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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>
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<p style="margin-top: 0;">On December 9th, 2014, 7:36 p.m. EST, <b>rmudgett</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/4108/diff/3/?file=68553#file68553line432" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/main/astobj2.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; ">static int internal_ao2_ref(void *user_data, int delta, const char *file, int line, const char *func)</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="k">if</span> <span class="p">(</span><span class="n">delta</span> <span class="o"><</span> <span class="mi">0</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">magic</span> <span class="o">==</span> <span class="n">AO2_MAGIC</span> <span class="o">&&</span> <span class="p">(</span><span class="n">weak</span> <span class="o">=</span> <span class="n">ao2_bump</span><span class="p">(</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="p">)))</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;">Use of obj->priv_data.weakptr is not protected from other threads creating a weak object from the object. This wouldn't be a problem if the object were required to be immediately weakened after creation.</pre>
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<p>On February 5th, 2015, 2:30 a.m. EST, <b>Corey Farrell</b> wrote:</p>
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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;">I've transfered the actual creation of weak proxy objects from ao2_weaken to ao2_alloc (with an option).</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;">I've changed my mind. Creation of ao2_weakproxy objects requires it's own allocation function. I'm envisioning scenarios where the weakproxy can be a persistant object. So after the object a weakproxy points to is free'd, we may want to point the weakproxy to a new object. Previous patches did not allow for this although there is no technical reason against it.
So to your original finding, I've documented the thread safety concerns about ao2_weakproxy_set_object. Documentation / wording is not my strongest area, I'm open to any suggestions that make it clear when it's safe to associate an object to a weakproxy.</pre>
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<p>- Corey</p>
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<p>On March 4th, 2015, 4:43 p.m. EST, Corey Farrell wrote:</p>
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<div>Review request for Asterisk Developers, George Joseph and rmudgett.</div>
<div>By Corey Farrell.</div>
<p style="color: grey;"><i>Updated March 4, 2015, 4:43 p.m.</i></p>
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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 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 the normal object is about to be destroyed.</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;">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>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>/trunk/tests/test_astobj2_weaken.c <span style="color: grey">(PRE-CREATION)</span></li>
<li>/trunk/main/astobj2.c <span style="color: grey">(432445)</span></li>
<li>/trunk/include/asterisk/astobj2.h <span style="color: grey">(432445)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/4108/diff/" style="margin-left: 3em;">View Diff</a></p>
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