[PATCH 4/5] rust: hrtimer: use READ_ONCE instead of read_volatile

[Alice Ryhl <aliceryhl@google.com>]

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

Signed-off-by: Alice Ryhl <aliceryhl@google.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