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[v4,04/15] rust: sync: add `assume_init` to `UniqueArc`

Message ID 20230331215053.585759-5-y86-dev@protonmail.com
State New
Headers
Series Rust pin-init API for pinned initialization of structs |

Commit Message

y86-dev March 31, 2023, 9:52 p.m. UTC 
  From: Benno Lossin <y86-dev@protonmail.com>

Adds the `assume_init` function to `UniqueArc<MaybeUninit<T>>` that
unsafely assumes the value to be initialized and yields a value of type
`UniqueArc<T>`. This function is used when manually initializing the
pointee of an `UniqueArc`.

Signed-off-by: Benno Lossin <y86-dev@protonmail.com>
Reviewed-by: Wedson Almeida Filho <walmeida@microsoft.com>
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
---
 rust/kernel/sync/arc.rs | 11 +++++++++++
 1 file changed, 11 insertions(+)

--
2.39.2
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Patch

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index aa7135f0f238..eee7008e5e3e 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -489,6 +489,17 @@  impl<T> UniqueArc<MaybeUninit<T>> {
     /// Converts a `UniqueArc<MaybeUninit<T>>` into a `UniqueArc<T>` by writing a value into it.
     pub fn write(mut self, value: T) -> UniqueArc<T> {
         self.deref_mut().write(value);
+        // SAFETY: We just wrote the value to be initialized.
+        unsafe { self.assume_init() }
+    }
+
+    /// Unsafely assume that `self` is initialized.
+    ///
+    /// # Safety
+    ///
+    /// The caller guarantees that the value behind this pointer has been initialized. It is
+    /// *immediate* UB to call this when the value is not initialized.
+    pub unsafe fn assume_init(self) -> UniqueArc<T> {
         let inner = ManuallyDrop::new(self).inner.ptr;
         UniqueArc {
             // SAFETY: The new `Arc` is taking over `ptr` from `self.inner` (which won't be