<html>
<head>
<base href="https://bugs.freedesktop.org/" />
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Priority</th>
<td>medium
</td>
</tr>
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - padsp: dlsym lookup on demand can lead to deadlocks"
href="https://bugs.freedesktop.org/show_bug.cgi?id=77948">77948</a>
</td>
</tr>
<tr>
<th>CC</th>
<td>lennart@poettering.net
</td>
</tr>
<tr>
<th>Assignee</th>
<td>pulseaudio-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Summary</th>
<td>padsp: dlsym lookup on demand can lead to deadlocks
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>pulseaudio-bugs@lists.freedesktop.org
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Reporter</th>
<td>fsateler@gmail.com
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Component</th>
<td>tools
</td>
</tr>
<tr>
<th>Product</th>
<td>PulseAudio
</td>
</tr></table>
<p>
<div>
<pre>Forwarded from a debian bug[1].
Summary from Mike Hommey:
---
- something calls access() before jemalloc is initialized.
- access() is caught by padsp, which locks a mutex, and resolves the
original access symbol with dlsym().
- dlsym() ends up allocating memory, which triggers jemalloc
initialization code.
- jemalloc init code open()s /proc/cpuinfo.
- open() is caught by padsp, which locks a mutex before resolving the
original open symbol with dlsym().
Except that it is using the same mutex as the first time...
Really, the dlsym lookup on demand seems a bad idea, and here we hit a
really bad corner case of that implementation. Even using separate
mutexes wouldn't solve it all: imagine the original call wasn't
access(), but open(), instead.
The best thing IMHO would be to have a constructor function that does
the symbol resolution at startup.
---
[1] <a href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=550674">https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=550674</a></pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are the QA Contact for the bug.</li>
<li>You are the assignee for the bug.</li>
</ul>
</body>
</html>