[PATCH v2 07/14] rust: hrtimer: add `UnsafeTimerPointer`
From: Andreas Hindborg
Date: Tue Sep 17 2024 - 18:31:23 EST
Add a trait to allow unsafely queuing stack allocated timers.
Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
---
rust/kernel/hrtimer.rs | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/rust/kernel/hrtimer.rs b/rust/kernel/hrtimer.rs
index d6c3fa89f77e..bb6349f440e2 100644
--- a/rust/kernel/hrtimer.rs
+++ b/rust/kernel/hrtimer.rs
@@ -191,6 +191,39 @@ pub trait TimerPointer: Sync + Sized {
fn schedule(self, expires: Ktime) -> Self::TimerHandle;
}
+/// Unsafe version of [`TimerPointer`] for situations where leaking the
+/// `TimerHandle` returned by `schedule` would be unsound. This is the case for
+/// stack allocated timers.
+///
+/// Typical implementers are pinned references such as [`Pin<&T>].
+///
+/// # Safety
+///
+/// Implementers of this trait must ensure that instances of types implementing
+/// [`UnsafeTimerPointer`] outlives any associated [`TimerPointer::TimerHandle`]
+/// instances.
+///
+/// [`Pin<&T>`]: Box
+pub unsafe trait UnsafeTimerPointer: Sync + Sized {
+ /// A handle representing a scheduled timer.
+ ///
+ /// # Safety
+ ///
+ /// If the timer is armed, or if the timer callback is running when the
+ /// handle is dropped, the drop method of `TimerHandle` must not return
+ /// until the timer is unarmed and the callback has completed.
+ type TimerHandle: TimerHandle;
+
+ /// Schedule the timer after `expires` time units. If the timer was already
+ /// scheduled, it is rescheduled at the new expiry time.
+ ///
+ /// # Safety
+ ///
+ /// Caller promises keep the timer structure alive until the timer is dead.
+ /// Caller can ensure this by not leaking the returned `Self::TimerHandle`.
+ unsafe fn schedule(self, expires: Ktime) -> Self::TimerHandle;
+}
+
/// Implemented by [`TimerPointer`] implementers to give the C timer callback a
/// function to call.
// This is split from `TimerPointer` to make it easier to specify trait bounds.
--
2.46.0