[PATCH] rust: sync: fix safety comment for `Arc::from_raw`

[Andreas Hindborg <a.hindborg@kernel.org>]

`Arc::from_raw` does not require `T: Send`. But if `Arc::from_raw` was
executed on a different thread than `Arc::into_raw`, `T` must implement
`Send` for the API to be sound. If this is not the case, ownership of `T`
may be sent across a thread boundary even if `T: !Send`.

Augment safety comment for `Arc::from_raw` to close this gap.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/sync/arc.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 8ae0fe6f19ec..06838ecf633c 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -276,6 +276,9 @@ pub fn as_ptr(this: &Self) -> *const T {
     ///
     /// `ptr` must have been returned by a previous call to [`Arc::into_raw`]. Additionally, it
     /// must not be called more than once for each previous call to [`Arc::into_raw`].
+    ///
+    /// If [`Arc::into_raw`] was executed on a different thread than the one executing
+    /// [`Arc::from_raw`], `T` must implement [`Send`].
     pub unsafe fn from_raw(ptr: *const T) -> Self {
         // SAFETY: The caller promises that this pointer originates from a call to `into_raw` on an
         // `Arc` that is still valid.

---
base-commit: df2908090cda368b01ff43709f51890076c56157
change-id: 20260923-aref-from-raw-safety-78a7283627fa

Best regards,
--  
Andreas Hindborg <a.hindborg@kernel.org>