| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/futures-util-0.3.28/src/stream/futures_unordered/ready_to_run_queue.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>ready_to_run_queue.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../../normalize.css"><link rel="stylesheet" href="../../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../../ayu.css" disabled><link rel="stylesheet" href="../../../../dark.css" disabled><link rel="stylesheet" href="../../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../../storage.js"></script><script defer src="../../../../source-script.js"></script><script defer src="../../../../source-files.js"></script><script defer src="../../../../main.js"></script><noscript><link rel="stylesheet" href="../../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../../futures_util/index.html"><div class="logo-container"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../../futures_util/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">crate</span>::task::AtomicWaker; |
| <span class="kw">use </span>alloc::sync::Arc; |
| <span class="kw">use </span>core::cell::UnsafeCell; |
| <span class="kw">use </span>core::ptr; |
| <span class="kw">use </span>core::sync::atomic::AtomicPtr; |
| <span class="kw">use </span>core::sync::atomic::Ordering::{AcqRel, Acquire, Relaxed, Release}; |
| |
| <span class="kw">use </span><span class="kw">super</span>::abort::abort; |
| <span class="kw">use </span><span class="kw">super</span>::task::Task; |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">enum </span>Dequeue<Fut> { |
| Data(<span class="kw-2">*const </span>Task<Fut>), |
| Empty, |
| Inconsistent, |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">struct </span>ReadyToRunQueue<Fut> { |
| <span class="comment">// The waker of the task using `FuturesUnordered`. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) waker: AtomicWaker, |
| |
| <span class="comment">// Head/tail of the readiness queue |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) head: AtomicPtr<Task<Fut>>, |
| <span class="kw">pub</span>(<span class="kw">super</span>) tail: UnsafeCell<<span class="kw-2">*const </span>Task<Fut>>, |
| <span class="kw">pub</span>(<span class="kw">super</span>) stub: Arc<Task<Fut>>, |
| } |
| |
| <span class="doccomment">/// An MPSC queue into which the tasks containing the futures are inserted |
| /// whenever the future inside is scheduled for polling. |
| </span><span class="kw">impl</span><Fut> ReadyToRunQueue<Fut> { |
| <span class="doccomment">/// The enqueue function from the 1024cores intrusive MPSC queue algorithm. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>enqueue(<span class="kw-2">&</span><span class="self">self</span>, task: <span class="kw-2">*const </span>Task<Fut>) { |
| <span class="kw">unsafe </span>{ |
| <span class="macro">debug_assert!</span>((<span class="kw-2">*</span>task).queued.load(Relaxed)); |
| |
| <span class="comment">// This action does not require any coordination |
| </span>(<span class="kw-2">*</span>task).next_ready_to_run.store(ptr::null_mut(), Relaxed); |
| |
| <span class="comment">// Note that these atomic orderings come from 1024cores |
| </span><span class="kw">let </span>task = task <span class="kw">as </span><span class="kw-2">*mut </span><span class="kw">_</span>; |
| <span class="kw">let </span>prev = <span class="self">self</span>.head.swap(task, AcqRel); |
| (<span class="kw-2">*</span>prev).next_ready_to_run.store(task, Release); |
| } |
| } |
| |
| <span class="doccomment">/// The dequeue function from the 1024cores intrusive MPSC queue algorithm |
| /// |
| /// Note that this is unsafe as it required mutual exclusion (only one |
| /// thread can call this) to be guaranteed elsewhere. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">unsafe fn </span>dequeue(<span class="kw-2">&</span><span class="self">self</span>) -> Dequeue<Fut> { |
| <span class="kw">let </span><span class="kw-2">mut </span>tail = <span class="kw-2">*</span><span class="self">self</span>.tail.get(); |
| <span class="kw">let </span><span class="kw-2">mut </span>next = (<span class="kw-2">*</span>tail).next_ready_to_run.load(Acquire); |
| |
| <span class="kw">if </span>tail == <span class="self">self</span>.stub() { |
| <span class="kw">if </span>next.is_null() { |
| <span class="kw">return </span>Dequeue::Empty; |
| } |
| |
| <span class="kw-2">*</span><span class="self">self</span>.tail.get() = next; |
| tail = next; |
| next = (<span class="kw-2">*</span>next).next_ready_to_run.load(Acquire); |
| } |
| |
| <span class="kw">if </span>!next.is_null() { |
| <span class="kw-2">*</span><span class="self">self</span>.tail.get() = next; |
| <span class="macro">debug_assert!</span>(tail != <span class="self">self</span>.stub()); |
| <span class="kw">return </span>Dequeue::Data(tail); |
| } |
| |
| <span class="kw">if </span><span class="self">self</span>.head.load(Acquire) <span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_ </span>!= tail { |
| <span class="kw">return </span>Dequeue::Inconsistent; |
| } |
| |
| <span class="self">self</span>.enqueue(<span class="self">self</span>.stub()); |
| |
| next = (<span class="kw-2">*</span>tail).next_ready_to_run.load(Acquire); |
| |
| <span class="kw">if </span>!next.is_null() { |
| <span class="kw-2">*</span><span class="self">self</span>.tail.get() = next; |
| <span class="kw">return </span>Dequeue::Data(tail); |
| } |
| |
| Dequeue::Inconsistent |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">super</span>) <span class="kw">fn </span>stub(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">*const </span>Task<Fut> { |
| Arc::as_ptr(<span class="kw-2">&</span><span class="self">self</span>.stub) |
| } |
| |
| <span class="comment">// Clear the queue of tasks. |
| // |
| // Note that each task has a strong reference count associated with it |
| // which is owned by the ready to run queue. This method just pulls out |
| // tasks and drops their refcounts. |
| // |
| // # Safety |
| // |
| // - All tasks **must** have had their futures dropped already (by FuturesUnordered::clear) |
| // - The caller **must** guarantee unique access to `self` |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">unsafe fn </span>clear(<span class="kw-2">&</span><span class="self">self</span>) { |
| <span class="kw">loop </span>{ |
| <span class="comment">// SAFETY: We have the guarantee of mutual exclusion required by `dequeue`. |
| </span><span class="kw">match </span><span class="self">self</span>.dequeue() { |
| Dequeue::Empty => <span class="kw">break</span>, |
| Dequeue::Inconsistent => abort(<span class="string">"inconsistent in drop"</span>), |
| Dequeue::Data(ptr) => drop(Arc::from_raw(ptr)), |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><Fut> Drop <span class="kw">for </span>ReadyToRunQueue<Fut> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="comment">// Once we're in the destructor for `Inner<Fut>` we need to clear out |
| // the ready to run queue of tasks if there's anything left in there. |
| |
| // All tasks have had their futures dropped already by the `FuturesUnordered` |
| // destructor above, and we have &mut self, so this is safe. |
| </span><span class="kw">unsafe </span>{ |
| <span class="self">self</span>.clear(); |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="futures_util" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
