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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="Acquire a critical section in the current thread."><title>acquire in critical_section - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Bold-a2c9cd1067f8b328.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-fa3bb1812debf86c.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="critical_section" data-themes="" data-resource-suffix="" data-rustdoc-version="1.75.0-nightly (2bbb61989 2023-10-04)" data-channel="nightly" data-search-js="search-8be46b629f5f14a8.js" data-settings-js="settings-74424d7eec62a23e.js" ><script src="../static.files/storage-fec3eaa3851e447d.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-c5bd66d33317d69f.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-5d8b3c7633ad77ba.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><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">☰</button><a class="logo-container" href="../critical_section/index.html"><img class="rust-logo" src="../static.files/rust-logo-151179464ae7ed46.svg" alt="logo"></a></nav><nav class="sidebar"><a class="logo-container" href="../critical_section/index.html"><img class="rust-logo" src="../static.files/rust-logo-151179464ae7ed46.svg" alt="logo"></a><div class="sidebar-elems"><h2><a href="index.html">In critical_section</a></h2></div></nav><main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><input class="search-input" name="search" aria-label="Run search in the documentation" 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="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Function <a href="index.html">critical_section</a>::<wbr><a class="fn" href="#">acquire</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/critical_section/lib.rs.html#177-184">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><code>pub unsafe fn acquire() -> <a class="struct" href="struct.RestoreState.html" title="struct critical_section::RestoreState">RestoreState</a></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Acquire a critical section in the current thread.</p>
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<p>This function is extremely low level. Strongly prefer using <a href="fn.with.html" title="fn critical_section::with"><code>with</code></a> instead.</p>
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<p>Nesting critical sections is allowed. The inner critical sections
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are mostly no-ops since they’re already protected by the outer one.</p>
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<h2 id="safety"><a href="#safety">Safety</a></h2>
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<ul>
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<li>Each <code>acquire</code> call must be paired with exactly one <code>release</code> call in the same thread.</li>
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<li><code>acquire</code> returns a “restore state” that you must pass to the corresponding <code>release</code> call.</li>
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<li><code>acquire</code>/<code>release</code> pairs must be “properly nested”, ie it’s not OK to do <code>a=acquire(); b=acquire(); release(a); release(b);</code>.</li>
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<li>It is UB to call <code>release</code> if the critical section is not acquired in the current thread.</li>
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<li>It is UB to call <code>release</code> with a “restore state” that does not come from the corresponding <code>acquire</code> call.</li>
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<li>It must provide ordering guarantees at least equivalent to a [<code>core::sync::atomic::Ordering::Acquire</code>]
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on a memory location shared by all critical sections, on which the <code>release</code> call will do a
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[<code>core::sync::atomic::Ordering::Release</code>] operation.</li>
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</ul>
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</div></details></section></div></main></body></html> |