linux-kernel - [PATCH 1/2] rust: sync: atomic: Remove bound `T: Sync` for `Atomci::from

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Message-ID: <20260120115207.55318-2-boqun.feng@gmail.com>
Date: Tue, 20 Jan 2026 19:52:06 +0800
From: Boqun Feng <boqun.feng@...il.com>
To: linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	kasan-dev@...glegroups.com
Cc: Will Deacon <will@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	Gary Guo <gary@...yguo.net>,
	Miguel Ojeda <ojeda@...nel.org>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Elle Rhumsaa <elle@...thered-steel.dev>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Marco Elver <elver@...gle.com>,
	FUJITA Tomonori <fujita.tomonori@...il.com>
Subject: [PATCH 1/2] rust: sync: atomic: Remove bound `T: Sync` for `Atomci::from_ptr()`

Originally, `Atomic::from_ptr()` requires `T` being a `Sync` because I
thought having the ability to do `from_ptr()` meant multiplle
`&Atomic<T>`s shared by different threads, which was identical (or
similar) to multiple `&T`s shared by different threads. Hence `T` was
required to be `Sync`. However this is not true, since `&Atomic<T>` is
not the same at `&T`. Moreover, having this bound makes `Atomic::<*mut
T>::from_ptr()` impossible, which is definitely not intended. Therefore
remove the `T: Sync` bound.

Fixes: 29c32c405e53 ("rust: sync: atomic: Add generic atomics")
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
---
 rust/kernel/sync/atomic.rs | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
index 224bd57da1ab..d49ee45c6eb7 100644
--- a/rust/kernel/sync/atomic.rs
+++ b/rust/kernel/sync/atomic.rs
@@ -215,10 +215,7 @@ pub const fn new(v: T) -> Self {
     /// // no data race.
     /// unsafe { Atomic::from_ptr(foo_a_ptr) }.store(2, Release);
     /// ```
-    pub unsafe fn from_ptr<'a>(ptr: *mut T) -> &'a Self
-    where
-        T: Sync,
-    {
+    pub unsafe fn from_ptr<'a>(ptr: *mut T) -> &'a Self {
         // CAST: `T` and `Atomic<T>` have the same size, alignment and bit validity.
         // SAFETY: Per function safety requirement, `ptr` is a valid pointer and the object will
         // live long enough. It's safe to return a `&Atomic<T>` because function safety requirement
-- 
2.51.0