Bug#390243: Why I wasn't using pkg-config to for libdevmapper....

[Theodore Tso]

On Wed, Jan 02, 2008 at 09:10:50AM -0600, Eric Sandeen wrote:
> > Is it possible that Fedora links selinux not against pthread or all
> > binaries against pthread?
> 
> Right, it appears that on Fedora, with a recent libselinux, pthreads is
> not needed.  So there appears to be no bug on Fedora.

I did some more digging and it looks way back when, Manoj had added a
patch to Debian's libselinux to replace the use of Thread Local
Storage with a pthread mutex[1].  This was done because of, as Manoj
put it in his e-mail to selinux mailing list, "the glacial pace at
which Debian releases", and the fact that Debian was still supporting
Linux 2.4 kernels, which did not have TLS support.  Hence, the patch
to rip out the use of __thread and replace it with a pthread mutex.

Given that Debian has stopped supporting the 2.4 kernel starting with
Debian etch (released April 2007), and I'm pretty sure our SELinux
support has no hope of working on the older 2.4 kernel anyway, it may
be that the better fix for Debian would be to rip out the pthread
mutex patch in libselinux1 altogether, and go back to upstream's
approach of using TLS.  I suspect it will be much more
efficient/faster than using a pthread mutex, and it will keep Debian
much more closely aligned with upstream.

Regards,

					- Ted

[1] http://readlist.com/lists/tycho.nsa.gov/selinux/0/2075.html