1 files changed, 27 insertions, 10 deletions

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index e6d206242465..3d496391a9bd 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -73,6 +73,7 @@ mod std_vendor;
 /// assert_eq!(cloned.b, 20);
 ///
 /// // The refcount drops to zero when `cloned` goes out of scope, and the memory is freed.
+/// # Ok::<(), Error>(())
 /// ```
 ///
 /// Using `Arc<T>` as the type of `self`:
@@ -98,6 +99,7 @@ mod std_vendor;
 /// let obj = Arc::try_new(Example { a: 10, b: 20 })?;
 /// obj.use_reference();
 /// obj.take_over();
+/// # Ok::<(), Error>(())
 /// ```
 ///
 /// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
@@ -121,6 +123,7 @@ mod std_vendor;
 ///
 /// // `coerced` has type `Arc<dyn MyTrait>`.
 /// let coerced: Arc<dyn MyTrait> = obj;
+/// # Ok::<(), Error>(())
 /// ```
 pub struct Arc<T: ?Sized> {
     ptr: NonNull<ArcInner<T>>,
@@ -146,13 +149,15 @@ impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Ar
 
 // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
 // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
-// `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for
-// example, when the reference count reaches zero and `T` is dropped.
+// `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` using a
+// mutable reference when the reference count reaches zero and `T` is dropped.
 unsafe impl<T: ?Sized + Sync + Send> Send for Arc<T> {}
 
-// SAFETY: It is safe to send `&Arc<T>` to another thread when the underlying `T` is `Sync` for the
-// same reason as above. `T` needs to be `Send` as well because a thread can clone an `&Arc<T>`
-// into an `Arc<T>`, which may lead to `T` being accessed by the same reasoning as above.
+// SAFETY: It is safe to send `&Arc<T>` to another thread when the underlying `T` is `Sync`
+// because it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally,
+// it needs `T` to be `Send` because any thread that has a `&Arc<T>` may clone it and get an
+// `Arc<T>` on that thread, so the thread may ultimately access `T` using a mutable reference when
+// the reference count reaches zero and `T` is dropped.
 unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> {}
 
 impl<T> Arc<T> {
@@ -185,7 +190,7 @@ impl<T> Arc<T> {
 
     /// Use the given initializer to in-place initialize a `T`.
     ///
-    /// This is equivalent to [`pin_init`], since an [`Arc`] is always pinned.
+    /// This is equivalent to [`Arc<T>::pin_init`], since an [`Arc`] is always pinned.
     #[inline]
     pub fn init<E>(init: impl Init<T, E>) -> error::Result<Self>
     where
@@ -221,6 +226,11 @@ impl<T: ?Sized> Arc<T> {
         // reference can be created.
         unsafe { ArcBorrow::new(self.ptr) }
     }
+
+    /// Compare whether two [`Arc`] pointers reference the same underlying object.
+    pub fn ptr_eq(this: &Self, other: &Self) -> bool {
+        core::ptr::eq(this.ptr.as_ptr(), other.ptr.as_ptr())
+    }
 }
 
 impl<T: 'static> ForeignOwnable for Arc<T> {
@@ -236,8 +246,7 @@ impl<T: 'static> ForeignOwnable for Arc<T> {
         let inner = NonNull::new(ptr as *mut ArcInner<T>).unwrap();
 
         // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive
-        // for the lifetime of the returned value. Additionally, the safety requirements of
-        // `ForeignOwnable::borrow_mut` ensure that no new mutable references are created.
+        // for the lifetime of the returned value.
         unsafe { ArcBorrow::new(inner) }
     }
 
@@ -259,6 +268,12 @@ impl<T: ?Sized> Deref for Arc<T> {
     }
 }
 
+impl<T: ?Sized> AsRef<T> for Arc<T> {
+    fn as_ref(&self) -> &T {
+        self.deref()
+    }
+}
+
 impl<T: ?Sized> Clone for Arc<T> {
     fn clone(&self) -> Self {
         // INVARIANT: C `refcount_inc` saturates the refcount, so it cannot overflow to zero.
@@ -324,7 +339,7 @@ impl<T: ?Sized> From<Pin<UniqueArc<T>>> for Arc<T> {
 /// # Example
 ///
 /// ```
-/// use crate::sync::{Arc, ArcBorrow};
+/// use kernel::sync::{Arc, ArcBorrow};
 ///
 /// struct Example;
 ///
@@ -337,12 +352,13 @@ impl<T: ?Sized> From<Pin<UniqueArc<T>>> for Arc<T> {
 ///
 /// // Assert that both `obj` and `cloned` point to the same underlying object.
 /// assert!(core::ptr::eq(&*obj, &*cloned));
+/// # Ok::<(), Error>(())
 /// ```
 ///
 /// Using `ArcBorrow<T>` as the type of `self`:
 ///
 /// ```
-/// use crate::sync::{Arc, ArcBorrow};
+/// use kernel::sync::{Arc, ArcBorrow};
 ///
 /// struct Example {
 ///     a: u32,
@@ -357,6 +373,7 @@ impl<T: ?Sized> From<Pin<UniqueArc<T>>> for Arc<T> {
 ///
 /// let obj = Arc::try_new(Example { a: 10, b: 20 })?;
 /// obj.as_arc_borrow().use_reference();
+/// # Ok::<(), Error>(())
 /// ```
 pub struct ArcBorrow<'a, T: ?Sized + 'a> {
     inner: NonNull<ArcInner<T>>,