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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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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Summary of this weak ref implementation:
weak_proxy_obj <-> obj
* The weak_proxy_obj and the obj get refs to each other on the initial call to ao2_weaken().
* The weak_proxy_obj will then stick around for as long as obj lives so it can be returned by subsequent ao2_weaken() calls.
* Once obj dies because its last external ref is released, the weak_proxy_obj will die when the last external ref to it is released.
This weak object strategy is workable for random objects. It seems rather expensive for use by keyed containers because the real obj needs to be referenced by container operations through the sort_fn, hash_fn, and cmp_fn callbacks.</pre>
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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;">What about exposing a field 'void *data;' to the weak objects? This would allow containers of weak proxy objects to make a copy of the data needed for some or all callbacks. Object types could sacrifice some memory in exchange for speed of container operations. Honestly I'm not sure if this would be a good thing or not.</pre>
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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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<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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<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 transfered the actual creation of weak proxy objects from ao2_weaken to ao2_alloc (with an option).</pre>
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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#file68553line798" 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 bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="tb"> </span><span class="n">weak</span> <span class="o">=</span> <span class="n">orig_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="n">ao2_bump</span><span class="p">(</span><span class="n">obj</span><span class="p">)</span> <span class="o">:</span> <span class="nb">NULL</span><span class="p">;</span></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="tb"> </span><span class="k">goto</span> <span class="n">clean_return</span><span class="p">;</span></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">orig_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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<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">/* passed object already has an initialized weak object, bump it */</span></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="tb"> </span><span class="n">weak</span> <span class="o">=</span> <span class="n">ao2_bump</span><span class="p">(</span><span class="n">orig_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></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 ao2_bump here is unnecessary since you already checked if the pointer was NULL.</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;">Thanks for pointing out. I tend to forget the overhead of the NULL check in ao2_bump and use it for the return value. Fixed.</pre>
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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=68554#file68554line91" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/tests/test_astobj2_weaken.c</a>
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(Diff revision 3)
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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="n">ao2_cleanup</span><span class="p">(</span><span class="n">weakref1</span><span class="p">);</span></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="n">weakref2</span> <span class="o">=</span> <span class="n">ao2_weaken</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="o">&</span><span class="n">test_obj_destroy_notify</span><span class="p">,</span> <span class="o">&</span><span class="n">notify3_called</span><span class="p">);</span></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="n">ao2_weak_unsubscribe</span><span class="p">(</span><span class="n">obj</span><span class="p">,</span> <span class="o">&</span><span class="n">test_obj_destroy_notify</span><span class="p">,</span> <span class="o">&</span><span class="n">notify3_called</span><span class="p">);</span></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">weakref1</span> <span class="o">!=</span> <span class="n">weakref2</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 weakref1 after ref released.</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;">This is intentional. I'm checking the pointer without dereferencing it, so this is ok.</pre>
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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=68554#file68554line118" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/tests/test_astobj2_weaken.c</a>
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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="tb"> </span><span class="k">goto</span> <span class="n">fail_cleanup2</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;">This should be fail_cleanup1 so obj gets cleaned up.</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;">This is a paranoia check - the test only passes if all conditions of the if statement are false. If obj were somehow freed early all conditions would be true. In that case obj points to an object that was already destroyed. I feel the best thing is for this test to risk leaking in this situation, since the other option would be to risk a crash.</pre>
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<p>- Corey</p>
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<p>On October 26th, 2014, 7:10 a.m. EDT, 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 Oct. 26, 2014, 7:10 a.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 weak object is a real ao2 with normal reference counting of its own. The original object is destroyed when the only reference remaining is from the weak object.</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;">Very little, I'm unsure how to actually test that this cannot race, since any potential for a race would be due to very exact timing.</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">(426139)</span></li>
<li>/trunk/include/asterisk/astobj2.h <span style="color: grey">(426139)</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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