1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>futex_requeue</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="Unreliable Guide To Locking"><link rel="up" href="apiref-futex.html" title="Chapter&#160;12.&#160;Futex API reference"><link rel="prev" href="API-futex-proxy-trylock-atomic.html" title="futex_proxy_trylock_atomic"><link rel="next" href="API-queue-me.html" title="queue_me"></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">futex_requeue</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-futex-proxy-trylock-atomic.html">Prev</a>&#160;</td><th width="60%" align="center">Chapter&#160;12.&#160;Futex API reference</th><td width="20%" align="right">&#160;<a accesskey="n" href="API-queue-me.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-futex-requeue"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>futex_requeue &#8212; 
2     Requeue waiters from uaddr1 to uaddr2
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">int <b class="fsfunc">futex_requeue </b>(</code></td><td>u32 __user * <var class="pdparam">uaddr1</var>, </td></tr><tr><td>&#160;</td><td>unsigned int <var class="pdparam">flags</var>, </td></tr><tr><td>&#160;</td><td>u32 __user * <var class="pdparam">uaddr2</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">nr_wake</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">nr_requeue</var>, </td></tr><tr><td>&#160;</td><td>u32 * <var class="pdparam">cmpval</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">requeue_pi</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1124878476"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>uaddr1</code></em></span></dt><dd><p>
4     source futex user address
5    </p></dd><dt><span class="term"><em class="parameter"><code>flags</code></em></span></dt><dd><p>
6     futex flags (FLAGS_SHARED, etc.)
7    </p></dd><dt><span class="term"><em class="parameter"><code>uaddr2</code></em></span></dt><dd><p>
8     target futex user address
9    </p></dd><dt><span class="term"><em class="parameter"><code>nr_wake</code></em></span></dt><dd><p>
10     number of waiters to wake (must be 1 for requeue_pi)
11    </p></dd><dt><span class="term"><em class="parameter"><code>nr_requeue</code></em></span></dt><dd><p>
12     number of waiters to requeue (0-INT_MAX)
13    </p></dd><dt><span class="term"><em class="parameter"><code>cmpval</code></em></span></dt><dd><p>
14     <em class="parameter"><code>uaddr1</code></em> expected value (or <code class="constant">NULL</code>)
15    </p></dd><dt><span class="term"><em class="parameter"><code>requeue_pi</code></em></span></dt><dd><p>
16     if we are attempting to requeue from a non-pi futex to a
17     pi futex (pi to pi requeue is not supported)
18    </p></dd></dl></div></div><div class="refsect1"><a name="idp1124886620"></a><h2>Description</h2><p>
19   Requeue waiters on uaddr1 to uaddr2. In the requeue_pi case, try to acquire
20   uaddr2 atomically on behalf of the top waiter.
21</p></div><div class="refsect1"><a name="idp1124887332"></a><h2>Return</h2><p>
22   &gt;=0 - on success, the number of tasks requeued or woken;
23   &lt;0 - on error
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