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Make some linked list operations unsafe, and document their safety at usage

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This commit is contained in:
Emil Fresk 2023-02-18 09:43:06 +01:00 • committed by Henrik Tjäder
parent 002d0b0d16
commit 1cda61fbda
6 changed files with 66 additions and 40 deletions
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4
rtic-common/src/lib.rs
View file

@ -4,6 +4,10 @@
#![deny(missing_docs)]
//deny_warnings_placeholder_for_ci
#[cfg(test)]
#[macro_use]
extern crate std;
pub mod dropper;
pub mod wait_queue;
pub mod waker_registration;

36
rtic-common/src/wait_queue.rs
View file

@ -68,7 +68,9 @@ impl<T: Clone> LinkedList<T> {
}
/// Put an element at the back of the queue.
pub fn push(&self, link: Pin<&mut Link<T>>) {
///
/// SAFETY: The link must live until it is removed from the queue.
pub unsafe fn push(&self, link: Pin<&Link<T>>) {
cs::with(|_| {
// Make sure all previous writes are visible
core::sync::atomic::fence(Ordering::SeqCst);
@ -76,17 +78,17 @@ impl<T: Clone> LinkedList<T> {
let tail = self.tail.load(Self::R);
// SAFETY: This datastructure does not move the underlying value.
let link = unsafe { link.get_unchecked_mut() };
let link = link.get_ref();
if let Some(tail_ref) = unsafe { tail.as_ref() } {
// Queue is not empty
link.prev.store(tail, Self::R);
self.tail.store(link, Self::R);
tail_ref.next.store(link, Self::R);
self.tail.store(link as *const _ as *mut _, Self::R);
tail_ref.next.store(link as *const _ as *mut _, Self::R);
} else {
// Queue is empty
self.tail.store(link, Self::R);
self.head.store(link, Self::R);
self.tail.store(link as *const _ as *mut _, Self::R);
self.head.store(link as *const _ as *mut _, Self::R);
}
});
}
@ -126,7 +128,7 @@ impl<T: Clone> Link<T> {
}
/// Remove this link from a linked list.
pub fn remove_from_list(&mut self, list: &LinkedList<T>) {
pub fn remove_from_list(&self, list: &LinkedList<T>) {
cs::with(|_| {
// Make sure all previous writes are visible
core::sync::atomic::fence(Ordering::SeqCst);
@ -230,17 +232,17 @@ mod tests {
fn linked_list() {
let wq = LinkedList::<u32>::new();
let mut i1 = Link::new(10);
let mut i2 = Link::new(11);
let mut i3 = Link::new(12);
let mut i4 = Link::new(13);
let mut i5 = Link::new(14);
let i1 = Link::new(10);
let i2 = Link::new(11);
let i3 = Link::new(12);
let i4 = Link::new(13);
let i5 = Link::new(14);
wq.push(unsafe { Pin::new_unchecked(&mut i1) });
wq.push(unsafe { Pin::new_unchecked(&mut i2) });
wq.push(unsafe { Pin::new_unchecked(&mut i3) });
wq.push(unsafe { Pin::new_unchecked(&mut i4) });
wq.push(unsafe { Pin::new_unchecked(&mut i5) });
unsafe { wq.push(Pin::new_unchecked(&i1)) };
unsafe { wq.push(Pin::new_unchecked(&i2)) };
unsafe { wq.push(Pin::new_unchecked(&i3)) };
unsafe { wq.push(Pin::new_unchecked(&i4)) };
unsafe { wq.push(Pin::new_unchecked(&i5)) };
wq.print();