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<a href="https://reviewboard.asterisk.org/r/4257/">https://reviewboard.asterisk.org/r/4257/</a>
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<a href="https://reviewboard.asterisk.org/r/4257/diff/1/?file=69645#file69645line526" style="color: black; font-weight: bold; text-decoration: underline;">branches/13/channels/chan_pjsip.c</a>
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(Diff revision 1)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">static int chan_pjsip_answer(struct ast_channel *ast)</pre></td>
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<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">526</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="n">ao2_ref</span><span class="p">(</span><span class="n">channel</span><span class="o">-></span><span class="n">session</span><span class="p">,</span> <span class="o">+</span><span class="mi">1</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="tb"> </span><span class="n">ao2_ref</span><span class="p">(</span><span class="n">channel</span><span class="o">-></span><span class="n">session</span><span class="p">,</span> <span class="o">+</span><span class="mi">1</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="k">if</span> <span class="p">(</span><span class="n">ast_sip_push_task</span><span class="p">(</span><span class="n">channel</span><span class="o">-></span><span class="n">session</span><span class="o">-></span><span class="n">serializer</span><span class="p">,</span> <span class="n">answer</span><span class="p">,</span> <span class="n">channel</span><span class="o">-></span><span class="n">session</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="cm">/* the answer task needs to be pushed synchronously otherwise a race condition</span></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"><span class="tb"> </span> can occur between this thread and bridging (specifically when native bridging</span></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"><span class="tb"> </span> attempts to do direct media) */</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">ast_channel_unlock</span><span class="p">(</span><span class="n">ast</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">ast_sip_push_task_synchronous</span><span class="p">(</span><span class="n">channel</span><span class="o">-></span><span class="n">session</span><span class="o">-></span><span class="n">serializer</span><span class="p">,</span> <span class="n">answer</span><span class="p">,</span> <span class="n">channel</span><span class="o">-></span><span class="n">session</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="tb"> </span><span class="tb"> </span><span class="n">ast_log</span><span class="p">(</span><span class="n">LOG_WARNING</span><span class="p">,</span> <span class="s">"Unable to push answer task to the threadpool. Cannot answer call</span><span class="se">\n</span><span class="s">"</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="tb"> </span><span class="tb"> </span><span class="n">ast_log</span><span class="p">(</span><span class="n">LOG_WARNING</span><span class="p">,</span> <span class="s">"Unable to push answer task to the threadpool. Cannot answer call</span><span class="se">\n</span><span class="s">"</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="tb"> </span><span class="tb"> </span><span class="n">ao2_cleanup</span><span class="p">(</span><span class="n">channel</span><span class="o">-></span><span class="n">session</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="tb"> </span><span class="tb"> </span><span class="n">ao2_cleanup</span><span class="p">(</span><span class="n">channel</span><span class="o">-></span><span class="n">session</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="n">ast_channel_lock</span><span class="p">(</span><span class="n">ast</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="tb"> </span><span class="tb"> </span><span class="k">return</span> <span class="o">-</span><span class="mi">1</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="tb"> </span><span class="tb"> </span><span class="k">return</span> <span class="o">-</span><span class="mi">1</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="tb"> </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="tb"> </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">ast_channel_lock</span><span class="p">(</span><span class="n">ast</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; "></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="tb"> </span><span class="k">return</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="tb"> </span><span class="k">return</span> <span class="mi">0</span><span class="p">;</span></pre></td>
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<pre style="margin-left: 2em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">I have a couple of recommendations here:
1) You bump the refcount of channel->session up here befor unlocking ast as a means of ensuring the session will not get torn down if ast is somehow hung up/masqueraded/whatever after unlocking. The problem is, when you push the task, you're referring to the session via the channel, which may just as well be affected by hangup/masquerade/etc. operation that affects ast. So my suggestion here is to save the reference to channel->session to a local variable and pass that to the synchronous task.
2) Since the task we're pushing is synchronous now, it's a bit weird that we bump the refcount of the session here and decrement the refcount in the pushed task. Since the pushed task is now synchronous, we may as well do all refcount manipulations here so the code is more clear.</pre>
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<p>- Mark Michelson</p>
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<p>On December 11th, 2014, 7:31 p.m. UTC, Kevin Harwell wrote:</p>
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<div>Review request for Asterisk Developers.</div>
<div>By Kevin Harwell.</div>
<p style="color: grey;"><i>Updated Dec. 11, 2014, 7:31 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-24563">ASTERISK-24563</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;">When direct media is enabled and a pjsip channel is answered a race would occur between the handling of the answer and bridge setup. Sometimes the media negotiation would take place after the native bridge was setup. This resulted in a NULL media address, which in turn resulted in Asterisk using its address as the remote media address when sending a reinvite. This patch makes the chan_pjsip answer handler synchronous thus alleviating the race condition (the bridge won't start setting things up until after it returns).</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;">Made around 100 phones calls with and did not issue occur again.</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/13/channels/chan_pjsip.c <span style="color: grey">(429386)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/4257/diff/" style="margin-left: 3em;">View Diff</a></p>
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