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This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/1137/">https://reviewboard.asterisk.org/r/1137/</a>
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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;">Just some comments about locking.</pre>
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<a href="https://reviewboard.asterisk.org/r/1137/diff/3/?file=16494#file16494line528" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/channels/chan_local.c</a>
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(Diff revision 3)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">static struct ast_frame *local_read(struct ast_channel *ast)</pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="cm">/* Just queue for delivery to the other side */</span></pre></td>
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<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="cm">/* Just queue for delivery to the other side */</span></pre></td>
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<td bgcolor="#fdfebc" 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 class="hl">;</span></span></pre></td>
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="hl"> </span><span class="k"><span class="hl">while</span></span><span class="p"><span class="hl">(</span></span><span class="n">ao2_<span class="hl">try</span>lock</span><span class="p">(</span><span class="n">p</span><span class="p">)<span class="hl">)</span></span><span class="hl"> </span><span class="p"><span class="hl">{</span></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">CHANNEL_DEADLOCK_AVOIDANCE</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="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">ao2_ref</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="cm">/* ref for local_queue_frame */</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">ao2_ref</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="cm">/* ref for local_queue_frame */</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">/* fixup formats nativeformat has changed we must adjust */</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="n">bridge</span> <span class="o">=</span> <span class="n">ast_bridged_channel</span><span class="p">(</span><span class="n">p</span><span class="o">-></span><span class="n">owner</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">if</span> <span class="p">(</span><span class="n">bridge</span> <span class="o">&&</span> <span class="o">!</span><span class="n">ast_format_cap_identical</span><span class="p">(</span><span class="n">bridge</span><span class="o">-></span><span class="n">nativeformats</span><span class="p">,</span> <span class="n">p</span><span class="o">-></span><span class="n">owner</span><span class="o">-></span><span class="n">nativeformats</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_format_cap_copy</span><span class="p">(</span><span class="n">bridge</span><span class="o">-></span><span class="n">nativeformats</span><span class="p">,</span> <span class="n">p</span><span class="o">-></span><span class="n">chan</span><span class="o">-></span><span class="n">nativeformats</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_format_cap_copy</span><span class="p">(</span><span class="n">bridge</span><span class="o">-></span><span class="n">nativeformats</span><span class="p">,</span> <span class="n">p</span><span class="o">-></span><span class="n">owner</span><span class="o">-></span><span class="n">nativeformats</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_set_read_format</span><span class="p">(</span><span class="n">p</span><span class="o">-></span><span class="n">owner</span><span class="p">,</span> <span class="o">&</span><span class="n">p</span><span class="o">-></span><span class="n">owner</span><span class="o">-></span><span class="n">readformat</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_set_write_format</span><span class="p">(</span><span class="n">p</span><span class="o">-></span><span class="n">owner</span><span class="p">,</span> <span class="o">&</span><span class="n">p</span><span class="o">-></span><span class="n">owner</span><span class="o">-></span><span class="n">writeformat</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_set_read_format</span><span class="p">(</span><span class="n">p</span><span class="o">-></span><span class="n">chan</span><span class="p">,</span> <span class="o">&</span><span class="n">p</span><span class="o">-></span><span class="n">chan</span><span class="o">-></span><span class="n">readformat</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; "></pre></td>
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<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">ast_set_write_format</span><span class="p">(</span><span class="n">p</span><span class="o">-></span><span class="n">chan</span><span class="p">,</span> <span class="o">&</span><span class="n">p</span><span class="o">-></span><span class="n">chan</span><span class="o">-></span><span class="n">writeformat</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; "></pre></td>
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<td bgcolor="#c5ffc4" 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;">The bridge channel will be locked in the set format functions... This will result in a deadlock if the bridge channel is not safely locked before entering those functions.</pre>
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<a href="https://reviewboard.asterisk.org/r/1137/diff/3/?file=16494#file16494line529" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/channels/chan_local.c</a>
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(Diff revision 3)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">static struct ast_frame *local_read(struct ast_channel *ast)</pre></td>
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<td bgcolor="#fdfebc" 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 class="hl">;</span></span></pre></td>
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="hl"> </span><span class="k"><span class="hl">while</span></span><span class="p"><span class="hl">(</span></span><span class="n">ao2_<span class="hl">try</span>lock</span><span class="p">(</span><span class="n">p</span><span class="p">)<span class="hl">)</span></span><span class="hl"> </span><span class="p"><span class="hl">{</span></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">CHANNEL_DEADLOCK_AVOIDANCE</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="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">ao2_ref</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="cm">/* ref for local_queue_frame */</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">ao2_ref</span><span class="p">(</span><span class="n">p</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span> <span class="cm">/* ref for local_queue_frame */</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;">The correct locking order is Channel then tech_pvt, so this deadlock avoidance is not necessary on ast.</pre>
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<p>- David</p>
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<p>On May 13th, 2011, 12:17 a.m., irroot wrote:</p>
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<div>Review request for Asterisk Developers.</div>
<div>By irroot.</div>
<p style="color: grey;"><i>Updated 2011-05-13 00:17:57</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;">This is a most annoying pain and tripped me up no end testing the T38 gateway patch for res_fax.
Scenario :-
i have a Linksys 2102 on a fax machine that uses G.729 and switches to ALAW on CNG and then negotiates T.38
this is awesome as i can now Chat/Fax from same terminal using most effective bandwidth [these are to be deployed
on sugar cane farms surrounding the kruger park here in south africa over wi-fi]
for testing purposes im using a local channel into T.30 fax app in res_fax.
Problem :-
when the device reinvites ALAW then T.38 it leaves the nativeformat on chan_local as G.729 this will not work
as it is transcoding the FAX from G.729 to SLIN this will not work and took me a while to spot the problem.
Soloution :-
Check the format on the proxy and adjust it if it changes this should be what Local does been a proxy of the channel
it should follow changes ...
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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_local.c <span style="color: grey">(318143)</span></li>
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<p><a href="https://reviewboard.asterisk.org/r/1137/diff/" style="margin-left: 3em;">View Diff</a></p>
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