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Message-Id: <20241017-hrtimer-v3-v6-12-rc2-v3-7-59a75cbb44da@kernel.org>
Date: Thu, 17 Oct 2024 15:04:34 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Miguel Ojeda <ojeda@...nel.org>,
Anna-Maria Behnsen <anna-maria@...utronix.de>,
Frederic Weisbecker <frederic@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>, Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>, Lyude Paul <lyude@...hat.com>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
Andreas Hindborg <a.hindborg@...nel.org>
Subject: [PATCH v3 07/13] rust: hrtimer: implement `UnsafeTimerPointer` for
`Pin<&T>`
Allow pinned references to structs that contain a `Timer` node to be
scheduled with the `hrtimer` subsystem.
Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
---
rust/kernel/hrtimer.rs | 1 +
rust/kernel/hrtimer/pin.rs | 97 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 98 insertions(+)
diff --git a/rust/kernel/hrtimer.rs b/rust/kernel/hrtimer.rs
index e97d7b8ec63ce6c9ac3fe9522192a28fba78b8ba..ceedf330a803ec2db7ff6c25713ae48e2fd1f4ca 100644
--- a/rust/kernel/hrtimer.rs
+++ b/rust/kernel/hrtimer.rs
@@ -362,3 +362,4 @@ unsafe fn raw_get_timer(ptr: *const Self) ->
}
mod arc;
+mod pin;
diff --git a/rust/kernel/hrtimer/pin.rs b/rust/kernel/hrtimer/pin.rs
new file mode 100644
index 0000000000000000000000000000000000000000..a2c1dbd5e48b668cc3dc540c5fd5514f5331d968
--- /dev/null
+++ b/rust/kernel/hrtimer/pin.rs
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use super::HasTimer;
+use super::RawTimerCallback;
+use super::Timer;
+use super::TimerCallback;
+use super::TimerHandle;
+use super::UnsafeTimerPointer;
+use crate::time::Ktime;
+use core::pin::Pin;
+
+/// A handle for a `Pin<&HasTimer>`. When the handle exists, the timer might be
+/// running.
+pub struct PinTimerHandle<'a, U>
+where
+ U: HasTimer<U>,
+{
+ pub(crate) inner: Pin<&'a U>,
+}
+
+// SAFETY: We cancel the timer when the handle is dropped. The implementation of
+// the `cancel` method will block if the timer handler is running.
+unsafe impl<'a, U> TimerHandle for PinTimerHandle<'a, U>
+where
+ U: HasTimer<U>,
+{
+ fn cancel(&mut self) -> bool {
+ let self_ptr = self.inner.get_ref() as *const U;
+
+ // SAFETY: As we got `self_ptr` from a reference above, it must point to
+ // a valid `U`.
+ let timer_ptr = unsafe { <U as HasTimer<U>>::raw_get_timer(self_ptr) };
+
+ // SAFETY: As `timer_ptr` is derived from a reference, it must point to
+ // a valid and initialized `Timer`.
+ unsafe { Timer::<U>::raw_cancel(timer_ptr) }
+ }
+}
+
+impl<'a, U> Drop for PinTimerHandle<'a, U>
+where
+ U: HasTimer<U>,
+{
+ fn drop(&mut self) {
+ self.cancel();
+ }
+}
+
+// SAFETY: We capture the lifetime of `Self` when we create a `PinTimerHandle`,
+// so `Self` will outlive the handle.
+unsafe impl<'a, U> UnsafeTimerPointer for Pin<&'a U>
+where
+ U: Send + Sync,
+ U: HasTimer<U>,
+ U: TimerCallback<CallbackTarget<'a> = Self>,
+{
+ type TimerHandle = PinTimerHandle<'a, U>;
+
+ unsafe fn start(self, expires: Ktime) -> Self::TimerHandle {
+ use core::ops::Deref;
+
+ // Cast to pointer
+ let self_ptr = self.deref() as *const U;
+
+ // SAFETY: As we derive `self_ptr` from a reference above, it must point
+ // to a valid `U`.
+ unsafe { U::start(self_ptr, expires) };
+
+ PinTimerHandle { inner: self }
+ }
+}
+
+impl<'a, U> RawTimerCallback for Pin<&'a U>
+where
+ U: HasTimer<U>,
+ U: TimerCallback<CallbackTarget<'a> = Self>,
+ U: TimerCallback<CallbackTargetParameter<'a> = Self>,
+{
+ unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
+ // `Timer` is `repr(C)`
+ let timer_ptr = ptr as *mut Timer<U>;
+
+ // SAFETY: By the safety requirement of this function, `timer_ptr`
+ // points to a `Timer<U>` contained in an `U`.
+ let receiver_ptr = unsafe { U::timer_container_of(timer_ptr) };
+
+ // SAFETY: By the safety requirement of this function, `timer_ptr`
+ // points to a `Timer<U>` contained in an `U`.
+ let receiver_ref = unsafe { &*receiver_ptr };
+
+ // SAFETY: `receiver_ref` only exists as pinned, so it is safe to pin it
+ // here.
+ let receiver_pin = unsafe { Pin::new_unchecked(receiver_ref) };
+
+ U::run(receiver_pin).into()
+ }
+}
--
2.46.0
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