kernel/time/hrtimer/
pin.rs

1// SPDX-License-Identifier: GPL-2.0
2
3use super::HasHrTimer;
4use super::HrTimer;
5use super::HrTimerCallback;
6use super::HrTimerCallbackContext;
7use super::HrTimerHandle;
8use super::HrTimerMode;
9use super::RawHrTimerCallback;
10use super::UnsafeHrTimerPointer;
11use core::pin::Pin;
12
13/// A handle for a `Pin<&HasHrTimer>`. When the handle exists, the timer might be
14/// running.
15pub struct PinHrTimerHandle<'a, T>
16where
17    T: HasHrTimer<T>,
18{
19    pub(crate) inner: Pin<&'a T>,
20}
21
22// SAFETY: We cancel the timer when the handle is dropped. The implementation of
23// the `cancel` method will block if the timer handler is running.
24unsafe impl<'a, T> HrTimerHandle for PinHrTimerHandle<'a, T>
25where
26    T: HasHrTimer<T>,
27{
28    fn cancel(&mut self) -> bool {
29        let self_ptr: *const T = self.inner.get_ref();
30
31        // SAFETY: As we got `self_ptr` from a reference above, it must point to
32        // a valid `T`.
33        let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self_ptr) };
34
35        // SAFETY: As `timer_ptr` is derived from a reference, it must point to
36        // a valid and initialized `HrTimer`.
37        unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
38    }
39}
40
41impl<'a, T> Drop for PinHrTimerHandle<'a, T>
42where
43    T: HasHrTimer<T>,
44{
45    fn drop(&mut self) {
46        self.cancel();
47    }
48}
49
50// SAFETY: We capture the lifetime of `Self` when we create a `PinHrTimerHandle`,
51// so `Self` will outlive the handle.
52unsafe impl<'a, T> UnsafeHrTimerPointer for Pin<&'a T>
53where
54    T: Send + Sync,
55    T: HasHrTimer<T>,
56    T: HrTimerCallback<Pointer<'a> = Self>,
57{
58    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
59    type TimerHandle = PinHrTimerHandle<'a, T>;
60
61    unsafe fn start(
62        self,
63        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
64    ) -> Self::TimerHandle {
65        // Cast to pointer
66        let self_ptr: *const T = self.get_ref();
67
68        // SAFETY:
69        //  - As we derive `self_ptr` from a reference above, it must point to a
70        //    valid `T`.
71        //  - We keep `self` alive by wrapping it in a handle below.
72        unsafe { T::start(self_ptr, expires) };
73
74        PinHrTimerHandle { inner: self }
75    }
76}
77
78impl<'a, T> RawHrTimerCallback for Pin<&'a T>
79where
80    T: HasHrTimer<T>,
81    T: HrTimerCallback<Pointer<'a> = Self>,
82{
83    type CallbackTarget<'b> = Self;
84
85    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
86        // `HrTimer` is `repr(C)`
87        let timer_ptr = ptr.cast::<HrTimer<T>>();
88
89        // SAFETY: By the safety requirement of this function, `timer_ptr`
90        // points to a `HrTimer<T>` contained in an `T`.
91        let receiver_ptr = unsafe { T::timer_container_of(timer_ptr) };
92
93        // SAFETY:
94        //  - By the safety requirement of this function, `timer_ptr`
95        //    points to a `HrTimer<T>` contained in an `T`.
96        //  - As per the safety requirements of the trait `HrTimerHandle`, the
97        //    `PinHrTimerHandle` associated with this timer is guaranteed to
98        //    be alive until this method returns. That handle borrows the `T`
99        //    behind `receiver_ptr`, thus guaranteeing the validity of
100        //    the reference created below.
101        let receiver_ref = unsafe { &*receiver_ptr };
102
103        // SAFETY: `receiver_ref` only exists as pinned, so it is safe to pin it
104        // here.
105        let receiver_pin = unsafe { Pin::new_unchecked(receiver_ref) };
106
107        // SAFETY:
108        // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
109        //   it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
110        // - We are within `RawHrTimerCallback::run`
111        let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };
112
113        T::run(receiver_pin, context).into_c()
114    }
115}
kernel/time/hrtimer/pin.rs

kernel/time/hrtimer/
pin.rs
