1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>cond_synchronize_rcu</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Linux Device Drivers"><link rel="up" href="ch01s09.html" title="Kernel utility functions"><link rel="prev" href="API-get-state-synchronize-rcu.html" title="get_state_synchronize_rcu"><link rel="next" href="API-synchronize-sched-expedited.html" title="synchronize_sched_expedited"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span class="phrase">cond_synchronize_rcu</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-get-state-synchronize-rcu.html">Prev</a>&#160;</td><th width="60%" align="center">Kernel utility functions</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-synchronize-sched-expedited.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-cond-synchronize-rcu"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>cond_synchronize_rcu &#8212; 
2     Conditionally wait for an RCU grace period
3 </p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">void <b class="fsfunc">cond_synchronize_rcu </b>(</code></td><td>unsigned long <var class="pdparam">oldstate</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1108651764"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>oldstate</code></em></span></dt><dd><p>
4     return value from earlier call to <code class="function">get_state_synchronize_rcu</code>
5    </p></dd></dl></div></div><div class="refsect1"><a name="idp1108653748"></a><h2>Description</h2><p>
6   If a full RCU grace period has elapsed since the earlier call to
7   <code class="function">get_state_synchronize_rcu</code>, just return.  Otherwise, invoke
8   <code class="function">synchronize_rcu</code> to wait for a full grace period.
9   </p><p>
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11   Yes, this function does not take counter wrap into account.  But
12   counter wrap is harmless.  If the counter wraps, we have waited for
13   more than 2 billion grace periods (and way more on a 64-bit system!),
14   so waiting for one additional grace period should be just fine.
15</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-get-state-synchronize-rcu.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="ch01s09.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="API-synchronize-sched-expedited.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">get_state_synchronize_rcu</span>&#160;</td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top">&#160;<span class="phrase">synchronize_sched_expedited</span></td></tr></table></div></body></html>
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