rust: sync: introduce `UniqueArc`

Since `Arc<T>` does not allow mutating `T` directly (i.e., without inner
mutability), it is currently not possible to do some initialisation of
`T` post construction but before being shared.

`UniqueArc<T>` addresses this problem essentially being an `Arc<T>` that
has a refcount of 1 and is therefore writable. Once initialisation is
completed, it can be transitioned (without failure paths) into an
`Arc<T>`.

Suggested-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 5de03ea83ea1..33da23e3076d 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -7,4 +7,4 @@
 
 mod arc;
 
-pub use arc::{Arc, ArcBorrow};
+pub use arc::{Arc, ArcBorrow, UniqueArc};