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| author | Tamir Duberstein <tamird@gmail.com> | 2024-11-07 13:36:46 +0300 |
|---|---|---|
| committer | Miguel Ojeda <ojeda@kernel.org> | 2024-12-18 02:37:21 +0300 |
| commit | 2dde1c8b04a5c415912bc3ffa8b677eb364dbcb7 (patch) | |
| tree | 79202a24dcc32027498cc6b8d66b3b6ad5152345 /rust | |
| parent | 3f4223c007b25327c49aabe3af8ecc72bb33dbf6 (diff) | |
| download | linux-2dde1c8b04a5c415912bc3ffa8b677eb364dbcb7.tar.xz | |
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>
Diffstat (limited to 'rust')
| -rw-r--r-- | rust/kernel/sync/arc.rs | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index fa4509406ee9..9f0b04400e8e 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -127,6 +127,14 @@ mod std_vendor; /// ``` pub struct Arc<T: ?Sized> { ptr: NonNull<ArcInner<T>>, + // NB: this informs dropck that objects of type `ArcInner<T>` may be used in `<Arc<T> as + // Drop>::drop`. Note that dropck already assumes that objects of type `T` may be used in + // `<Arc<T> as Drop>::drop` and the distinction between `T` and `ArcInner<T>` is not presently + // meaningful with respect to dropck - but this may change in the future so this is left here + // out of an abundance of caution. + // + // See https://doc.rust-lang.org/nomicon/phantom-data.html#generic-parameters-and-drop-checking + // for more detail on the semantics of dropck in the presence of `PhantomData`. _p: PhantomData<ArcInner<T>>, } |