1 // SPDX-License-Identifier: GPL-2.0 2 3 use super::HasHrTimer; 4 use super::HrTimer; 5 use super::HrTimerCallback; 6 use super::HrTimerCallbackContext; 7 use super::HrTimerHandle; 8 use super::HrTimerMode; 9 use super::HrTimerPointer; 10 use super::RawHrTimerCallback; 11 use crate::sync::Arc; 12 use crate::sync::ArcBorrow; 13 14 /// A handle for an `Arc<HasHrTimer<T>>` returned by a call to 15 /// [`HrTimerPointer::start`]. 16 pub struct ArcHrTimerHandle<T> 17 where 18 T: HasHrTimer<T>, 19 { 20 pub(crate) inner: Arc<T>, 21 } 22 23 // SAFETY: We implement drop below, and we cancel the timer in the drop 24 // implementation. 25 unsafe impl<T> HrTimerHandle for ArcHrTimerHandle<T> 26 where 27 T: HasHrTimer<T>, 28 { 29 fn cancel(&mut self) -> bool { 30 let self_ptr = Arc::as_ptr(&self.inner); 31 32 // SAFETY: As we obtained `self_ptr` from a valid reference above, it 33 // must point to a valid `T`. 34 let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self_ptr) }; 35 36 // SAFETY: As `timer_ptr` points into `T` and `T` is valid, `timer_ptr` 37 // must point to a valid `HrTimer` instance. 38 unsafe { HrTimer::<T>::raw_cancel(timer_ptr) } 39 } 40 } 41 42 impl<T> Drop for ArcHrTimerHandle<T> 43 where 44 T: HasHrTimer<T>, 45 { 46 fn drop(&mut self) { 47 self.cancel(); 48 } 49 } 50 51 impl<T> HrTimerPointer for Arc<T> 52 where 53 T: 'static, 54 T: Send + Sync, 55 T: HasHrTimer<T>, 56 T: for<'a> HrTimerCallback<Pointer<'a> = Self>, 57 { 58 type TimerMode = <T as HasHrTimer<T>>::TimerMode; 59 type TimerHandle = ArcHrTimerHandle<T>; 60 61 fn start( 62 self, 63 expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires, 64 ) -> ArcHrTimerHandle<T> { 65 // SAFETY: 66 // - We keep `self` alive by wrapping it in a handle below. 67 // - Since we generate the pointer passed to `start` from a valid 68 // reference, it is a valid pointer. 69 unsafe { T::start(Arc::as_ptr(&self), expires) }; 70 ArcHrTimerHandle { inner: self } 71 } 72 } 73 74 impl<T> RawHrTimerCallback for Arc<T> 75 where 76 T: 'static, 77 T: HasHrTimer<T>, 78 T: for<'a> HrTimerCallback<Pointer<'a> = Self>, 79 { 80 type CallbackTarget<'a> = ArcBorrow<'a, T>; 81 82 unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart { 83 // `HrTimer` is `repr(C)` 84 let timer_ptr = ptr.cast::<super::HrTimer<T>>(); 85 86 // SAFETY: By C API contract `ptr` is the pointer we passed when 87 // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`. 88 let data_ptr = unsafe { T::timer_container_of(timer_ptr) }; 89 90 // SAFETY: 91 // - `data_ptr` is derived form the pointer to the `T` that was used to 92 // queue the timer. 93 // - As per the safety requirements of the trait `HrTimerHandle`, the 94 // `ArcHrTimerHandle` associated with this timer is guaranteed to 95 // be alive until this method returns. That handle borrows the `T` 96 // behind `data_ptr` thus guaranteeing the validity of 97 // the `ArcBorrow` created below. 98 // - We own one refcount in the `ArcTimerHandle` associated with this 99 // timer, so it is not possible to get a `UniqueArc` to this 100 // allocation from other `Arc` clones. 101 let receiver = unsafe { ArcBorrow::from_raw(data_ptr) }; 102 103 // SAFETY: 104 // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so 105 // it is a valid pointer to a `HrTimer<T>` embedded in a `T`. 106 // - We are within `RawHrTimerCallback::run` 107 let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) }; 108 109 T::run(receiver, context).into_c() 110 } 111 } 112