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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/1557/">https://reviewboard.asterisk.org/r/1557/</a>
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<a href="https://reviewboard.asterisk.org/r/1557/diff/2/?file=21580#file21580line16690" style="color: black; font-weight: bold; text-decoration: underline;">/branches/1.8/channels/chan_sip.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; ">static void cleanup_stale_contexts(char *new, char *old)</pre></td>
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<th bgcolor="#ebb1ba" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">16547</font></th>
<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="cm">/* We absolutely cannot destroy the rtp struct while a bridge is active or we WILL crash */</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">if</span> <span class="p">(</span><span class="n">dialog</span><span class="o">-></span><span class="n">rtp</span> <span class="o">&&</span> <span class="n">ast_rtp_instance_get_bridged</span><span class="p">(</span><span class="n">dialog</span><span class="o">-></span><span class="n">rtp</span><span class="p">))</span> <span class="p">{</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_debug</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="s">"Bridge still active. Delaying destroy of SIP dialog '%s' Method: %s</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">dialog</span><span class="o">-></span><span class="n">callid</span><span class="p">,</span> <span class="n">sip_methods</span><span class="p">[</span><span class="n">dialog</span><span class="o">-></span><span class="n">method</span><span class="p">].</span><span class="n">text</span><span class="p">);</span></pre></td>
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<th bgcolor="#ebb1ba" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">16550</font></th>
<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">sip_pvt_unlock</span><span class="p">(</span><span class="n">dialog</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">return</span> <span class="mi">0</span><span class="p">;</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="p">}</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">if</span> <span class="p">(</span><span class="n">dialog</span><span class="o">-></span><span class="n">vrtp</span> <span class="o">&&</span> <span class="n">ast_rtp_instance_get_bridged</span><span class="p">(</span><span class="n">dialog</span><span class="o">-></span><span class="n">vrtp</span><span class="p">))</span> <span class="p">{</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_debug</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="s">"Bridge still active. Delaying destroy of SIP dialog '%s' Method: %s</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">dialog</span><span class="o">-></span><span class="n">callid</span><span class="p">,</span> <span class="n">sip_methods</span><span class="p">[</span><span class="n">dialog</span><span class="o">-></span><span class="n">method</span><span class="p">].</span><span class="n">text</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">sip_pvt_unlock</span><span class="p">(</span><span class="n">dialog</span><span class="p">);</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">return</span> <span class="mi">0</span><span class="p">;</span></pre></td>
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<td bgcolor="#ffc5ce" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <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;">These tests seem to be redundant with the same tests later in the function. They also prevent the check_rtp_timeout() call from checking for timeouts which is likely a bug anyway.</pre>
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<p>- rmudgett</p>
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<p>On November 2nd, 2011, 8:25 p.m., rmudgett wrote:</p>
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<div>Review request for Asterisk Developers and David Vossel.</div>
<div>By rmudgett.</div>
<p style="color: grey;"><i>Updated Nov. 2, 2011, 8:25 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;">Timing between dialog destruction and a MWI event sending a message could result in a deadlock.
Order of events causing deadlock:
1a) The event subscription system calls the registered callbacks with its list RWLOCK held.
1b) The SIP monitor checks for dialogs needing destruction. It does an ao2_callback that holds the dialogs container lock while searching for dialogs to destroy.
2a) The event subscription SIP callback needs to create a temporary dialog to send out the MWI notification. That temporary dialog needs to be inserted in the dialogs container so it must wait.
2b) The dialog search finds a dialog to destroy and as a result releases the last reference for a peer. The peer destructor attempts to get the subscription RWLOCK but must wait.
3) deadlock
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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;">It compiles. :)</pre>
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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-18747">ASTERISK-18747</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/channels/chan_sip.c <span style="color: grey">(343275)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/1557/diff/" style="margin-left: 3em;">View Diff</a></p>
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