1<html><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"><title>test_and_clear_bit</title><meta name="generator" content="DocBook XSL Stylesheets V1.78.1"><link rel="home" href="index.html" title="The Linux Kernel API"><link rel="up" href="ch02s03.html" title="Bit Operations"><link rel="prev" href="API---test-and-set-bit.html" title="__test_and_set_bit"><link rel="next" href="API---test-and-clear-bit.html" title="__test_and_clear_bit"></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">test_and_clear_bit</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API---test-and-set-bit.html">Prev</a>&#160;</td><th width="60%" align="center">Bit Operations</th><td width="20%" align="right">&#160;<a accesskey="n" href="API---test-and-clear-bit.html">Next</a></td></tr></table><hr></div><div class="refentry"><a name="API-test-and-clear-bit"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>test_and_clear_bit &#8212; 
2     Clear a bit and return its old value
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">test_and_clear_bit </b>(</code></td><td>long <var class="pdparam">nr</var>, </td></tr><tr><td>&#160;</td><td>volatile unsigned long * <var class="pdparam">addr</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer">&#160;</div></div></div><div class="refsect1"><a name="idp1123150644"></a><h2>Arguments</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="parameter"><code>nr</code></em></span></dt><dd><p>
4     Bit to clear
5    </p></dd><dt><span class="term"><em class="parameter"><code>addr</code></em></span></dt><dd><p>
6     Address to count from
7    </p></dd></dl></div></div><div class="refsect1"><a name="idp1123153164"></a><h2>Description</h2><p>
8   This operation is atomic and cannot be reordered.
9   It also implies a memory barrier.
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