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<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="memory_order" title="cpp/atomic/memory order"><span class="t-lines"><span>memory_order</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="kill_dependency.html" title="cpp/atomic/kill dependency"><span class="t-lines"><span>kill_dependency</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><strong class="selflink"><span class="t-lines"><span>atomic_thread_fence</span></span></strong></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
<tr class="t-nv"><td colspan="5"><div class="t-nv-ln-table"><div><a href="atomic_signal_fence.html" title="cpp/atomic/atomic signal fence"><span class="t-lines"><span>atomic_signal_fence</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div></td></tr>
</table></div><div><span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/atomic/navbar_content&amp;action=edit">&#91;edit&#93;</a></span></div></div></div></div><div class="t-navbar-sep">&#160;</div></div>
<table class="t-dcl-begin"><tbody>
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<td> <div>Defined in header <code><a href="../header/atomic.html" title="cpp/header/atomic">&lt;atomic&gt;</a></code>
 </div></td>
<td></td>
<td></td>
</tr><tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
<tr class="t-dcl t-since-cxx11">
<td> <div><span class="mw-geshi cpp source-cpp"><span class="kw4">extern</span> <span class="st0">&quot;C&quot;</span> <span class="kw4">void</span> atomic_thread_fence<span class="br0">&#40;</span> <a href="memory_order"><span class="kw1772">std::<span class="me2">memory_order</span></span></a> order <span class="br0">&#41;</span><span class="sy4">;</span></span></div></td>
<td class="t-dcl-nopad">  </td>
<td> <span class="t-mark-rev t-since-cxx11">(since C++11)</span> </td>
</tr>
<tr class="t-dcl-sep"><td></td><td></td><td></td></tr>
</tbody></table>
<p>Establishes memory synchronization ordering of non-atomic and relaxed atomic accesses, as instructed by <code>order</code>, without an associated atomic operation. For example, all non-atomic and relaxed atomic stores that happen before a <span class="t-lc"><a href="memory_order" title="cpp/atomic/memory order">std::memory_order_release</a></span> fence in thread A will be synchronized with non-atomic and relaxed atomic loads from the same locations made in thread B after an <span class="t-lc"><a href="memory_order" title="cpp/atomic/memory order">std::memory_order_acquire</a></span> fence.
</p>
<table id="toc" class="toc"><tr><td><div id="toctitle"><h2>Contents</h2></div>
<ul>
<li class="toclevel-1 tocsection-1"><a href="#Parameters"><span class="tocnumber">1</span> <span class="toctext">Parameters</span></a></li>
<li class="toclevel-1 tocsection-2"><a href="#Return_value"><span class="tocnumber">2</span> <span class="toctext">Return value</span></a></li>
<li class="toclevel-1 tocsection-3"><a href="#Exceptions"><span class="tocnumber">3</span> <span class="toctext">Exceptions</span></a></li>
<li class="toclevel-1 tocsection-4"><a href="#Notes"><span class="tocnumber">4</span> <span class="toctext">Notes</span></a></li>
<li class="toclevel-1 tocsection-5"><a href="#Examples"><span class="tocnumber">5</span> <span class="toctext">Examples</span></a></li>
<li class="toclevel-1 tocsection-6"><a href="#See_also"><span class="tocnumber">6</span> <span class="toctext">See also</span></a></li>
</ul>
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_thread_fence&amp;action=edit&amp;section=1" title="Edit section: Parameters">edit</a>]</span> <span class="mw-headline" id="Parameters">Parameters</span></h3>
<table class="t-par-begin">


<tr class="t-par">
<td>  order
</td>
<td> -
</td>
<td>  the memory ordering executed by this fence
</td></tr></table>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_thread_fence&amp;action=edit&amp;section=2" title="Edit section: Return value">edit</a>]</span> <span class="mw-headline" id="Return_value">Return value</span></h3>
<p>(none)
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_thread_fence&amp;action=edit&amp;section=3" title="Edit section: Exceptions">edit</a>]</span> <span class="mw-headline" id="Exceptions">Exceptions</span></h3>
<div class="t-noexcept-inline"><a href="../language/noexcept_spec.html" title="cpp/language/noexcept spec"><tt>noexcept</tt></a> specification:&#160;&#160;<div class="t-noexcept-box"><span class="t-cc"><span class="mw-geshi cpp source-cpp"><span class="kw1">noexcept</span></span></span></div>&#160;&#160;</div>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_thread_fence&amp;action=edit&amp;section=4" title="Edit section: Notes">edit</a>]</span> <span class="mw-headline" id="Notes">Notes</span></h3>
<p><code>atomic_thread_fence</code> imposes stronger synchronization constraints than an atomic store operation with the same <span class="t-lc"><a href="memory_order" title="cpp/atomic/memory order">std::memory_order</a></span>. While an atomic store-release operation prevents all preceding writes from moving past the store-release, an <code>atomic_thread_fence</code> with <code>memory_order_release</code> ordering prevents all preceding writes from moving past all subsequent stores.
</p>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_thread_fence&amp;action=edit&amp;section=5" title="Edit section: Examples">edit</a>]</span> <span class="mw-headline" id="Examples">Examples</span></h3>
<div class="t-example"><p> Scan an array of mailboxes, and process only the ones intended for us, without unnecessary synchronization. 
 </p><div class="t-example-live-link"><div class="coliru-btn coliru-btn-run-init">Run this code</div></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;"><div class="cpp source-cpp"><pre class="de1"><span class="kw4">const</span> <span class="kw4">int</span> num_mailboxes <span class="sy1">=</span> <span class="nu0">32</span><span class="sy4">;</span>
<a href="atomic.html"><span class="kw1746">std::<span class="me2">atomic</span></span></a><span class="sy1">&lt;</span><span class="kw4">int</span><span class="sy1">&gt;</span> mailbox<span class="br0">&#91;</span>num_mailboxes<span class="br0">&#93;</span><span class="sy4">;</span>
&#160;
<span class="co1">// The writer threads update non-atomic shared data and then update mailbox[i] as follows</span>
 <a href="atomic_store.html"><span class="kw1749">std::<span class="me2">atomic_store_explicit</span></span></a><span class="br0">&#40;</span><span class="sy3">&amp;</span>mailbox<span class="br0">&#91;</span>i<span class="br0">&#93;</span>, <a href="memory_order"><span class="kw1776">std::<span class="me2">memory_order_release</span></span></a><span class="br0">&#41;</span><span class="sy4">;</span>
&#160;
<span class="co1">// Reader thread needs to check all mailbox[i], but only needs to sync with one</span>
 <span class="kw1">for</span> <span class="br0">&#40;</span><span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">0</span><span class="sy4">;</span> i <span class="sy1">&lt;</span> num_mailboxes<span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">&#41;</span> <span class="br0">&#123;</span>
    <span class="kw1">if</span> <span class="br0">&#40;</span><a href="atomic_load.html"><span class="kw1751">std::<span class="me2">atomic_load_explicit</span></span></a><span class="br0">&#40;</span><span class="sy3">&amp;</span>mailbox<span class="br0">&#91;</span>i<span class="br0">&#93;</span>,  <a href="memory_order"><span class="kw1773">std::<span class="me2">memory_order_relaxed</span></span></a><span class="br0">&#41;</span> <span class="sy1">==</span> my_id<span class="br0">&#41;</span> <span class="br0">&#123;</span>
        std<span class="sy4">::</span><span class="me2">atomic_thread_fence</span><span class="br0">&#40;</span><a href="memory_order"><span class="kw1775">std::<span class="me2">memory_order_acquire</span></span></a><span class="br0">&#41;</span><span class="sy4">;</span> <span class="co1">// synchronize with just one writer</span>
        do_work<span class="br0">&#40;</span>i<span class="br0">&#41;</span><span class="sy4">;</span> <span class="co1">// guaranteed to observe everything done in the writer thread before</span>
                    <span class="co1">// the atomic_store_explicit()</span>
    <span class="br0">&#125;</span>
 <span class="br0">&#125;</span></pre></div></div>
<p><br /> 
</p>
</div>
<h3><span class="editsection">[<a href="http://en.cppreference.com/mwiki/index.php?title=cpp/atomic/atomic_thread_fence&amp;action=edit&amp;section=6" title="Edit section: See also">edit</a>]</span> <span class="mw-headline" id="See_also">See also</span></h3>
<table class="t-dsc-begin">

<tr class="t-dsc-sep">
<td colspan="2">
</td></tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="memory_order" title="cpp/atomic/memory order"> <span class="t-lines"><span>memory_order</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div>
</td>
<td>   defines memory ordering constraints for the given atomic operation  <br /> <span class="t-mark">(typedef)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/atomic/dsc_memory_order&amp;action=edit">&#91;edit&#93;</a></span>
</td></tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td></tr>
<tr class="t-dsc">
<td>  <div class="t-dsc-member-div"><div><a href="atomic_signal_fence.html" title="cpp/atomic/atomic signal fence"> <span class="t-lines"><span>atomic_signal_fence</span></span></a></div><div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx11">(C++11)</span></span></span></div></div>
</td>
<td>   fence between a thread and a signal handler executed in the same thread  <br /> <span class="t-mark">(function)</span> <span class="editsection noprint plainlinks" title="Edit this template"><a rel="nofollow" class="external text" href="http://en.cppreference.com/mwiki/index.php?title=Template:cpp/atomic/dsc_atomic_signal_fence&amp;action=edit">&#91;edit&#93;</a></span>
</td></tr>

<tr class="t-dsc-sep">
<td colspan="2">
</td></tr>
<tr class="t-dsc">
<td colspan="2"> <div class="t-dsc-see"><span><a href="../../c/atomic/atomic_thread_fence.html" title="c/atomic/atomic thread fence">C documentation</a></span> for <span class="t-dsc-see-tt"><span>atomic_thread_fence</span></span></div>
</td></tr>

</table>

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