linux-kernel - [PATCH 4/5] rust: hrtimer: use READ_ONCE instead of read

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Message-ID: <20251231-rwonce-v1-4-702a10b85278@google.com>
Date: Wed, 31 Dec 2025 12:22:28 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Boqun Feng <boqun.feng@...il.com>, Will Deacon <will@...nel.org>, 
	Peter Zijlstra <peterz@...radead.org>
Cc: Richard Henderson <richard.henderson@...aro.org>, Matt Turner <mattst88@...il.com>, 
	Magnus Lindholm <linmag7@...il.com>, Catalin Marinas <catalin.marinas@....com>, 
	Miguel Ojeda <ojeda@...nel.org>, Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	FUJITA Tomonori <fujita.tomonori@...il.com>, Frederic Weisbecker <frederic@...nel.org>, 
	Lyude Paul <lyude@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Anna-Maria Behnsen <anna-maria@...utronix.de>, John Stultz <jstultz@...gle.com>, 
	Stephen Boyd <sboyd@...nel.org>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org, 
	linux-alpha@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	rust-for-linux@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH 4/5] rust: hrtimer: use READ_ONCE instead of read_volatile

Using `READ_ONCE` is the correct way to read the `node.expires` field.

Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
 rust/kernel/time/hrtimer.rs | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 856d2d929a00892dc8eaec63cebdf547817953d3..e2b7a26f8aade972356c3eb5f6489bcda3e2e849 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -239,11 +239,9 @@ pub fn expires(&self) -> HrTimerInstant<T>
         // - Timers cannot have negative ktime_t values as their expiration time.
         // - There's no actual locking here, a racy read is fine and expected
         unsafe {
-            Instant::from_ktime(
-                // This `read_volatile` is intended to correspond to a READ_ONCE call.
-                // FIXME(read_once): Replace with `read_once` when available on the Rust side.
-                core::ptr::read_volatile(&raw const ((*c_timer_ptr).node.expires)),
-            )
+            Instant::from_ktime(kernel::sync::READ_ONCE(
+                &raw const (*c_timer_ptr).node.expires,
+            ))
         }
     }
 }

-- 
2.52.0.351.gbe84eed79e-goog