206 lines
21 KiB
HTML
206 lines
21 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::condition_variable_any::wait_for</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_thread_condition_variable_any_wait_for skin-cppreference2 action-view cpp-page-template cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::condition_variable_any::</span>wait_for</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-thread.html">thread</a>‎ | <a href="cpp-thread-condition_variable_any.html">condition variable any</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<div class="t-page-template" style="">
|
|
<p></p>
|
|
</div>
|
|
<table class="t-dcl-begin">
|
|
<tbody>
|
|
<tr class="t-dcl t-since-cxx11">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Lock, <span class="kw1">class</span> Rep, <span class="kw1">class</span> Period <span class="sy1">></span><br /></span>
|
|
<p><a href="cpp-thread-cv_status.html"><span class="kw2176">std::<span class="me2">cv_status</span></span></a> wait_for<span class="br0">(</span> Lock<span class="sy3">&</span> lock,<br /></p>
|
|
<span class="kw4">const</span> <a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1"><</span>Rep, Period<span class="sy1">></span><span class="sy3">&</span> rel_time<span class="br0">)</span><span class="sy4">;</span></div>
|
|
</td>
|
|
<td>(1)</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx11">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Lock, <span class="kw1">class</span> Rep, <span class="kw1">class</span> Period, <span class="kw1">class</span> Predicate <span class="sy1">></span><br /></span>
|
|
<p><span class="kw4">bool</span> wait_for<span class="br0">(</span> Lock<span class="sy3">&</span> lock,<br />
|
|
<span class="kw4">const</span> <a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1"><</span>Rep, Period<span class="sy1">></span><span class="sy3">&</span> rel_time,<br /></p>
|
|
Predicate pred<span class="br0">)</span><span class="sy4">;</span></div>
|
|
</td>
|
|
<td>(2)</td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx20">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw1">template</span><span class="sy1"><</span> <span class="kw1">class</span> Lock, <span class="kw1">class</span> Rep, <span class="kw1">class</span> Period, <span class="kw1">class</span> Predicate <span class="sy1">></span><br /></span>
|
|
<p><span class="kw4">bool</span> wait_for<span class="br0">(</span> Lock<span class="sy3">&</span> lock,<br />
|
|
std<span class="sy4">::</span><span class="me2">stop_token</span> stoken,<br />
|
|
<span class="kw4">const</span> <a href="cpp-chrono-duration.html"><span class="kw993">std::<span class="me2">chrono</span><span class="sy4">::</span><span class="me2">duration</span></span></a><span class="sy1"><</span>Rep, Period<span class="sy1">></span><span class="sy3">&</span> rel_time,<br /></p>
|
|
Predicate pred<span class="br0">)</span><span class="sy4">;</span></div>
|
|
</td>
|
|
<td>(3)</td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<div class="t-li1"><span class="t-li">1)</span> 原子地释放 <code>lock</code> ，阻塞当前线程，并将它添加到等待在 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy2">*</span>this</span></span> 上的线程列表。线程将在执行 <span class="t-lc"><a href="cpp-thread-condition_variable_any-notify_all.html">notify_all()</a></span> 或 <span class="t-lc"><a href="cpp-thread-condition_variable_any-notify_one.html">notify_one()</a></span> 时，或度过相对时限 <code>rel_time</code> 时被解除阻塞。它亦可被虚假地解除阻塞。解阻塞时，无关缘由，重获得 <code>lock</code> 并退出 <code>wait_for()</code> 退出。</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> wait_until<span class="br0">(</span>lock, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">steady_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">+</span> rel_time, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>pred<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></span></span> 。此重载可用于忽略虚假唤醒。</div>
|
|
<p>用稳定时钟度量时长。由于调度或资源争议，此函数可能阻塞长于 <code>timeout_duration</code> 。</p>
|
|
<div class="t-li1"><span class="t-li">3)</span> 等价于 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw1">return</span> wait_until<span class="br0">(</span>lock, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>stoken<span class="br0">)</span>, std<span class="sy4">::</span><span class="me2">chrono</span><span class="sy4">::</span><span class="me2">steady_clock</span><span class="sy4">::</span><span class="me2">now</span><span class="br0">(</span><span class="br0">)</span> <span class="sy2">+</span> rel_time, std<span class="sy4">::</span><span class="me2">move</span><span class="br0">(</span>pred<span class="br0">)</span><span class="br0">)</span><span class="sy4">;</span></span></span></div>
|
|
<p><br /></p>
|
|
<p>若这些函数不能满足后条件（调用方线程锁定 <span class="t-c"><span class="mw-geshi cpp source-cpp">lock</span></span> ），则调用 <span class="t-lc"><a href="cpp-error-terminate.html">std::terminate</a></span> 。例如，这可能在重锁定互斥抛异常的情况下发生。</p>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par">
|
|
<td>lock</td>
|
|
<td>-</td>
|
|
<td>满足<a href="cpp-named_req-BasicLockable.html"><span style="font-style:italic">基本可锁定</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(BasicLockable)</span></a> 要求的 <code>Lock</code> 类型对象，必须为当前线程所锁定</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>stoken</td>
|
|
<td>-</td>
|
|
<td>用于注册中断的 <code>std::stop_token</code></td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>rel_time</td>
|
|
<td>-</td>
|
|
<td>表示等待所耗的最大时间的 <span class="t-lc"><a href="cpp-chrono-duration.html">std::chrono::duration</a></span> 类型对象。注意 rel_time 必须足够小，以在加到 <span class="t-lc"><a href="cpp-chrono-steady_clock-now.html">std::chrono::steady_clock::now()</a></span> 时不溢出。</td>
|
|
</tr>
|
|
<tr class="t-par">
|
|
<td>pred</td>
|
|
<td>-</td>
|
|
<td>是否应该持续等待则返回 ​<span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 的谓词。<br />
|
|
<p>谓词函数的签名应等价于如下者：</p>
|
|
<p><span class="t-cc"><span class="mw-geshi cpp source-cpp"> <span class="kw4">bool</span> pred<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></span>​</p>
|
|
</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<div class="t-li1"><span class="t-li">1)</span> 若经过 <code>rel_time</code> 所指定的关联时限则为 <span class="t-lc"><a href="cpp-thread-cv_status.html">std::cv_status::timeout</a></span> ，否则为 <span class="t-lc"><a href="cpp-thread-cv_status.html">std::cv_status::no_timeout</a></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 若经过 <code>rel_time</code> 时限后谓词 <code>pred</code> 仍求值为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> 则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> ，否则为 <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> 。</div>
|
|
<div class="t-li1"><span class="t-li">3)</span> <span class="t-c"><span class="mw-geshi cpp source-cpp">pred<span class="br0">(</span><span class="br0">)</span></span></span> ，无关乎是否达到时限或停止请求。</div>
|
|
<h3><span class="mw-headline" id=".E5.BC.82.E5.B8.B8">异常</span></h3>
|
|
<div class="t-li1"><span class="t-li">1)</span> 执行期间时钟、时间点或时长可能抛出的任何异常（标准库提供的时钟、时间点和时长决不抛出）</div>
|
|
<div class="t-li1"><span class="t-li">2)</span> 同 <span class="t-v">(1)</span> ，但亦可传播 <code>pred</code> 所抛的异常</div>
|
|
<div class="t-li1"><span class="t-li">3)</span> 同 <span class="t-v">(2)</span></div>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p>即使在锁定时通知，重载 <span class="t-v">(1)</span> 在因时限退出时也不对关联谓词的状态做出保证。</p>
|
|
<p><code>notify_one()</code>/<code>notify_all()</code> 的效果与 <code>wait()</code>/<code>wait_for()</code>/<code>wait_until()</code> 的三个原子部分的每一者（解锁+等待、唤醒和锁定）以能看做原子变量<a href="cpp-atomic-memory_order.html#.E4.BF.AE.E6.94.B9.E9.A1.BA.E5.BA.8F">修改顺序</a>单独全序发生：顺序对此单独的 condition_variable 是特定的。譬如，这使得 <code>notify_one()</code> 不可能被延迟并解锁正好在进行 <code>notify_one()</code> 调用后开始等待的线程。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <atomic></span>
|
|
<span class="co2">#include <condition_variable></span>
|
|
<span class="co2">#include <thread></span>
|
|
<span class="co2">#include <chrono></span>
|
|
<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">chrono_literals</span><span class="sy4">;</span>
|
|
|
|
<a href="cpp-thread-condition_variable_any.html"><span class="kw2172">std::<span class="me2">condition_variable_any</span></span></a> cv<span class="sy4">;</span>
|
|
<a href="cpp-thread-mutex.html"><span class="kw2154">std::<span class="me2">mutex</span></span></a> cv_m<span class="sy4">;</span>
|
|
<span class="kw4">int</span> i<span class="sy4">;</span>
|
|
|
|
<span class="kw4">void</span> waits<span class="br0">(</span><span class="kw4">int</span> idx<span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-thread-unique_lock.html"><span class="kw2167">std::<span class="me2">unique_lock</span></span></a><span class="sy1"><</span><a href="cpp-thread-mutex.html"><span class="kw2154">std::<span class="me2">mutex</span></span></a><span class="sy1">></span> lk<span class="br0">(</span>cv_m<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="kw1">if</span><span class="br0">(</span>cv.<span class="me1">wait_for</span><span class="br0">(</span>lk, idx<span class="sy2">*</span>100ms, <span class="br0">[</span><span class="br0">]</span><span class="br0">{</span><span class="kw1">return</span> i <span class="sy1">==</span> <span class="nu0">1</span><span class="sy4">;</span><span class="br0">}</span><span class="br0">)</span><span class="br0">)</span>
|
|
<a href="cpp-io-cerr.html"><span class="kw1760">std::<span class="me2">cerr</span></span></a> <span class="sy1"><<</span> <span class="st0">"Thread "</span> <span class="sy1"><<</span> idx <span class="sy1"><<</span> <span class="st0">" finished waiting. i == "</span> <span class="sy1"><<</span> i <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="kw1">else</span>
|
|
<a href="cpp-io-cerr.html"><span class="kw1760">std::<span class="me2">cerr</span></span></a> <span class="sy1"><<</span> <span class="st0">"Thread "</span> <span class="sy1"><<</span> idx <span class="sy1"><<</span> <span class="st0">" timed out. i == "</span> <span class="sy1"><<</span> i <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="kw4">void</span> signals<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-thread-sleep_for.html"><span class="kw2149">std::<span class="me2">this_thread</span><span class="sy4">::</span><span class="me2">sleep_for</span></span></a><span class="br0">(</span>120ms<span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cerr.html"><span class="kw1760">std::<span class="me2">cerr</span></span></a> <span class="sy1"><<</span> <span class="st0">"Notifying...<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
cv.<span class="me1">notify_all</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-thread-sleep_for.html"><span class="kw2149">std::<span class="me2">this_thread</span><span class="sy4">::</span><span class="me2">sleep_for</span></span></a><span class="br0">(</span>100ms<span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-thread-lock_guard.html"><span class="kw2166">std::<span class="me2">lock_guard</span></span></a><span class="sy1"><</span><a href="cpp-thread-mutex.html"><span class="kw2154">std::<span class="me2">mutex</span></span></a><span class="sy1">></span> lk<span class="br0">(</span>cv_m<span class="br0">)</span><span class="sy4">;</span>
|
|
i <span class="sy1">=</span> <span class="nu0">1</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
<a href="cpp-io-cerr.html"><span class="kw1760">std::<span class="me2">cerr</span></span></a> <span class="sy1"><<</span> <span class="st0">"Notifying again...<span class="es1">\n</span>"</span><span class="sy4">;</span>
|
|
cv.<span class="me1">notify_all</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-thread-thread.html"><span class="kw2146">std::<span class="me2">thread</span></span></a> t1<span class="br0">(</span>waits, <span class="nu0">1</span><span class="br0">)</span>, t2<span class="br0">(</span>waits, <span class="nu0">2</span><span class="br0">)</span>, t3<span class="br0">(</span>waits, <span class="nu0">3</span><span class="br0">)</span>, t4<span class="br0">(</span>signals<span class="br0">)</span><span class="sy4">;</span>
|
|
t1.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span> t2.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span>, t3.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span>, t4.<span class="me1">join</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">Thread 1 timed out. i == 0
|
|
Notifying...
|
|
Thread 2 timed out. i == 0
|
|
Notifying again...
|
|
Thread 3 finished waiting. i == 1</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E7.BC.BA.E9.99.B7.E6.8A.A5.E5.91.8A">缺陷报告</span></h3>
|
|
<p>下列更改行为的缺陷报告追溯地应用于以前出版的 C++ 标准。</p>
|
|
<table class="dsctable" style="font-size:0.8em">
|
|
<tr>
|
|
<th>DR</th>
|
|
<th>应用于</th>
|
|
<th>出版时的行为</th>
|
|
<th>正确行为</th>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2093">LWG 2093</a></td>
|
|
<td>C++11</td>
|
|
<td>规范中缺失超时相关异常</td>
|
|
<td>已提及</td>
|
|
</tr>
|
|
<tr>
|
|
<td><a rel="nofollow" class="external text" href="https://cplusplus.github.io/LWG/issue2135">LWG 2135</a></td>
|
|
<td>C++11</td>
|
|
<td><code>wait_for</code> 在解锁/重锁失败时抛异常</td>
|
|
<td>调用 <span class="t-lc"><a href="cpp-error-terminate.html">std::terminate</a></span></td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-thread-condition_variable_any-wait.html"><span class="t-lines"><span>wait</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>阻塞当前线程，直到条件变量被唤醒<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-thread-condition_variable_any-wait_until.html"><span class="t-lines"><span>wait_until</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>阻塞当前线程，直到条件变量被唤醒，或直到抵达指定时间点<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|