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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><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="critical_section" 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="../critical_section/index.html">critical_<wbr>section</a><span class="version">1.2.0</span></h2></div><div class="sidebar-elems"></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">critical_section</a>::<wbr><a class="fn" href="#">acquire</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/critical_section/lib.rs.html#196-203">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 class="doc-anchor" href="#safety">§</a>Safety</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 <a href="https://doc.rust-lang.org/1.82.0/core/sync/atomic/enum.Ordering.html#variant.Acquire" title="variant core::sync::atomic::Ordering::Acquire"><code>core::sync::atomic::Ordering::Acquire</code></a>
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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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<a href="https://doc.rust-lang.org/1.82.0/core/sync/atomic/enum.Ordering.html#variant.Release" title="variant core::sync::atomic::Ordering::Release"><code>core::sync::atomic::Ordering::Release</code></a> operation.</li>
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</ul>
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</div></details></section></div></main></body></html>
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