Xen users - Nov 2008 - [booting message]: WARNING: ****/lib/tls glibc libraries****

Hi,

On booting, how can I avoid the following messages?
What does it mean? Can anyone provide with some detail?

  ***************************************************************
  ***************************************************************
  ** WARNING: Currently emulating unsupported memory accesses  **
  **          in /lib/tls glibc libraries. The emulation is    **
  **          slow. To ensure full performance you should      **
  **          install a ''xen-friendly'' (nosegneg) version of  
**
  **          the library, or disable tls support by executing **
  **          the following as root:                           **
  **          mv /lib/tls /lib/tls.disabled                    **
  ** Offending process: init (pid=699)                         **
  ***************************************************************
  ***************************************************************

Thanks,

Shawn


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Hi,

I moved the /usr/lib/tls to /usr/lib/tls.disabled as told by the message, but
the warning did not disappear.
I just commented the lines in arck/i386/kernel/fixup.c, then recompiled the
kernel.
Now, it is eventually avoided. I don't know if it is the rightest way,
nonetheless it works.

Thanks,
Shawn

------------------				 
Y. D.
2008-11-08

-------------------------------------------------------------
From：javera
Date：2008-11-08 21:37:37
To：Y. D.
Cc：
Subject：Re: [Xen-users] [booting message]: WARNING: ****/lib/tls
glibclibraries****

Hi list.  

You should move /usr/lib/tls to /usr/lib/tls.org for removing these messages
when system boots.


---

-----Original Message-----
From: "Y. D." <duyuyang@gmail.com>

Date: Sat, 8 Nov 2008 19:33:17 
To: xen-users<xen-users@lists.xensource.com>
Subject: [Xen-users] [booting message]: WARNING: ****/lib/tls glibc
	libraries****


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On Sat, 2008-11-08 at 22:08 +0800, Y. D. wrote:
> Hi,
> 
> I moved the /usr/lib/tls to /usr/lib/tls.disabled as told by the message,
but the warning did not disappear.
> I just commented the lines in arck/i386/kernel/fixup.c, then recompiled the
kernel.
> Now, it is eventually avoided. I don''t know if it is the rightest
way, nonetheless it works.
Init is probably statically linked against your C library (in this case
glibc). Your version of init was not built against Xen friendly libc,
hence you see this warning every time init runs.

The reason that disabling tls did not make it go away is because init is
not loading those shared objects. Your better off installing libc-xen
and recompiling init. 

Taking that code out of fixup is most decidedly a bad idea. If for some
reason you happen upon some threading service that is statically linked,
you''ll have very little clue as to why things keep dying :)

For something like init, the warning is trivial. If something like ... a
web server threw that warning, it would be a big problem, as it
indicates that the service itself is statically linked against a
xen-unfriendly libc.

Really, in most cases, its safe to ignore. If a boss or co-worker is
panicking about it, just rebuild the offending program.

Cheers,
--Tim



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Init is probably statically linked against your C library (in this case
glibc). Your version of init was not built against Xen friendly libc,
hence you see this warning every time init runs.

I have libc6-xen installed already, however, the xen friendly library is not
statically linked by init according to your explanation. How should it be?

The reason that disabling tls did not make it go away is because init is
not loading those shared objects. Your better off installing libc-xen
and recompiling init. 

I don''t know much about this. How should libc-xen be properly used as
an substitute of libc in face of libc''s being.

Thanks,
Shawn


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On Sun, 2008-11-09 at 14:44 +0800, Y. D. wrote:
> Init is probably statically linked against your C library (in this case
> glibc). Your version of init was not built against Xen friendly libc,
> hence you see this warning every time init runs.
> 
>  
> I have libc6-xen installed already, however, the xen friendly library
> is not statically linked by init according to your explanation. How
> should it be?
Its not going to be unless you get the source package to init and
recompile it. Your copy of init was built by your distribution and links
against a regular libc (likely, statically).

In order to change that, you will have to recompile it after installing
xen friendly libc. There is __really__ no need to do this, warnings
thrown by programs like init are completely harmless and can be ignored.
 
> I don''t know much about this. How should libc-xen be properly used
as
> an substitute of libc in face of libc''s being.
libc-xen replaces most things in /lib/tls. That means, any process using
those objects is safe, which is 99.9% of everything installed by your
OS. Most programs just link dynamically, loading lib-foo.so at run time.

If, however, a program is statically linked, libc becomes a part of that
program. This means future updates to libc will make no difference to
the program, as a copy of whatever version was linked in becomes a part
of the executable itself. If you rename /lib/tls to something else ...
and the program still throws the warning .. its statically linked.

In your case, the only thing statically linked is init, which isn''t
worth fussing with unless you __really__ need that warning to go away.

What I would not do is remove the warning entirely, or you will not be
alerted if you install some threading service that happens to be
statically linked with unfriendly tls.

I know its a little confusing .. but really, when talking about init ..
that warning is completely harmless.


Cheers,
--Tim



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