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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/1563/">https://reviewboard.asterisk.org/r/1563/</a>
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<p style="margin-top: 0;">On November 4th, 2011, 12:03 p.m., <b>David Vossel</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/1563/diff/2/?file=21625#file21625line14395" style="color: black; font-weight: bold; text-decoration: underline;">trunk/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 mwi_event_cb(const struct ast_event *event, void *userdata)</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ao2_ref</span><span class="p">(</span><span class="n">peer</span><span class="p">,</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="n">sip_send_mwi_to_peer</span><span class="p">(</span><span class="n">peer</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">sip_send_mwi_to_peer</span><span class="p">(</span><span class="n">peer</span><span class="p">,</span> <span class="mi">0</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="n">ao2_ref</span><span class="p">(</span><span class="n">peer</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="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 ref counts here should be removed. If we don't already own a ref before entering this function, grabbing one now doesn't help anything.
I've looked at this callback in quite a bit of detail. Because of the way the event is removed during the "clear_peer_mailboxes(peer)" function in the peer's destructor, we are guaranteed this peer will always be valid regardless of any ref counting. The event can not be removed in clear_peer_mailboxes until the event lock is grabbed, if the mwi_event_cb is taking place at that exact moment then the event lock is held in that thread. This syncs the threads up in a way that prevents the peer pointer from existing in the mwi_event_cb after destruction.
This is why the clear_peer_mailboxes(peer) call was moved to the top of the destructor. We don't want to start tearing down peer information if the peer is somehow in the mwi_event_cb function before the event is removed. Note that richard's patch moves the clear_peer_mailboxes(peer) call up as well. So depending on who commits first, this may already be done.
Hope this makes sense.</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;">Done.</pre>
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<p style="margin-top: 0;">On November 4th, 2011, 12:03 p.m., <b>David Vossel</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/1563/diff/2/?file=21625#file21625line14757" style="color: black; font-weight: bold; text-decoration: underline;">trunk/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 enum check_auth_result register_verify(struct sip_pvt *p, struct ast_sockaddr *addr,</pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ao2_ref</span><span class="p">(</span><span class="n">peer</span><span class="p">,</span> <span class="mi">1</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="n">ao2_unlock</span><span class="p">(</span><span class="n">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="n">sip_send_mwi_to_peer</span><span class="p">(</span><span class="n">peer</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">sip_send_mwi_to_peer</span><span class="p">(</span><span class="n">peer</span><span class="p">,</span> <span class="mi">0</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="n">ao2_lock</span><span class="p">(</span><span class="n">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="n">ao2_ref</span><span class="p">(</span><span class="n">peer</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</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;">I believe the peer already has a ref in this function, so the ref bumping should not be necessary.
Unlocking the pvt however is a good idea, nice catch.</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;">Done.</pre>
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<p>- opticron</p>
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<p>On November 4th, 2011, 1 p.m., opticron wrote:</p>
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<div>Review request for Asterisk Developers and David Vossel.</div>
<div>By opticron.</div>
<p style="color: grey;"><i>Updated Nov. 4, 2011, 1 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;">Fix a locking inversion that causes deadlocks during BLF subscriptions.</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;">Compile</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-18663">ASTERISK-18663</a>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>trunk/channels/chan_sip.c <span style="color: grey">(342600)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/1563/diff/" style="margin-left: 3em;">View Diff</a></p>
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