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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/1313/">https://reviewboard.asterisk.org/r/1313/</a>
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<p style="margin-top: 0;">On July 21st, 2011, 12:32 p.m., <b>David Vossel</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/1313/diff/2/?file=17546#file17546line4347" style="color: black; font-weight: bold; text-decoration: underline;">/branches/1.8/main/pbx.c</a>
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(Diff revision 2)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">int ast_extension_state(struct ast_channel *c, const char *context, const char *exten)</pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">cb_iter</span> <span class="o">=</span> <span class="n">ao2_iterator_init</span><span class="p">(</span><span class="n">statecbs</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">cb_iter</span> <span class="o">=</span> <span class="n">ao2_iterator_init</span><span class="p">(</span><span class="n">statecbs</span><span class="p">,</span> <span class="mi">0</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">for</span> <span class="p">(</span><span class="n">state_cb</span> <span class="o">=</span> <span class="n">ao2_iterator_next</span><span class="p">(</span><span class="o">&</span><span class="n">cb_iter</span><span class="p">);</span> <span class="n">state_cb</span><span class="p">;</span> <span class="n">ao2_ref</span><span class="p">(</span><span class="n">state_cb</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">),</span> <span class="n">state_cb</span> <span class="o">=</span> <span class="n">ao2_iterator_next</span><span class="p">(</span><span class="o">&</span><span class="n">cb_iter</span><span class="p">))</span> <span class="p">{</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">for</span> <span class="p">(</span><span class="n">state_cb</span> <span class="o">=</span> <span class="n">ao2_iterator_next</span><span class="p">(</span><span class="o">&</span><span class="n">cb_iter</span><span class="p">);</span> <span class="n">state_cb</span><span class="p">;</span> <span class="n">ao2_ref</span><span class="p">(</span><span class="n">state_cb</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">),</span> <span class="n">state_cb</span> <span class="o">=</span> <span class="n">ao2_iterator_next</span><span class="p">(</span><span class="o">&</span><span class="n">cb_iter</span><span class="p">))</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="n">state_cb</span><span class="o">-></span><span class="n">callback</span><span class="p">(</span><span class="n"><span class="hl">hint</span></span><span class="o"><span class="hl">-></span></span><span class="n">ext<span class="hl">en</span></span><span class="o"><span class="hl">-></span></span><span class="n"><span class="hl">parent</span></span><span class="o"><span class="hl">-></span></span><span class="n">name</span><span class="p">,</span> <span class="n"><span class="hl">hint</span></span><span class="o"><span class="hl">-></span></span><span class="n">exten</span><span class="o"><span class="hl">-></span></span><span class="n"><span class="hl">exten</span></span><span class="p">,</span> <span class="n">state</span><span class="p">,</span> <span class="n">state_cb</span><span class="o">-></span><span class="n">data</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="n">state_cb</span><span class="o">-></span><span class="n">callback</span><span class="p">(</span><span class="n"><span class="hl">cont</span>ext<span class="hl">_</span>name</span><span class="p">,</span> <span class="n">exten<span class="hl">_name</span></span><span class="p">,</span> <span class="n">state</span><span class="p">,</span> <span class="n">state_cb</span><span class="o">-></span><span class="n">data</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="p">}</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="p">}</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ao2_iterator_destroy</span><span class="p">(</span><span class="o">&</span><span class="n">cb_iter</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ao2_iterator_destroy</span><span class="p">(</span><span class="o">&</span><span class="n">cb_iter</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;">The statecbs container is protected by the statecbs lock. When this lock is held in ast_extension_state_add() the data pointer for a element already existing within the container can change. I notice we do not protect that data pointer during the callback here. Could that be an issue?
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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;">Theoretically, it could be an issue. I don't think it is likely. However, I will add protection.</pre>
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<p>- rmudgett</p>
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<p>On July 14th, 2011, 8:20 p.m., rmudgett wrote:</p>
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<div>Review request for Asterisk Developers, Russell Bryant, David Vossel, and irroot.</div>
<div>By rmudgett.</div>
<p style="color: grey;"><i>Updated July 14, 2011, 8:20 p.m.</i></p>
<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;">There are two remaining different deadlocks reported dealing with dialplan
hints.
The deadlock in ASTERISK-17666 is caused by invalid locking order in
ast_remove_hint(). The hints container must be locked before the hint
object.
The deadlock in ASTERISK-17760 is caused by a catch-22 situation in
handle_statechange(). The deadlock is caused by not having the conlock
before calling the watcher callbacks. Unfortunately, having that lock
causes a different deadlock as reported in ASTERISK-16961.
* Fixed ast_remove_hint() locking order.
* Made handle_statechange() no longer call the watcher callbacks holding
any locks that matter.
* Made hint ao2 destructor do the watcher callbacks for extension
deactivation to guarantee that they get called.
* Fixed hint reference leak in ast_add_hint() if the callback container
constructor failed.
* Fixed hint reference leak in complete_core_show_hint() for every hint it
found for CLI tab completion.
* Adjusted locking in ast_merge_contexts_and_delete() for safety.
* Added context_merge_lock to prevent ast_merge_contexts_and_delete() and
handle_statechange() from interfering with each other.
* Fixed ast_change_hint() not taking into account that the extension is
used for the hash key.
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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;">* Did some calls that changed the state of some hints.
* Reloaded the dialplan.
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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-17666">ASTERISK-17666</a>,
<a href="https://issues.asterisk.org/jira/browse/ASTERISK-17760">ASTERISK-17760</a>
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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/main/pbx.c <span style="color: grey">(328355)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/1313/diff/" style="margin-left: 3em;">View Diff</a></p>
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