89 lines
2.4 KiB
Rust
89 lines
2.4 KiB
Rust
use core::ops::{Deref, DerefMut};
|
|
use core::sync::atomic::{AtomicU32, Ordering};
|
|
use core::cell::UnsafeCell;
|
|
use super::{
|
|
spin_lock_yield, notify_spin_lock,
|
|
asm::{enter_critical, exit_critical}
|
|
};
|
|
|
|
const LOCKED: u32 = 1;
|
|
const UNLOCKED: u32 = 0;
|
|
|
|
/// Mutex implementation for Cortex-A9
|
|
///
|
|
/// [ARM Synchronization Primitives Development Article: Implementing a mutex](http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dht0008a/ch01s03s02.html)
|
|
pub struct Mutex<T> {
|
|
locked: AtomicU32,
|
|
inner: UnsafeCell<T>,
|
|
}
|
|
|
|
unsafe impl<T: Send> Sync for Mutex<T> {}
|
|
unsafe impl<T: Send> Send for Mutex<T> {}
|
|
|
|
impl<T> Mutex<T> {
|
|
/// Constructor, const-fn
|
|
pub const fn new(inner: T) -> Self {
|
|
Mutex{
|
|
locked: AtomicU32::new(UNLOCKED),
|
|
inner: UnsafeCell::new(inner),
|
|
}
|
|
}
|
|
|
|
/// Lock the Mutex, blocks when already locked
|
|
pub fn lock(&self) -> MutexGuard<T> {
|
|
let mut irq = unsafe { enter_critical() };
|
|
while self.locked.compare_exchange_weak(UNLOCKED, LOCKED, Ordering::AcqRel, Ordering::Relaxed).is_err() {
|
|
unsafe {
|
|
exit_critical(irq);
|
|
spin_lock_yield();
|
|
irq = enter_critical();
|
|
}
|
|
}
|
|
MutexGuard { mutex: self, irq }
|
|
}
|
|
|
|
pub fn try_lock(&self) -> Option<MutexGuard<T>> {
|
|
let irq = unsafe { enter_critical() };
|
|
if self.locked.compare_exchange_weak(UNLOCKED, LOCKED, Ordering::AcqRel, Ordering::Relaxed).is_err() {
|
|
unsafe { exit_critical(irq) };
|
|
None
|
|
} else {
|
|
Some(MutexGuard { mutex: self, irq })
|
|
}
|
|
}
|
|
|
|
fn unlock(&self) {
|
|
self.locked.store(UNLOCKED, Ordering::Release);
|
|
|
|
notify_spin_lock();
|
|
}
|
|
}
|
|
|
|
/// Returned by `Mutex.lock()`, allows access to data via
|
|
/// `Deref`/`DerefMutx`
|
|
pub struct MutexGuard<'a, T> {
|
|
mutex: &'a Mutex<T>,
|
|
irq: bool,
|
|
}
|
|
|
|
impl<'a, T> Deref for MutexGuard<'a, T> {
|
|
type Target = T;
|
|
fn deref(&self) -> &T {
|
|
unsafe { &*self.mutex.inner.get() }
|
|
}
|
|
}
|
|
|
|
impl<'a, T> DerefMut for MutexGuard<'a, T> {
|
|
fn deref_mut(&mut self) -> &mut T {
|
|
unsafe { &mut *self.mutex.inner.get() }
|
|
}
|
|
}
|
|
|
|
/// Automatically `Mutex.unlock()` when this reference is dropped
|
|
impl<'a, T> Drop for MutexGuard<'a, T> {
|
|
fn drop(&mut self) {
|
|
self.mutex.unlock();
|
|
unsafe { exit_critical(self.irq) };
|
|
}
|
|
}
|