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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/2756/">https://reviewboard.asterisk.org/r/2756/</a>
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<p style="margin-top: 0;">On August 12th, 2013, 11:13 a.m. CDT, <b>Mark Michelson</b> wrote:</p>
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<a href="https://reviewboard.asterisk.org/r/2756/diff/1/?file=43958#file43958line26405" style="color: black; font-weight: bold; text-decoration: underline;">trunk/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 int handle_request_bye(struct sip_pvt *p, struct sip_request *req)</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>RAII_VAR(struct ast_channel *, transferer_owner_locked, NULL, ao2_cleanup);</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>/* Established locking order here is bridge, channel, pvt</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> * and the bridge will be locked during ast_channel_bridge_peer */</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>ast_channel_unlock(p->owner);</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>sip_pvt_unlock(p);</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>peer_channel = ast_channel_bridge_peer(p->owner);</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>transferer_owner_locked = sip_pvt_lock_full(p);</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>if (!transferer_owner_locked) {</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="tb"> </span>ast_debug(3, "Unable to reacquire owner channel lock, channel is gone\n");</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="tb"> </span>return 0;</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>}</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;">Like with your previous case, get a reference to p->owner before unlocking p.
Since this is the exact same sequence as the previous case where the bridged peer is acquired, I think it should exist as its own function.
Since this case also then uses the same deadlock avoidance technique in order to lock the bridged peer, I think the function you create should also try to return with all components (sip_pvt, sip_pvt's owner, bridged peer) locked.</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;">It actually turns out that I need to remove the deadlock avoidance code altogether in favor of keeping both channels unlocked during those calls so the call could lock the channel itself after I found another deadlock condition.</pre>
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<p>- opticron</p>
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<p>On August 12th, 2013, 10:51 a.m. CDT, opticron wrote:</p>
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<div>Review request for Asterisk Developers and Mark Michelson.</div>
<div>By opticron.</div>
<p style="color: grey;"><i>Updated Aug. 12, 2013, 10:51 a.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-22215">ASTERISK-22215</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;">This resolves several deadlocks in chan_sip relating to usage of ast_channel_bridge_peer and improves accessibility of lock debugging function calls.
These issues were found while fixing the sip attended transfer integration tests for the referenced bug.</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;">With these changes, chan_sip no longer stalls part of the way through the rewritten sip attended transfer tests on the REFER or at the end on the final BYE.</pre>
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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">(396504)</span></li>
<li>trunk/include/asterisk/lock.h <span style="color: grey">(396504)</span></li>
<li>trunk/main/utils.c <span style="color: grey">(396504)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/2756/diff/" style="margin-left: 3em;">View Diff</a></p>
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