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Add a spin loop hint for Arc::downgrade

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This commit is contained in:
Nicolas Nattis 2020-09-12 13:53:30 -03:00
parent 07a63e6d1f
commit 929f80ece9
2 changed files with 3 additions and 0 deletions
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1
library/alloc/src/lib.rs
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@ -118,6 +118,7 @@
#![feature(raw_ref_op)] #![feature(raw_ref_op)]
#![feature(rustc_attrs)] #![feature(rustc_attrs)]
#![feature(receiver_trait)] #![feature(receiver_trait)]
#![feature(renamed_spin_loop)]
#![feature(min_specialization)] #![feature(min_specialization)]
#![feature(slice_ptr_get)] #![feature(slice_ptr_get)]
#![feature(slice_ptr_len)] #![feature(slice_ptr_len)]

2
library/alloc/src/sync.rs
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@ -10,6 +10,7 @@ use core::cmp::Ordering;
use core::convert::{From, TryFrom}; use core::convert::{From, TryFrom};
use core::fmt; use core::fmt;
use core::hash::{Hash, Hasher}; use core::hash::{Hash, Hasher};
use core::hint;
use core::intrinsics::abort; use core::intrinsics::abort;
use core::iter; use core::iter;
use core::marker::{PhantomData, Unpin, Unsize}; use core::marker::{PhantomData, Unpin, Unsize};
@ -764,6 +765,7 @@ impl<T: ?Sized> Arc<T> {
loop { loop {
// check if the weak counter is currently "locked"; if so, spin. // check if the weak counter is currently "locked"; if so, spin.
if cur == usize::MAX { if cur == usize::MAX {
hint::spin_loop();
cur = this.inner().weak.load(Relaxed); cur = this.inner().weak.load(Relaxed);
continue; continue;
} }