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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/1610/">https://reviewboard.asterisk.org/r/1610/</a>
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<p style="margin-top: 0;">On December 6th, 2011, 10:33 a.m., <b>David Vossel</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/1610/diff/1/?file=22117#file22117line14289" style="color: black; font-weight: bold; text-decoration: underline;">/branches/1.8/channels/chan_sip.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 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">ref_peer</span><span class="p">(</span><span class="n">peer</span><span class="p">,</span> <span class="s">"Holding peer while sending MWI in event callback</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="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">unref_peer</span><span class="p">(</span><span class="n">peer</span><span class="p">,</span> <span class="s">"Releasing peer after sending MWI in event callback</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="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;">I know we talked about this briefly, but I still have reservations about this.
Just to be clear for historical reasons. The use of ref counting here does nothing to give the event thread ownership of a reference to the peer. If the event thread does not have a reference handed to it at subscription time, then adding the reference here in the callback will not do anything to prevent the peer from being destroyed as it may have already been destroyed before we even add the ref count.
Also, given that the un-subscription to this event occurs during the peer's ao2 destructor callback, we actually run the risk of adding and removing a reference to the peer while it is in the destructor callback... I really don't know what that will do.