rust/kernel/time/hrtimer/pin.rs

Source file repositories/reference/linux-study-clean/rust/kernel/time/hrtimer/pin.rs

File Facts

System
Linux kernel
Corpus path
rust/kernel/time/hrtimer/pin.rs
Extension
.rs
Size
3834 bytes
Lines
116
Domain
Rust Kernel Layer
Bucket
Rust API Membrane
Inferred role
Rust Kernel Layer: implementation source
Status
source implementation candidate

Why This File Exists

Rust-side wrappers and abstractions around kernel C APIs, ownership contracts, allocation, synchronization, and module integration.

Dependency Surface

Detected Declarations

Annotated Snippet

fn drop(&mut self) {
        self.cancel();
    }
}

// SAFETY: We capture the lifetime of `Self` when we create a `PinHrTimerHandle`,
// so `Self` will outlive the handle.
unsafe impl<'a, T> UnsafeHrTimerPointer for Pin<&'a T>
where
    T: Send + Sync,
    T: HasHrTimer<T>,
    T: HrTimerCallback<Pointer<'a> = Self>,
{
    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
    type TimerHandle = PinHrTimerHandle<'a, T>;

    unsafe fn start(
        self,
        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
    ) -> Self::TimerHandle {
        // Cast to pointer
        let self_ptr: *const T = self.get_ref();

        // SAFETY:
        //  - As we derive `self_ptr` from a reference above, it must point to a
        //    valid `T`.
        //  - We keep `self` alive by wrapping it in a handle below.
        unsafe { T::start(self_ptr, expires) };

        PinHrTimerHandle { inner: self }
    }
}

impl<'a, T> RawHrTimerCallback for Pin<&'a T>
where
    T: HasHrTimer<T>,
    T: HrTimerCallback<Pointer<'a> = Self>,
{
    type CallbackTarget<'b> = Self;

    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
        // `HrTimer` is `repr(C)`
        let timer_ptr = ptr.cast::<HrTimer<T>>();

        // SAFETY: By the safety requirement of this function, `timer_ptr`
        // points to a `HrTimer<T>` contained in an `T`.
        let receiver_ptr = unsafe { T::timer_container_of(timer_ptr) };

        // SAFETY:
        //  - By the safety requirement of this function, `timer_ptr`
        //    points to a `HrTimer<T>` contained in an `T`.
        //  - As per the safety requirements of the trait `HrTimerHandle`, the
        //    `PinHrTimerHandle` associated with this timer is guaranteed to
        //    be alive until this method returns. That handle borrows the `T`
        //    behind `receiver_ptr`, thus guaranteeing the validity of
        //    the reference created below.
        let receiver_ref = unsafe { &*receiver_ptr };

        // SAFETY: `receiver_ref` only exists as pinned, so it is safe to pin it
        // here.
        let receiver_pin = unsafe { Pin::new_unchecked(receiver_ref) };

        // SAFETY:
        // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
        //   it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
        // - We are within `RawHrTimerCallback::run`
        let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };

        T::run(receiver_pin, context).into_c()
    }
}

Annotation

Implementation Notes