kernel/time/hrtimer/
pin_mut.rs

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

kernel/time/hrtimer/
pin_mut.rs
