26 lines
14 KiB
Plaintext
26 lines
14 KiB
Plaintext
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rust
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5 #rustc 1.96.0 (ac68faa20 2026-05-25)ÁíàÄTËŸ ÜJîÄ)'ß\¥! -3d1337db07d0b3aeÁ ¤°ð ¾ä-±($²ï=©Ã -7e98a21bfd32b0edÁ‰ AtomicUsizeÁ\§ » portable-atomicÁÜô í AtomicWakerÁ º wakerÁ WAITINGÁ REGISTERINGÁ WAKINGÁ æ
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AssertSyncÁ registerÁ wakeÁ takeÁ > ×
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ã�ã� WakerÁ ä�ƒ¸� È
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õ0ۼݼ޼© ß¼ à¼ÛἈ cSñŸ«‡zÙ¿ ‚ “ ¢G ü¿Fo G ´G ü«E‰ ý $ÁE ¤]¤] V ¦]Á‚] üß3ø¤”&‘ _ î0î0
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UnsafeCellÁ ð0»Ì- ·}—KEüC£Ä d Ä d ¢� ‘ í ¸T¯ î0 × Å ` F4í ÃÀ F ÄÀ G<õ ÁÀ G ÂÀ Ì<þ ¿À Ì ÀÀ Ë,˜ ã� Š\á „Ä
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ü §� ü > ; `futures::task::AtomicWaker` extracted into its own crate.Á ? ú tC # FeaturesÁ R ú 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 ú 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 ahttps://raw.githubusercontent.com/smol-rs/smol/master/assets/images/logo_fullsize_transparent.pngÁ„¡ Þl§ íÈ ¸É î0 ×È ` FÇ ÃÀ FÙ ÄÀ GÇ ÁÀ GÙ ÂÀ ÌÇ ¿À ÌÚ ÀÀ ËÇ ã� ŠÆ „Ä
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”––´£ ‘L¿ …äÎ z}Z]9<ŒŒ üÍ ´Ù üµ0 - A synchronization primitive for task wakeup.Á æ ú 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 „ ú 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 ú ü½Q N A single `AtomicWaker` may be reused for any number of calls to `register` orÁ \� `wake`.Á › ú ¬Ÿ # Memory orderingÁ µ ú 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 � ú ü¡O L For concurrent calls to `register` (should be avoided) the ordering is onlyÁ üñ$ ! guaranteed for the winning call.Á – ú tš # ExamplesÁ © ú üN K Here is a simple example providing a `Flag` that can be signalled manuallyÁ ¬ü when it is ready.Á ’ ú <– ```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 ú ”ü struct Inner {Á Ü� waker: AtomicWaker,Á Ä« set: AtomicBool,Á ,Ä }Á Ê ú ¤Î #[derive(Clone)]Á äã struct Flag(Arc<Inner>);Á € ú |„ 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 ú ôË pub fn signal(&self) {Á üê, ) self.0.set.store(true, Relaxed);Á ü— self.0.waker.wake();Á L¸ ¼% , è" È ú ÔÌ impl Future for Flag {Á Ìç type Output = ();Á � ú 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 ú üõ. + self.0.waker.register(cx.waker());Á ¤ ú ü¨K H // Need to check condition **after** `register` to avoid a raceÁ üôA > // condition that would result in lost notifications.Á ü¶ ) õ( üà Poll::Ready(())Á ¤€ } else {Á ì• Poll::PendingÁ l³ Ø) LÁ ¼% ,Ë è" <Ñ Þ \ä ý ³ª2G“*
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”ö ,ö ùüŽ ,Ž ® ¤ƒC <‰C ‘ÄåC \ëC ‘œÖD 4ÜD ‘„óD ý Ô«E äŠE Create an `AtomicWaker`.Á ¸E ý
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´÷E TýE Îì Ì÷E � 0 $‰F ¥0% ·0 ¥0/ ·0% Ì™F ¿ ü©W% üºG: 7 Registers the waker to be notified on calls to `wake`.Á ùG ú ü�HK H The new task will take place of any previous tasks that were registeredÁ üÑHJ G by previous calls to `register`. Any calls to `wake` that happen afterÁ ü IH E a call to `register` (as defined by the memory ordering rules), willÁ üíIL I notify the `register` caller's task and deregister the waker from futureÁ ü¾JI F notifications. Because of this, callers should ensure `register` getsÁ üŒKC @ invoked with a new `Waker` **each** time they require a wakeup.Á ÔK ú üÜKJ G It is safe to call `register` with multiple other threads concurrentlyÁ ü«LG D calling `wake`. This will result in the `register` caller's currentÁ ì÷L task being notified once.Á ™M ú ü¡MK H This function is safe to call concurrently, but this is generally a badÁ üñMK H idea. Concurrent calls to `register` will attempt to register differentÁ üÁNL I tasks to be notified. One of the callers will win and have its task set,Á ü’O> ; but there is no guarantee as to which caller will succeed.Á ÕO ú tÝO ¹ ðO ú üøO< 9 Here is how `register` is used when implementing a flag.Á ¹P ú <ÁP Þ üÍP ï üòP4 ™ ü«Q& ÷ üÖQ- §! ´ˆR Ý! £R ú Œ«R struct Flag {Á ÜÁR £" ÄáR Ç" ,þR è" ˆS ú Ô�S …' ̯S ¨' ÍS ú üÕSI ×' ü£TK H // Register **before** checking `set` to avoid a race conditionÁ üóT7 4 // that would result in lost notifications.Á ü¯U, ) self.waker.register(cx.waker());Á àU ú üèU' $ if self.set.load(Relaxed) {Á ü”V ì+ ¤¸V ”, ìÑV ±, lóV Ø) L…W ¼% ,“W è" <�W Þ D°W ý ¿ ¹W
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