diff options
Diffstat (limited to 'rtic-time/src/lib.rs')
| -rw-r--r-- | rtic-time/src/lib.rs | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/rtic-time/src/lib.rs b/rtic-time/src/lib.rs index 5e4457cc..3126e6b7 100644 --- a/rtic-time/src/lib.rs +++ b/rtic-time/src/lib.rs @@ -208,7 +208,8 @@ impl<Mono: Monotonic> TimerQueue<Mono> { let mut link_ptr: Option<linked_list::Link<WaitingWaker<Mono>>> = None; - // Make this future `Drop`-safe, also shadow the original definition so we can't abuse it. + // Make this future `Drop`-safe + // SAFETY(link_ptr): Shadow the original definition of `link_ptr` so we can't abuse it. let mut link_ptr = LinkPtr(&mut link_ptr as *mut Option<linked_list::Link<WaitingWaker<Mono>>>); let mut link_ptr2 = link_ptr.clone(); @@ -226,18 +227,24 @@ impl<Mono: Monotonic> TimerQueue<Mono> { } // SAFETY: This pointer is only dereferenced here and on drop of the future - // which happens outside this `poll_fn`'s stack frame. + // which happens outside this `poll_fn`'s stack frame, so this mutable access cannot + // happen at the same time as `dropper` runs. let link = unsafe { link_ptr2.get() }; if link.is_none() { - let mut link_ref = link.insert(Link::new(WaitingWaker { + let link_ref = link.insert(Link::new(WaitingWaker { waker: cx.waker().clone(), release_at: instant, was_poped: AtomicBool::new(false), })); - // SAFETY: The address to the link is stable as it is defined outside this stack - // frame. - let (was_empty, addr) = queue.insert(unsafe { Pin::new_unchecked(&mut link_ref) }); + // SAFETY(new_unchecked): The address to the link is stable as it is defined + //outside this stack frame. + // SAFETY(insert): `link_ref` lifetime comes from `link_ptr` that is shadowed, and + // we make sure in `dropper` that the link is removed from the queue before + // dropping `link_ptr` AND `dropper` makes sure that the shadowed `link_ptr` lives + // until the end of the stack frame. + let (was_empty, addr) = unsafe { queue.insert(Pin::new_unchecked(&link_ref)) }; + marker.store(addr, Ordering::Relaxed); if was_empty { |