kernel/time/hrtimer/
arc.rs

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1// SPDX-License-Identifier: GPL-2.0
2
3use super::HasHrTimer;
4use super::HrTimer;
5use super::HrTimerCallback;
6use super::HrTimerHandle;
7use super::HrTimerMode;
8use super::HrTimerPointer;
9use super::RawHrTimerCallback;
10use crate::sync::Arc;
11use crate::sync::ArcBorrow;
12
13/// A handle for an `Arc<HasHrTimer<T>>` returned by a call to
14/// [`HrTimerPointer::start`].
15pub struct ArcHrTimerHandle<T>
16where
17    T: HasHrTimer<T>,
18{
19    pub(crate) inner: Arc<T>,
20}
21
22// SAFETY: We implement drop below, and we cancel the timer in the drop
23// implementation.
24unsafe impl<T> HrTimerHandle for ArcHrTimerHandle<T>
25where
26    T: HasHrTimer<T>,
27{
28    fn cancel(&mut self) -> bool {
29        let self_ptr = Arc::as_ptr(&self.inner);
30
31        // SAFETY: As we obtained `self_ptr` from a valid reference above, it
32        // must point to a valid `T`.
33        let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self_ptr) };
34
35        // SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr`
36        // must point to a valid `HrTimer` instance.
37        unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
38    }
39}
40
41impl<T> Drop for ArcHrTimerHandle<T>
42where
43    T: HasHrTimer<T>,
44{
45    fn drop(&mut self) {
46        self.cancel();
47    }
48}
49
50impl<T> HrTimerPointer for Arc<T>
51where
52    T: 'static,
53    T: Send + Sync,
54    T: HasHrTimer<T>,
55    T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
56{
57    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
58    type TimerHandle = ArcHrTimerHandle<T>;
59
60    fn start(
61        self,
62        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
63    ) -> ArcHrTimerHandle<T> {
64        // SAFETY:
65        //  - We keep `self` alive by wrapping it in a handle below.
66        //  - Since we generate the pointer passed to `start` from a valid
67        //    reference, it is a valid pointer.
68        unsafe { T::start(Arc::as_ptr(&self), expires) };
69        ArcHrTimerHandle { inner: self }
70    }
71}
72
73impl<T> RawHrTimerCallback for Arc<T>
74where
75    T: 'static,
76    T: HasHrTimer<T>,
77    T: for<'a> HrTimerCallback<Pointer<'a> = Self>,
78{
79    type CallbackTarget<'a> = ArcBorrow<'a, T>;
80
81    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
82        // `HrTimer` is `repr(C)`
83        let timer_ptr = ptr.cast::<super::HrTimer<T>>();
84
85        // SAFETY: By C API contract `ptr` is the pointer we passed when
86        // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`.
87        let data_ptr = unsafe { T::timer_container_of(timer_ptr) };
88
89        // SAFETY:
90        //  - `data_ptr` is derived form the pointer to the `T` that was used to
91        //    queue the timer.
92        //  - As per the safety requirements of the trait `HrTimerHandle`, the
93        //    `ArcHrTimerHandle` associated with this timer is guaranteed to
94        //    be alive until this method returns. That handle borrows the `T`
95        //    behind `data_ptr` thus guaranteeing the validity of
96        //    the `ArcBorrow` created below.
97        //  - We own one refcount in the `ArcTimerHandle` associated with this
98        //    timer, so it is not possible to get a `UniqueArc` to this
99        //    allocation from other `Arc` clones.
100        let receiver = unsafe { ArcBorrow::from_raw(data_ptr) };
101
102        T::run(receiver).into_c()
103    }
104}
kernel/time/hrtimer/arc.rs

kernel/time/hrtimer/
arc.rs
