1 files changed, 100 insertions, 0 deletions
diff --git a/rust/kernel/time/hrtimer/arc.rs b/rust/kernel/time/hrtimer/arc.rs
new file mode 100644
index 000000000000..4a984d85b4a1
--- /dev/null
+++ b/rust/kernel/time/hrtimer/arc.rs
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use super::HasHrTimer;
+use super::HrTimer;
+use super::HrTimerCallback;
+use super::HrTimerHandle;
+use super::HrTimerPointer;
+use super::RawHrTimerCallback;
+use crate::sync::Arc;
+use crate::sync::ArcBorrow;
+use crate::time::Ktime;
+
+/// A handle for an `Arc<HasHrTimer<T>>` returned by a call to
+/// [`HrTimerPointer::start`].
+pub struct ArcHrTimerHandle<T>
+where
+    T: HasHrTimer<T>,
+{
+    pub(crate) inner: Arc<T>,
+}
+
+// SAFETY: We implement drop below, and we cancel the timer in the drop
+// implementation.
+unsafe impl<T> HrTimerHandle for ArcHrTimerHandle<T>
+where
+    T: HasHrTimer<T>,
+{
+    fn cancel(&mut self) -> bool {
+        let self_ptr = Arc::as_ptr(&self.inner);
+
+        // SAFETY: As we obtained `self_ptr` from a valid reference above, it
+        // must point to a valid `T`.
+        let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self_ptr) };
+
+        // SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr`
+        // must point to a valid `HrTimer` instance.
+        unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
+    }
+}
+
+impl<T> Drop for ArcHrTimerHandle<T>
+where
+    T: HasHrTimer<T>,
+{
+    fn drop(&mut self) {
+        self.cancel();
+    }
+}
+
+impl<T> HrTimerPointer for Arc<T>
+where
+    T: 'static,
+    T: Send + Sync,
+    T: HasHrTimer<T>,
+    T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
+{
+    type TimerHandle = ArcHrTimerHandle<T>;
+
+    fn start(self, expires: Ktime) -> ArcHrTimerHandle<T> {
+        // SAFETY:
+        //  - We keep `self` alive by wrapping it in a handle below.
+        //  - Since we generate the pointer passed to `start` from a valid
+        //    reference, it is a valid pointer.
+        unsafe { T::start(Arc::as_ptr(&self), expires) };
+        ArcHrTimerHandle { inner: self }
+    }
+}
+
+impl<T> RawHrTimerCallback for Arc<T>
+where
+    T: 'static,
+    T: HasHrTimer<T>,
+    T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
+{
+    type CallbackTarget<'a> = ArcBorrow<'a, T>;
+
+    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
+        // `HrTimer` is `repr(C)`
+        let timer_ptr = ptr.cast::<super::HrTimer<T>>();
+
+        // SAFETY: By C API contract `ptr` is the pointer we passed when
+        // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`.
+        let data_ptr = unsafe { T::timer_container_of(timer_ptr) };
+
+        // SAFETY:
+        //  - `data_ptr` is derived form the pointer to the `T` that was used to
+        //    queue the timer.
+        //  - As per the safety requirements of the trait `HrTimerHandle`, the
+        //    `ArcHrTimerHandle` associated with this timer is guaranteed to
+        //    be alive until this method returns. That handle borrows the `T`
+        //    behind `data_ptr` thus guaranteeing the validity of
+        //    the `ArcBorrow` created below.
+        //  - We own one refcount in the `ArcTimerHandle` associated with this
+        //    timer, so it is not possible to get a `UniqueArc` to this
+        //    allocation from other `Arc` clones.
+        let receiver = unsafe { ArcBorrow::from_raw(data_ptr) };
+
+        T::run(receiver).into_c()
+    }
+}