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27 lines
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<!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="Yields execution back to the Tokio runtime."><meta name="keywords" content="rust, rustlang, rust-lang, yield_now"><title>yield_now in tokio::task - Rust</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" type="text/css" href="../../normalize.css"><link rel="stylesheet" type="text/css" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../ayu.css" disabled><link rel="stylesheet" type="text/css" href="../../dark.css" disabled><link rel="stylesheet" type="text/css" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script src="../../crates.js"></script><script defer src="../../main.js"></script>
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</a><div class="sidebar-elems"><h2 class="location">Other items in<br><a href="../index.html">tokio</a>::<wbr><a href="index.html">task</a></h2><div id="sidebar-vars" data-name="yield_now" data-ty="fn" data-relpath=""></div><script defer src="sidebar-items.js"></script></div></nav><main><div class="width-limiter"><div class="sub-container"><a class="sub-logo-container" href="../../tokio/index.html"><img class="rust-logo" src="../../rust-logo.png" alt="logo"></a><nav class="sub"><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!" aria-haspopup="menu" title="themes"><img width="18" height="18" alt="Pick another theme!" src="../../brush.svg"></button><div id="theme-choices" role="menu"></div></div><form class="search-form"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><button type="button" id="help-button" title="help">?</button><a id="settings-menu" href="../../settings.html" title="settings"><img width="18" height="18" alt="Change settings" src="../../wheel.svg"></a></div></form></nav></div><section id="main-content" class="content"><h1 class="fqn"><span class="in-band">Function <a href="../index.html">tokio</a>::<wbr><a href="index.html">task</a>::<wbr><a class="fn" href="#">yield_now</a><button id="copy-path" onclick="copy_path(this)" title="Copy item path to clipboard"><img src="../../clipboard.svg" width="19" height="18" alt="Copy item path"></button></span><span class="out-of-band"><span id="render-detail"><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class="inner">−</span>]</a></span><a class="srclink" href="../../src/tokio/task/yield_now.rs.html#37-58" title="goto source code">[src]</a></span></h1><div class="docblock item-decl"><pre class="rust fn"><code>pub async fn yield_now()</code></pre></div><details class="rustdoc-toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Yields execution back to the Tokio runtime.</p>
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<p>A task yields by awaiting on <code>yield_now()</code>, and may resume when that future
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completes (with no output.) The current task will be re-added as a pending
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task at the <em>back</em> of the pending queue. Any other pending tasks will be
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scheduled. No other waking is required for the task to continue.</p>
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<p>See also the usage example in the <a href="index.html#yield_now">task module</a>.</p>
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<h3 id="non-guarantees" class="section-header"><a href="#non-guarantees">Non-guarantees</a></h3>
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<p>This function may not yield all the way up to the executor if there are any
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special combinators above it in the call stack. For example, if a
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<a href="../macro.select.html"><code>tokio::select!</code></a> has another branch complete during the same poll as the
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<code>yield_now()</code>, then the yield is not propagated all the way up to the
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runtime.</p>
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<p>It is generally not guaranteed that the runtime behaves like you expect it
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to when deciding which task to schedule next after a call to <code>yield_now()</code>.
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In particular, the runtime may choose to poll the task that just ran
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<code>yield_now()</code> again immediately without polling any other tasks first. For
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example, the runtime will not drive the IO driver between every poll of a
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task, and this could result in the runtime polling the current task again
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immediately even if there is another task that could make progress if that
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other task is waiting for a notification from the IO driver.</p>
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<p>In general, changes to the order in which the runtime polls tasks is not
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considered a breaking change, and your program should be correct no matter
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which order the runtime polls your tasks in.</p>
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