1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>get_futex_key</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-struct-futex-q.html" title="struct futex_q"><link rel="next" href="API-fault-in-user-writeable.html" title="fault_in_user_writeable"></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">get_futex_key</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-struct-futex-q.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-fault-in-user-writeable.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-get-futex-key"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>get_futex_key &#8212; 
2     Get parameters which are the keys for a futex
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">get_futex_key </b>(</code></td><td>u32 __user * <var class="pdparam">uaddr</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">fshared</var>, </td></tr><tr><td>&#160;</td><td>union futex_key * <var class="pdparam">key</var>, </td></tr><tr><td>&#160;</td><td>int <var class="pdparam">rw</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1124791644"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>uaddr</code></em></span></dt><dd><p>
4     virtual address of the futex
5    </p></dd><dt><span class="term"><em class="parameter"><code>fshared</code></em></span></dt><dd><p>
6     0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
7    </p></dd><dt><span class="term"><em class="parameter"><code>key</code></em></span></dt><dd><p>
8     address where result is stored.
9    </p></dd><dt><span class="term"><em class="parameter"><code>rw</code></em></span></dt><dd><p>
10     mapping needs to be read/write (values: VERIFY_READ,
11     VERIFY_WRITE)
12    </p></dd></dl></div></div><div class="refsect1"><a name="idp1124796284"></a><h2>Return</h2><p>
13   a negative error code or 0
14   </p><p>
15
16   The key words are stored in *key on success.
17   </p><p>
18
19   For shared mappings, it's (page-&gt;index, file_inode(vma-&gt;vm_file),
20   offset_within_page).  For private mappings, it's (uaddr, current-&gt;mm).
21   We can usually work out the index without swapping in the page.
22   </p><p>
23
24   <code class="function">lock_page</code> might sleep, the caller should not hold a spinlock.
25</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="API-struct-futex-q.html">Prev</a>&#160;</td><td width="20%" align="center"><a accesskey="u" href="apiref-futex.html">Up</a></td><td width="40%" align="right">&#160;<a accesskey="n" href="API-fault-in-user-writeable.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="phrase">struct futex_q</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">fault_in_user_writeable</span></td></tr></table></div></body></html>
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