30 lines
13 KiB
Plaintext
30 lines
13 KiB
Plaintext
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rust
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æ3 #rustc 1.93.0 (254b59607 2026-01-19)Á³VOÐêùÿ²?ÑL¼�§Ì± -a7a40eb546f9e2b0Á ë&Gf·Ã ¬ëñq:¤»b -bb76018b1173caf6Á‰ b\§ ¶<ô portable-atomicÁŒþ Üô ³ AtomicWakerÁ � wakerÁ WAITINGÁ REGISTERINGÁ WAKINGÁ •
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AssertSyncÁ registerÁ wakeÁ takeÁ > Í
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ü §� ü > ; `futures::task::AtomicWaker` extracted into its own crate.Á ? Ë tC # FeaturesÁ R Ë üVG D This crate adds a feature, `portable-atomic`, which uses a polyfillÁ üžH E from the [`portable-atomic`] crate in order to provide functionalityÁ üçN K to targets without atomics. See the [`README`] for the [`portable-atomic`]Á ü¶0 - crate for more information on how to use it.Á ç Ë üëA > [`portable-atomic`]: https://crates.io/crates/portable-atomicÁ ü[ X [`README`]: https://github.com/taiki-e/portable-atomic/blob/main/README.md#optional-cfgÁ¡ ˜ › ˜ 8µ „¡ ² 7 ahttps://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.pngÁ ü´c ü•… ¡ ž ¡ › 8¶ l§ µ 7Ü ü·c ü›‚ ³ ¨ Ç. Í Á] F
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………´£ •L¿ ¨üÎ8 ººŸ¢~�ŒŒ `üÍ V´Ù üµ0 - A synchronization primitive for task wakeup.Á æ Ë üêI F Sometimes the task interested in a given event will change over time.Á ü´ N K An `AtomicWaker` can coordinate concurrent notifications with the consumerÁ üƒ
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L I potentially "updating" the underlying task to wake up. This is useful inÁ üÐ
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J G scenarios where a computation completes in another thread and wants toÁ ü› P M notify the consumer, but the consumer is in the process of being migrated toÁ ¼ì a new logical task.Á „ Ë üˆ P M Consumers should call `register` before checking the result of a computationÁ üÙ J G and producers should call `wake` after producing the computation (thisÁ ü¤
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L I differs from the usual `thread::park` pattern). It is also permitted forÁ üñ
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G D `wake` to be called **before** `register`. This results in a no-op.Á ¹ Ë ü½Q N A single `AtomicWaker` may be reused for any number of calls to `register` orÁ \� `wake`.Á › Ë ¬Ÿ # Memory orderingÁ µ Ë ü¹J G Calling `register` "acquires" all memory "released" by calls to `wake`Á ü„G D before the call to `register`. Later calls to `wake` will wake theÁ üÌP M registered waker (on contention this wake might be triggered in `register`).Á � Ë ü¡O L For concurrent calls to `register` (should be avoided) the ordering is onlyÁ üñ$ ! guaranteed for the winning call.Á – Ë tš # ExamplesÁ © Ë üN K Here is a simple example providing a `Flag` that can be signalled manuallyÁ ¬ü when it is ready.Á ’ Ë <– ```Á üž use futures::future::Future;Á ü¿4 1 use futures::task::{Context, Poll, AtomicWaker};Á ¼ô use std::sync::Arc;Á üŒ& # use std::sync::atomic::AtomicBool;Á ü³- * use std::sync::atomic::Ordering::Relaxed;Á ´á use std::pin::Pin;Á ø Ë ”ü struct Inner {Á Ü� waker: AtomicWaker,Á Ä« set: AtomicBool,Á ,Ä }Á Ê Ë ¤Î #[derive(Clone)]Á äã struct Flag(Arc<Inner>);Á € Ë |„ impl Flag {Á ô” pub fn new() -> Self {Á ü³! Flag(Arc::new(Inner {Á üÕ* ' waker: AtomicWaker::new(),Á ü€, ) set: AtomicBool::new(false),Á | }))Á L½ }Á Ç Ë ôË pub fn signal(&self) {Á üê, ) self.0.set.store(true, Relaxed);Á ü— self.0.waker.wake();Á L¸ º% , ñ" È Ë ÔÌ impl Future for Flag {Á Ìç type Output = ();Á � Ë ü…I F fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {Á üÏA > // quick check to avoid registration if already done.Á ü‘) & if self.0.set.load(Relaxed) {Á ü»' $ return Poll::Ready(());Á lã
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}Á ñ Ë üõ. + self.0.waker.register(cx.waker());Á ¤ Ë ü¨K H // Need to check condition **after** `register` to avoid a raceÁ üôA > // condition that would result in lost notifications.Á ü¶ ) æ( üà Poll::Ready(())Á ¤€ } else {Á ì• Poll::PendingÁ l³ Ç) LÁ º% ,Ë ñ" <Ñ ò \ä ï ÑãWÑŠL�
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”ö ,ö èüŽ ,Ž ž ¤ƒC <‰C �ÄåC \ëC �œÖD 4ÜD �„óD ï Ô«E äŠE Create an `AtomicWaker`.Á ¸E ï
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