Bug#265486: NPTL-related

[GOTO Masanori <gotom@debian.or.jp>]

At Mon, 16 Aug 2004 17:04:26 +0100,
Rev Simon Rumble wrote:
> This one time, at band camp, GOTO Masanori gotom-at-debian.or.jp |Debian bugs| wrote:
> 
> > At least we have not heard about UML problem with the 2.6 kernel.  The
> > current user-mode-linux 2.4 kernel and uml\* packages in debian works
> > well.  The recent modification for glibc from -13 to -16 is not so
> > large.  
> >
> > Please investigate more and report us the detailed information.  If
> > you don't have spare time to check it, and you have no objection,
> > we'll close it.
> 
> This is beyond me, but I'm quoting from the forum for linode.com:

Thanks for your point.

> UML does not (yet) support Thread Local Storage (TLS) in either 2.4 or 
> 2.6. TLS is required by the Native POSIX Thread Library (NPTL) so NPTL 
> is also not supported by UML.

OK, that makes sense.

> The difference in the way the problem manifests itself (or not)
> between 2.4 and 2.6 is because NPTL enabled /lib/ld.so checks
> 'uname' in 2.4 kernels. If extraversion begins with "-ntpl" then
> this 2.4 kernel has NPTL (and TLS) support.  If extraversion doesn't
> have that string, ld.so assumes that the kernel doesn't have NPTL
> (or TLS) support.

This is RedHat/SuSE related issue.  We debian does not support nptl
2.4 kernel.

> If the kernel is >=2.6, then ld.so assumes that NPTL (and TLS)
> support is present, so things start to go haywire under UML, where
> this assumption is invalid.

NPTL/TLS is enabled when:

    (1) libc6-i686 is installed.
    (2) LD_ASSUME_KERNEL environment variable is not used or is set >2.6.

So you can disable TLS/NPTL using LD_ASSUME_KERNEL=2.4.1 or removing
libc6-i686.  If UML can provide information about TLS support for
ld.so, we can implement to disable NPTL/TLS under UML.  If not - you
need to disable NPTL/TLS by your hand.

It's UML issue, not glibc.  Should this report be opened for a while?
If you have no objection, we'll close this bug.

Regards,
-- gotom