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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>utrace_barrier</title><meta name="generator" content="DocBook XSL Stylesheets V1.75.2" /><link rel="home" href="index.html" title="The utrace User Debugging Infrastructure" /><link rel="up" href="ch02.html" title="Chapter 2. utrace core API" /><link rel="prev" href="re18.html" title="utrace_control" /><link rel="next" href="re20.html" title="utrace_prepare_examine" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"><span>utrace_barrier</span></th></tr><tr><td width="20%" align="left"><a accesskey="p" href="re18.html">Prev</a> </td><th width="60%" align="center">Chapter 2. utrace core API</th><td width="20%" align="right"> <a accesskey="n" href="re20.html">Next</a></td></tr></table><hr /></div><div class="refentry" title="utrace_barrier"><a id="API-utrace-barrier"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>utrace_barrier —
synchronize with simultaneous tracing callbacks
</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 <b class="fsfunc">utrace_barrier </b>(</code></td><td>struct task_struct * <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>struct utrace_engine * <var class="pdparam">engine</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Arguments"><a id="id2893164"></a><h2>Arguments</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>target</code></em></span></dt><dd><p>
thread to affect
</p></dd><dt><span class="term"><em class="parameter"><code>engine</code></em></span></dt><dd><p>
engine to affect (can be detached)
</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="id2893207"></a><h2>Description</h2><p>
This blocks while <em class="parameter"><code>target</code></em> might be in the midst of making a callback to
<em class="parameter"><code>engine</code></em>. It can be interrupted by signals and will return -<code class="constant">ERESTARTSYS</code>.
A return value of zero means no callback from <em class="parameter"><code>target</code></em> to <em class="parameter"><code>engine</code></em> was
in progress. Any effect of its return value (such as <code class="constant">UTRACE_STOP</code>) has
already been applied to <em class="parameter"><code>engine</code></em>.
</p><p>
It's not necessary to keep the <em class="parameter"><code>target</code></em> pointer alive for this call.
It's only necessary to hold a ref on <em class="parameter"><code>engine</code></em>. This will return
safely even if <em class="parameter"><code>target</code></em> has been reaped and has no task refs.
</p><p>
A successful return from <code class="function">utrace_barrier</code> guarantees its ordering
with respect to <code class="function">utrace_set_events</code> and <code class="function">utrace_control</code> calls. If
<em class="parameter"><code>target</code></em> was not properly stopped, event callbacks just disabled might
still be in progress; <code class="function">utrace_barrier</code> waits until there is no chance
an unwanted callback can be in progress.
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="re18.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ch02.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="re20.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span>utrace_control</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span>utrace_prepare_examine</span></td></tr></table></div></body></html>
