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fix: remove portable-atomic from rng

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This commit is contained in:
Ulf Lilleengen 2024-01-23 23:16:06 +01:00
parent 25f82538ae
commit 6126183db8
1 changed files with 67 additions and 60 deletions
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127
embassy-nrf/src/rng.rs
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@ -9,8 +9,6 @@ use core::task::Poll;
use embassy_hal_internal::drop::OnDrop;
use embassy_hal_internal::{into_ref, PeripheralRef};
use embassy_sync::waitqueue::AtomicWaker;
use portable_atomic::{AtomicPtr, Ordering};
use crate::interrupt::typelevel::Interrupt;
use crate::{interrupt, Peripheral};
@ -22,7 +20,6 @@ pub struct InterruptHandler<T: Instance> {
impl<T: Instance> interrupt::typelevel::Handler<T::Interrupt> for InterruptHandler<T> {
unsafe fn on_interrupt() {
let s = T::state();
let r = T::regs();
// Clear the event.
@ -30,46 +27,26 @@ impl<T: Instance> interrupt::typelevel::Handler<T::Interrupt> for InterruptHandl
// Mutate the slice within a critical section,
// so that the future isn't dropped in between us loading the pointer and actually dereferencing it.
let (ptr, end) = critical_section::with(|_| {
let ptr = s.ptr.load(Ordering::Relaxed);
critical_section::with(|cs| {
let mut state = T::state().borrow_mut(cs);
// We need to make sure we haven't already filled the whole slice,
// in case the interrupt fired again before the executor got back to the future.
let end = s.end.load(Ordering::Relaxed);
if !ptr.is_null() && ptr != end {
if !state.ptr.is_null() && state.ptr != state.end {
// If the future was dropped, the pointer would have been set to null,
// so we're still good to mutate the slice.
// The safety contract of `Rng::new` means that the future can't have been dropped
// without calling its destructor.
unsafe {
*ptr = r.value.read().value().bits();
*state.ptr = r.value.read().value().bits();
state.ptr = state.ptr.add(1);
}
if state.ptr == state.end {
state.waker.wake();
}
}
(ptr, end)
});
if ptr.is_null() || ptr == end {
// If the future was dropped, there's nothing to do.
// If `ptr == end`, we were called by mistake, so return.
return;
}
let new_ptr = unsafe { ptr.add(1) };
match s
.ptr
.compare_exchange(ptr, new_ptr, Ordering::Relaxed, Ordering::Relaxed)
{
Ok(_) => {
let end = s.end.load(Ordering::Relaxed);
// It doesn't matter if `end` was changed under our feet, because then this will just be false.
if new_ptr == end {
s.waker.wake();
}
}
Err(_) => {
// If the future was dropped or finished, there's no point trying to wake it.
// It will have already stopped the RNG, so there's no need to do that either.
}
}
}
}
@ -136,13 +113,15 @@ impl<'d, T: Instance> Rng<'d, T> {
return; // Nothing to fill
}
let s = T::state();
let range = dest.as_mut_ptr_range();
// Even if we've preempted the interrupt, it can't preempt us again,
// so we don't need to worry about the order we write these in.
s.ptr.store(range.start, Ordering::Relaxed);
s.end.store(range.end, Ordering::Relaxed);
critical_section::with(|cs| {
let mut state = T::state().borrow_mut(cs);
state.ptr = range.start;
state.end = range.end;
});
self.enable_irq();
self.start();
@ -151,24 +130,24 @@ impl<'d, T: Instance> Rng<'d, T> {
self.stop();
self.disable_irq();
// The interrupt is now disabled and can't preempt us anymore, so the order doesn't matter here.
s.ptr.store(ptr::null_mut(), Ordering::Relaxed);
s.end.store(ptr::null_mut(), Ordering::Relaxed);
critical_section::with(|cs| {
let mut state = T::state().borrow_mut(cs);
state.ptr = ptr::null_mut();
state.end = ptr::null_mut();
});
});
poll_fn(|cx| {
s.waker.register(cx.waker());
// The interrupt will never modify `end`, so load it first and then get the most up-to-date `ptr`.
let end = s.end.load(Ordering::Relaxed);
let ptr = s.ptr.load(Ordering::Relaxed);
if ptr == end {
// We're done.
Poll::Ready(())
} else {
Poll::Pending
}
critical_section::with(|cs| {
let mut s = T::state().borrow_mut(cs);
s.waker.register(cx.waker());
if s.ptr == s.end {
// We're done.
Poll::Ready(())
} else {
Poll::Pending
}
})
})
.await;
@ -194,9 +173,11 @@ impl<'d, T: Instance> Rng<'d, T> {
impl<'d, T: Instance> Drop for Rng<'d, T> {
fn drop(&mut self) {
self.stop();
let s = T::state();
s.ptr.store(ptr::null_mut(), Ordering::Relaxed);
s.end.store(ptr::null_mut(), Ordering::Relaxed);
critical_section::with(|cs| {
let mut state = T::state().borrow_mut(cs);
state.ptr = ptr::null_mut();
state.end = ptr::null_mut();
});
}
}
@ -227,21 +208,47 @@ impl<'d, T: Instance> rand_core::RngCore for Rng<'d, T> {
impl<'d, T: Instance> rand_core::CryptoRng for Rng<'d, T> {}
pub(crate) mod sealed {
use core::cell::{Ref, RefMut, RefCell};
use critical_section::Mutex;
use critical_section::CriticalSection;
use embassy_sync::waitqueue::WakerRegistration;
use super::*;
/// Peripheral static state
pub struct State {
pub ptr: AtomicPtr<u8>,
pub end: AtomicPtr<u8>,
pub waker: AtomicWaker,
inner: Mutex<RefCell<InnerState>>,
}
pub struct InnerState {
pub ptr: *mut u8,
pub end: *mut u8,
pub waker: WakerRegistration,
}
impl State {
pub const fn new() -> Self {
Self {
ptr: AtomicPtr::new(ptr::null_mut()),
end: AtomicPtr::new(ptr::null_mut()),
waker: AtomicWaker::new(),
inner: Mutex::new(RefCell::new(InnerState::new())),
}
}
pub fn borrow<'cs>(&'cs self, cs: CriticalSection<'cs>) -> Ref<'cs, InnerState> {
self.inner.borrow(cs).borrow()
}
pub fn borrow_mut<'cs>(&'cs self, cs: CriticalSection<'cs>) -> RefMut<'cs, InnerState> {
self.inner.borrow(cs).borrow_mut()
}
}
impl InnerState {
pub const fn new() -> Self {
Self {
ptr: ptr::null_mut(),
end: ptr::null_mut(),
waker: WakerRegistration::new(),
}
}
}