projects/linux·blob master · refs

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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}