From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E3D24216605; Fri, 10 Jan 2025 20:17:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736540249; cv=none; b=sldBwPoeGn9GvKLacR7EwXQkGNBXPGwkYKCYk3xcbHbsVaIxnPIhvkz6WSRjNNMCfexiYPUY+hWKfizVqo3qg3VNaMmQa5AXyMV4YZuk0l2DWQ0n5Ok/zmSSa4evi2Mo8u0ifr616IaGSP9leyoaBFnpB8QlTkpPu9yucEGxlsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736540249; c=relaxed/simple; bh=WI1QQEthNUXkpNxEYU0KTttYKrKnItbb/aigqwxV3+k=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=bEbMvsYkRW9ZG6UeagqxJGmGezasYP8qvV+rVQgt9V1SkIHukx8x1DDznTn1cXBNa0TyT69Q7tDogPRYBHLCek6RZO8KW7+WLTO7m4r8MeT2K+NTBKKkZBXTl6vNY6fUTiK1Nbn7PZ9xFcD8szEe8YOHsJNPH88p9FAAvFk2wGI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WDbkVTfQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WDbkVTfQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26698C4CEDD; Fri, 10 Jan 2025 20:17:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1736540248; bh=WI1QQEthNUXkpNxEYU0KTttYKrKnItbb/aigqwxV3+k=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=WDbkVTfQaIW43iyh6+06COvUtK4M0I4yfWhIVsF/7oKSyG2np3/Hn07ze9ajUGuGO YsGdjLa27GAq/eYcErUS9eYPHIrLTOWN6S+jiXJr6WDhmyDKFZMtt2MAFV3bWwqC+V G7KicqV0NMWMWvkmAbJzbnWcsQ1dJ+suWlV+60fgbKq+qAkpRVuMkzjdTwWqPGuZ3B 2dbDTRIBUX24hpaq6fL2IqGB8UxpmgNoe6yy2wpqM/bvF8RgW90mtTaGbzBv5QXoPN YutaP4cUexvjhqsILLDz0P6mIo8+W2R4nVRTOGCU6GqINj5I4TT2jykheww8d//jdP 2ebhoutJ0Hg6w== From: Andreas Hindborg Date: Fri, 10 Jan 2025 21:15:25 +0100 Subject: [PATCH v6 02/14] rust: hrtimer: introduce hrtimer support Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250110-hrtimer-v3-v6-12-rc2-v6-2-f71d50f16482@kernel.org> References: <20250110-hrtimer-v3-v6-12-rc2-v6-0-f71d50f16482@kernel.org> In-Reply-To: <20250110-hrtimer-v3-v6-12-rc2-v6-0-f71d50f16482@kernel.org> To: Miguel Ojeda , Anna-Maria Behnsen , Frederic Weisbecker , Thomas Gleixner , Danilo Krummrich Cc: Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Benno Lossin , Alice Ryhl , Trevor Gross , Lyude Paul , Guangbo Cui <2407018371@qq.com>, Dirk Behme , Daniel Almeida , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, Andreas Hindborg X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=openpgp-sha256; l=12380; i=a.hindborg@kernel.org; h=from:subject:message-id; bh=WI1QQEthNUXkpNxEYU0KTttYKrKnItbb/aigqwxV3+k=; b=owEBbQKS/ZANAwAIAeG4Gj55KGN3AcsmYgBngX/g0DmBALe8IDpO6WL1vfrNUfQPuezd4hvhc dd+CCRrdcKJAjMEAAEIAB0WIQQSwflHVr98KhXWwBLhuBo+eShjdwUCZ4F/4AAKCRDhuBo+eShj d+ThD/9A9vn9DTN8tEFe0W2SzHH8Vek4QOcwGLJpcLGeSWpTurw0K5fFTSQWHVHeAaGWTNAjR0E +IPXYyX3IR/2nFRA2ElWS/SB07MNZrOoAExoPwnwwYSdrHPEvlRd8jO3DDm+gExHZYEoRMNNNAE gykbXwj0dyJp6Xp1pvQ0QF0NyavddB2KhI1sdTf4yf7ioPZFmfxgAo5rt7htHxB4YfgWchBPtaH DsxAVB/R5UD51GuJy7Vr4hE+TwsuXYHN6cP03MZxYU+f/qyMRk2Y6fc+ZiSpWmZpvL7N7qr8tjX gseVcEYi0bC8rZW7pKak2+fEcU0M4B7PSLOg5cozUUQOkyO+e8IDtOJMthOOylPa8JfAbrTzrUd O0/MxF3W8UsRTYRqaCmIj7SloISH0bewxKTJqiYiMumhXoxB6ACpA58IwFWaaR8TxZ16ynvNwUz uzwYA498vLzx0KxvIYUAEQvRjAO8YEIdp8Fs3TFIL47Q5Op0bmEjOt3LokHyo2IjsD3v7Tg6a2e TFCdsZu16SFrVFiBbtl4Up8zR2AqydOYlJXvR6digf9Z1F2ZKcs1r0urzkPOUk1wlA6PdrFrgIp s0+5pR+jyqf5awM/OKVSt69M/MRslQd1JH1WRRVJTURZFlgniU/4CbWroyrtAZkxCUjIV/ukIxv Z1yJpQZrTXeDnPA== X-Developer-Key: i=a.hindborg@kernel.org; a=openpgp; fpr=3108C10F46872E248D1FB221376EB100563EF7A7 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 --- 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..31c461ddd2c377101ed6c1c7e009f7dccf458ebc --- /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 HrTimer { + #[pin] + timer: Opaque, + _t: PhantomData, +} + +// SAFETY: A `HrTimer` can be moved to other threads and used/dropped from there. +unsafe impl Send for HrTimer {} + +// SAFETY: Timer operations are locked on C side, so it is safe to operate on a +// timer from multiple threads +unsafe impl Sync for HrTimer {} + +impl HrTimer { + /// Return an initializer for a new timer instance. + pub fn new() -> impl PinInit + where + T: HrTimerCallback, + { + 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 `HrTimer` size. + let c_timer_ptr = unsafe { HrTimer::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 [`HrTimer`]. +/// +/// Typical implementers would be [`Box`], [`Arc`], [`ARef`] where `T` +/// has a field of type [`HrTimer`]. +/// +/// Target must be [`Sync`] because timer callbacks happen in another thread of +/// execution (hard or soft interrupt context). +/// +/// Starting a timer returns a [`HrTimerHandle`] that can be used to manipulate +/// the timer. Note that it is OK to call the start function repeatedly, and +/// that more than one [`HrTimerHandle`] associated with a [`HrTimerPointer`] may +/// exist. A timer can be manipulated through any of the handles, and a handle +/// may represent a cancelled timer. +/// +/// [`Box`]: Box +/// [`Arc`]: crate::sync::Arc +/// [`ARef`]: crate::types::ARef +pub trait HrTimerPointer: 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 [`HrTimerHandle`] should not return + /// until the timer is stopped and the callback has completed. + /// + /// Note: It must be safe to leak the handle. + type TimerHandle: HrTimerHandle; + + /// 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 [`HrTimerPointer`] implementers to give the C timer callback a +/// function to call. +// This is split from `HrTimerPointer` to make it easier to specify trait bounds. +pub trait RawHrTimerCallback { + /// 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 HrTimerCallback { + /// The type that was used for starting the timer. + type CallbackTarget<'a>: RawHrTimerCallback; + + /// 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 HrTimerHandle { + /// 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 [`crate::impl_has_hr_timer`] macro. +/// +/// # Safety +/// +/// Implementers of this trait must ensure that the implementer has a [`HrTimer`] +/// 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 HasHrTimer { + /// Offset of the [`HrTimer`] field within `Self` + const OFFSET: usize; + + /// Return a pointer to the [`HrTimer`] within `Self`. + /// + /// # Safety + /// + /// `ptr` must point to a valid struct of type `Self`. + unsafe fn raw_get_timer(ptr: *const Self) -> *const HrTimer { + // SAFETY: By the safety requirement of this trait, the trait + // implementor will have a `HrTimer` field at the specified offset. + unsafe { ptr.cast::().add(Self::OFFSET).cast::>() } + } + + /// Return a pointer to the struct that is embedding the [`HrTimer`] pointed + /// to by `ptr`. + /// + /// # Safety + /// + /// `ptr` must point to a [`HrTimer`] field in a struct of type `Self`. + unsafe fn timer_container_of(ptr: *mut HrTimer) -> *mut Self + where + Self: Sized, + { + // SAFETY: By the safety requirement of this function and the `HasHrTimer` + // trait, the following expression will yield a pointer to the `Self` + // containing the timer addressed by `ptr`. + unsafe { ptr.cast::().sub(Self::OFFSET).cast::() } + } + + /// 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 `HrTimer` size. + unsafe { HrTimer::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 [`HasHrTimer`] trait. +/// +/// See [`module`] documentation for an example. +/// +/// [`module`]: crate::time::hrtimer +#[macro_export] +macro_rules! impl_has_hr_timer { + ( + impl$({$($generics:tt)*})? + HasHrTimer<$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)*>)? $crate::time::hrtimer::HasHrTimer<$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 $crate::time::hrtimer::HrTimer<$timer_type> + { + // SAFETY: The caller promises that the pointer is not dangling. + unsafe { + ::core::ptr::addr_of!((*ptr).$field) + } + } + } + } +} -- 2.47.0