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libasync: adapt from async-on-embedded/async-cortex-m

This commit is contained in:
Astro 2020-03-26 01:35:05 +01:00
parent d2fc0ecc14
commit 5b95410244
9 changed files with 267 additions and 1 deletions

16
Cargo.lock generated
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@ -24,12 +24,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
name = "experiments"
version = "0.0.0"
dependencies = [
"libasync 0.0.0",
"libboard_zynq 0.0.0",
"libcortex_a9 0.0.0",
"libregister 0.0.0",
"libsupport_zynq 0.0.0",
]
[[package]]
name = "libasync"
version = "0.0.0"
dependencies = [
"libboard_zynq 0.0.0",
"libcortex_a9 0.0.0",
"pin-utils 0.1.0-alpha.4 (registry+https://github.com/rust-lang/crates.io-index)",
]
[[package]]
name = "libboard_zynq"
version = "0.0.0"
@ -80,6 +90,11 @@ name = "managed"
version = "0.7.1"
source = "registry+https://github.com/rust-lang/crates.io-index"
[[package]]
name = "pin-utils"
version = "0.1.0-alpha.4"
source = "registry+https://github.com/rust-lang/crates.io-index"
[[package]]
name = "r0"
version = "1.0.0"
@ -115,6 +130,7 @@ dependencies = [
"checksum compiler_builtins 0.1.26 (registry+https://github.com/rust-lang/crates.io-index)" = "036b035e9ebcd705affece16319223d19f229e2358be6e3b7b094e57193312e6"
"checksum linked_list_allocator 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "5825aea823c659d0fdcdbe8c9b78baf56f3a10365d783db874f6d360df72626f"
"checksum managed 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "fdcec5e97041c7f0f1c5b7d93f12e57293c831c646f4cc7a5db59460c7ea8de6"
"checksum pin-utils 0.1.0-alpha.4 (registry+https://github.com/rust-lang/crates.io-index)" = "5894c618ce612a3fa23881b152b608bafb8c56cfc22f434a3ba3120b40f7b587"
"checksum r0 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "bd7a31eed1591dcbc95d92ad7161908e72f4677f8fabf2a32ca49b4237cbf211"
"checksum smoltcp 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0fe46639fd2ec79eadf8fe719f237a7a0bd4dac5d957f1ca5bbdbc1c3c39e53a"
"checksum vcell 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "876e32dcadfe563a4289e994f7cb391197f362b6315dc45e8ba4aa6f564a4b3c"

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@ -2,6 +2,7 @@
members = [
"libregister", "libcortex_a9",
"libboard_zynq", "libsupport_zynq",
"libasync",
"experiments",
]

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@ -49,7 +49,7 @@ let
name = "${crate}";
src = ./.;
crateSubdir = crate;
cargoSha256 = "0106i3qg44gvcv18bq3854lbj7x4qkjzqpw5ldrxjlzf6h13gfgv";
cargoSha256 = "1fvild4mygcvnfcnmni4icg5nj16dj7hkzjpahzhpbyv9rr24722";
cargoFeatures = features;
doCheck = false;
};

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@ -15,3 +15,4 @@ libregister = { path = "../libregister" }
libcortex_a9 = { path = "../libcortex_a9" }
libboard_zynq = { path = "../libboard_zynq" }
libsupport_zynq = { path = "../libsupport_zynq" }
libasync = { path = "../libasync" }

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@ -18,6 +18,7 @@ use libsupport_zynq::{
ram, alloc::{vec, vec::Vec},
boot,
};
use libasync::task;
const HWADDR: [u8; 6] = [0, 0x23, 0xde, 0xea, 0xbe, 0xef];
@ -100,6 +101,26 @@ pub fn main_core0() {
flash = flash_io.stop();
}
task::spawn(async {
println!("outer task");
});
task::spawn(async {
for i in 1..=3 {
println!("outer task2: {}", i);
task::r#yield().await;
}
});
task::block_on(async {
task::spawn(async {
println!("inner task");
});
for i in 1..=10 {
println!("yield {}", i);
task::r#yield().await;
}
});
let core1_stack = unsafe { &mut STACK_CORE1[..] };
println!("{} bytes stack for core1", core1_stack.len());
let core1 = boot::Core1::start(core1_stack);

13
libasync/Cargo.toml Normal file
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@ -0,0 +1,13 @@
[package]
name = "libasync"
description = "low-level async support"
version = "0.0.0"
authors = ["Astro <astro@spaceboyz.net>"]
edition = "2018"
[dependencies]
#futures = { version = "0.3", default-features = false }
pin-utils = "0.1.0-alpha.4"
libcortex_a9 = { path = "../libcortex_a9" }
# TODO: delete
libboard_zynq = { path = "../libboard_zynq" }

158
libasync/src/executor.rs Normal file
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@ -0,0 +1,158 @@
use core::{
cell::{Cell, UnsafeCell},
future::Future,
mem::MaybeUninit,
pin::Pin,
sync::atomic::{self, AtomicBool, Ordering},
task::{Context, Poll, RawWaker, RawWakerVTable, Waker},
};
use alloc::{boxed::Box, collections::VecDeque as Deque};
//use futures::future::FutureExt;
use pin_utils::pin_mut;
use libcortex_a9::mutex::Mutex;
// TODO: delete
use libboard_zynq::println;
// NOTE `*const ()` is &AtomicBool
static VTABLE: RawWakerVTable = {
unsafe fn clone(p: *const ()) -> RawWaker {
RawWaker::new(p, &VTABLE)
}
unsafe fn wake(p: *const ()) {
wake_by_ref(p)
}
unsafe fn wake_by_ref(p: *const ()) {
(*(p as *const AtomicBool)).store(true, Ordering::Relaxed)
}
unsafe fn drop(_: *const ()) {
// no-op
}
RawWakerVTable::new(clone, wake, wake_by_ref, drop)
};
/// A single-threaded executor
///
/// This is a singleton
pub struct Executor {
in_block_on: Mutex<bool>,
tasks: Mutex<Deque<Task>>,
}
impl Executor {
/// Creates a new instance of the executor
pub fn new() -> Self {
Self {
in_block_on: Mutex::new(false),
tasks: Mutex::new(Deque::new()),
}
}
pub fn block_on<T>(&self, f: impl Future<Output = T>) -> T {
// we want to avoid reentering `block_on` because then all the code
// below has to become more complex. It's also likely that the
// application will only call `block_on` once on an infinite task
// (`Future<Output = !>`)
{
let mut in_block_on = self.in_block_on.lock();
if *in_block_on {
panic!("nested `block_on`");
}
*in_block_on = true;
}
pin_mut!(f);
let ready = AtomicBool::new(true);
let waker =
unsafe { Waker::from_raw(RawWaker::new(&ready as *const _ as *const _, &VTABLE)) };
let val = loop {
// advance the main task
if ready.load(Ordering::Relaxed) {
ready.store(false, Ordering::Relaxed);
let mut cx = Context::from_waker(&waker);
if let Poll::Ready(val) = f.as_mut().poll(&mut cx) {
break val;
}
}
// advance other tasks
let next_task = self.tasks.lock().pop_front();
if let Some(mut task) = next_task {
// NOTE we don't need a CAS operation here because `wake` invocations that come from
// interrupt handlers (the only source of 'race conditions' (!= data races)) are
// "oneshot": they'll issue a `wake` and then disable themselves to not run again
// until the woken task has made more work
if task.ready.load(Ordering::Relaxed) {
// we are about to service the task so switch the `ready` flag to `false`
task.ready.store(false, Ordering::Relaxed);
// NOTE we never deallocate tasks so `&ready` is always pointing to
// allocated memory (`&'static AtomicBool`)
let waker = unsafe {
Waker::from_raw(RawWaker::new(&task.ready as *const _ as *const _, &VTABLE))
};
let mut cx = Context::from_waker(&waker);
// this points into a `static` memory so it's already pinned
let r = unsafe {
Pin::new_unchecked(&mut *task.f)
.poll(&mut cx)
.is_ready()
};
if !r {
// Task is not finished, requeue
self.tasks.lock().push_back(task);
}
}
}
// // try to sleep; this will be a no-op if any of the previous tasks generated a SEV or an
// // interrupt ran (regardless of whether it generated a wake-up or not)
// asm::wfe();
};
*self.in_block_on.lock() = false;
val
}
// NOTE CAREFUL! this method can overlap with `block_on`
// FIXME we want to use `Future<Output = !>` here but the never type (`!`) is unstable; so as a
// workaround we'll "abort" if the task / future terminates (see `Task::new`)
pub fn spawn(&self, f: impl Future + 'static) {
// NOTE(unsafe) only safe as long as `spawn` is never re-entered and this does not overlap
// with operation `(A)` (see `Task::block_on`)
self.tasks.lock().push_back(Task::new(f));
}
}
pub struct Task {
ready: AtomicBool,
f: Box<Future<Output = ()>>,
}
impl Task {
fn new(f: impl Future + 'static) -> Self {
Task {
ready: AtomicBool::new(true),
f: Box::new(async { f.await; }),
}
}
}
/// Returns a handle to the executor singleton
///
/// This lazily initializes the executor and allocator when first called
pub(crate) fn current() -> &'static Executor {
static INIT: AtomicBool = AtomicBool::new(false);
static mut EXECUTOR: UnsafeCell<MaybeUninit<Executor>> = UnsafeCell::new(MaybeUninit::uninit());
if INIT.load(Ordering::Relaxed) {
unsafe { &*(EXECUTOR.get() as *const Executor) }
} else {
unsafe {
let executorp = EXECUTOR.get() as *mut Executor;
executorp.write(Executor::new());
INIT.store(true, Ordering::Relaxed);
&*executorp
}
}
}

6
libasync/src/lib.rs Normal file
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@ -0,0 +1,6 @@
#![no_std]
extern crate alloc;
pub mod task;
pub mod executor;

50
libasync/src/task.rs Normal file
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@ -0,0 +1,50 @@
//! Asynchronous tasks
use core::{
future::Future,
pin::Pin,
task::{Context, Poll},
};
use super::executor;
/// Drives the future `f` to completion
///
/// This also makes any previously `spawn`-ed future make progress
pub fn block_on<T>(f: impl Future<Output = T>) -> T {
executor::current().block_on(f)
}
/// Spawns a task onto the executor
///
/// The spawned task will not make any progress until `block_on` is called.
///
/// The future `f` must never terminate. The program will *abort* if `f` (the async code) returns.
/// The right signature here would be `f: impl Future<Output = !>` but that requires nightly
pub fn spawn<T>(f: impl Future<Output = T> + 'static) {
executor::current().spawn(f)
}
/// Use `r#yield.await` to suspend the execution of a task
pub async fn r#yield() {
struct Yield {
yielded: bool,
}
impl Future for Yield {
type Output = ();
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
if self.yielded {
Poll::Ready(())
} else {
self.yielded = true;
// wake ourselves
cx.waker().wake_by_ref();
//asm::sev();
Poll::Pending
}
}
}
Yield { yielded: false }.await
}