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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968" /><title>wait_on_bit</title><meta name="generator" content="DocBook XSL Stylesheets V1.76.1" /><link rel="home" href="index.html" title="Linux Device Drivers" /><link rel="up" href="ch01s04.html" title="Wait queues and Wake events" /><link rel="prev" href="API-wait-event-killable.html" title="wait_event_killable" /><link rel="next" href="API-wait-on-bit-lock.html" title="wait_on_bit_lock" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>wait_on_bit</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="API-wait-event-killable.html">Prev</a> </td><th width="60%" align="center">Wait queues and Wake events</th><td width="20%" align="right"> <a accesskey="n" href="API-wait-on-bit-lock.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="wait_on_bit"><a id="API-wait-on-bit"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>wait_on_bit —
wait for a bit to be cleared
</p></div><div class="refsynopsisdiv" title="Synopsis"><h2>Synopsis</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" class="funcprototype-table"><tr><td><code class="funcdef">int <strong>fsfuncwait_on_bit </strong>(</code></td><td>void * <var class="pdparam">word</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">bit</var>, </td></tr><tr><td> </td><td>int (*<var class="pdparam">action</var>)
<code>(</code>void *<code>)</code>, </td></tr><tr><td> </td><td>unsigned <var class="pdparam">mode</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id3052819"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>word</code></em></span></dt><dd><p>
the word being waited on, a kernel virtual address
</p></dd><dt><span class="term"><em class="parameter"><code>bit</code></em></span></dt><dd><p>
the bit of the word being waited on
</p></dd><dt><span class="term"><em class="parameter"><code>action</code></em></span></dt><dd><p>
the function used to sleep, which may take special actions
</p></dd><dt><span class="term"><em class="parameter"><code>mode</code></em></span></dt><dd><p>
the task state to sleep in
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id3052896"></a><h2>Description</h2><p>
There is a standard hashed waitqueue table for generic use. This
is the part of the hashtable's accessor API that waits on a bit.
For instance, if one were to have waiters on a bitflag, one would
call <code class="function">wait_on_bit</code> in threads waiting for the bit to clear.
One uses <code class="function">wait_on_bit</code> where one is waiting for the bit to clear,
but has no intention of setting it.
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