Commit 768dfbfc authored by FUJITA Tomonori's avatar FUJITA Tomonori Committed by Andreas Hindborg
Browse files

rust: time: Make Instant generic over ClockSource 



Refactor the Instant type to be generic over a ClockSource type
parameter, enabling static enforcement of clock correctness across
APIs that deal with time. Previously, the clock source was implicitly
fixed (typically CLOCK_MONOTONIC), and developers had to ensure
compatibility manually.

This design eliminates runtime mismatches between clock sources, and
enables stronger type-level guarantees throughout the timer subsystem.

Reviewed-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarFUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://lore.kernel.org/r/20250610093258.3435874-3-fujita.tomonori@gmail.com


Signed-off-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
parent 1664a671

rust/kernel/time.rs

+17 −5
Original line number Diff line number Diff line
@@ -24,6 +24,8 @@ 
//! C header: [`include/linux/jiffies.h`](srctree/include/linux/jiffies.h).

//! C header: [`include/linux/ktime.h`](srctree/include/linux/ktime.h).



use core::marker::PhantomData;



pub mod hrtimer;



/// The number of nanoseconds per microsecond.
@@ -136,12 +138,21 @@ impl ClockSource for Tai { 
///

/// The `inner` value is in the range from 0 to `KTIME_MAX`.

#[repr(transparent)]

#[derive(Copy, Clone, PartialEq, PartialOrd, Eq, Ord)]

pub struct Instant {

#[derive(PartialEq, PartialOrd, Eq, Ord)]

pub struct Instant<C: ClockSource> {

    inner: bindings::ktime_t,

    _c: PhantomData<C>,

}



impl<C: ClockSource> Clone for Instant<C> {

    fn clone(&self) -> Self {

        *self

    }

}



impl<C: ClockSource> Copy for Instant<C> {}



impl Instant {

impl<C: ClockSource> Instant<C> {

    /// Get the current time using `CLOCK_MONOTONIC`.

    #[inline]

    pub fn now() -> Self {
@@ -150,6 +161,7 @@ pub fn now() -> Self { 
        Self {

            // SAFETY: It is always safe to call `ktime_get()` outside of NMI context.

            inner: unsafe { bindings::ktime_get() },

            _c: PhantomData,

        }

    }
@@ -160,12 +172,12 @@ pub fn elapsed(&self) -> Delta { 
    }

}



impl core::ops::Sub for Instant {

impl<C: ClockSource> core::ops::Sub for Instant<C> {

    type Output = Delta;



    // By the type invariant, it never overflows.

    #[inline]

    fn sub(self, other: Instant) -> Delta {

    fn sub(self, other: Instant<C>) -> Delta {

        Delta {

            nanos: self.inner - other.inner,

        }