linux-kernel - [PATCH] rust: sync: fix safety comment for `static_lock

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Message-ID: <20250520231714.323931-1-lossin@kernel.org>
Date: Wed, 21 May 2025 01:17:13 +0200
From: Benno Lossin <lossin@...nel.org>
To: Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Lyude Paul <lyude@...hat.com>,
	Mitchell Levy <levymitchell0@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>
Cc: Benno Lossin <lossin@...nel.org>,
	rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] rust: sync: fix safety comment for `static_lock_class`

The safety comment mentions lockdep -- which from a Rust perspective
isn't important -- and doesn't mention the real reason for why it's
sound to create `LockClassKey` as uninitialized memory.

Signed-off-by: Benno Lossin <lossin@...nel.org>
---

I don't think we need to backport this.

---
 rust/kernel/sync.rs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 36a719015583..a10c812d8777 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -93,8 +93,11 @@ fn drop(self: Pin<&mut Self>) {
 macro_rules! static_lock_class {
     () => {{
         static CLASS: $crate::sync::LockClassKey =
-            // SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated
-            // lock_class_key
+            // Lockdep expects uninitialized memory when it's handed a statically allocated `struct
+            // lock_class_key`.
+            //
+            // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized
+            // memory.
             unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
         $crate::prelude::Pin::static_ref(&CLASS)
     }};

base-commit: a5806cd506af5a7c19bcd596e4708b5c464bfd21
-- 
2.49.0