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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>trace_printk</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="Linux Device Drivers" /><link rel="up" href="ch01s08.html" title="Kernel utility functions" /><link rel="prev" href="re131.html" title="might_sleep" /><link rel="next" href="re133.html" title="clamp" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>trace_printk</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re131.html">Prev</a> </td><th width="60%" align="center">Kernel utility functions</th><td width="20%" align="right"> <a accesskey="n" href="re133.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="trace_printk"><a id="API-trace-printk"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>trace_printk —
printf formatting in the ftrace buffer
</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"> <b class="fsfunc">trace_printk </b>(</code></td><td> <var class="pdparam">fmt</var>, </td></tr><tr><td> </td><td> <var class="pdparam">args...</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id3042816"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>fmt</code></em></span></dt><dd><p>
the printf format for printing
</p></dd><dt><span class="term"><em class="parameter"><code>args...</code></em></span></dt><dd><p>
variable arguments
</p></dd></dl></div></div><div class="refsect1" title="Note"><a id="id3042860"></a><h2>Note</h2><p>
__trace_printk is an internal function for trace_printk and
the <em class="parameter"><code>ip</code></em> is passed in via the trace_printk macro.
</p><p>
This function allows a kernel developer to debug fast path sections
that printk is not appropriate for. By scattering in various
printk like tracing in the code, a developer can quickly see
where problems are occurring.
</p><p>
This is intended as a debugging tool for the developer only.
Please refrain from leaving trace_printks scattered around in
your code.
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