libcortex_a9: implemented semaphore.

master
pca006132 3 years ago
parent b65606f2d0
commit 9e97102e12
  1. 1
      libcortex_a9/src/lib.rs
  2. 71
      libcortex_a9/src/semaphore.rs

@ -11,6 +11,7 @@ pub mod cache;
pub mod mmu;
pub mod mutex;
pub mod sync_channel;
pub mod semaphore;
mod uncached;
mod fpu;
pub use uncached::UncachedSlice;

@ -0,0 +1,71 @@
use super::asm::{sev, wfe};
use core::{
task::{Context, Poll},
pin::Pin,
future::Future
};
use core::sync::atomic::{AtomicI32, Ordering};
pub struct Semaphore {
value: AtomicI32,
max: i32
}
impl Semaphore {
pub fn new(value: i32, max: i32) -> Self {
Semaphore { value: AtomicI32::new(value), max}
}
pub fn try_wait(&self) -> Option<()> {
loop {
let value = self.value.load(Ordering::Relaxed);
if value > 0 {
if self.value.compare_and_swap(value, value - 1, Ordering::SeqCst) == value {
return Some(());
}
} else {
return None;
}
}
}
pub fn wait(&self) {
while self.try_wait().is_none() {
wfe();
}
}
pub async fn async_wait(&self) {
struct Fut<'a>(&'a Semaphore);
impl Future for Fut<'_> {
type Output = ();
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
match self.0.try_wait() {
Some(_) => Poll::Ready(()),
None => {
cx.waker().wake_by_ref();
Poll::Pending
}
}
}
}
Fut(&self).await
}
pub fn signal(&self) {
loop {
let value = self.value.load(Ordering::Relaxed);
if value < self.max {
if self.value.compare_and_swap(value, value + 1, Ordering::SeqCst) == value {
sev();
return;
}
} else {
return;
}
}
}
}
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