kernel/time/hrtimer/
tbox.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::HrTimerPointer;
10use super::RawHrTimerCallback;
11use crate::prelude::*;
12use core::ptr::NonNull;
13
14/// A handle for a [`Box<HasHrTimer<T>>`] returned by a call to
15/// [`HrTimerPointer::start`].
16///
17/// # Invariants
18///
19/// - `self.inner` comes from a `Box::into_raw` call.
20pub struct BoxHrTimerHandle<T, A>
21where
22    T: HasHrTimer<T>,
23    A: crate::alloc::Allocator,
24{
25    pub(crate) inner: NonNull<T>,
26    _p: core::marker::PhantomData<A>,
27}
28
29// SAFETY: We implement drop below, and we cancel the timer in the drop
30// implementation.
31unsafe impl<T, A> HrTimerHandle for BoxHrTimerHandle<T, A>
32where
33    T: HasHrTimer<T>,
34    A: crate::alloc::Allocator,
35{
36    fn cancel(&mut self) -> bool {
37        // SAFETY: As we obtained `self.inner` from a valid reference when we
38        // created `self`, it must point to a valid `T`.
39        let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self.inner.as_ptr()) };
40
41        // SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr`
42        // must point to a valid `HrTimer` instance.
43        unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
44    }
45}
46
47impl<T, A> Drop for BoxHrTimerHandle<T, A>
48where
49    T: HasHrTimer<T>,
50    A: crate::alloc::Allocator,
51{
52    fn drop(&mut self) {
53        self.cancel();
54        // SAFETY: By type invariant, `self.inner` came from a `Box::into_raw`
55        // call.
56        drop(unsafe { Box::<T, A>::from_raw(self.inner.as_ptr()) })
57    }
58}
59
60impl<T, A> HrTimerPointer for Pin<Box<T, A>>
61where
62    T: 'static,
63    T: Send + Sync,
64    T: HasHrTimer<T>,
65    T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
66    A: crate::alloc::Allocator,
67{
68    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
69    type TimerHandle = BoxHrTimerHandle<T, A>;
70
71    fn start(
72        self,
73        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
74    ) -> Self::TimerHandle {
75        // SAFETY:
76        //  - We will not move out of this box during timer callback (we pass an
77        //    immutable reference to the callback).
78        //  - `Box::into_raw` is guaranteed to return a valid pointer.
79        let inner =
80            unsafe { NonNull::new_unchecked(Box::into_raw(Pin::into_inner_unchecked(self))) };
81
82        // SAFETY:
83        //  - We keep `self` alive by wrapping it in a handle below.
84        //  - Since we generate the pointer passed to `start` from a valid
85        //    reference, it is a valid pointer.
86        unsafe { T::start(inner.as_ptr(), expires) };
87
88        // INVARIANT: `inner` came from `Box::into_raw` above.
89        BoxHrTimerHandle {
90            inner,
91            _p: core::marker::PhantomData,
92        }
93    }
94}
95
96impl<T, A> RawHrTimerCallback for Pin<Box<T, A>>
97where
98    T: 'static,
99    T: HasHrTimer<T>,
100    T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
101    A: crate::alloc::Allocator,
102{
103    type CallbackTarget<'a> = Pin<&'a mut T>;
104
105    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
106        // `HrTimer` is `repr(C)`
107        let timer_ptr = ptr.cast::<super::HrTimer<T>>();
108
109        // SAFETY: By C API contract `ptr` is the pointer we passed when
110        // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`.
111        let data_ptr = unsafe { T::timer_container_of(timer_ptr) };
112
113        // SAFETY:
114        //  - As per the safety requirements of the trait `HrTimerHandle`, the
115        //   `BoxHrTimerHandle` associated with this timer is guaranteed to
116        //   be alive until this method returns. That handle owns the `T`
117        //   behind `data_ptr` thus guaranteeing the validity of
118        //   the reference created below.
119        // - As `data_ptr` comes from a `Pin<Box<T>>`, only pinned references to
120        //   `data_ptr` exist.
121        let data_mut_ref = unsafe { Pin::new_unchecked(&mut *data_ptr) };
122
123        // SAFETY:
124        // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
125        //   it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
126        // - We are within `RawHrTimerCallback::run`
127        let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };
128
129        T::run(data_mut_ref, context).into_c()
130    }
131}
kernel/time/hrtimer/tbox.rs

kernel/time/hrtimer/
tbox.rs
