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rust: sync: document `PhantomData` in `Arc`
Add a comment explaining the relevant semantics of `PhantomData`. This
should help future readers who may, as I did, assume that this field is
redundant at first glance.
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20241107-simplify-arc-v2-1-7256e638aac1@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
authored by
Tamir Duberstein
and committed by
Miguel Ojeda
2dde1c8b
3f4223c0
+8
+8
rust/kernel/sync/arc.rs
+8
rust/kernel/sync/arc.rs
···
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/// ```
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pub struct Arc<T: ?Sized> {
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ptr: NonNull<ArcInner<T>>,
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// NB: this informs dropck that objects of type `ArcInner<T>` may be used in `<Arc<T> as
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// Drop>::drop`. Note that dropck already assumes that objects of type `T` may be used in
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// `<Arc<T> as Drop>::drop` and the distinction between `T` and `ArcInner<T>` is not presently
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// meaningful with respect to dropck - but this may change in the future so this is left here
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// out of an abundance of caution.
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//
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// See https://doc.rust-lang.org/nomicon/phantom-data.html#generic-parameters-and-drop-checking
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// for more detail on the semantics of dropck in the presence of `PhantomData`.
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_p: PhantomData<ArcInner<T>>,
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}
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