[PATCH 6/6] rust: hrtimer: Add HrTimerCallback::expires()

Lyude Paul
2025-04-02T21:41:44Z

This adds the ability to read the expiry time of the current timer from the
HrTimerCallbackContext.

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
rust/kernel/time/hrtimer.rs | 29 +++++++++++++++++++++++++++--
1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index d52cbb6cfc57f..e28b7895d8f37 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -69,7 +69,7 @@

use super::ClockId;
use crate::{init::PinInit, prelude::*, time::Ktime, types::Opaque};
-use core::{marker::PhantomData, ptr::NonNull};
+use core::{marker::PhantomData, ptr::{NonNull, addr_of}};

/// A timer backed by a C `struct hrtimer`.
///
@@ -131,7 +131,7 @@ unsafe fn raw_get(this: *const Self) -> *mut bindings::hrtimer {
// SAFETY: The field projection to `timer` does not go out of bounds,
// because the caller of this function promises that `this` points to an
// allocation of at least the size of `Self`.
- unsafe { Opaque::raw_get(core::ptr::addr_of!((*this).timer)) }
+ unsafe { Opaque::raw_get(addr_of!((*this).timer)) }
}

/// Cancel an initialized and potentially running timer.
@@ -163,6 +163,31 @@ pub(crate) unsafe fn raw_cancel(this: *const Self) -> bool {
// handled on the C side.
unsafe { bindings::hrtimer_cancel(c_timer_ptr) != 0 }
}
+
+ /// Return the time expiry for the given timer pointer.
+ ///
+ /// This value should only be used as a snapshot, as the actual expiry time could change after
+ /// this function is called.
+ ///
+ /// # Safety
+ ///
+ /// `self_ptr` must point to a valid `Self`.
+ unsafe fn raw_expires(self_ptr: *const Self) -> Ktime {
+ // SAFETY: self_ptr points to an allocation of at least `HrTimer` size.
+ let c_timer_ptr = unsafe { HrTimer::raw_get(self_ptr) };
+
+ // SAFETY: There's no actual locking here, a racy read is fine and expected.
+ Ktime::from_raw(unsafe { core::ptr::read(addr_of!((*c_timer_ptr).node.expires)) })
+ }
+
+ /// Return the time expiry for this [`HrTimer`].
+ ///
+ /// This value should only be used as a snapshot, as the actual expiry time could change after
+ /// this function is called.
+ pub fn expires(&self) -> Ktime {
+ // SAFETY: By our type invariants, `self.0` always points to a valid `HrTimer<T>`.
+ unsafe { HrTimer::raw_expires(self) }
+ }
}

/// The timer base for a specific clock.
--
2.48.1