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POC: allow custom executors

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This commit is contained in:
Dániel Buga 2023-08-12 16:00:18 +02:00
parent 0727f8690c
commit 675b7fb605
10 changed files with 448 additions and 388 deletions
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7
embassy-executor/Cargo.toml
View File

@ -31,11 +31,11 @@ features = ["nightly", "defmt", "pender-callback", "arch-cortex-m", "executor-th
# Architecture
_arch = [] # some arch was picked
arch-std = ["_arch", "critical-section/std"]
arch-std = ["_arch", "critical-section/std", "thread-context"]
arch-cortex-m = ["_arch", "dep:cortex-m"]
arch-xtensa = ["_arch"]
arch-riscv32 = ["_arch"]
arch-wasm = ["_arch", "dep:wasm-bindgen", "dep:js-sys"]
arch-wasm = ["_arch", "dep:wasm-bindgen", "dep:js-sys", "thread-context"]
# Enable creating a `Pender` from an arbitrary function pointer callback.
pender-callback = []
@ -45,6 +45,9 @@ executor-thread = []
# Enable the interrupt-mode executor (available in Cortex-M only)
executor-interrupt = []
# Pass a context to the thread-mode executor.
thread-context = []
# Enable nightly-only features
nightly = []

252
embassy-executor/src/arch/cortex_m.rs
View File

@ -1,224 +1,98 @@
#[cfg(feature = "executor-thread")]
pub use thread::*;
#[cfg(feature = "executor-thread")]
mod thread {
use core::arch::asm;
use core::marker::PhantomData;
#[cfg(feature = "nightly")]
pub use embassy_macros::main_cortex_m as main;
use crate::raw::{Pender, PenderInner};
use crate::{raw, Spawner};
use crate::raw::OpaqueThreadContext;
use crate::thread::ThreadContext;
#[derive(Copy, Clone)]
pub(crate) struct ThreadPender;
#[export_name = "__thread_mode_pender"]
fn __thread_mode_pender(_core_id: OpaqueThreadContext) {
unsafe { core::arch::asm!("sev") }
}
impl ThreadPender {
pub(crate) fn pend(self) {
unsafe { core::arch::asm!("sev") }
/// TODO
// Name pending
#[derive(Default)] // Default enables Executor::new
pub struct CortexMThreadContext {
_not_send: core::marker::PhantomData<*mut ()>,
}
impl ThreadContext for CortexMThreadContext {
#[cfg(feature = "thread-context")]
fn context(&self) -> OpaqueThreadContext {
// Enabling thread-context is not incorrect, just wasteful.
OpaqueThreadContext(0)
}
#[cfg(not(feature = "thread-context"))]
fn context(&self) -> OpaqueThreadContext {
OpaqueThreadContext(())
}
fn wait(&mut self) {
unsafe { core::arch::asm!("wfe") }
}
}
/// Thread mode executor, using WFE/SEV.
///
/// This is the simplest and most common kind of executor. It runs on
/// thread mode (at the lowest priority level), and uses the `WFE` ARM instruction
/// to sleep when it has no more work to do. When a task is woken, a `SEV` instruction
/// is executed, to make the `WFE` exit from sleep and poll the task.
///
/// This executor allows for ultra low power consumption for chips where `WFE`
/// triggers low-power sleep without extra steps. If your chip requires extra steps,
/// you may use [`raw::Executor`] directly to program custom behavior.
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(Pender(PenderInner::Thread(ThreadPender))),
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();
asm!("wfe");
};
}
}
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<CortexMThreadContext>;
}
// None of this has to be public, I guess?
#[cfg(feature = "executor-interrupt")]
pub use interrupt::*;
#[cfg(feature = "executor-interrupt")]
mod interrupt {
use core::cell::UnsafeCell;
use core::mem::MaybeUninit;
use atomic_polyfill::{AtomicBool, Ordering};
use cortex_m::interrupt::InterruptNumber;
use cortex_m::peripheral::NVIC;
use crate::raw::{self, Pender, PenderInner};
use crate::interrupt::InterruptContext;
use crate::raw::OpaqueInterruptContext;
#[derive(Clone, Copy)]
pub(crate) struct InterruptPender(u16);
struct CortexMInterruptContext(u16);
impl InterruptPender {
pub(crate) fn pend(self) {
// STIR is faster, but is only available in v7 and higher.
#[cfg(not(armv6m))]
{
let mut nvic: cortex_m::peripheral::NVIC = unsafe { core::mem::transmute(()) };
nvic.request(self);
}
#[cfg(armv6m)]
cortex_m::peripheral::NVIC::pend(self);
}
}
unsafe impl cortex_m::interrupt::InterruptNumber for InterruptPender {
unsafe impl cortex_m::interrupt::InterruptNumber for CortexMInterruptContext {
fn number(self) -> u16 {
self.0
}
}
/// Interrupt mode executor.
///
/// This executor runs tasks in interrupt mode. The interrupt handler is set up
/// to poll tasks, and when a task is woken the interrupt is pended from software.
///
/// This allows running async tasks at a priority higher than thread mode. One
/// use case is to leave thread mode free for non-async tasks. Another use case is
/// to run multiple executors: one in thread mode for low priority tasks and another in
/// interrupt mode for higher priority tasks. Higher priority tasks will preempt lower
/// priority ones.
///
/// It is even possible to run multiple interrupt mode executors at different priorities,
/// by assigning different priorities to the interrupts. For an example on how to do this,
/// See the 'multiprio' example for 'embassy-nrf'.
///
/// To use it, you have to pick an interrupt that won't be used by the hardware.
/// Some chips reserve some interrupts for this purpose, sometimes named "software interrupts" (SWI).
/// If this is not the case, you may use an interrupt from any unused peripheral.
///
/// 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 {
started: AtomicBool,
executor: UnsafeCell<MaybeUninit<raw::Executor>>,
}
unsafe impl Send for InterruptExecutor {}
unsafe impl Sync for InterruptExecutor {}
impl InterruptExecutor {
/// Create a new, not started `InterruptExecutor`.
#[inline]
pub const fn new() -> Self {
Self {
started: AtomicBool::new(false),
executor: UnsafeCell::new(MaybeUninit::uninit()),
}
impl<T> InterruptContext for T
where
T: InterruptNumber,
{
fn context(&self) -> OpaqueInterruptContext {
OpaqueInterruptContext(self.number() as usize)
}
/// 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, 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`]
/// is returned instead of a [`Spawner`](embassy_executor::Spawner) because the executor effectively runs in a
/// different "thread" (the interrupt), so spawning tasks on it is effectively
/// sending them.
///
/// 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.
///
/// # Interrupt requirements
///
/// You must write the interrupt handler yourself, and make it call [`on_interrupt()`](Self::on_interrupt).
///
/// This method already enables (unmasks) the interrupt, you must NOT do it yourself.
///
/// You must set the interrupt priority before calling this method. You MUST NOT
/// do it after.
///
pub fn start(&'static self, irq: impl InterruptNumber) -> crate::SendSpawner {
if self
.started
.compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
.is_err()
{
panic!("InterruptExecutor::start() called multiple times on the same executor.");
}
unsafe {
(&mut *self.executor.get())
.as_mut_ptr()
.write(raw::Executor::new(Pender(PenderInner::Interrupt(InterruptPender(
irq.number(),
)))))
}
let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
unsafe { NVIC::unmask(irq) }
executor.spawner().make_send()
}
/// Get a SendSpawner for this executor
///
/// This returns a [`SendSpawner`] you can use to spawn tasks on this
/// executor.
///
/// This MUST only be called on an executor that has already been spawned.
/// The function will panic otherwise.
pub fn spawner(&'static self) -> crate::SendSpawner {
if !self.started.load(Ordering::Acquire) {
panic!("InterruptExecutor::spawner() called on uninitialized executor.");
}
let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
executor.spawner().make_send()
fn enable(&self) {
unsafe { NVIC::unmask(*self) }
}
}
#[export_name = "__interrupt_mode_pender"]
fn __interrupt_mode_pender(interrupt: OpaqueInterruptContext) {
let interrupt = CortexMInterruptContext(unsafe { core::mem::transmute::<_, usize>(interrupt) as u16 });
// STIR is faster, but is only available in v7 and higher.
#[cfg(not(armv6m))]
{
let mut nvic: NVIC = unsafe { core::mem::transmute(()) };
nvic.request(interrupt);
}
#[cfg(armv6m)]
NVIC::pend(interrupt);
}
/// TODO
// Type alias for backwards compatibility
pub type InterruptExecutor = crate::interrupt::InterruptModeExecutor;
}

100
embassy-executor/src/arch/riscv32.rs
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@ -1,6 +1,9 @@
#[cfg(feature = "executor-interrupt")]
compile_error!("`executor-interrupt` is not supported with `arch-riscv32`.");
#[cfg(feature = "thread-context")]
compile_error!("`thread-context` is not supported with `arch-riscv32`.");
#[cfg(feature = "executor-thread")]
pub use thread::*;
#[cfg(feature = "executor-thread")]
@ -11,77 +14,50 @@ mod thread {
#[cfg(feature = "nightly")]
pub use embassy_macros::main_riscv as main;
use crate::raw::{Pender, PenderInner};
use crate::{raw, Spawner};
#[derive(Copy, Clone)]
pub(crate) struct ThreadPender;
impl ThreadPender {
#[allow(unused)]
pub(crate) fn pend(self) {
SIGNAL_WORK_THREAD_MODE.store(true, core::sync::atomic::Ordering::SeqCst);
}
}
use crate::raw::OpaqueThreadContext;
use crate::thread::ThreadContext;
/// global atomic used to keep track of whether there is work to do since sev() is not available on RISCV
static SIGNAL_WORK_THREAD_MODE: AtomicBool = AtomicBool::new(false);
/// RISCV32 Executor
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
#[export_name = "__thread_mode_pender"]
fn __thread_mode_pender(_core_id: OpaqueThreadContext) {
SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
}
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
Self {
inner: raw::Executor::new(Pender(PenderInner::Thread(ThreadPender))),
not_send: PhantomData,
}
/// TODO
// Name pending
#[derive(Default)] // Default enables Executor::new
pub struct RiscVThreadContext {
_not_send: PhantomData<*mut ()>,
}
impl ThreadContext for RiscVThreadContext {
fn context(&self) -> OpaqueThreadContext {
OpaqueThreadContext(())
}
/// 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();
// we do not care about race conditions between the load and store operations, interrupts
//will only set this value to true.
critical_section::with(|_| {
// if there is work to do, loop back to polling
// TODO can we relax this?
if SIGNAL_WORK_THREAD_MODE.load(Ordering::SeqCst) {
SIGNAL_WORK_THREAD_MODE.store(false, Ordering::SeqCst);
}
// if not, wait for interrupt
else {
core::arch::asm!("wfi");
}
});
// if an interrupt occurred while waiting, it will be serviced here
fn wait(&mut self) {
// We do not care about race conditions between the load and store operations,
// interrupts will only set this value to true.
critical_section::with(|_| {
// if there is work to do, loop back to polling
// TODO can we relax this?
if SIGNAL_WORK_THREAD_MODE.load(Ordering::SeqCst) {
SIGNAL_WORK_THREAD_MODE.store(false, Ordering::SeqCst);
}
}
// if not, wait for interrupt
else {
unsafe {
core::arch::asm!("wfi");
}
}
});
// if an interrupt occurred while waiting, it will be serviced here
}
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<RiscVThreadContext>;
}

76
embassy-executor/src/arch/std.rs
View File

@ -1,6 +1,9 @@
#[cfg(feature = "executor-interrupt")]
compile_error!("`executor-interrupt` is not supported with `arch-std`.");
#[cfg(not(feature = "thread-context"))]
compile_error!("`arch-std` requires `thread-context`.");
#[cfg(feature = "executor-thread")]
pub use thread::*;
#[cfg(feature = "executor-thread")]
@ -11,63 +14,40 @@ mod thread {
#[cfg(feature = "nightly")]
pub use embassy_macros::main_std as main;
use crate::raw::{Pender, PenderInner};
use crate::{raw, Spawner};
use crate::raw::OpaqueThreadContext;
use crate::thread::ThreadContext;
#[derive(Copy, Clone)]
pub(crate) struct ThreadPender(&'static Signaler);
impl ThreadPender {
#[allow(unused)]
pub(crate) fn pend(self) {
self.0.signal()
}
}
/// Single-threaded std-based executor.
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
/// TODO
// Name pending
pub struct StdThreadCtx {
_not_send: PhantomData<*mut ()>,
signaler: &'static Signaler,
}
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
impl Default for StdThreadCtx {
fn default() -> Self {
let signaler = &*Box::leak(Box::new(Signaler::new()));
Self {
inner: raw::Executor::new(Pender(PenderInner::Thread(ThreadPender(signaler)))),
not_send: PhantomData,
_not_send: PhantomData,
signaler,
}
}
}
/// 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() };
self.signaler.wait()
}
impl ThreadContext for StdThreadCtx {
fn context(&self) -> OpaqueThreadContext {
OpaqueThreadContext(self.signaler as *const _ as usize)
}
fn wait(&mut self) {
self.signaler.wait()
}
}
#[export_name = "__thread_mode_pender"]
fn __thread_mode_pender(core_id: OpaqueThreadContext) {
let signaler: &'static Signaler = unsafe { std::mem::transmute(core_id) };
signaler.signal()
}
struct Signaler {
@ -97,4 +77,8 @@ mod thread {
self.condvar.notify_one();
}
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<StdThreadCtx>;
}

37
embassy-executor/src/arch/wasm.rs
View File

@ -1,6 +1,9 @@
#[cfg(feature = "executor-interrupt")]
compile_error!("`executor-interrupt` is not supported with `arch-wasm`.");
#[cfg(not(feature = "thread-context"))]
compile_error!("`arch-wasm` requires `thread-context`.");
#[cfg(feature = "executor-thread")]
pub use thread::*;
#[cfg(feature = "executor-thread")]
@ -14,14 +17,13 @@ mod thread {
use wasm_bindgen::prelude::*;
use crate::raw::util::UninitCell;
use crate::raw::{Pender, PenderInner};
use crate::raw::{OpaqueThreadContext, Pender, PenderInner};
use crate::{raw, Spawner};
/// WASM executor, wasm_bindgen to schedule tasks on the JS event loop.
pub struct Executor {
inner: raw::Executor,
ctx: &'static WasmContext,
not_send: PhantomData<*mut ()>,
#[export_name = "__thread_mode_pender"]
fn __thread_mode_pender(context: OpaqueThreadContext) {
let signaler: &'static WasmContext = unsafe { std::mem::transmute(context) };
let _ = signaler.promise.then(unsafe { signaler.closure.as_mut() });
}
pub(crate) struct WasmContext {
@ -29,16 +31,6 @@ mod thread {
closure: UninitCell<Closure<dyn FnMut(JsValue)>>,
}
#[derive(Copy, Clone)]
pub(crate) struct ThreadPender(&'static WasmContext);
impl ThreadPender {
#[allow(unused)]
pub(crate) fn pend(self) {
let _ = self.0.promise.then(unsafe { self.0.closure.as_mut() });
}
}
impl WasmContext {
pub fn new() -> Self {
Self {
@ -48,14 +40,23 @@ mod thread {
}
}
/// WASM executor, wasm_bindgen to schedule tasks on the JS event loop.
pub struct Executor {
inner: raw::Executor,
ctx: &'static WasmContext,
not_send: PhantomData<*mut ()>,
}
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
let ctx = &*Box::leak(Box::new(WasmContext::new()));
Self {
inner: raw::Executor::new(Pender(PenderInner::Thread(ThreadPender(ctx)))),
not_send: PhantomData,
inner: raw::Executor::new(Pender(PenderInner::Thread(OpaqueThreadContext(
ctx as *const _ as usize,
)))),
ctx,
not_send: PhantomData,
}
}

117
embassy-executor/src/arch/xtensa.rs
View File

@ -1,6 +1,12 @@
#[cfg(feature = "executor-interrupt")]
compile_error!("`executor-interrupt` is not supported with `arch-xtensa`.");
#[cfg(feature = "thread-context")]
compile_error!(
"`thread-context` is not supported with `arch-xtensa`.\
Use a multicore-safe executor from esp-hal instead." // obviously, this is too specific to ESP32
);
#[cfg(feature = "executor-thread")]
pub use thread::*;
#[cfg(feature = "executor-thread")]
@ -8,86 +14,63 @@ mod thread {
use core::marker::PhantomData;
use core::sync::atomic::{AtomicBool, Ordering};
use crate::raw::{Pender, PenderInner};
use crate::{raw, Spawner};
use crate::raw::OpaqueThreadContext;
use crate::thread::ThreadContext;
#[derive(Copy, Clone)]
pub(crate) struct ThreadPender;
impl ThreadPender {
#[allow(unused)]
pub(crate) fn pend(self) {
SIGNAL_WORK_THREAD_MODE.store(true, core::sync::atomic::Ordering::SeqCst);
}
}
/// global atomic used to keep track of whether there is work to do since sev() is not available on Xtensa
/// global atomic used to keep track of whether there is work to do since sev() is not available on RISCV
static SIGNAL_WORK_THREAD_MODE: AtomicBool = AtomicBool::new(false);
/// Xtensa Executor
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
#[export_name = "__thread_mode_pender"]
fn __thread_mode_pender(_core_id: OpaqueThreadContext) {
SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
}
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
Self {
inner: raw::Executor::new(Pender(PenderInner::Thread(ThreadPender))),
not_send: PhantomData,
}
/// TODO
// Name pending
pub struct XtensaThreadContext {
_not_send: PhantomData<*mut ()>,
}
impl Default for XtensaThreadContext {
fn default() -> Self {
Self { _not_send: PhantomData }
}
}
impl ThreadContext for XtensaThreadContext {
fn context(&self) -> OpaqueThreadContext {
OpaqueThreadContext(())
}
/// 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());
fn wait(&mut self) {
unsafe {
// 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);
loop {
unsafe {
self.inner.poll();
// 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);
// 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!(
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
}
} 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
}
}
}
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<XtensaThreadContext>;
}

127
embassy-executor/src/interrupt.rs Normal file
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@ -0,0 +1,127 @@
//! Interrupt-mode executor.
use core::cell::UnsafeCell;
use core::mem::MaybeUninit;
use atomic_polyfill::{AtomicBool, Ordering};
use crate::raw::{self, OpaqueInterruptContext, Pender, PenderInner};
/// An interrupt source that can be used to drive an [`InterruptExecutor`].
// Name pending
pub trait InterruptContext {
/// Creates an opaque identifier for this interrupt.
fn context(&self) -> OpaqueInterruptContext;
/// Sets up the interrupt request.
fn enable(&self);
}
/// Interrupt mode executor.
///
/// This executor runs tasks in interrupt mode. The interrupt handler is set up
/// to poll tasks, and when a task is woken the interrupt is pended from software.
///
/// This allows running async tasks at a priority higher than thread mode. One
/// use case is to leave thread mode free for non-async tasks. Another use case is
/// to run multiple executors: one in thread mode for low priority tasks and another in
/// interrupt mode for higher priority tasks. Higher priority tasks will preempt lower
/// priority ones.
///
/// It is even possible to run multiple interrupt mode executors at different priorities,
/// by assigning different priorities to the interrupts. For an example on how to do this,
/// See the 'multiprio' example for 'embassy-nrf'.
///
/// To use it, you have to pick an interrupt that won't be used by the hardware.
/// Some chips reserve some interrupts for this purpose, sometimes named "software interrupts" (SWI).
/// If this is not the case, you may use an interrupt from any unused peripheral.
///
/// 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 InterruptModeExecutor {
started: AtomicBool,
executor: UnsafeCell<MaybeUninit<raw::Executor>>,
}
unsafe impl Send for InterruptModeExecutor {}
unsafe impl Sync for InterruptModeExecutor {}
impl InterruptModeExecutor {
/// Create a new, not started `InterruptExecutor`.
#[inline]
pub const fn new() -> Self {
Self {
started: AtomicBool::new(false),
executor: UnsafeCell::new(MaybeUninit::uninit()),
}
}
/// 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, 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`]
/// is returned instead of a [`Spawner`](embassy_executor::Spawner) because the executor effectively runs in a
/// different "thread" (the interrupt), so spawning tasks on it is effectively
/// sending them.
///
/// 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.
///
/// # Interrupt requirements
///
/// You must write the interrupt handler yourself, and make it call [`on_interrupt()`](Self::on_interrupt).
///
/// This method already enables (unmasks) the interrupt, you must NOT do it yourself.
///
/// You must set the interrupt priority before calling this method. You MUST NOT
/// do it after.
///
pub fn start(&'static self, irq: impl InterruptContext) -> crate::SendSpawner {
if self
.started
.compare_exchange(false, true, Ordering::Acquire, Ordering::Relaxed)
.is_err()
{
panic!("InterruptExecutor::start() called multiple times on the same executor.");
}
unsafe {
(&mut *self.executor.get())
.as_mut_ptr()
.write(raw::Executor::new(Pender(PenderInner::Interrupt(irq.context()))))
}
let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
irq.enable();
executor.spawner().make_send()
}
/// Get a SendSpawner for this executor
///
/// This returns a [`SendSpawner`] you can use to spawn tasks on this
/// executor.
///
/// This MUST only be called on an executor that has already been spawned.
/// The function will panic otherwise.
pub fn spawner(&'static self) -> crate::SendSpawner {
if !self.started.load(Ordering::Acquire) {
panic!("InterruptExecutor::spawner() called on uninitialized executor.");
}
let executor = unsafe { (&*self.executor.get()).assume_init_ref() };
executor.spawner().make_send()
}
}

5
embassy-executor/src/lib.rs
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@ -37,6 +37,11 @@ pub use arch::*;
pub mod raw;
#[cfg(feature = "executor-interrupt")]
pub mod interrupt;
#[cfg(feature = "executor-thread")]
pub mod thread;
mod spawner;
pub use spawner::*;

35
embassy-executor/src/raw/mod.rs
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@ -291,12 +291,29 @@ impl<F: Future + 'static, const N: usize> TaskPool<F, N> {
}
}
/// Context given to the thread-mode executor's pender.
#[cfg(all(feature = "executor-thread", not(feature = "thread-context")))]
#[derive(Clone, Copy)]
#[repr(transparent)]
pub struct OpaqueThreadContext(pub(crate) ());
/// Context given to the thread-mode executor's pender.
#[cfg(all(feature = "executor-thread", feature = "thread-context"))]
#[repr(transparent)]
#[derive(Clone, Copy)]
pub struct OpaqueThreadContext(pub(crate) usize);
/// Context given to the interrupt-mode executor's pender.
#[derive(Clone, Copy)]
#[repr(transparent)]
pub struct OpaqueInterruptContext(pub(crate) usize);
#[derive(Clone, Copy)]
pub(crate) enum PenderInner {
#[cfg(feature = "executor-thread")]
Thread(crate::arch::ThreadPender),
Thread(OpaqueThreadContext),
#[cfg(feature = "executor-interrupt")]
Interrupt(crate::arch::InterruptPender),
Interrupt(OpaqueInterruptContext),
#[cfg(feature = "pender-callback")]
Callback { func: fn(*mut ()), context: *mut () },
}
@ -333,9 +350,19 @@ impl Pender {
pub(crate) fn pend(&self) {
match self.0 {
#[cfg(feature = "executor-thread")]
PenderInner::Thread(x) => x.pend(),
PenderInner::Thread(core_id) => {
extern "Rust" {
fn __thread_mode_pender(core_id: OpaqueThreadContext);
}
unsafe { __thread_mode_pender(core_id) };
}
#[cfg(feature = "executor-interrupt")]
PenderInner::Interrupt(x) => x.pend(),
PenderInner::Interrupt(interrupt) => {
extern "Rust" {
fn __interrupt_mode_pender(interrupt: OpaqueInterruptContext);
}
unsafe { __interrupt_mode_pender(interrupt) };
}
#[cfg(feature = "pender-callback")]
PenderInner::Callback { func, context } => func(context),
}

80
embassy-executor/src/thread.rs Normal file
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@ -0,0 +1,80 @@
//! Thread-mode executor.
use core::marker::PhantomData;
use crate::raw::{OpaqueThreadContext, Pender, PenderInner};
use crate::{raw, Spawner};
/// TODO
// Name pending
pub trait ThreadContext: Sized {
/// TODO
fn context(&self) -> OpaqueThreadContext;
/// TODO
fn wait(&mut self);
}
/// Thread mode executor, using WFE/SEV.
///
/// This is the simplest and most common kind of executor. It runs on
/// thread mode (at the lowest priority level), and uses the `WFE` ARM instruction
/// to sleep when it has no more work to do. When a task is woken, a `SEV` instruction
/// is executed, to make the `WFE` exit from sleep and poll the task.
///
/// This executor allows for ultra low power consumption for chips where `WFE`
/// triggers low-power sleep without extra steps. If your chip requires extra steps,
/// you may use [`raw::Executor`] directly to program custom behavior.
pub struct ThreadModeExecutor<C: ThreadContext> {
inner: raw::Executor,
context: C,
not_send: PhantomData<*mut ()>,
}
impl<C: ThreadContext> ThreadModeExecutor<C> {
/// Create a new Executor.
pub fn new() -> Self
where
C: Default,
{
Self::with_context(C::default())
}
/// Create a new Executor.
pub fn with_context(context: C) -> Self {
Self {
inner: raw::Executor::new(Pender(PenderInner::Thread(context.context()))),
context,
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();
self.context.wait();
};
}
}
}