124 lines
8.1 KiB
HTML
124 lines
8.1 KiB
HTML
<!DOCTYPE html>
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<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
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<head><meta http-equiv="x-ua-compatible" content="ie=edge">
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<title>thrd_yield</title>
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<link rel="stylesheet" href="ext.css" />
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<link rel="stylesheet" href="site_modules.css" />
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</head>
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<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-c_thread_thrd_yield skin-cppreference2 action-view cpp-navbar">
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<div id="cpp-content-base">
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<div id="content"><a id="top"></a>
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<h1 id="firstHeading" class="firstHeading">thrd_yield</h1>
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<div id="bodyContent">
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<div id="contentSub"><span class="subpages">< <a href="c.html">c</a>‎ | <a href="c-thread.html">thread</a></span></div>
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<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
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<table class="t-dcl-begin">
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<tbody>
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<tr class="t-dsc-header">
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<td>
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<div>定义于头文件 <code><threads.h></code></div>
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</td>
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<td></td>
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<td></td>
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</tr>
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<tr class="t-dcl t-since-c11">
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<div><span class="mw-geshi c source-c"><span class="kw4">void</span> thrd_yield<span class="br0">(</span><span class="kw4">void</span><span class="br0">)</span><span class="sy4">;</span></span></div>
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</td>
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<td class="t-dcl-nopad"></td>
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<td><span class="t-mark-rev t-since-c11">(C11 起)</span></td>
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</tr>
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<tr class="t-dcl-sep">
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<td></td>
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<td></td>
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<td></td>
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</tr>
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</tbody>
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</table>
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<p>向实现提供一个重新安排线程执行的提示，允许其他线程运行。</p>
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<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
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<p>（无）</p>
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<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
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<p>（无）</p>
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<h3><span class="mw-headline" id=".E6.B3.A8.E6.84.8F">注意</span></h3>
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<p>此函数的准确行为取决于实现，特别是使用中的 OS 编排机制和系统状态。例如，先进先出的实时调度器（ Linux 的<code>SCHED_FIFO</code> ）会悬停当前线程，并将它放在准备运行的同优先级线程队列尾部（而若无在同优先级的线程，则 <code>yield</code> 无效）。</p>
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<p>此函数的 POSIX 等价版本是 <a rel="nofollow" class="external text" href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/sched_yield.html">sched_yield</a> 。</p>
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<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
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<div class="t-example">
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<div class="t-example-live-link"></div>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="c source-c">
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<pre class="de1"><span class="co2">#include <stdio.h></span>
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<span class="co2">#include <time.h></span>
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<span class="co2">#include <threads.h></span>
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<span class="co1">// 工具函数：微秒单位的 timespec 差</span>
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<span class="kw4">double</span> usdiff<span class="br0">(</span><span class="kw1">struct</span> timespec s, <span class="kw1">struct</span> timespec e<span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw4">double</span> sdiff <span class="sy1">=</span> <a href="c-chrono-difftime.html"><span class="kw512">difftime</span></a><span class="br0">(</span>e.<span class="me1">tv_sec</span>, s.<span class="me1">tv_sec</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="kw4">long</span> nsdiff <span class="sy1">=</span> e.<span class="me1">tv_nsec</span> <span class="sy2">-</span> s.<span class="me1">tv_nsec</span><span class="sy4">;</span>
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<span class="kw1">if</span><span class="br0">(</span>nsdiff <span class="sy1"><</span> <span class="nu0">0</span><span class="br0">)</span> <span class="kw1">return</span> <span class="nu0">1000000</span><span class="sy2">*</span><span class="br0">(</span>sdiff<span class="sy2">-</span><span class="nu0">1</span><span class="br0">)</span> <span class="sy2">+</span> <span class="br0">(</span><span class="nu0">1000000000L</span><span class="sy2">+</span>nsdiff<span class="br0">)</span><span class="sy2">/</span><span class="nu16">1000.0</span><span class="sy4">;</span>
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<span class="kw1">else</span> <span class="kw1">return</span> <span class="nu0">1000000</span><span class="sy2">*</span><span class="br0">(</span>sdiff<span class="br0">)</span> <span class="sy2">+</span> nsdiff<span class="sy2">/</span><span class="nu16">1000.0</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="co1">// 在让出时等待</span>
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<span class="kw4">void</span> sleep_100us<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">struct</span> timespec start, end<span class="sy4">;</span>
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timespec_get<span class="br0">(</span><span class="sy3">&</span>start, TIME_UTC<span class="br0">)</span><span class="sy4">;</span>
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<span class="kw1">do</span> <span class="br0">{</span>
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thrd_yield<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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timespec_get<span class="br0">(</span><span class="sy3">&</span>end, TIME_UTC<span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span> <span class="kw1">while</span><span class="br0">(</span>usdiff<span class="br0">(</span>start, end<span class="br0">)</span> <span class="sy1"><</span> <span class="nu16">100.0</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span>
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<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
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<span class="br0">{</span>
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<span class="kw1">struct</span> timespec start, end<span class="sy4">;</span>
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timespec_get<span class="br0">(</span><span class="sy3">&</span>start, TIME_UTC<span class="br0">)</span><span class="sy4">;</span>
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sleep_100us<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
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timespec_get<span class="br0">(</span><span class="sy3">&</span>end, TIME_UTC<span class="br0">)</span><span class="sy4">;</span>
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<a href="c-io-fprintf.html"><span class="kw851">printf</span></a><span class="br0">(</span><span class="st0">"Waited for %.3f us<span class="es1">\n</span>"</span>, usdiff<span class="br0">(</span>start, end<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span>
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<span class="br0">}</span></pre></div>
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</div>
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<p>可能的输出：</p>
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<div dir="ltr" class="mw-geshi" style="text-align: left;">
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<div class="text source-text">
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<pre class="de1">Waited for 100.344 us</pre></div>
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</div>
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</div>
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<h3><span class="mw-headline" id=".E5.BC.95.E7.94.A8">引用</span></h3>
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<div class="t-ref-std-11">
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<ul>
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<li>C11 标准（ISO/IEC 9899:2011）：</li>
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</ul>
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<dl>
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<dd>
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<ul>
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<li>7.26.5.8 The thrd_yield function (p: 385)</li>
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</ul>
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</dd>
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</dl>
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</div>
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<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
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<table class="t-dsc-begin">
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<tr class="t-dsc">
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<td>
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<div class="t-dsc-member-div">
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<div><a href="c-thread-thrd_sleep.html"><span class="t-lines"><span>thrd_sleep</span></span></a></div>
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<div><span class="t-lines"><span><span class="t-mark-rev t-since-c11">(C11)</span></span></span></div>
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</div>
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</td>
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<td>在给定的时间段内暂停调用方线程的执行<br />
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<span class="t-mark">(函数)</span></td>
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</tr>
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</table>
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</div>
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<div class="visualClear"></div>
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</div>
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</div>
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</body>
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</html>
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