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With Linux's hrtimer API, there's a number of methods that can only be called in two situations: * When we have exclusive access to the hrtimer and it is not currently active * When we're within the context of an hrtimer callback context This commit handles the second situation and implements hrtimer_forward() support in the context of a timer callback. We do this by introducing a HrTimerCallbackContext type which is provided to users during the RawHrTimerCallback::run() callback, and then add a forward() function to the type. Signed-off-by: Lyude Paul <lyude@redhat.com> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com> Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org> Link: https://lore.kernel.org/r/20250821193259.964504-5-lyude@redhat.com Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
111 lines
3.6 KiB
Rust
111 lines
3.6 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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use super::HasHrTimer;
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use super::HrTimer;
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use super::HrTimerCallback;
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use super::HrTimerCallbackContext;
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use super::HrTimerHandle;
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use super::HrTimerMode;
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use super::HrTimerPointer;
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use super::RawHrTimerCallback;
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use crate::sync::Arc;
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use crate::sync::ArcBorrow;
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/// A handle for an `Arc<HasHrTimer<T>>` returned by a call to
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/// [`HrTimerPointer::start`].
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pub struct ArcHrTimerHandle<T>
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where
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T: HasHrTimer<T>,
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{
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pub(crate) inner: Arc<T>,
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}
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// SAFETY: We implement drop below, and we cancel the timer in the drop
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// implementation.
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unsafe impl<T> HrTimerHandle for ArcHrTimerHandle<T>
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where
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T: HasHrTimer<T>,
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{
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fn cancel(&mut self) -> bool {
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let self_ptr = Arc::as_ptr(&self.inner);
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// SAFETY: As we obtained `self_ptr` from a valid reference above, it
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// must point to a valid `T`.
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let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self_ptr) };
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// SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr`
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// must point to a valid `HrTimer` instance.
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unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
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}
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}
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impl<T> Drop for ArcHrTimerHandle<T>
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where
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T: HasHrTimer<T>,
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{
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fn drop(&mut self) {
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self.cancel();
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}
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}
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impl<T> HrTimerPointer for Arc<T>
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where
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T: 'static,
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T: Send + Sync,
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T: HasHrTimer<T>,
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T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
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{
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type TimerMode = <T as HasHrTimer<T>>::TimerMode;
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type TimerHandle = ArcHrTimerHandle<T>;
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fn start(
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self,
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expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
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) -> ArcHrTimerHandle<T> {
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// SAFETY:
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// - We keep `self` alive by wrapping it in a handle below.
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// - Since we generate the pointer passed to `start` from a valid
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// reference, it is a valid pointer.
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unsafe { T::start(Arc::as_ptr(&self), expires) };
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ArcHrTimerHandle { inner: self }
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}
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}
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impl<T> RawHrTimerCallback for Arc<T>
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where
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T: 'static,
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T: HasHrTimer<T>,
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T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
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{
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type CallbackTarget<'a> = ArcBorrow<'a, T>;
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unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
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// `HrTimer` is `repr(C)`
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let timer_ptr = ptr.cast::<super::HrTimer<T>>();
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// SAFETY: By C API contract `ptr` is the pointer we passed when
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// queuing the timer, so it is a `HrTimer<T>` embedded in a `T`.
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let data_ptr = unsafe { T::timer_container_of(timer_ptr) };
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// SAFETY:
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// - `data_ptr` is derived form the pointer to the `T` that was used to
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// queue the timer.
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// - As per the safety requirements of the trait `HrTimerHandle`, the
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// `ArcHrTimerHandle` associated with this timer is guaranteed to
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// be alive until this method returns. That handle borrows the `T`
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// behind `data_ptr` thus guaranteeing the validity of
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// the `ArcBorrow` created below.
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// - We own one refcount in the `ArcTimerHandle` associated with this
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// timer, so it is not possible to get a `UniqueArc` to this
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// allocation from other `Arc` clones.
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let receiver = unsafe { ArcBorrow::from_raw(data_ptr) };
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// SAFETY:
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// - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
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// it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
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// - We are within `RawHrTimerCallback::run`
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let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };
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T::run(receiver, context).into_c()
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}
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}
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