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Add report on loading libthr dynamically

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Approved by:	hrs (mentor, implicit)
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Benjamin Kaduk 2015-04-15 03:02:06 +00:00
parent 6c95c01a38
commit 1b22bc5abe
Notes: svn2git 2020-12-08 03:00:23 +00:00 
svn path=/head/; revision=46553
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en_US.ISO8859-1/htdocs/news/status/report-2015-01-2015-03.xml
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@ -1802,4 +1802,53 @@ WITHOUT_FORTH=y</pre>
<sponsor>The &os; Foundation</sponsor>
</project>
<project cat='bin'>
<title>libthr improvements</title>
<contact>
<person>
<name>
<given>Konstantin</given>
<common>Belousov</common>
</name>
<email>kib@FreeBSD.org</email>
</person>
</contact>
<body>
<p>Historically, dynamic loading of the libthr.so thread
library into a single-threaded process did not work in &os;.
The longstanding recommendation to work-around the problem has
been to always link the main binary with -lpthread if there was
any chance of a need for threading functionality. This project
converted libthr.so into a plugin for libc, which fixed the
known issues preventing dynaic loading of libthr.so.</p>
<p>After the fix, linking the main binary with -lpthread is
no longer requred, but is not harmful. I recommend thoroughly
testing before removing libpthread from the libraries list in
favor of dynamic loading, though. Note that potential problems
will be subtle and their user-visible manifestations in the
affected program even more surprising.</p>
<p>The following issues were present in the old version of
libthr with respect to dynamic loading, but are fixed as
a result of this work:</p>
<ul>
<li>Invalid errno value seen after failed syscalls.</li>
<li>Broken libthr internal locks and critical sections ignored
by signals.</li>
<li>Hung attempts to lock mutexes.</li>
<li>Thread cancellation not occuring at guaranteed cancellation
points.</li>
</ul>
<p>The main change was committed as r276630 to HEAD, with many
follow ups. It was merged to stable/10 in r277317.</p>
</body>
<sponsor>The &os; Foundation</sponsor>
</project>
</report>