumber) -> SendSpawner {
+        if self
+            .started
+            .compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
+            .is_err()
+        {
+            panic!("InterruptExecutor::start() called multiple times on the same executor.");
+        }
 
-        self.irq.set_handler(|ctx| unsafe {
+        unsafe {
-            let executor = &*(ctx as *const raw::Executor);
+            (&mut *self.executor.get()).as_mut_ptr().write(raw::Executor::new(
-            executor.poll();
+                |ctx| pend_by_number(ctx as u16),
-        });
+                irq.number() as *mut (),
-        self.irq.set_handler_context(&self.inner as *const _ as _);
+            ))
-        self.irq.enable();
+        }
 
-        self.inner.spawner().make_send()
+        let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
+
+        unsafe { NVIC::unmask(irq) }
+
+        executor.spawner().make_send()
     }
 }

examples/nrf52840/src/bin/multiprio.rs

@@ -57,11 +57,14 @@
 #![no_main]
 #![feature(type_alias_impl_trait)]
 
+use core::mem;
+
+use cortex_m::peripheral::NVIC;
 use cortex_m_rt::entry;
 use defmt::{info, unwrap};
 use embassy_nrf::executor::{Executor, InterruptExecutor};
 use embassy_nrf::interrupt;
-use embassy_nrf::interrupt::InterruptExt;
+use embassy_nrf::pac::Interrupt;
 use embassy_time::{Duration, Instant, Timer};
 use static_cell::StaticCell;
 use {defmt_rtt as _, panic_probe as _};
@@ -108,28 +111,35 @@ async fn run_low() {
     }
 }
 
-static EXECUTOR_HIGH: StaticCell<InterruptExecutor<interrupt::SWI1_EGU1>> = StaticCell::new();
+static EXECUTOR_HIGH: InterruptExecutor = InterruptExecutor::new();
-static EXECUTOR_MED: StaticCell<InterruptExecutor<interrupt::SWI0_EGU0>> = StaticCell::new();
+static EXECUTOR_MED: InterruptExecutor = InterruptExecutor::new();
 static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
 
+#[interrupt]
+unsafe fn SWI1_EGU1() {
+    EXECUTOR_HIGH.on_interrupt()
+}
+
+#[interrupt]
+unsafe fn SWI0_EGU0() {
+    EXECUTOR_MED.on_interrupt()
+}
+
 #[entry]
 fn main() -> ! {
     info!("Hello World!");
 
     let _p = embassy_nrf::init(Default::default());
+    let mut nvic: NVIC = unsafe { mem::transmute(()) };
 
     // High-priority executor: SWI1_EGU1, priority level 6
-    let irq = interrupt::take!(SWI1_EGU1);
+    unsafe { nvic.set_priority(Interrupt::SWI1_EGU1, 6 << 5) };
-    irq.set_priority(interrupt::Priority::P6);
+    let spawner = EXECUTOR_HIGH.start(Interrupt::SWI1_EGU1);
-    let executor = EXECUTOR_HIGH.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_high()));
 
     // Medium-priority executor: SWI0_EGU0, priority level 7
-    let irq = interrupt::take!(SWI0_EGU0);
+    unsafe { nvic.set_priority(Interrupt::SWI0_EGU0, 7 << 5) };
-    irq.set_priority(interrupt::Priority::P7);
+    let spawner = EXECUTOR_MED.start(Interrupt::SWI0_EGU0);
-    let executor = EXECUTOR_MED.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_med()));
 
     // Low priority executor: runs in thread mode, using WFE/SEV

examples/stm32f0/Cargo.toml

@@ -15,5 +15,5 @@ panic-probe = "0.3"
 embassy-sync = { version = "0.1.0", path = "../../embassy-sync", features = ["defmt"] }
 embassy-executor = { version = "0.1.0", path = "../../embassy-executor", features = ["defmt", "integrated-timers"] }
 embassy-time = { version = "0.1.0", path = "../../embassy-time", features = ["defmt", "defmt-timestamp-uptime", "tick-hz-32_768"] }
-embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "memory-x", "stm32f091rc", "time-driver-any", "exti"] }
+embassy-stm32 = { version = "0.1.0", path = "../../embassy-stm32", features = ["nightly", "defmt", "memory-x", "stm32f091rc", "time-driver-any", "exti", "unstable-pac"] }
 static_cell = "1.0"

examples/stm32f0/src/bin/multiprio.rs

@@ -57,11 +57,14 @@
 #![no_main]
 #![feature(type_alias_impl_trait)]
 
+use core::mem;
+
+use cortex_m::peripheral::NVIC;
 use cortex_m_rt::entry;
 use defmt::*;
 use embassy_stm32::executor::{Executor, InterruptExecutor};
 use embassy_stm32::interrupt;
-use embassy_stm32::interrupt::InterruptExt;
+use embassy_stm32::pac::Interrupt;
 use embassy_time::{Duration, Instant, Timer};
 use static_cell::StaticCell;
 use {defmt_rtt as _, panic_probe as _};
@@ -108,27 +111,34 @@ async fn run_low() {
     }
 }
 
-static EXECUTOR_HIGH: StaticCell<InterruptExecutor<interrupt::USART1>> = StaticCell::new();
+static EXECUTOR_HIGH: InterruptExecutor = InterruptExecutor::new();
-static EXECUTOR_MED: StaticCell<InterruptExecutor<interrupt::USART2>> = StaticCell::new();
+static EXECUTOR_MED: InterruptExecutor = InterruptExecutor::new();
 static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
 
+#[interrupt]
+unsafe fn USART1() {
+    EXECUTOR_HIGH.on_interrupt()
+}
+
+#[interrupt]
+unsafe fn USART2() {
+    EXECUTOR_MED.on_interrupt()
+}
+
 #[entry]
 fn main() -> ! {
     // Initialize and create handle for devicer peripherals
     let _p = embassy_stm32::init(Default::default());
+    let mut nvic: NVIC = unsafe { mem::transmute(()) };
 
     // High-priority executor: USART1, priority level 6
-    let irq = interrupt::take!(USART1);
+    unsafe { nvic.set_priority(Interrupt::USART1, 6 << 4) };
-    irq.set_priority(interrupt::Priority::P6);
+    let spawner = EXECUTOR_HIGH.start(Interrupt::USART1);
-    let executor = EXECUTOR_HIGH.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_high()));
 
     // Medium-priority executor: USART2, priority level 7
-    let irq = interrupt::take!(USART2);
+    unsafe { nvic.set_priority(Interrupt::USART2, 7 << 4) };
-    irq.set_priority(interrupt::Priority::P7);
+    let spawner = EXECUTOR_MED.start(Interrupt::USART2);
-    let executor = EXECUTOR_MED.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_med()));
 
     // Low priority executor: runs in thread mode, using WFE/SEV

examples/stm32f3/src/bin/multiprio.rs

@@ -57,11 +57,14 @@
 #![no_main]
 #![feature(type_alias_impl_trait)]
 
+use core::mem;
+
+use cortex_m::peripheral::NVIC;
 use cortex_m_rt::entry;
 use defmt::*;
 use embassy_stm32::executor::{Executor, InterruptExecutor};
 use embassy_stm32::interrupt;
-use embassy_stm32::interrupt::InterruptExt;
+use embassy_stm32::pac::Interrupt;
 use embassy_time::{Duration, Instant, Timer};
 use static_cell::StaticCell;
 use {defmt_rtt as _, panic_probe as _};
@@ -108,28 +111,35 @@ async fn run_low() {
     }
 }
 
-static EXECUTOR_HIGH: StaticCell<InterruptExecutor<interrupt::UART4>> = StaticCell::new();
+static EXECUTOR_HIGH: InterruptExecutor = InterruptExecutor::new();
-static EXECUTOR_MED: StaticCell<InterruptExecutor<interrupt::UART5>> = StaticCell::new();
+static EXECUTOR_MED: InterruptExecutor = InterruptExecutor::new();
 static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
 
+#[interrupt]
+unsafe fn UART4() {
+    EXECUTOR_HIGH.on_interrupt()
+}
+
+#[interrupt]
+unsafe fn UART5() {
+    EXECUTOR_MED.on_interrupt()
+}
+
 #[entry]
 fn main() -> ! {
     info!("Hello World!");
 
     let _p = embassy_stm32::init(Default::default());
+    let mut nvic: NVIC = unsafe { mem::transmute(()) };
 
-    // High-priority executor: SWI1_EGU1, priority level 6
+    // High-priority executor: UART4, priority level 6
-    let irq = interrupt::take!(UART4);
+    unsafe { nvic.set_priority(Interrupt::UART4, 6 << 4) };
-    irq.set_priority(interrupt::Priority::P6);
+    let spawner = EXECUTOR_HIGH.start(Interrupt::UART4);
-    let executor = EXECUTOR_HIGH.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_high()));
 
-    // Medium-priority executor: SWI0_EGU0, priority level 7
+    // Medium-priority executor: UART5, priority level 7
-    let irq = interrupt::take!(UART5);
+    unsafe { nvic.set_priority(Interrupt::UART5, 7 << 4) };
-    irq.set_priority(interrupt::Priority::P7);
+    let spawner = EXECUTOR_MED.start(Interrupt::UART5);
-    let executor = EXECUTOR_MED.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_med()));
 
     // Low priority executor: runs in thread mode, using WFE/SEV

examples/stm32f4/src/bin/multiprio.rs

@@ -57,11 +57,14 @@
 #![no_main]
 #![feature(type_alias_impl_trait)]
 
+use core::mem;
+
+use cortex_m::peripheral::NVIC;
 use cortex_m_rt::entry;
 use defmt::*;
 use embassy_stm32::executor::{Executor, InterruptExecutor};
 use embassy_stm32::interrupt;
-use embassy_stm32::interrupt::InterruptExt;
+use embassy_stm32::pac::Interrupt;
 use embassy_time::{Duration, Instant, Timer};
 use static_cell::StaticCell;
 use {defmt_rtt as _, panic_probe as _};
@@ -108,28 +111,35 @@ async fn run_low() {
     }
 }
 
-static EXECUTOR_HIGH: StaticCell<InterruptExecutor<interrupt::UART4>> = StaticCell::new();
+static EXECUTOR_HIGH: InterruptExecutor = InterruptExecutor::new();
-static EXECUTOR_MED: StaticCell<InterruptExecutor<interrupt::UART5>> = StaticCell::new();
+static EXECUTOR_MED: InterruptExecutor = InterruptExecutor::new();
 static EXECUTOR_LOW: StaticCell<Executor> = StaticCell::new();
 
+#[interrupt]
+unsafe fn UART4() {
+    EXECUTOR_HIGH.on_interrupt()
+}
+
+#[interrupt]
+unsafe fn UART5() {
+    EXECUTOR_MED.on_interrupt()
+}
+
 #[entry]
 fn main() -> ! {
     info!("Hello World!");
 
     let _p = embassy_stm32::init(Default::default());
+    let mut nvic: NVIC = unsafe { mem::transmute(()) };
 
-    // High-priority executor: SWI1_EGU1, priority level 6
+    // High-priority executor: UART4, priority level 6
-    let irq = interrupt::take!(UART4);
+    unsafe { nvic.set_priority(Interrupt::UART4, 6 << 4) };
-    irq.set_priority(interrupt::Priority::P6);
+    let spawner = EXECUTOR_HIGH.start(Interrupt::UART4);
-    let executor = EXECUTOR_HIGH.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_high()));
 
-    // Medium-priority executor: SWI0_EGU0, priority level 7
+    // Medium-priority executor: UART5, priority level 7
-    let irq = interrupt::take!(UART5);
+    unsafe { nvic.set_priority(Interrupt::UART5, 7 << 4) };
-    irq.set_priority(interrupt::Priority::P7);
+    let spawner = EXECUTOR_MED.start(Interrupt::UART5);
-    let executor = EXECUTOR_MED.init(InterruptExecutor::new(irq));
-    let spawner = executor.start();
     unwrap!(spawner.spawn(run_med()));
 
     // Low priority executor: runs in thread mode, using WFE/SEV