libcortex_a9: implemented semaphore.
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@ -11,6 +11,7 @@ pub mod cache;
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pub mod mmu;
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pub mod mutex;
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pub mod sync_channel;
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pub mod semaphore;
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mod uncached;
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mod fpu;
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pub use uncached::UncachedSlice;
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71
libcortex_a9/src/semaphore.rs
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71
libcortex_a9/src/semaphore.rs
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@ -0,0 +1,71 @@
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use super::asm::{sev, wfe};
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use core::{
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task::{Context, Poll},
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pin::Pin,
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future::Future
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};
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use core::sync::atomic::{AtomicI32, Ordering};
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pub struct Semaphore {
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value: AtomicI32,
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max: i32
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}
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impl Semaphore {
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pub fn new(value: i32, max: i32) -> Self {
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Semaphore { value: AtomicI32::new(value), max}
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}
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pub fn try_wait(&self) -> Option<()> {
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loop {
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let value = self.value.load(Ordering::Relaxed);
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if value > 0 {
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if self.value.compare_and_swap(value, value - 1, Ordering::SeqCst) == value {
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return Some(());
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}
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} else {
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return None;
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}
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}
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}
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pub fn wait(&self) {
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while self.try_wait().is_none() {
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wfe();
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}
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}
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pub async fn async_wait(&self) {
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struct Fut<'a>(&'a Semaphore);
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impl Future for Fut<'_> {
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type Output = ();
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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match self.0.try_wait() {
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Some(_) => Poll::Ready(()),
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None => {
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cx.waker().wake_by_ref();
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Poll::Pending
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}
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}
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}
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}
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Fut(&self).await
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}
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pub fn signal(&self) {
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loop {
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let value = self.value.load(Ordering::Relaxed);
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if value < self.max {
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if self.value.compare_and_swap(value, value + 1, Ordering::SeqCst) == value {
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sev();
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return;
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}
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} else {
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return;
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}
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}
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}
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}
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