kernel/time/hrtimer/
tbox.rs

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::prelude::*;
11use core::ptr::NonNull;
12
13/// A handle for a [`Box<HasHrTimer<T>>`] returned by a call to
14/// [`HrTimerPointer::start`].
15///
16/// # Invariants
17///
18/// - `self.inner` comes from a `Box::into_raw` call.
19pub struct BoxHrTimerHandle<T, A>
20where
21    T: HasHrTimer<T>,
22    A: crate::alloc::Allocator,
23{
24    pub(crate) inner: NonNull<T>,
25    _p: core::marker::PhantomData<A>,
26}
27
28// SAFETY: We implement drop below, and we cancel the timer in the drop
29// implementation.
30unsafe impl<T, A> HrTimerHandle for BoxHrTimerHandle<T, A>
31where
32    T: HasHrTimer<T>,
33    A: crate::alloc::Allocator,
34{
35    fn cancel(&mut self) -> bool {
36        // SAFETY: As we obtained `self.inner` from a valid reference when we
37        // created `self`, it must point to a valid `T`.
38        let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self.inner.as_ptr()) };
39
40        // SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr`
41        // must point to a valid `HrTimer` instance.
42        unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
43    }
44}
45
46impl<T, A> Drop for BoxHrTimerHandle<T, A>
47where
48    T: HasHrTimer<T>,
49    A: crate::alloc::Allocator,
50{
51    fn drop(&mut self) {
52        self.cancel();
53        // SAFETY: By type invariant, `self.inner` came from a `Box::into_raw`
54        // call.
55        drop(unsafe { Box::<T, A>::from_raw(self.inner.as_ptr()) })
56    }
57}
58
59impl<T, A> HrTimerPointer for Pin<Box<T, A>>
60where
61    T: 'static,
62    T: Send + Sync,
63    T: HasHrTimer<T>,
64    T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
65    A: crate::alloc::Allocator,
66{
67    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
68    type TimerHandle = BoxHrTimerHandle<T, A>;
69
70    fn start(
71        self,
72        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
73    ) -> Self::TimerHandle {
74        // SAFETY:
75        //  - We will not move out of this box during timer callback (we pass an
76        //    immutable reference to the callback).
77        //  - `Box::into_raw` is guaranteed to return a valid pointer.
78        let inner =
79            unsafe { NonNull::new_unchecked(Box::into_raw(Pin::into_inner_unchecked(self))) };
80
81        // SAFETY:
82        //  - We keep `self` alive by wrapping it in a handle below.
83        //  - Since we generate the pointer passed to `start` from a valid
84        //    reference, it is a valid pointer.
85        unsafe { T::start(inner.as_ptr(), expires) };
86
87        // INVARIANT: `inner` came from `Box::into_raw` above.
88        BoxHrTimerHandle {
89            inner,
90            _p: core::marker::PhantomData,
91        }
92    }
93}
94
95impl<T, A> RawHrTimerCallback for Pin<Box<T, A>>
96where
97    T: 'static,
98    T: HasHrTimer<T>,
99    T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
100    A: crate::alloc::Allocator,
101{
102    type CallbackTarget<'a> = Pin<&'a mut T>;
103
104    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
105        // `HrTimer` is `repr(C)`
106        let timer_ptr = ptr.cast::<super::HrTimer<T>>();
107
108        // SAFETY: By C API contract `ptr` is the pointer we passed when
109        // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`.
110        let data_ptr = unsafe { T::timer_container_of(timer_ptr) };
111
112        // SAFETY:
113        //  - As per the safety requirements of the trait `HrTimerHandle`, the
114        //   `BoxHrTimerHandle` associated with this timer is guaranteed to
115        //   be alive until this method returns. That handle owns the `T`
116        //   behind `data_ptr` thus guaranteeing the validity of
117        //   the reference created below.
118        // - As `data_ptr` comes from a `Pin<Box<T>>`, only pinned references to
119        //   `data_ptr` exist.
120        let data_mut_ref = unsafe { Pin::new_unchecked(&mut *data_ptr) };
121
122        T::run(data_mut_ref).into_c()
123    }
124}
kernel/time/hrtimer/tbox.rs

kernel/time/hrtimer/
tbox.rs
