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Add a spin loop hint for Arc::downgrade #76649

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merged 1 commit into from
Oct 24, 2020
Merged

Add a spin loop hint for Arc::downgrade #76649

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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 @@ -118,6 +118,7 @@
#![feature(raw_ref_op)]
#![feature(rustc_attrs)]
#![feature(receiver_trait)]
#![feature(renamed_spin_loop)]
#![feature(min_specialization)]
#![feature(slice_ptr_get)]
#![feature(slice_ptr_len)]
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2 changes: 2 additions & 0 deletions library/alloc/src/sync.rs
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Expand Up @@ -10,6 +10,7 @@ use core::cmp::Ordering;
use core::convert::{From, TryFrom};
use core::fmt;
use core::hash::{Hash, Hasher};
use core::hint;
use core::intrinsics::abort;
use core::iter;
use core::marker::{PhantomData, Unpin, Unsize};
Expand Down Expand Up @@ -764,6 +765,7 @@ impl<T: ?Sized> Arc<T> {
loop {
// check if the weak counter is currently "locked"; if so, spin.
if cur == usize::MAX {
hint::spin_loop();
cur = this.inner().weak.load(Relaxed);
continue;
}
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