<html>
<body>
<div style="font-family: Verdana, Arial, Helvetica, Sans-Serif;">
<table bgcolor="#f9f3c9" width="100%" cellpadding="8" style="border: 1px #c9c399 solid;">
<tr>
<td>
This is an automatically generated e-mail. To reply, visit:
<a href="https://reviewboard.asterisk.org/r/2323/">https://reviewboard.asterisk.org/r/2323/</a>
</td>
</tr>
</table>
<br />
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<p style="margin-top: 0;">On February 8th, 2013, 4:23 p.m., <b>Mark Michelson</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; border-collapse: collapse; margin: 2px padding: 2px;">
<thead>
<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; font-size: 9pt; padding: 4px 8px; text-align: left;">
<a href="https://reviewboard.asterisk.org/r/2323/diff/1/?file=33339#file33339line677" style="color: black; font-weight: bold; text-decoration: underline;">/trunk/main/taskprocessor.c</a>
<span style="font-weight: normal;">
(Diff revision 1)
</span>
</th>
</tr>
</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">void *ast_taskprocessor_unreference(struct ast_taskprocessor *tps)</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">668</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="p">(</span><span class="n">t</span> <span class="o">=</span> <span class="n">tps_taskprocessor_pop</span><span class="p">(</span><span class="n">tps</span><span class="p">)))</span> <span class="p">{</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">677</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="p">(</span><span class="n">t</span> <span class="o">=</span> <span class="n">tps_taskprocessor_pop</span><span class="p">(</span><span class="n">tps</span><span class="p">)))</span> <span class="p">{</span></pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#e9eaa8" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">669</font></th>
<td bgcolor="#fdfebc" 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>
<th bgcolor="#e9eaa8" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">678</font></th>
<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">tps</span><span class="p">);</span></pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">679</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="cm">/* We need to check size in the same critical section where we</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">680</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"> * reset the executing bit. Avoids a race condition where a task</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">681</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"> * is pushed right after we pop an empty stack.</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">682</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "><span class="cm"> */</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">683</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">tps</span><span class="o">-></span><span class="n">executing</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">684</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">size</span> <span class="o">=</span> <span class="n">tps_taskprocessor_depth</span><span class="p">(</span><span class="n">tps</span><span class="p">);</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">685</font></th>
<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">tps</span><span class="p">);</span></pre></td>
</tr>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2"></font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td>
<th bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">686</font></th>
<td bgcolor="#c5ffc4" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="k">return</span> <span class="n">size</span> <span class="o">></span> <span class="mi">0</span><span class="p">;</span></pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#f0f0f0" style="border-right: 1px solid #C0C0C0;" align="right"><font size="2">670</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="p">}</span></pre></td>
<th bgcolor="#f0f0f0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" align="right"><font size="2">687</font></th>
<td bgcolor="#ffffff" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="p">}</span></pre></td>
</tr>
</tbody>
</table>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">This change is a bit troublesome. One of the reasons that tps_taskprocessor_pop() can return NULL is if the taskprocessor is shutting down. A common idiom in use is to loop calling ast_taskprocessor_execute() until it returns 0. Now if someone decides to shut down a taskprocessor that still has tasks in it, then the code that is looping over ast_taskprocessor_execute will not break out of its loop since ast_taskprocessor_execute will continually return non-zero.
I think that if tps_taskprocessor_pop() returns NULL, we should unconditionally return 0 because either
1) There were no tasks to pop off
2) The taskprocessor has shut down and so we shouldn't be attempting to execute any more. </pre>
</blockquote>
<p>On February 11th, 2013, 8:51 a.m., <b>David Lee</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<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 problem there is the mentioned race condition. The listener never gets the 'was_empty' param set, but the processing thread stops processing.
The shutdown case is a problem, though. I'll create a unit test for it and take care of it.</pre>
</blockquote>
</blockquote>
<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;">Actually; shutting_down is never set by anything, so tps_taskprocessor_pop() only returns NULL when the queue is actually empty.
I could fix the glitch, but I have misgivings about not executing tasks that have been enqueued. That would leak any resources that would have been unref'ed by the dropped tasks. I'd be more inclined to keep the current behavior: shutdown completes once all tasks are finished executing. Objections?</pre>
<br />
<p>- David</p>
<br />
<p>On February 8th, 2013, 3:24 p.m., David Lee wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" style="background-image: url('https://reviewboard.asterisk.org/media/rb/images/review_request_box_top_bg.png'); background-position: left top; background-repeat: repeat-x; border: 1px black solid;">
<tr>
<td>
<div>Review request for Asterisk Developers and Mark Michelson.</div>
<div>By David Lee.</div>
<p style="color: grey;"><i>Updated Feb. 8, 2013, 3:24 p.m.</i></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid #b8b5a0">
<tr>
<td>
<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 patch adds the ability to create a serializer from a thread pool. A
serializer is a ast_taskprocessor with the same contract as a default
taskprocessor (tasks execute serially) except instead of executing out
of a dedicated thread, execution occurs in a thread from a
ast_threadpool. Think of it as a lightweight thread.
While it guarantees that each task will complete before executing the
next, there is no guarantee as to which thread from the pool individual
tasks will execute. This normally only matters if your code relys on
thread specific information, such as thread locals.
This patch also fixes a bug in how the 'was_empty' parameter is computed
for the push callback.</pre>
</td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid #b8b5a0">
<tr>
<td>
<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;">Unit testing.</pre>
</td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>/trunk/include/asterisk/threadpool.h <span style="color: grey">(381085)</span></li>
<li>/trunk/main/taskprocessor.c <span style="color: grey">(381085)</span></li>
<li>/trunk/main/threadpool.c <span style="color: grey">(381085)</span></li>
<li>/trunk/tests/test_threadpool.c <span style="color: grey">(381085)</span></li>
</ul>
<p><a href="https://reviewboard.asterisk.org/r/2323/diff/" style="margin-left: 3em;">View Diff</a></p>
</td>
</tr>
</table>
</div>
</body>
</html>