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Remove the non-specific thread-mode executor

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This commit is contained in:
Dániel Buga 2023-08-14 15:35:22 +02:00
parent 4c4b12c307
commit 986a63ebb8
7 changed files with 369 additions and 276 deletions
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296
embassy-executor/src/arch/cortex_m.rs
View File

@ -1,122 +1,236 @@
#[cfg(feature = "executor-thread")]
pub use thread::*;
const THREAD_PENDER: usize = usize::MAX;
use crate::raw::PenderContext;
#[cfg(feature = "executor-interrupt")]
/// # Safety
///
/// `irq` must be a valid interrupt request number
unsafe fn nvic_pend(irq: u16) {
use cortex_m::interrupt::InterruptNumber;
#[derive(Clone, Copy)]
struct Irq(u16);
unsafe impl InterruptNumber for Irq {
fn number(self) -> u16 {
self.0
}
}
let irq = Irq(irq);
// 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(irq);
}
#[cfg(armv6m)]
cortex_m::peripheral::NVIC::pend(irq);
}
#[cfg(all(feature = "executor-thread", feature = "executor-interrupt"))]
#[export_name = "__pender"]
fn __pender(context: PenderContext) {
#[cfg(any(feature = "executor-thread", feature = "executor-interrupt"))]
fn __pender(context: crate::raw::PenderContext) {
unsafe {
let context: usize = core::mem::transmute(context);
// Safety: `context` is either `usize::MAX` created by `Executor::run`, or a valid interrupt
// request number given to `InterruptExecutor::start`.
if context as usize == usize::MAX {
core::arch::asm!("sev")
} else {
nvic_pend(context as u16)
let context: usize = core::mem::transmute(context);
#[cfg(feature = "executor-thread")]
if context == THREAD_PENDER {
core::arch::asm!("sev");
return;
}
#[cfg(feature = "executor-interrupt")]
{
use cortex_m::interrupt::InterruptNumber;
use cortex_m::peripheral::NVIC;
#[derive(Clone, Copy)]
struct Irq(u16);
unsafe impl InterruptNumber for Irq {
fn number(self) -> u16 {
self.0
}
}
let irq = Irq(context as u16);
// STIR is faster, but is only available in v7 and higher.
#[cfg(not(armv6m))]
{
let mut nvic: NVIC = core::mem::transmute(());
nvic.request(irq);
}
#[cfg(armv6m)]
NVIC::pend(irq);
}
}
}
#[cfg(all(feature = "executor-thread", not(feature = "executor-interrupt")))]
#[export_name = "__pender"]
fn __pender(_context: PenderContext) {
unsafe { core::arch::asm!("sev") }
}
#[cfg(all(not(feature = "executor-thread"), feature = "executor-interrupt"))]
#[export_name = "__pender"]
fn __pender(context: PenderContext) {
unsafe {
let context: usize = core::mem::transmute(context);
// Safety: `context` is the same value we passed to `InterruptExecutor::start`, which must
// be a valid interrupt request number.
nvic_pend(context as u16)
}
}
#[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::PenderContext;
use crate::thread::ThreadContext;
use crate::arch::THREAD_PENDER;
use crate::{raw, Spawner};
/// TODO
// Name pending
#[derive(Default)] // Default enables Executor::new
pub struct Context;
impl ThreadContext for Context {
fn context(&self) -> PenderContext {
unsafe { core::mem::transmute(usize::MAX) }
}
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 ()>,
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<Context>;
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
Self {
inner: raw::Executor::new(unsafe { core::mem::transmute(THREAD_PENDER) }),
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");
};
}
}
}
}
#[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::interrupt::InterruptContext;
use crate::raw::PenderContext;
use crate::raw;
impl<T> InterruptContext for T
where
T: InterruptNumber,
{
fn context(&self) -> PenderContext {
unsafe { core::mem::transmute(self.number() as usize) }
}
fn enable(&self) {
unsafe { NVIC::unmask(*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 InterruptExecutor {
started: AtomicBool,
executor: UnsafeCell<MaybeUninit<raw::Executor>>,
}
/// TODO
// Type alias for backwards compatibility
pub type InterruptExecutor = crate::interrupt::InterruptModeExecutor;
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()),
}
}
/// 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 {
let context = core::mem::transmute(irq.number() as usize);
(&mut *self.executor.get())
.as_mut_ptr()
.write(raw::Executor::new(context))
}
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()
}
}
}

92
embassy-executor/src/arch/riscv32.rs
View File

@ -5,53 +5,77 @@ compile_error!("`executor-interrupt` is not supported with `arch-riscv32`.");
pub use thread::*;
#[cfg(feature = "executor-thread")]
mod thread {
use core::marker::PhantomData;
use core::sync::atomic::{AtomicBool, Ordering};
#[cfg(feature = "nightly")]
pub use embassy_macros::main_riscv as main;
use crate::raw::PenderContext;
use crate::thread::ThreadContext;
use crate::{raw, Spawner};
/// 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);
#[export_name = "__pender"]
fn __thread_mode_pender(_context: PenderContext) {
fn __thread_mode_pender(_context: crate::raw::PenderContext) {
SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
}
/// TODO
// Name pending
#[derive(Default)] // Default enables Executor::new
pub struct Context;
impl ThreadContext for Context {
fn context(&self) -> PenderContext {
unsafe { core::mem::transmute(0) }
}
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
}
/// RISCV32 Executor
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<Context>;
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
Self {
inner: raw::Executor::new(unsafe { core::mem::transmute(0) }),
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();
// 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
}
}
}
}
}

70
embassy-executor/src/arch/std.rs
View File

@ -5,42 +5,64 @@ compile_error!("`executor-interrupt` is not supported with `arch-std`.");
pub use thread::*;
#[cfg(feature = "executor-thread")]
mod thread {
use std::marker::PhantomData;
use std::sync::{Condvar, Mutex};
#[cfg(feature = "nightly")]
pub use embassy_macros::main_std as main;
use crate::raw::PenderContext;
use crate::thread::ThreadContext;
use crate::{raw, Spawner};
/// TODO
// Name pending
pub struct Context {
#[export_name = "__pender"]
fn __pender(context: crate::raw::PenderContext) {
let signaler: &'static Signaler = unsafe { std::mem::transmute(context) };
signaler.signal()
}
/// Single-threaded std-based executor.
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
signaler: &'static Signaler,
}
impl Default for Context {
fn default() -> Self {
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
let signaler = &*Box::leak(Box::new(Signaler::new()));
Self {
signaler: &*Box::leak(Box::new(Signaler::new())),
inner: raw::Executor::new(unsafe { std::mem::transmute(signaler) }),
not_send: PhantomData,
signaler,
}
}
}
impl ThreadContext for Context {
fn context(&self) -> PenderContext {
unsafe { core::mem::transmute(self.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()
}
}
fn wait(&mut self) {
self.signaler.wait()
}
}
#[export_name = "__pender"]
fn __pender(context: PenderContext) {
let signaler: &'static Signaler = unsafe { std::mem::transmute(context) };
signaler.signal()
}
struct Signaler {
@ -70,8 +92,4 @@ mod thread {
self.condvar.notify_one();
}
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<Context>;
}

94
embassy-executor/src/arch/xtensa.rs
View File

@ -8,56 +8,80 @@ mod thread {
use core::marker::PhantomData;
use core::sync::atomic::{AtomicBool, Ordering};
use crate::raw::PenderContext;
use crate::thread::ThreadContext;
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 = "__thread_mode_pender"]
fn __thread_mode_pender(_context: PenderContext) {
fn __thread_mode_pender(_context: crate::raw::PenderContext) {
SIGNAL_WORK_THREAD_MODE.store(true, Ordering::SeqCst);
}
/// TODO
// Name pending
#[derive(Default)] // Default enables Executor::new
pub struct Context;
/// Xtensa Executor
pub struct Executor {
inner: raw::Executor,
not_send: PhantomData<*mut ()>,
}
impl ThreadContext for Context {
fn context(&self) -> PenderContext {
unsafe { core::mem::transmute(0) }
impl Executor {
/// Create a new Executor.
pub fn new() -> Self {
Self {
inner: raw::Executor::new(unsafe { core::mem::transmute(0) }),
not_send: PhantomData,
}
}
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);
/// 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());
// 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);
loop {
unsafe {
self.inner.poll();
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
// 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
}
}
}
}
}
/// TODO
// Type alias for backwards compatibility
pub type Executor = crate::thread::ThreadModeExecutor<Context>;
}

2
embassy-executor/src/interrupt.rs
View File

@ -41,7 +41,7 @@ pub trait InterruptContext {
/// 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
/// [`crate::thread::ThreadModeExecutor`] instead, if it works for your use case.
/// thread-mode executor instead, if it works for your use case.
pub struct InterruptModeExecutor {
started: AtomicBool,
executor: UnsafeCell<MaybeUninit<raw::Executor>>,

4
embassy-executor/src/lib.rs
View File

@ -39,8 +39,8 @@ pub mod raw;
#[cfg(feature = "executor-interrupt")]
pub mod interrupt;
#[cfg(feature = "executor-thread")]
pub mod thread;
#[cfg(feature = "executor-interrupt")]
pub use interrupt::*;
mod spawner;
pub use spawner::*;

87
embassy-executor/src/thread.rs
View File

@ -1,87 +0,0 @@
//! Thread-mode executor.
use core::marker::PhantomData;
use crate::raw::{self, PenderContext};
use crate::Spawner;
/// Architecture-specific interface for a thread-mode executor. This trait describes what the
/// executor should do when idle, and what data should be passed to its pender.
// TODO: Name pending
pub trait ThreadContext: Sized {
/// A pointer-sized piece of data that is passed to the pender function.
///
/// For example, on multi-core systems, this can be used to store the ID of the core that
/// should be woken up.
fn context(&self) -> PenderContext;
/// Waits for the executor to be waken.
///
/// While it is valid for this function can be empty, it is recommended to use a WFE instruction
/// or equivalent to let the CPU sleep.
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 using the given thread context.
pub fn with_context(context: C) -> Self {
Self {
inner: raw::Executor::new(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();
};
}
}
}