"Boqun Feng" <[email protected]> writes: > On Mon, Jul 07, 2025 at 03:38:58PM +0200, Alice Ryhl wrote: >> On Mon, Jul 7, 2025 at 3:32 PM Andreas Hindborg <[email protected]> >> wrote: >> > >> > Introduce the `SetOnce` type, a container that can only be written once. >> > The container uses an internal atomic to synchronize writes to the internal >> > value. >> > >> > Signed-off-by: Andreas Hindborg <[email protected]> >> >> LGTM: >> Reviewed-by: Alice Ryhl <[email protected]> >> >> > +impl<T> Drop for SetOnce<T> { >> > + fn drop(&mut self) { >> > + if self.init.load(Acquire) == 2 { >> > + // SAFETY: By the type invariants of `Self`, `self.init == 2` >> > means that `self.value` >> > + // contains a valid value. We have exclusive access, as we >> > hold a `mut` reference to >> > + // `self`. >> > + unsafe { drop_in_place(self.value.get()) }; >> >> This load does not need to be Acquire. It can be a Relaxed load or >> even an unsynchronized one since the access is exclusive. > > Right, I think we can do the similar as Revocable here: > > if *self.init.get_mut() == 2 { } > > Further, with my following Benno's suggestion and making `Atomic<T>` an > `UnsafeCell<T>: > > https://lore.kernel.org/rust-for-linux/[email protected]/ > > compiler can generate a noalias reference here, which allows further > optimization. >
You would like to remove `PhantomPinned` to enable noalias? I guess that makes sense in this case. I'll fix that for next spin. Best regards, Andreas Hindborg
