[PATCH v4 00/14] hrtimer Rust API

[PATCH v4 00/14] hrtimer Rust API

[Andreas Hindborg]

This series adds support for using the `hrtimer` subsystem from Rust code.

This version adds support for timer mode and clock source configuration during
timer initialization. Examples and functionality to execute closures at timer
expiration has been removed, as these depend on either atomics [3] or
`SpinLockIrq` [4], which are still being worked on.

This series is a dependency for unmerged features of the Rust null block driver
[1], and for rkvms [2].

Link: https://git.kernel.org/pub/scm/linux/kernel/git/a.hindborg/linux.git/log/?h=rnull-v6.11-rc2 [1]
Link: https://gitlab.freedesktop.org/lyudess/linux/-/tree/rvkms-wip [2]
Link: https://lore.kernel.org/rust-for-linux/20240612223025.1158537-1-boqun.feng@gmail.com/ [3]
Link: https://lore.kernel.org/rust-for-linux/20240916213025.477225-1-lyude@redhat.com/ [4]
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
Changes in v4:
- rebase on v6.13-rc1 and adapt to kernel `Box`
- add a missing safety comment to `hrtimer::start`
- use `hrtimer_setup`
- fix a build issue when `bindings::hrtimer_restart` is signed
- fix a memory leak where box was not destroyed
- fix a documentation typo
- remove `as` coercion at multiple locations
- use fully qualified syntax when invoking `deref`
- move `hrtimer` into `time` module
- Link to v3: https://lore.kernel.org/r/20241017-hrtimer-v3-v6-12-rc2-v3-0-59a75cbb44da@kernel.org

Changes in v3:
- support timer mode selection
- support clock source selection
- eliminate `Arc::clone_from_raw` in favor of using `ArcBorrow`
- make `Arc::as_ptr` an associated method
- update safety requirement for `ArcBorrow::from_raw`
- remove examples (pending `SpinLockIrq` and `CondVar` patches)
- remove `start_function` (v2 `schedule_function`, pending `SpinLockIrq` and `CondVar` patches)
- change function naming from schedule/armed to start/running
- add vocabulary to documentation
- update safety comment in `Arc::as_ptr`
- Link to v2: https://lore.kernel.org/r/20240917222739.1298275-1-a.hindborg@kernel.org

Changes in v2:
- use a handle to own the timer callback target
- add ability to for callback to reschedule timer
- improve `impl_has_timer` to allow generics
- add support for stack allocated timers
- add support for scheduling closures
- use `Ktime` for setting expiration
- use `CondVar` instead of `AtomicBool` in examples
- rebase on 6.11
- improve documentation
- Link to v1: https://lore.kernel.org/r/20240425094634.262674-1-nmi@metaspace.dk

---
Andreas Hindborg (13):
      rust: hrtimer: introduce hrtimer support
      rust: sync: add `Arc::as_ptr`
      rust: hrtimer: implement `TimerPointer` for `Arc`
      rust: hrtimer: allow timer restart from timer handler
      rust: hrtimer: add `UnsafeTimerPointer`
      rust: hrtimer: implement `UnsafeTimerPointer` for `Pin<&T>`
      rust: hrtimer: implement `UnsafeTimerPointer` for `Pin<&mut T>`
      rust: hrtimer: add `hrtimer::ScopedTimerPointer`
      rust: alloc: add `Box::into_pin`
      rust: hrtimer: implement `TimerPointer` for `Pin<Box<T>>`
      rust: hrtimer: add `TimerMode`
      rust: hrtimer: add clocksource selection through `ClockSource`
      rust: hrtimer: add maintainer entry

Lyude Paul (1):
      rust: time: Add Ktime::from_ns()

 MAINTAINERS                         |  10 +
 rust/kernel/alloc/kbox.rs           |  10 +
 rust/kernel/sync/arc.rs             |  13 +-
 rust/kernel/time.rs                 |  10 +
 rust/kernel/time/hrtimer.rs         | 532 ++++++++++++++++++++++++++++++++++++
 rust/kernel/time/hrtimer/arc.rs     |  87 ++++++
 rust/kernel/time/hrtimer/pin.rs     |  95 +++++++
 rust/kernel/time/hrtimer/pin_mut.rs |  97 +++++++
 rust/kernel/time/hrtimer/tbox.rs    | 102 +++++++
 9 files changed, 954 insertions(+), 2 deletions(-)
---
base-commit: 40384c840ea1944d7c5a392e8975ed088ecf0b37
change-id: 20241017-hrtimer-v3-v6-12-rc2-215dc6b169bf

Best regards,
-- 
Andreas Hindborg <a.hindborg@kernel.org>

[PATCH v4 01/14] rust: time: Add Ktime::from_ns()

[Andreas Hindborg]

From: Lyude Paul <lyude@redhat.com>

A simple function to turn the provided value in nanoseconds into a Ktime
value. We allow any type which implements Into<bindings::ktime_t>, which
resolves to Into<i64>.

This is useful for some of the older DRM APIs that never got moved to Ktime

Signed-off-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index 379c0f5772e575c9ceacb9c85255b13501db8f30..f59e0fea79d3acfddd922f601f569353609aeec1 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -8,6 +8,8 @@
 //! C header: [`include/linux/jiffies.h`](srctree/include/linux/jiffies.h).
 //! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h).
 
+use core::convert::Into;
+
 /// The number of nanoseconds per millisecond.
 pub const NSEC_PER_MSEC: i64 = bindings::NSEC_PER_MSEC as i64;
 
@@ -63,6 +65,12 @@ pub fn to_ns(self) -> i64 {
     pub fn to_ms(self) -> i64 {
         self.divns_constant::<NSEC_PER_MSEC>()
     }
+
+    /// Creates a new Ktime from the given duration in nanoseconds
+    #[inline]
+    pub fn from_ns(ns: impl Into<bindings::ktime_t>) -> Self {
+        Self { inner: ns.into() }
+    }
 }
 
 /// Returns the number of milliseconds between two ktimes.

-- 
2.46.0

[PATCH v4 02/14] rust: hrtimer: introduce hrtimer support

[Andreas Hindborg]

This patch adds support for intrusive use of the hrtimer system. For now,
only one timer can be embedded in a Rust struct.

The hrtimer Rust API is based on the intrusive style pattern introduced by
the Rust workqueue API.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time.rs         |   2 +
 rust/kernel/time/hrtimer.rs | 296 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 298 insertions(+)

diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
index f59e0fea79d3acfddd922f601f569353609aeec1..51c3532eee0184495ed5b7d717860c9980ff2a43 100644
--- a/rust/kernel/time.rs
+++ b/rust/kernel/time.rs
@@ -10,6 +10,8 @@
 
 use core::convert::Into;
 
+pub mod hrtimer;
+
 /// The number of nanoseconds per millisecond.
 pub const NSEC_PER_MSEC: i64 = bindings::NSEC_PER_MSEC as i64;
 
diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
new file mode 100644
index 0000000000000000000000000000000000000000..646cd5bfa6623aec62294f9115fbf6fedc0a426c
--- /dev/null
+++ b/rust/kernel/time/hrtimer.rs
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Intrusive high resolution timers.
+//!
+//! Allows running timer callbacks without doing allocations at the time of
+//! starting the timer. For now, only one timer per type is allowed.
+//!
+//! # Vocabulary
+//!
+//! A timer is initialized in the **stopped** state. A stopped timer can be
+//! **started** with an **expiry** time. After the timer is started, it is
+//! **running**. When the timer **expires**, the timer handler is executed.
+//! After the handler has executed, the timer may be **restarted** or
+//! **stopped**. A running timer can be **cancelled** before it's handler is
+//! executed. A timer that is cancelled enters the **stopped** state.
+//!
+//! States:
+//!
+//! * Stopped
+//! * Running
+//!
+//! Operations:
+//!
+//! * Start
+//! * Cancel
+//! * Stop
+//! * Restart
+//!
+//! Events:
+//!
+//! * Expire
+
+use crate::{init::PinInit, prelude::*, time::Ktime, types::Opaque};
+use core::marker::PhantomData;
+
+/// A timer backed by a C `struct hrtimer`.
+///
+/// # Invariants
+///
+/// * `self.timer` is initialized by `bindings::hrtimer_setup`.
+#[pin_data]
+#[repr(C)]
+pub struct Timer<U> {
+    #[pin]
+    timer: Opaque<bindings::hrtimer>,
+    _t: PhantomData<U>,
+}
+
+// SAFETY: A `Timer` can be moved to other threads and used/dropped from there.
+unsafe impl<U> Send for Timer<U> {}
+
+// SAFETY: Timer operations are locked on C side, so it is safe to operate on a
+// timer from multiple threads
+unsafe impl<U> Sync for Timer<U> {}
+
+impl<T> Timer<T> {
+    /// Return an initializer for a new timer instance.
+    pub fn new() -> impl PinInit<Self>
+    where
+        T: TimerCallback,
+    {
+        pin_init!(Self {
+            // INVARIANTS: We initialize `timer` with `hrtimer_setup` below.
+            timer <- Opaque::ffi_init(move |place: *mut bindings::hrtimer| {
+                // SAFETY: By design of `pin_init!`, `place` is a pointer live
+                // allocation. hrtimer_setup will initialize `place` and does
+                // not require `place` to be initialized prior to the call.
+                unsafe {
+                    bindings::hrtimer_setup(
+                        place,
+                        Some(T::CallbackTarget::run),
+                        bindings::CLOCK_MONOTONIC as i32,
+                        bindings::hrtimer_mode_HRTIMER_MODE_REL,
+                    );
+                }
+            }),
+            _t: PhantomData,
+        })
+    }
+
+    /// Get a pointer to the contained `bindings::hrtimer`.
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must point to a live allocation of at least the size of `Self`.
+    unsafe fn raw_get(ptr: *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 `ptr` points to an
+        // allocation of at least the size of `Self`.
+        unsafe { Opaque::raw_get(core::ptr::addr_of!((*ptr).timer)) }
+    }
+
+    /// Cancel an initialized and potentially running timer.
+    ///
+    /// If the timer handler is running, this will block until the handler is
+    /// finished.
+    ///
+    /// # Safety
+    ///
+    /// `self_ptr` must point to a valid `Self`.
+    #[allow(dead_code)]
+    pub(crate) unsafe fn raw_cancel(self_ptr: *const Self) -> bool {
+        // SAFETY: timer_ptr points to an allocation of at least `Timer` size.
+        let c_timer_ptr = unsafe { Timer::raw_get(self_ptr) };
+
+        // If handler is running, this will wait for handler to finish before
+        // returning.
+        // SAFETY: `c_timer_ptr` is initialized and valid. Synchronization is
+        // handled on C side.
+        unsafe { bindings::hrtimer_cancel(c_timer_ptr) != 0 }
+    }
+}
+
+/// Implemented by pointer types that point to structs that embed a [`Timer`].
+///
+/// Typical implementers would be [`Box<T>`], [`Arc<T>`], [`ARef<T>`] where `T`
+/// has a field of type `Timer`.
+///
+/// Target must be [`Sync`] because timer callbacks happen in another thread of
+/// execution (hard or soft interrupt context).
+///
+/// Starting a timer returns a [`TimerHandle`] that can be used to manipulate
+/// the timer. Note that it is OK to call the start function repeatedly, and
+/// that more than one [`TimerHandle`] associated with a `TimerPointer` may
+/// exist. A timer can be manipulated through any of the handles, and a handle
+/// may represent a cancelled timer.
+///
+/// [`Box<T>`]: Box
+/// [`Arc<T>`]: crate::sync::Arc
+/// [`ARef<T>`]: crate::types::ARef
+pub trait TimerPointer: Sync + Sized {
+    /// A handle representing a running timer.
+    ///
+    /// If the timer is running or if the timer callback is executing when the
+    /// handle is dropped, the drop method of `TimerHandle` should not return
+    /// until the timer is stopped and the callback has completed.
+    ///
+    /// Note: It must be safe to leak the handle.
+    type TimerHandle: TimerHandle;
+
+    /// Start the timer with expiry after `expires` time units. If the timer was
+    /// already running, it is restarted with the new expiry time.
+    fn start(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.
+pub trait RawTimerCallback {
+    /// Callback to be called from C when timer fires.
+    ///
+    /// # Safety
+    ///
+    /// Only to be called by C code in `hrtimer` subsystem. `ptr` must point to
+    /// the `bindings::hrtimer` structure that was used to start the timer.
+    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart;
+}
+
+/// Implemented by structs that can the target of a timer callback.
+pub trait TimerCallback {
+    /// The type that was used for starting the timer.
+    type CallbackTarget<'a>: RawTimerCallback;
+
+    /// This type is passed to the timer callback function. It may be a borrow
+    /// of [`Self::CallbackTarget`], or it may be `Self::CallbackTarget` if the
+    /// implementation can guarantee exclusive access to the target during timer
+    /// handler execution.
+    type CallbackTargetParameter<'a>;
+
+    /// Called by the timer logic when the timer fires.
+    fn run(this: Self::CallbackTargetParameter<'_>)
+    where
+        Self: Sized;
+}
+
+/// A handle representing a potentially running timer.
+///
+/// More than one handle representing the same timer might exist.
+///
+/// # Safety
+///
+/// When dropped, the timer represented by this handle must be cancelled, if it
+/// is running. If the timer handler is running when the handle is dropped, the
+/// drop method must wait for the handler to finish before returning.
+pub unsafe trait TimerHandle {
+    /// Cancel the timer, if it is running. If the timer handler is running, block
+    /// till the handler has finished.
+    fn cancel(&mut self) -> bool;
+}
+
+/// Implemented by structs that contain timer nodes.
+///
+/// Clients of the timer API would usually safely implement this trait by using
+/// the [`impl_has_timer`] macro.
+///
+/// # Safety
+///
+/// Implementers of this trait must ensure that the implementer has a [`Timer`]
+/// field at the offset specified by `OFFSET` and that all trait methods are
+/// implemented according to their documentation.
+///
+/// [`impl_has_timer`]: crate::impl_has_timer
+pub unsafe trait HasTimer<U> {
+    /// Offset of the [`Timer`] field within `Self`
+    const OFFSET: usize;
+
+    /// Return a pointer to the [`Timer`] within `Self`.
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must point to a valid struct of type `Self`.
+    unsafe fn raw_get_timer(ptr: *const Self) -> *const Timer<U> {
+        // SAFETY: By the safety requirement of this trait, the trait
+        // implementor will have a `Timer` field at the specified offset.
+        unsafe { ptr.cast::<u8>().add(Self::OFFSET).cast::<Timer<U>>() }
+    }
+
+    /// Return a pointer to the struct that is embedding the [`Timer`] pointed
+    /// to by `ptr`.
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must point to a [`Timer<U>`] field in a struct of type `Self`.
+    unsafe fn timer_container_of(ptr: *mut Timer<U>) -> *mut Self
+    where
+        Self: Sized,
+    {
+        // SAFETY: By the safety requirement of this function and the `HasTimer`
+        // trait, the following expression will yield a pointer to the `Self`
+        // containing the timer addressed by `ptr`.
+        unsafe { ptr.cast::<u8>().sub(Self::OFFSET).cast::<Self>() }
+    }
+
+    /// Get pointer to embedded `bindings::hrtimer` struct.
+    ///
+    /// # Safety
+    ///
+    /// `self_ptr` must point to a valid `Self`.
+    unsafe fn c_timer_ptr(self_ptr: *const Self) -> *const bindings::hrtimer {
+        // SAFETY: `self_ptr` is a valid pointer to a `Self`.
+        let timer_ptr = unsafe { Self::raw_get_timer(self_ptr) };
+
+        // SAFETY: timer_ptr points to an allocation of at least `Timer` size.
+        unsafe { Timer::raw_get(timer_ptr) }
+    }
+
+    /// Start the timer contained in the `Self` pointed to by `self_ptr`. If
+    /// it is already running it is removed and inserted.
+    ///
+    /// # Safety
+    ///
+    /// `self_ptr` must point to a valid `Self`.
+    unsafe fn start(self_ptr: *const Self, expires: Ktime) {
+        // SAFETY: By function safety requirement, `self_ptr`is a valid `Self`.
+        unsafe {
+            bindings::hrtimer_start_range_ns(
+                Self::c_timer_ptr(self_ptr).cast_mut(),
+                expires.to_ns(),
+                0,
+                bindings::hrtimer_mode_HRTIMER_MODE_REL,
+            );
+        }
+    }
+}
+
+/// Use to implement the [`HasTimer<T>`] trait.
+///
+/// See [`module`] documentation for an example.
+///
+/// [`module`]: crate::time::hrtimer
+#[macro_export]
+macro_rules! impl_has_timer {
+    (
+        impl$({$($generics:tt)*})?
+            HasTimer<$timer_type:ty>
+            for $self:ty
+        { self.$field:ident }
+        $($rest:tt)*
+    ) => {
+        // SAFETY: This implementation of `raw_get_timer` only compiles if the
+        // field has the right type.
+        unsafe impl$(<$($generics)*>)? $crate::time::hrtimer::HasTimer<$timer_type> for $self {
+            const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
+
+            #[inline]
+            unsafe fn raw_get_timer(ptr: *const Self) ->
+                *const $crate::::time::hrtimer::Timer<$timer_type>
+            {
+                // SAFETY: The caller promises that the pointer is not dangling.
+                unsafe {
+                    ::core::ptr::addr_of!((*ptr).$field)
+                }
+            }
+        }
+    }
+}

-- 
2.46.0

[PATCH v4 03/14] rust: sync: add `Arc::as_ptr`

[Andreas Hindborg]

Add a method to get a pointer to the data contained in an `Arc`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/sync/arc.rs | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index fa4509406ee909ca0677b78d5ece966089ce6366..3d6111ddb007285b26eca2177a412033f4ac5dcb 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -233,6 +233,15 @@ pub fn into_raw(self) -> *const T {
         unsafe { core::ptr::addr_of!((*ptr).data) }
     }
 
+    /// Return a raw pointer to the data in this arc.
+    pub fn as_ptr(this: &Self) -> *const T {
+        let ptr = this.ptr.as_ptr();
+
+        // SAFETY: As `ptr` points to a valid allocation of type `ArcInner`,
+        // field projection to `data`is within bounds of the allocation.
+        unsafe { core::ptr::addr_of!((*ptr).data) }
+    }
+
     /// Recreates an [`Arc`] instance previously deconstructed via [`Arc::into_raw`].
     ///
     /// # Safety
@@ -508,11 +517,11 @@ unsafe fn new(inner: NonNull<ArcInner<T>>) -> Self {
     }
 
     /// Creates an [`ArcBorrow`] to an [`Arc`] that has previously been deconstructed with
-    /// [`Arc::into_raw`].
+    /// [`Arc::into_raw`] or [`Arc::as_ptr`].
     ///
     /// # Safety
     ///
-    /// * The provided pointer must originate from a call to [`Arc::into_raw`].
+    /// * The provided pointer must originate from a call to [`Arc::into_raw`] or [`Arc::as_ptr`].
     /// * For the duration of the lifetime annotated on this `ArcBorrow`, the reference count must
     ///   not hit zero.
     /// * For the duration of the lifetime annotated on this `ArcBorrow`, there must not be a

-- 
2.46.0

[PATCH v4 04/14] rust: hrtimer: implement `TimerPointer` for `Arc`

[Andreas Hindborg]

This patch allows the use of intrusive `hrtimer` fields in structs that are
managed by an `Arc`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs     |  3 +-
 rust/kernel/time/hrtimer/arc.rs | 89 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 646cd5bfa6623aec62294f9115fbf6fedc0a426c..e76b864f3435667f56ed607fd3bf029317eb1332 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -98,7 +98,6 @@ unsafe fn raw_get(ptr: *const Self) -> *mut bindings::hrtimer {
     /// # Safety
     ///
     /// `self_ptr` must point to a valid `Self`.
-    #[allow(dead_code)]
     pub(crate) unsafe fn raw_cancel(self_ptr: *const Self) -> bool {
         // SAFETY: timer_ptr points to an allocation of at least `Timer` size.
         let c_timer_ptr = unsafe { Timer::raw_get(self_ptr) };
@@ -294,3 +293,5 @@ unsafe fn raw_get_timer(ptr: *const Self) ->
         }
     }
 }
+
+mod arc;
diff --git a/rust/kernel/time/hrtimer/arc.rs b/rust/kernel/time/hrtimer/arc.rs
new file mode 100644
index 0000000000000000000000000000000000000000..3b256292bc86160a495f7b192b3eda92f2dfcb31
--- /dev/null
+++ b/rust/kernel/time/hrtimer/arc.rs
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use super::HasTimer;
+use super::RawTimerCallback;
+use super::Timer;
+use super::TimerCallback;
+use super::TimerHandle;
+use super::TimerPointer;
+use crate::sync::Arc;
+use crate::sync::ArcBorrow;
+use crate::time::Ktime;
+
+/// A handle for an `Arc<HasTimer<U>>` returned by a call to
+/// [`TimerPointer::start`].
+pub struct ArcTimerHandle<U>
+where
+    U: HasTimer<U>,
+{
+    pub(crate) inner: Arc<U>,
+}
+
+// SAFETY: We implement drop below, and we cancel the timer in the drop
+// implementation.
+unsafe impl<U> TimerHandle for ArcTimerHandle<U>
+where
+    U: HasTimer<U>,
+{
+    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 `U`.
+        let timer_ptr = unsafe { <U as HasTimer<U>>::raw_get_timer(self_ptr) };
+
+        // SAFETY: As `timer_ptr` points into `U` and `U` is valid, `timer_ptr`
+        // must point to a valid `Timer` instance.
+        unsafe { Timer::<U>::raw_cancel(timer_ptr) }
+    }
+}
+
+impl<U> Drop for ArcTimerHandle<U>
+where
+    U: HasTimer<U>,
+{
+    fn drop(&mut self) {
+        self.cancel();
+    }
+}
+
+impl<U> TimerPointer for Arc<U>
+where
+    U: Send + Sync,
+    U: HasTimer<U>,
+    U: for<'a> TimerCallback<CallbackTarget<'a> = Self>,
+{
+    type TimerHandle = ArcTimerHandle<U>;
+
+    fn start(self, expires: Ktime) -> ArcTimerHandle<U> {
+        // SAFETY: Since we generate the pointer passed to `start` from a
+        // valid reference, it is a valid pointer.
+        unsafe { U::start(Arc::as_ptr(&self), expires) };
+
+        ArcTimerHandle { inner: self }
+    }
+}
+
+impl<U> RawTimerCallback for Arc<U>
+where
+    U: HasTimer<U>,
+    U: for<'a> TimerCallback<CallbackTarget<'a> = Self>,
+    U: for<'a> TimerCallback<CallbackTargetParameter<'a> = ArcBorrow<'a, U>>,
+{
+    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
+        // `Timer` is `repr(C)`
+        let timer_ptr = ptr.cast::<super::Timer<U>>();
+
+        // SAFETY: By C API contract `ptr` is the pointer we passed when
+        // queuing the timer, so it is a `Timer<T>` embedded in a `T`.
+        let data_ptr = unsafe { U::timer_container_of(timer_ptr) };
+
+        // SAFETY: `data_ptr` points to the `U` that was used to queue the
+        // timer. This `U` is contained in an `Arc`.
+        let receiver = unsafe { ArcBorrow::from_raw(data_ptr) };
+
+        U::run(receiver);
+
+        bindings::hrtimer_restart_HRTIMER_NORESTART
+    }
+}

-- 
2.46.0

[PATCH v4 05/14] rust: hrtimer: allow timer restart from timer handler

[Andreas Hindborg]

This patch allows timer handlers to report that they want a timer to be
restarted after the timer handler has finished executing.

Also update the `hrtimer` documentation to showcase the new feature.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs     | 37 ++++++++++++++++++++++++++++++++++++-
 rust/kernel/time/hrtimer/arc.rs |  4 +---
 2 files changed, 37 insertions(+), 4 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index e76b864f3435667f56ed607fd3bf029317eb1332..632b28a8a6338e2841c59412f22268ff86410a8f 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -167,7 +167,7 @@ pub trait TimerCallback {
     type CallbackTargetParameter<'a>;
 
     /// Called by the timer logic when the timer fires.
-    fn run(this: Self::CallbackTargetParameter<'_>)
+    fn run(this: Self::CallbackTargetParameter<'_>) -> TimerRestart
     where
         Self: Sized;
 }
@@ -262,6 +262,41 @@ unsafe fn start(self_ptr: *const Self, expires: Ktime) {
     }
 }
 
+/// Restart policy for timers.
+pub enum TimerRestart {
+    /// Timer should not be restarted.
+    NoRestart,
+    /// Timer should be restarted.
+    Restart,
+}
+
+impl From<u32> for TimerRestart {
+    fn from(value: u32) -> Self {
+        match value {
+            0 => Self::NoRestart,
+            _ => Self::Restart,
+        }
+    }
+}
+
+impl From<i32> for TimerRestart {
+    fn from(value: i32) -> Self {
+        match value {
+            0 => Self::NoRestart,
+            _ => Self::Restart,
+        }
+    }
+}
+
+impl From<TimerRestart> for bindings::hrtimer_restart {
+    fn from(value: TimerRestart) -> Self {
+        match value {
+            TimerRestart::NoRestart => bindings::hrtimer_restart_HRTIMER_NORESTART,
+            TimerRestart::Restart => bindings::hrtimer_restart_HRTIMER_RESTART,
+        }
+    }
+}
+
 /// Use to implement the [`HasTimer<T>`] trait.
 ///
 /// See [`module`] documentation for an example.
diff --git a/rust/kernel/time/hrtimer/arc.rs b/rust/kernel/time/hrtimer/arc.rs
index 3b256292bc86160a495f7b192b3eda92f2dfcb31..1711b41ab32aef0c6f5263eab38bc61d6c2a189c 100644
--- a/rust/kernel/time/hrtimer/arc.rs
+++ b/rust/kernel/time/hrtimer/arc.rs
@@ -82,8 +82,6 @@ impl<U> RawTimerCallback for Arc<U>
         // timer. This `U` is contained in an `Arc`.
         let receiver = unsafe { ArcBorrow::from_raw(data_ptr) };
 
-        U::run(receiver);
-
-        bindings::hrtimer_restart_HRTIMER_NORESTART
+        U::run(receiver).into()
     }
 }

-- 
2.46.0

[PATCH v4 06/14] rust: hrtimer: add `UnsafeTimerPointer`

[Andreas Hindborg]

Add a trait to allow unsafely queuing stack allocated timers.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 632b28a8a6338e2841c59412f22268ff86410a8f..fab9bf2612ceaa1ce936ab9b9bc31b018a1a9aef 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -142,6 +142,39 @@ pub trait TimerPointer: Sync + Sized {
     fn start(self, expires: Ktime) -> Self::TimerHandle;
 }
 
+/// Unsafe version of [`TimerPointer`] for situations where leaking the
+/// `TimerHandle` returned by `start` 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 running timer.
+    ///
+    /// # Safety
+    ///
+    /// If the timer is running, or if the timer callback is executing when the
+    /// handle is dropped, the drop method of `TimerHandle` must not return
+    /// until the timer is stopped and the callback has completed.
+    type TimerHandle: TimerHandle;
+
+    /// Start the timer after `expires` time units. If the timer was already
+    /// running, it is restarted 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 start(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

[PATCH v4 07/14] rust: hrtimer: implement `UnsafeTimerPointer` for `Pin<&T>`

[Andreas Hindborg]

Allow pinned references to structs that contain a `Timer` node to be
scheduled with the `hrtimer` subsystem.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs     |  1 +
 rust/kernel/time/hrtimer/pin.rs | 95 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 96 insertions(+)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index fab9bf2612ceaa1ce936ab9b9bc31b018a1a9aef..ad02e023b78062b368af1849063d830ffba5f29b 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -363,3 +363,4 @@ unsafe fn raw_get_timer(ptr: *const Self) ->
 }
 
 mod arc;
+mod pin;
diff --git a/rust/kernel/time/hrtimer/pin.rs b/rust/kernel/time/hrtimer/pin.rs
new file mode 100644
index 0000000000000000000000000000000000000000..7b251f157b2c196a3bde220b12619ce0c0ecce6c
--- /dev/null
+++ b/rust/kernel/time/hrtimer/pin.rs
@@ -0,0 +1,95 @@
+// 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: *const U = self.inner.get_ref();
+
+        // 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 {
+        // Cast to pointer
+        let self_ptr: *const U = <Self as core::ops::Deref>::deref(&self);
+
+        // 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

[PATCH v4 08/14] rust: hrtimer: implement `UnsafeTimerPointer` for `Pin<&mut T>`

[Andreas Hindborg]

Allow pinned mutable references to structs that contain a `Timer` node to
be scheduled with the `hrtimer` subsystem.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs         |  1 +
 rust/kernel/time/hrtimer/pin_mut.rs | 97 +++++++++++++++++++++++++++++++++++++
 2 files changed, 98 insertions(+)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index ad02e023b78062b368af1849063d830ffba5f29b..efcb5e44a0dc3660a09f230c01cca998b763e8d9 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -364,3 +364,4 @@ unsafe fn raw_get_timer(ptr: *const Self) ->
 
 mod arc;
 mod pin;
+mod pin_mut;
diff --git a/rust/kernel/time/hrtimer/pin_mut.rs b/rust/kernel/time/hrtimer/pin_mut.rs
new file mode 100644
index 0000000000000000000000000000000000000000..50ba9109919838aa9b09381000bab4ab8d3a2340
--- /dev/null
+++ b/rust/kernel/time/hrtimer/pin_mut.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<&mut HasTimer>`. When the handle exists, the timer might
+/// be running.
+pub struct PinMutTimerHandle<'a, U>
+where
+    U: HasTimer<U>,
+{
+    pub(crate) inner: Pin<&'a mut 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 PinMutTimerHandle<'a, U>
+where
+    U: HasTimer<U>,
+{
+    fn cancel(&mut self) -> bool {
+        // SAFETY: We are not moving out of `self` or handing out mutable
+        // references to `self`.
+        let self_ptr = unsafe { self.inner.as_mut().get_unchecked_mut() as *mut 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 PinMutTimerHandle<'a, U>
+where
+    U: HasTimer<U>,
+{
+    fn drop(&mut self) {
+        self.cancel();
+    }
+}
+
+// SAFETY: We capture the lifetime of `Self` when we create a
+// `PinMutTimerHandle`, so `Self` will outlive the handle.
+unsafe impl<'a, U> UnsafeTimerPointer for Pin<&'a mut U>
+where
+    U: Send + Sync,
+    U: HasTimer<U>,
+    U: TimerCallback<CallbackTarget<'a> = Self>,
+{
+    type TimerHandle = PinMutTimerHandle<'a, U>;
+
+    unsafe fn start(self, expires: Ktime) -> Self::TimerHandle {
+        // Cast to pointer
+        let self_ptr: *const U = <Self as core::ops::Deref>::deref(&self);
+
+        // SAFETY: As we derive `self_ptr` from a reference above, it must point
+        // to a valid `U`.
+        unsafe { U::start(self_ptr, expires) };
+
+        PinMutTimerHandle { inner: self }
+    }
+}
+
+impl<'a, U> RawTimerCallback for Pin<&'a mut 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 { &mut *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

[PATCH v4 09/14] rust: hrtimer: add `hrtimer::ScopedTimerPointer`

[Andreas Hindborg]

Add the trait `ScopedTimerPointer` to allow safe use of stack allocated
timers. Safety is achieved by pinning the stack in place while timers are
running.

Implement the trait for all types that implement `UnsafeTimerPointer`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index efcb5e44a0dc3660a09f230c01cca998b763e8d9..7835a33677ec32999c495d5b874ded2ff0786c9e 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -175,6 +175,39 @@ pub unsafe trait UnsafeTimerPointer: Sync + Sized {
     unsafe fn start(self, expires: Ktime) -> Self::TimerHandle;
 }
 
+/// A trait for stack allocated timers.
+///
+/// # Safety
+///
+/// Implementers must ensure that `start_scoped` does not return until the
+/// timer is dead and the timer handler is not running.
+pub unsafe trait ScopedTimerPointer {
+    /// Start the timer to run after `expires` time units and immediately
+    /// after call `f`. When `f` returns, the timer is cancelled.
+    fn start_scoped<T, F>(self, expires: Ktime, f: F) -> T
+    where
+        F: FnOnce() -> T;
+}
+
+// SAFETY: By the safety requirement of `UnsafeTimerPointer`, dropping the
+// handle returned by [`UnsafeTimerPointer::start`] ensures that the timer is
+// killed.
+unsafe impl<U> ScopedTimerPointer for U
+where
+    U: UnsafeTimerPointer,
+{
+    fn start_scoped<T, F>(self, expires: Ktime, f: F) -> T
+    where
+        F: FnOnce() -> T,
+    {
+        // SAFETY: We drop the timer handle below before returning.
+        let handle = unsafe { UnsafeTimerPointer::start(self, expires) };
+        let t = f();
+        drop(handle);
+        t
+    }
+}
+
 /// 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

[PATCH v4 10/14] rust: alloc: add `Box::into_pin`

[Andreas Hindborg]

Add an associated function to convert a `Box<T>` into a `Pin<Box<T>>`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/alloc/kbox.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index 9ce414361c2c6dd8eea09b11041f6c307cbc7864..1a993ec8602b37041c192458d8b6acff30769a04 100644
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -245,6 +245,16 @@ pub fn pin(x: T, flags: Flags) -> Result<Pin<Box<T, A>>, AllocError>
         Ok(Self::new(x, flags)?.into())
     }
 
+    /// Convert a [`Box<T,A>`] to a [`Pin<Box<T,A>>`]. If `T` does not implement
+    /// [`Unpin`], then `x` will be pinned in memory and can't be moved.
+    pub fn into_pin(boxed: Self) -> Pin<Self> {
+        // SAFETY: `Self` is guaranteed to be the only pointer to the boxed
+        // value. Thus, if `T: !Unpin`, `T` is guaranteed to stay pinned; there
+        // is no way to get rid of the `Pin` and move out of the returned
+        // `Pin<Box<T>>`.
+        unsafe { Pin::new_unchecked(boxed) }
+    }
+
     /// Forgets the contents (does not run the destructor), but keeps the allocation.
     fn forget_contents(this: Self) -> Box<MaybeUninit<T>, A> {
         let ptr = Self::into_raw(this);

-- 
2.46.0

[PATCH v4 11/14] rust: hrtimer: implement `TimerPointer` for `Pin<Box<T>>`

[Andreas Hindborg]

Allow `Pin<Box<T>>` to be the target of a timer callback.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs      |   3 ++
 rust/kernel/time/hrtimer/tbox.rs | 102 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 105 insertions(+)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 7835a33677ec32999c495d5b874ded2ff0786c9e..976a7350d6bee0cebe3dcca04ccbe48fef31e430 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -395,6 +395,9 @@ unsafe fn raw_get_timer(ptr: *const Self) ->
     }
 }
 
+// `box` is a reserved keyword, so prefix with `t` for timer
+mod tbox;
+
 mod arc;
 mod pin;
 mod pin_mut;
diff --git a/rust/kernel/time/hrtimer/tbox.rs b/rust/kernel/time/hrtimer/tbox.rs
new file mode 100644
index 0000000000000000000000000000000000000000..4b932a20cf6fcacdff7c40fc280f8d73a45addc0
--- /dev/null
+++ b/rust/kernel/time/hrtimer/tbox.rs
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use super::HasTimer;
+use super::RawTimerCallback;
+use super::Timer;
+use super::TimerCallback;
+use super::TimerHandle;
+use super::TimerPointer;
+use crate::prelude::*;
+use crate::time::Ktime;
+use core::mem::ManuallyDrop;
+
+/// A handle for a `Box<HasTimer<U>>` returned by a call to
+/// [`TimerPointer::start`].
+pub struct BoxTimerHandle<U, A>
+where
+    U: HasTimer<U>,
+    A: crate::alloc::Allocator,
+{
+    pub(crate) inner: *mut U,
+    _p: core::marker::PhantomData<A>,
+}
+
+// SAFETY: We implement drop below, and we cancel the timer in the drop
+// implementation.
+unsafe impl<U, A> TimerHandle for BoxTimerHandle<U, A>
+where
+    U: HasTimer<U>,
+    A: crate::alloc::Allocator,
+{
+    fn cancel(&mut self) -> bool {
+        // SAFETY: As we obtained `self.inner` from a valid reference when we
+        // created `self`, it must point to a valid `U`.
+        let timer_ptr = unsafe { <U as HasTimer<U>>::raw_get_timer(self.inner) };
+
+        // SAFETY: As `timer_ptr` points into `U` and `U` is valid, `timer_ptr`
+        // must point to a valid `Timer` instance.
+        unsafe { Timer::<U>::raw_cancel(timer_ptr) }
+    }
+}
+
+impl<U, A> Drop for BoxTimerHandle<U, A>
+where
+    U: HasTimer<U>,
+    A: crate::alloc::Allocator,
+{
+    fn drop(&mut self) {
+        self.cancel();
+        // SAFETY: `self.inner` came from a `Box::into_raw` call
+        drop(unsafe { Box::<U, A>::from_raw(self.inner) })
+    }
+}
+
+impl<U, A> TimerPointer for Pin<Box<U, A>>
+where
+    U: Send + Sync,
+    U: HasTimer<U>,
+    U: for<'a> TimerCallback<CallbackTarget<'a> = Pin<Box<U, A>>>,
+    U: for<'a> TimerCallback<CallbackTargetParameter<'a> = Pin<&'a U>>,
+    A: crate::alloc::Allocator,
+{
+    type TimerHandle = BoxTimerHandle<U, A>;
+
+    fn start(self, expires: Ktime) -> Self::TimerHandle {
+        let self_ptr: *const U = <Self as core::ops::Deref>::deref(&self);
+
+        // SAFETY: Since we generate the pointer passed to `start` from a valid
+        // reference, it is a valid pointer.
+        unsafe { U::start(self_ptr, expires) };
+
+        // SAFETY: We will not move out of this box during timer callback (we
+        // pass an immutable reference to the callback).
+        let inner = unsafe { Pin::into_inner_unchecked(self) };
+
+        BoxTimerHandle {
+            inner: Box::into_raw(inner),
+            _p: core::marker::PhantomData,
+        }
+    }
+}
+
+impl<U, A> RawTimerCallback for Pin<Box<U, A>>
+where
+    U: HasTimer<U>,
+    U: for<'a> TimerCallback<CallbackTarget<'a> = Pin<Box<U, A>>>,
+    U: for<'a> TimerCallback<CallbackTargetParameter<'a> = Pin<&'a U>>,
+    A: crate::alloc::Allocator,
+{
+    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
+        // `Timer` is `repr(C)`
+        let timer_ptr = ptr.cast::<super::Timer<U>>();
+
+        // SAFETY: By C API contract `ptr` is the pointer we passed when
+        // queuing the timer, so it is a `Timer<T>` embedded in a `T`.
+        let data_ptr = unsafe { U::timer_container_of(timer_ptr) };
+
+        // SAFETY: We called `Box::into_raw` when we queued the timer.
+        let tbox = ManuallyDrop::new(Box::into_pin(unsafe { Box::<U, A>::from_raw(data_ptr) }));
+
+        U::run(tbox.as_ref()).into()
+    }
+}

-- 
2.46.0

[PATCH v4 12/14] rust: hrtimer: add `TimerMode`

[Andreas Hindborg]

Allow selection of timer mode by passing a `TimerMode` variant to
`Timer::new`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs | 87 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 84 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 976a7350d6bee0cebe3dcca04ccbe48fef31e430..3bcc45dae130448173be157ce60395e2b9d46a10 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -43,6 +43,8 @@
 pub struct Timer<U> {
     #[pin]
     timer: Opaque<bindings::hrtimer>,
+    // This field goes away when `bindings::hrtimer_setup` is added.
+    mode: TimerMode,
     _t: PhantomData<U>,
 }
 
@@ -55,7 +57,7 @@ unsafe impl<U> Sync for Timer<U> {}
 
 impl<T> Timer<T> {
     /// Return an initializer for a new timer instance.
-    pub fn new() -> impl PinInit<Self>
+    pub fn new(mode: TimerMode) -> impl PinInit<Self>
     where
         T: TimerCallback,
     {
@@ -70,10 +72,11 @@ pub fn new() -> impl PinInit<Self>
                         place,
                         Some(T::CallbackTarget::run),
                         bindings::CLOCK_MONOTONIC as i32,
-                        bindings::hrtimer_mode_HRTIMER_MODE_REL,
+                        mode.into(),
                     );
                 }
             }),
+            mode: mode,
             _t: PhantomData,
         })
     }
@@ -322,7 +325,7 @@ unsafe fn start(self_ptr: *const Self, expires: Ktime) {
                 Self::c_timer_ptr(self_ptr).cast_mut(),
                 expires.to_ns(),
                 0,
-                bindings::hrtimer_mode_HRTIMER_MODE_REL,
+                (*Self::raw_get_timer(self_ptr)).mode.into(),
             );
         }
     }
@@ -363,6 +366,84 @@ fn from(value: TimerRestart) -> Self {
     }
 }
 
+/// Operational mode of [`Timer`].
+#[derive(Clone, Copy)]
+pub enum TimerMode {
+    /// Timer expires at the given expiration time.
+    Absolute,
+    /// Timer expires after the given expiration time interpreted as a duration from now.
+    Relative,
+    /// Timer does not move between CPU cores.
+    Pinned,
+    /// Timer handler is executed in soft irq context.
+    Soft,
+    /// Timer handler is executed in hard irq context.
+    Hard,
+    /// Timer expires at the given expiration time.
+    /// Timer does not move between CPU cores.
+    AbsolutePinned,
+    /// Timer expires after the given expiration time interpreted as a duration from now.
+    /// Timer does not move between CPU cores.
+    RelativePinned,
+    /// Timer expires at the given expiration time.
+    /// Timer handler is executed in soft irq context.
+    AbsoluteSoft,
+    /// Timer expires after the given expiration time interpreted as a duration from now.
+    /// Timer handler is executed in soft irq context.
+    RelativeSoft,
+    /// Timer expires at the given expiration time.
+    /// Timer does not move between CPU cores.
+    /// Timer handler is executed in soft irq context.
+    AbsolutePinnedSoft,
+    /// Timer expires after the given expiration time interpreted as a duration from now.
+    /// Timer does not move between CPU cores.
+    /// Timer handler is executed in soft irq context.
+    RelativePinnedSoft,
+    /// Timer expires at the given expiration time.
+    /// Timer handler is executed in hard irq context.
+    AbsoluteHard,
+    /// Timer expires after the given expiration time interpreted as a duration from now.
+    /// Timer handler is executed in hard irq context.
+    RelativeHard,
+    /// Timer expires at the given expiration time.
+    /// Timer does not move between CPU cores.
+    /// Timer handler is executed in hard irq context.
+    AbsolutePinnedHard,
+    /// Timer expires after the given expiration time interpreted as a duration from now.
+    /// Timer does not move between CPU cores.
+    /// Timer handler is executed in hard irq context.
+    RelativePinnedHard,
+}
+
+impl From<TimerMode> for bindings::hrtimer_mode {
+    fn from(value: TimerMode) -> Self {
+        use bindings::*;
+        match value {
+            TimerMode::Absolute => hrtimer_mode_HRTIMER_MODE_ABS,
+            TimerMode::Relative => hrtimer_mode_HRTIMER_MODE_REL,
+            TimerMode::Pinned => hrtimer_mode_HRTIMER_MODE_PINNED,
+            TimerMode::Soft => hrtimer_mode_HRTIMER_MODE_SOFT,
+            TimerMode::Hard => hrtimer_mode_HRTIMER_MODE_HARD,
+            TimerMode::AbsolutePinned => hrtimer_mode_HRTIMER_MODE_ABS_PINNED,
+            TimerMode::RelativePinned => hrtimer_mode_HRTIMER_MODE_REL_PINNED,
+            TimerMode::AbsoluteSoft => hrtimer_mode_HRTIMER_MODE_ABS_SOFT,
+            TimerMode::RelativeSoft => hrtimer_mode_HRTIMER_MODE_REL_SOFT,
+            TimerMode::AbsolutePinnedSoft => hrtimer_mode_HRTIMER_MODE_ABS_PINNED_SOFT,
+            TimerMode::RelativePinnedSoft => hrtimer_mode_HRTIMER_MODE_REL_PINNED_SOFT,
+            TimerMode::AbsoluteHard => hrtimer_mode_HRTIMER_MODE_ABS_HARD,
+            TimerMode::RelativeHard => hrtimer_mode_HRTIMER_MODE_REL_HARD,
+            TimerMode::AbsolutePinnedHard => hrtimer_mode_HRTIMER_MODE_ABS_PINNED_HARD,
+            TimerMode::RelativePinnedHard => hrtimer_mode_HRTIMER_MODE_REL_PINNED_HARD,
+        }
+    }
+}
+
+impl From<TimerMode> for u64 {
+    fn from(value: TimerMode) -> Self {
+        Into::<bindings::hrtimer_mode>::into(value) as u64
+    }
+}
+
 /// Use to implement the [`HasTimer<T>`] trait.
 ///
 /// See [`module`] documentation for an example.

-- 
2.46.0

[PATCH v4 13/14] rust: hrtimer: add clocksource selection through `ClockSource`

[Andreas Hindborg]

Allow selecting a clock source for timers by passing a `ClockSource`
variant to `Timer::new`.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/time/hrtimer.rs | 52 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
index 3bcc45dae130448173be157ce60395e2b9d46a10..ef1c404c7d3e859b8ac70316b6bb44302130dd95 100644
--- a/rust/kernel/time/hrtimer.rs
+++ b/rust/kernel/time/hrtimer.rs
@@ -57,7 +57,7 @@ unsafe impl<U> Sync for Timer<U> {}
 
 impl<T> Timer<T> {
     /// Return an initializer for a new timer instance.
-    pub fn new(mode: TimerMode) -> impl PinInit<Self>
+    pub fn new(mode: TimerMode, clock: ClockSource) -> impl PinInit<Self>
     where
         T: TimerCallback,
     {
@@ -71,7 +71,7 @@ pub fn new(mode: TimerMode) -> impl PinInit<Self>
                     bindings::hrtimer_setup(
                         place,
                         Some(T::CallbackTarget::run),
-                        bindings::CLOCK_MONOTONIC as i32,
+                        clock.into(),
                         mode.into(),
                     );
                 }
@@ -444,6 +444,54 @@ fn from(value: TimerMode) -> Self {
     }
 }
 
+/// The clock source to use for a [`Timer`].
+pub enum ClockSource {
+    /// A settable system-wide clock that measures real (i.e., wall-clock) time.
+    /// Setting this clock requires appropriate privileges. This clock is
+    /// affected by discontinuous jumps in the system time (e.g., if the system
+    /// administrator manually changes the clock), and by frequency adjustments
+    /// performed by NTP and similar applications via adjtime(3), adjtimex(2),
+    /// clock_adjtime(2), and ntp_adjtime(3). This clock normally counts the
+    /// number of seconds since 1970-01-01 00:00:00 Coordinated Universal Time
+    /// (UTC) except that it ignores leap seconds; near a leap second it is
+    /// typically adjusted by NTP to stay roughly in sync with UTC.
+    RealTime,
+    /// A nonsettable system-wide clock that represents monotonic time since—as
+    /// described by POSIX—"some unspecified point in the past". On Linux, that
+    /// point corresponds to the number of seconds that the system has been
+    /// running since it was booted.
+    ///
+    /// The CLOCK_MONOTONIC clock is not affected by discontinuous jumps in the
+    /// system time (e.g., if the system administrator manually changes the
+    /// clock), but is affected by frequency adjustments. This clock does not
+    /// count time that the system is suspended.
+    Monotonic,
+    /// A nonsettable system-wide clock that is identical to CLOCK_MONOTONIC,
+    /// except that it also includes any time that the system is suspended. This
+    /// allows applications to get a suspend-aware monotonic clock without
+    /// having to deal with the complications of CLOCK_REALTIME, which may have
+    /// discontinuities if the time is changed using settimeofday(2) or similar.
+    BootTime,
+    /// A nonsettable system-wide clock derived from wall-clock time but
+    /// counting leap seconds. This clock does not experience discontinuities or
+    /// frequency adjustments caused by inserting leap seconds as CLOCK_REALTIME
+    /// does.
+    ///
+    /// The acronym TAI refers to International Atomic Time.
+    TAI,
+}
+
+impl From<ClockSource> for bindings::clockid_t {
+    fn from(value: ClockSource) -> Self {
+        match value {
+            ClockSource::RealTime => bindings::CLOCK_REALTIME as i32,
+            ClockSource::Monotonic => bindings::CLOCK_MONOTONIC as i32,
+            ClockSource::BootTime => bindings::CLOCK_BOOTTIME as i32,
+            ClockSource::TAI => bindings::CLOCK_TAI as i32,
+        }
+    }
+}
+
 /// Use to implement the [`HasTimer<T>`] trait.
 ///
 /// See [`module`] documentation for an example.

-- 
2.46.0

[PATCH v4 14/14] rust: hrtimer: add maintainer entry

[Andreas Hindborg]

Add Andreas Hindborg as maintainer for Rust `hrtimer` abstractions. Also
add Boqun Feng as reviewer.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
---
 MAINTAINERS | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 1e930c7a58b13d8bbe6bf133ba7b36aa24c2b5e0..4b29b00f740bcb24d25dbcf45f265eea6b4cd980 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10251,6 +10251,16 @@ F:	kernel/time/timer_list.c
 F:	kernel/time/timer_migration.*
 F:	tools/testing/selftests/timers/
 
+HIGH-RESOLUTION TIMERS [RUST]
+M:	Andreas Hindborg <a.hindborg@kernel.org>
+R:	Boqun Feng <boqun.feng@gmail.com>
+L:	rust-for-linux@vger.kernel.org
+S:	Supported
+W:	https://rust-for-linux.com
+B:	https://github.com/Rust-for-Linux/linux/issues
+F:	rust/kernel/hrtimer.rs
+F:	rust/kernel/hrtimer/
+
 HIGH-SPEED SCC DRIVER FOR AX.25
 L:	linux-hams@vger.kernel.org
 S:	Orphan

-- 
2.46.0

Re: [PATCH v4 10/14] rust: alloc: add `Box::into_pin`

[Danilo Krummrich]

On Fri, Dec 06, 2024 at 08:33:02PM +0100, Andreas Hindborg wrote:
> Add an associated function to convert a `Box<T>` into a `Pin<Box<T>>`.

What do you need this function for?

There is an `impl<T, A> From<Box<T, A>> for Pin<Box<T, A>>` already.

> 
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
>  rust/kernel/alloc/kbox.rs | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
> index 9ce414361c2c6dd8eea09b11041f6c307cbc7864..1a993ec8602b37041c192458d8b6acff30769a04 100644
> --- a/rust/kernel/alloc/kbox.rs
> +++ b/rust/kernel/alloc/kbox.rs
> @@ -245,6 +245,16 @@ pub fn pin(x: T, flags: Flags) -> Result<Pin<Box<T, A>>, AllocError>
>          Ok(Self::new(x, flags)?.into())
>      }
>  
> +    /// Convert a [`Box<T,A>`] to a [`Pin<Box<T,A>>`]. If `T` does not implement
> +    /// [`Unpin`], then `x` will be pinned in memory and can't be moved.
> +    pub fn into_pin(boxed: Self) -> Pin<Self> {
> +        // SAFETY: `Self` is guaranteed to be the only pointer to the boxed
> +        // value. Thus, if `T: !Unpin`, `T` is guaranteed to stay pinned; there
> +        // is no way to get rid of the `Pin` and move out of the returned
> +        // `Pin<Box<T>>`.
> +        unsafe { Pin::new_unchecked(boxed) }
> +    }
> +
>      /// Forgets the contents (does not run the destructor), but keeps the allocation.
>      fn forget_contents(this: Self) -> Box<MaybeUninit<T>, A> {
>          let ptr = Self::into_raw(this);
> 
> -- 
> 2.46.0
> 
> 

Re: [PATCH v4 10/14] rust: alloc: add `Box::into_pin`

[Andreas Hindborg]

"Danilo Krummrich" <dakr@kernel.org> writes:

> On Fri, Dec 06, 2024 at 08:33:02PM +0100, Andreas Hindborg wrote:
>> Add an associated function to convert a `Box<T>` into a `Pin<Box<T>>`.
>
> What do you need this function for?
>
> There is an `impl<T, A> From<Box<T, A>> for Pin<Box<T, A>>` already.
>

I didn't realize, but that could work as well. I was rebasing this
series from before we did our own `Box`, and rust `Box` has this method,
which I was using.

At any rate, I think it would make sense to have `into_pin` as well as
the `From` impl, to match the standard library. We could always
implement one in terms of the other.


Best regards,
Andreas Hindborg

Re: [PATCH v4 02/14] rust: hrtimer: introduce hrtimer support

[Guangbo Cui]

> +#[macro_export]
> +macro_rules! impl_has_timer {
> +    (
> +        impl$({$($generics:tt)*})?
> +            HasTimer<$timer_type:ty>
> +            for $self:ty
> +        { self.$field:ident }
> +        $($rest:tt)*
> +    ) => {
> +        // SAFETY: This implementation of `raw_get_timer` only compiles if the
> +        // field has the right type.
> +        unsafe impl$(<$($generics)*>)? $crate::time::hrtimer::HasTimer<$timer_type> for $self {
> +            const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
> +
> +            #[inline]
> +            unsafe fn raw_get_timer(ptr: *const Self) ->
> +                *const $crate::::time::hrtimer::Timer<$timer_type>

Hi Andreas, an extra `::` here.

Best regards,
Guangbo Cui

Re: [PATCH v4 02/14] rust: hrtimer: introduce hrtimer support

[Andreas Hindborg]

"Guangbo Cui" <2407018371@qq.com> writes:

>> +#[macro_export]
>> +macro_rules! impl_has_timer {
>> +    (
>> +        impl$({$($generics:tt)*})?
>> +            HasTimer<$timer_type:ty>
>> +            for $self:ty
>> +        { self.$field:ident }
>> +        $($rest:tt)*
>> +    ) => {
>> +        // SAFETY: This implementation of `raw_get_timer` only compiles if the
>> +        // field has the right type.
>> +        unsafe impl$(<$($generics)*>)? $crate::time::hrtimer::HasTimer<$timer_type> for $self {
>> +            const OFFSET: usize = ::core::mem::offset_of!(Self, $field) as usize;
>> +
>> +            #[inline]
>> +            unsafe fn raw_get_timer(ptr: *const Self) ->
>> +                *const $crate::::time::hrtimer::Timer<$timer_type>
>
> Hi Andreas, an extra `::` here.

One of these days I hope to have refined my workflow to a degree that
would prevent things like this. I thought I was there, but not yet it
seems. Thanks for spotting.

I _did_ actually fix this, but the fix was hiding in a commit with test
code that did not make it in to the series 🤦 And when ran my script to
make sure all the commits build, this macro was no longer invoked and
the typo was hiding.

For reference, I am holding the examples back until we get either a
spinlock/condvar combo that can work in irq disabled context, or atomics
that work with LKMM.

Best regards,
Andreas Hindborg

Re: [PATCH v4 10/14] rust: alloc: add `Box::into_pin`

[Danilo Krummrich]

On Fri, Dec 06, 2024 at 10:25:02PM +0100, Andreas Hindborg wrote:
> "Danilo Krummrich" <dakr@kernel.org> writes:
> 
> > On Fri, Dec 06, 2024 at 08:33:02PM +0100, Andreas Hindborg wrote:
> >> Add an associated function to convert a `Box<T>` into a `Pin<Box<T>>`.
> >
> > What do you need this function for?
> >
> > There is an `impl<T, A> From<Box<T, A>> for Pin<Box<T, A>>` already.
> >
> 
> I didn't realize, but that could work as well. I was rebasing this
> series from before we did our own `Box`, and rust `Box` has this method,
> which I was using.
> 
> At any rate, I think it would make sense to have `into_pin` as well as
> the `From` impl, to match the standard library. We could always
> implement one in terms of the other.

I'm not against that -- one of my earlier allocator series actually even had
this function. However, the feedback was to rather not have it at the time.

As mentioned, I'm still fine with including this function though.

Please implement `ìnto_pin` using the existing `From` trait for the next
iteration.

- Danilo

> 
> 
> Best regards,
> Andreas Hindborg
> 
>