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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="Emits a machine instruction to signal the processor that it is running in a busy-wait spin-loop (“spin lock”)."><title>spin_loop in portable_atomic::hint - Rust</title><script>if(window.location.protocol!=="file:")document.head.insertAdjacentHTML("beforeend","SourceSerif4-Regular-46f98efaafac5295.ttf.woff2,FiraSans-Regular-018c141bf0843ffd.woff2,FiraSans-Medium-8f9a781e4970d388.woff2,SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2,SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2".split(",").map(f=>`<link rel="preload" as="font" type="font/woff2" crossorigin href="../../static.files/${f}">`).join(""))</script><link rel="stylesheet" href="../../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../../static.files/rustdoc-492a78a4a87dcc01.css"><meta name="rustdoc-vars" data-root-path="../../" data-static-root-path="../../static.files/" data-current-crate="portable_atomic" data-themes="" data-resource-suffix="" data-rustdoc-version="1.82.0 (f6e511eec 2024-10-15)" data-channel="1.82.0" data-search-js="search-a99f1315e7cc5121.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../../static.files/storage-118b08c4c78b968e.js"></script><script defer src="sidebar-items.js"></script><script defer src="../../static.files/main-921df33f47b8780c.js"></script><noscript><link rel="stylesheet" href="../../static.files/noscript-3b12f09e550e0385.css"></noscript><link rel="alternate icon" type="image/png" href="../../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle" title="show sidebar"></button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../../portable_atomic/index.html">portable_<wbr>atomic</a><span class="version">1.9.0</span></h2></div><div class="sidebar-elems"><h2><a href="index.html">In portable_<wbr>atomic::<wbr>hint</a></h2></div></nav><div class="sidebar-resizer"></div><main><div class="width-limiter"><rustdoc-search></rustdoc-search><section id="main-content" class="content"><div class="main-heading"><h1>Function <a href="../index.html">portable_atomic</a>::<wbr><a href="index.html">hint</a>::<wbr><a class="fn" href="#">spin_loop</a><button id="copy-path" title="Copy item path to clipboard">Copy item path</button></h1><span class="out-of-band"><a class="src" href="../../src/portable_atomic/lib.rs.html#513-516">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>&#x2212;</span>]</button></span></div><pre class="rust item-decl"><code>pub fn spin_loop()</code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Emits a machine instruction to signal the processor that it is running in
a busy-wait spin-loop (“spin lock”).</p>
<p>Upon receiving the spin-loop signal the processor can optimize its behavior by,
for example, saving power or switching hyper-threads.</p>
<p>This function is different from <a href="https://doc.rust-lang.org/std/thread/fn.yield_now.html"><code>thread::yield_now</code></a> which directly
yields to the systems scheduler, whereas <code>spin_loop</code> does not interact
with the operating system.</p>
<p>A common use case for <code>spin_loop</code> is implementing bounded optimistic
spinning in a CAS loop in synchronization primitives. To avoid problems
like priority inversion, it is strongly recommended that the spin loop is
terminated after a finite amount of iterations and an appropriate blocking
syscall is made.</p>
<p><strong>Note:</strong> On platforms that do not support receiving spin-loop hints this
function does not do anything at all.</p>
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