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Implement stable-wakers RFC #109706

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Implement stable-wakers RFC #109706

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a21854f
implement stable-wakers RFC
p-avital Mar 28, 2023
257e871
botched attribute macros earlier, fixed now
p-avital Mar 28, 2023
ffa028d
add stability annotations
p-avital Mar 29, 2023
47f3542
update safety comments
p-avital Mar 29, 2023
a7e8f91
missed a safety comment
p-avital Mar 29, 2023
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1 change: 1 addition & 0 deletions library/alloc/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,7 @@
#![feature(slice_ptr_get)]
#![feature(slice_ptr_len)]
#![feature(slice_range)]
#![feature(stable_wakers)]
#![feature(str_internals)]
#![feature(strict_provenance)]
#![feature(trusted_len)]
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24 changes: 18 additions & 6 deletions library/alloc/src/task.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,33 +121,45 @@ impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for RawWaker {
#[inline(always)]
fn raw_waker<W: Wake + Send + Sync + 'static>(waker: Arc<W>) -> RawWaker {
// Increment the reference count of the arc to clone it.
unsafe fn clone_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) -> RawWaker {
unsafe extern "C" fn clone_waker<W: Wake + Send + Sync + 'static>(
waker: *const (),
) -> RawWaker {
unsafe { Arc::increment_strong_count(waker as *const W) };
RawWaker::new(
waker as *const (),
&RawWakerVTable::new(clone_waker::<W>, wake::<W>, wake_by_ref::<W>, drop_waker::<W>),
&RawWakerVTable::new_with_c_abi(
clone_waker::<W>,
wake::<W>,
wake_by_ref::<W>,
drop_waker::<W>,
),
)
}

// Wake by value, moving the Arc into the Wake::wake function
unsafe fn wake<W: Wake + Send + Sync + 'static>(waker: *const ()) {
unsafe extern "C" fn wake<W: Wake + Send + Sync + 'static>(waker: *const ()) {
let waker = unsafe { Arc::from_raw(waker as *const W) };
<W as Wake>::wake(waker);
}

// Wake by reference, wrap the waker in ManuallyDrop to avoid dropping it
unsafe fn wake_by_ref<W: Wake + Send + Sync + 'static>(waker: *const ()) {
unsafe extern "C" fn wake_by_ref<W: Wake + Send + Sync + 'static>(waker: *const ()) {
let waker = unsafe { ManuallyDrop::new(Arc::from_raw(waker as *const W)) };
<W as Wake>::wake_by_ref(&waker);
}

// Decrement the reference count of the Arc on drop
unsafe fn drop_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) {
unsafe extern "C" fn drop_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) {
unsafe { Arc::decrement_strong_count(waker as *const W) };
}

RawWaker::new(
Arc::into_raw(waker) as *const (),
&RawWakerVTable::new(clone_waker::<W>, wake::<W>, wake_by_ref::<W>, drop_waker::<W>),
&RawWakerVTable::new_with_c_abi(
clone_waker::<W>,
wake::<W>,
wake_by_ref::<W>,
drop_waker::<W>,
),
)
}
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