<html>
<body>
<div style="font-family: Verdana, Arial, Helvetica, Sans-Serif;">
<table bgcolor="#f9f3c9" width="100%" cellpadding="8" style="border: 1px #c9c399 solid;">
<tr>
<td>
This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/4108/">https://reviewboard.asterisk.org/r/4108/</a>
</td>
</tr>
</table>
<br />
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">I'm posting my next diff here, then I will discard this review then post the same change to gerrit. This way you can look at reviewboard to see the changes between patches.</pre>
<br />
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<p style="margin-top: 0;">On April 10th, 2015, 7:05 p.m. EDT, <b>rmudgett</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; border-collapse: collapse; margin: 2px padding: 2px;">
<thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; font-size: 9pt; padding: 4px 8px; text-align: left;">
<a href="https://reviewboard.asterisk.org/r/4108/diff/5-6/?file=71780#file71780line455" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/main/astobj2.c</a>
<span style="font-weight: normal;">
(Diff revisions 5 - 6)
</span>
</th>
</tr>
</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">static int internal_ao2_ref(void *user_data, int delta, const char *file, int line, const char *func)</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">450</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">ref_counter</span><span class="o">++</span><span class="p">;</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">453</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">ref_counter</span><span class="o">++</span><span class="p">;</span></pre></td>
</tr>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">451</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">internal_weakproxy</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">weakptr</span> <span class="o">=</span> <span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">weakptr</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">454</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">internal_weakproxy</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">weakptr</span> <span class="o">=</span> <span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">weakptr</span> <span class="o">=</span> <span class="nb">NULL</span><span class="p">;</span></pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#ebb1ba" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">452</font></th>
<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">ao2_ref</span><span class="p">(</span><span class="n">weakproxy</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">);</span></pre></td>
<th bgcolor="#ebb1ba" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">453</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="cm">/* weak is already unlinked from obj so this won't recurse */</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">455</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="cm">/* weak is already unlinked from obj so this won't recurse */</span></pre></td>
</tr>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">454</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">ao2_ref</span><span class="p">(</span><span class="n">user_data</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">);</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">456</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">ao2_ref</span><span class="p">(</span><span class="n">user_data</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">);</span></pre></td>
</tr>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">455</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">ret</span> <span class="o">=</span> <span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">ref_counter</span><span class="p">;</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">457</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">ret</span> <span class="o">=</span> <span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">ref_counter</span><span class="p">;</span></pre></td>
</tr>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">456</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">current_value</span> <span class="o">=</span> <span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">ref_counter</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">458</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">current_value</span> <span class="o">=</span> <span class="n">obj</span><span class="o">-></span><span class="n">priv_data</span><span class="p">.</span><span class="n">ref_counter</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span></pre></td>
</tr>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">457</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">459</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
</tr>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">458</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">weakproxy_run_callbacks</span><span class="p">(</span><span class="n">weakproxy</span><span class="p">);</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">460</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="tb"> </span><span class="n">weakproxy_run_callbacks</span><span class="p">(</span><span class="n">weakproxy</span><span class="p">);</span></pre></td>
</tr>
</tbody>
</table>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Rather than play games with the real object's ref count. How about replacing the indicated code with this:
----------
/* Unlink the obj from the weak proxy */
internal_weakproxy->priv_data.weakptr = NULL;
obj->priv_data.weakptr = NULL;
/* Notify the subscribers that obj is about to die. */
weakproxy_run_callbacks(weakproxy);
/*
* Weak is already unlinked from obj so this won't recurse.
* This will destroy obj.
*/
ao2_ref(user_data, -1);
----------
The test to release the weakproxy ref below needs to be adjusted to:
if (current_value == 1)
and that code moved to just after the unlock of weakproxy.</pre>
</blockquote>
</blockquote>
<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;">Retested, although the last two reference lines are out of order this is tolerated by refcounter.py.</pre>
<br />
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<p style="margin-top: 0;">On April 10th, 2015, 7:05 p.m. EDT, <b>rmudgett</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; border-collapse: collapse; margin: 2px padding: 2px;">
<thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; font-size: 9pt; padding: 4px 8px; text-align: left;">
<a href="https://reviewboard.asterisk.org/r/4108/diff/5-6/?file=71780#file71780line492" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/main/astobj2.c</a>
<span style="font-weight: normal;">
(Diff revisions 5 - 6)
</span>
</th>
</tr>
</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">static int internal_ao2_ref(void *user_data, int delta, const char *file, int line, const char *func)</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">488</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="cm">/* This must be done after destructor_fn finishes. It is possible this</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">489</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"><span class="tb"> </span><span class="tb"> </span> * unref will destroy weakproxy and we need to ensure it is safe for</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">490</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"><span class="tb"> </span><span class="tb"> </span> * destructor_fn to read values that are stored by the weakproxy. */</span></pre></td>
</tr>
</tbody>
</table>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">The comment doesn't make sense. How is destructor_fn supposed to access values in the weak proxy? The real object is no longer linked with the weakproxy.</pre>
</blockquote>
<p>On April 10th, 2015, 7:59 p.m. EDT, <b>Corey Farrell</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">The following is allowed and a reasonable thing to do:
weakproxy->name = ast_strdup(name);
realobj->name = weakproxy->name;
The idea is that weakproxy has to own storage of any shared fields since realobj could be destroyed at any time. So if the destructor uses realobj->name, it is accessing memory that is owned by the weakproxy.</pre>
</blockquote>
</blockquote>
<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;">While addressing the other finding about the ref count games, I realized this comment no longer applies. ao2_ref(user_data, -1) happens inside the lock of weakproxy, and ao2_ref(weakproxy, -1) must happen after it's unlocked. Originally it wasn't clear without a comment that the weakproxy release couldn't be moved higher in internal_ao2_ref.</pre>
<br />
<p>- Corey</p>
<br />
<p>On April 3rd, 2015, 12:58 p.m. EDT, Corey Farrell wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" style="background-image: url('https://reviewboard.asterisk.org/static/rb/images/review_request_box_top_bg.ab6f3b1072c9.png'); background-position: left top; background-repeat: repeat-x; border: 1px black solid;">
<tr>
<td>
<div>Review request for Asterisk Developers, George Joseph and rmudgett.</div>
<div>By Corey Farrell.</div>
<p style="color: grey;"><i>Updated April 3, 2015, 12:58 p.m.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Bugs: </b>
<a href="https://issues.asterisk.org/jira/browse/ASTERISK-24936">ASTERISK-24936</a>
</div>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
Asterisk
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid #b8b5a0">
<tr>
<td>
<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 implements "weak" references. The weakproxy object is a real ao2 with normal reference counting of its own. When a weakproxy is pointed to a normal object they hold references to each other. The normal object is automatically freed when a single reference remains (the weakproxy). The weakproxy also supports subscriptions that will notify callbacks when it does not point to any real object.</pre>
</td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid #b8b5a0">
<tr>
<td>
<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;">Ran the included test with REF_DEBUG enabled under valgrind. No reference leaks or improper memory access. Though this does not test for races, I don't know of an automated way to do that.</pre>
</td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>/trunk/tests/test_astobj2_weaken.c <span style="color: grey">(PRE-CREATION)</span></li>
<li>/trunk/main/astobj2.c <span style="color: grey">(433964)</span></li>
<li>/trunk/include/asterisk/astobj2.h <span style="color: grey">(433964)</span></li>
</ul>
<p><a href="https://reviewboard.asterisk.org/r/4108/diff/" style="margin-left: 3em;">View Diff</a></p>
</td>
</tr>
</table>
</div>
</body>
</html>