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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/2826/">https://reviewboard.asterisk.org/r/2826/</a>
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<p style="margin-top: 0;">On September 20th, 2013, 11:11 p.m. CDT, <b>rmudgett</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/2826/diff/3/?file=45654#file45654line146" style="color: black; font-weight: bold; text-decoration: underline;">/branches/1.8/main/lock.c</a>
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(Diff revision 3)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">int __ast_pthread_mutex_init(int tracking, const char *filename, int lineno, const char *func,</pre></td>
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<th bgcolor="#e9eaa8" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">87</font></th>
<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="n">ast_reentrancy<span class="hl">_init</span></span><span class="p">(</span><span class="o">&</span><span class="n">t</span><span class="o">-></span><span class="n">track</span><span class="p">);</span></pre></td>
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="n">as<span class="hl">t_ge</span>t_reentrancy</span><span class="p">(</span><span class="o">&</span><span class="n">t</span><span class="o">-></span><span class="n">track</span><span class="p">);</span></pre></td>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Lock tracking initialization must be deferred until the mutex or rwlock is actually used. Otherwise, it is no different than putting the tracking memory into the ast_mutex_t struct.
Lock tracking used to be part of the ast_mutex_t until it was discovered that chan_iax was using 100M bytes just being loaded. chan_iax has a 32k element lock array that it initializes when it loads.</pre>
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<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">That's the whole problem, though. There's no way to synchronize
initialization on first use. Multiple threads trying to simultaneously
acquire a lock with uninitialized lock tracking could result in double
initialization.
Maybe it would be better if DEBUG_THREADS dramatically reduced the
size of that array in chan_iax.</pre>
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<p>- David</p>
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<p>On September 5th, 2013, 1:24 p.m. CDT, David Lee wrote:</p>
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<div>Review request for Asterisk Developers and Matt Jordan.</div>
<div>By David Lee.</div>
<p style="color: grey;"><i>Updated Sept. 5, 2013, 1:24 p.m.</i></p>
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<b style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Bugs: </b>
<a href="https://issues.asterisk.org/jira/browse/ASTERISK-19463">ASTERISK-19463</a>
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<b style="color: #575012; font-size: 10pt;">Repository: </b>
Asterisk
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">This patch corrects a consistency issue with debug threads that I
noticed while fixing ASTERISK-22455.
The initialization of a mutex's lock tracking structure was not
protected in a critical section. This is fine for any mutex that is
explicitly initialized, but a static mutex may have its lock tracking
double-initialized if multiple threads attempt the first lock
simultaneously.
This patch creates a global mutex to properly serialize the
initialization of the lock tracking structure for a mutex. It also
changes lock.c to properly handle allocation failures of the lock
tracking structure.</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">I propose we setup Bamboo to run the TestSuite with DEBUG_THREADS
enabled on this branch nightly for a few weeks.</pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>/branches/1.8/include/asterisk/lock.h <span style="color: grey">(398421)</span></li>
<li>/branches/1.8/main/lock.c <span style="color: grey">(398421)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/2826/diff/" style="margin-left: 3em;">View Diff</a></p>
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