projects/linux·blob master · refs

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1// SPDX-License-Identifier: GPL-2.0
2
3use super::{
4 HasHrTimer, HrTimer, HrTimerCallback, HrTimerCallbackContext, HrTimerHandle, HrTimerMode,
5 RawHrTimerCallback, UnsafeHrTimerPointer,
6};
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 TimerMode = <T as HasHrTimer<T>>::TimerMode;
56 type TimerHandle = PinMutHrTimerHandle<'a, T>;
57
58 unsafe fn start(
59 mut self,
60 expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
61 ) -> Self::TimerHandle {
62 // SAFETY:
63 // - We promise not to move out of `self`. We only pass `self`
64 // back to the caller as a `Pin<&mut self>`.
65 // - The return value of `get_unchecked_mut` is guaranteed not to be null.
66 let self_ptr = unsafe { NonNull::new_unchecked(self.as_mut().get_unchecked_mut()) };
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.as_ptr(), expires) };
73
74 PinMutHrTimerHandle {
75 inner: self_ptr,
76 _p: PhantomData,
77 }
78 }
79}
80
81impl<'a, T> RawHrTimerCallback for Pin<&'a mut T>
82where
83 T: HasHrTimer<T>,
84 T: HrTimerCallback<Pointer<'a> = Self>,
85{
86 type CallbackTarget<'b> = Self;
87
88 unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
89 // `HrTimer` is `repr(C)`
90 let timer_ptr = ptr.cast::<HrTimer<T>>();
91
92 // SAFETY: By the safety requirement of this function, `timer_ptr`
93 // points to a `HrTimer<T>` contained in an `T`.
94 let receiver_ptr = unsafe { T::timer_container_of(timer_ptr) };
95
96 // SAFETY:
97 // - By the safety requirement of this function, `timer_ptr`
98 // points to a `HrTimer<T>` contained in an `T`.
99 // - As per the safety requirements of the trait `HrTimerHandle`, the
100 // `PinMutHrTimerHandle` associated with this timer is guaranteed to
101 // be alive until this method returns. That handle borrows the `T`
102 // behind `receiver_ptr` mutably thus guaranteeing the validity of
103 // the reference created below.
104 let receiver_ref = unsafe { &mut *receiver_ptr };
105
106 // SAFETY: `receiver_ref` only exists as pinned, so it is safe to pin it
107 // here.
108 let receiver_pin = unsafe { Pin::new_unchecked(receiver_ref) };
109
110 // SAFETY:
111 // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
112 // it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
113 // - We are within `RawHrTimerCallback::run`
114 let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };
115
116 T::run(receiver_pin, context).into_c()
117 }
118}