Bug 135201

Summary:	sys-libs/glibc-2.4 tls/xen-support request (-mno-tls-direct-seg-refs)
Product:	Gentoo Linux	Reporter:	Daniel Webert <rockoo>
Component:	New packages	Assignee:	Gentoo Toolchain Maintainers <toolchain>
Status:	RESOLVED FIXED
Severity:	enhancement	CC:	chrb
Priority:	High
Version:	unspecified
Hardware:	All
OS:	All
Whiteboard:
Package list:		Runtime testing required:	---

Description Daniel Webert 2006-06-01 14:07:45 UTC

sys-libs/glibc-2.4 tls/xen-support request

<snip>
http://wiki.xensource.com/xenwiki/XenSpecificGlibc
It is possible to rebuild glibc so that it only uses segments such that there is no performance penalty. To do this, you need to apply the patch below to the glibc sources and then rebuild glibc with the -mno-tls-direct-seg-refs option.

This patch is not needed for glibc-2.4. It automatically accesses the segments correctly when it detects that it is compiled with the -mno-tls-direct-seg-refs option.
</snip>

Comment 1 Chris Bainbridge (RETIRED) gentoo-dev

2006-06-01 15:05:02 UTC

Well, you can compile with -mno-tls-direct-seg-refs already in CFLAGS.

I don't maintain glibc, so passing this over. As you say, you could just use glibc-2.4.

Comment 2 SpanKY gentoo-dev

2006-06-04 02:13:23 UTC

those fixes are already in glibc-2.3.5 and glibc-2.3.6
http://sourceware.org/ml/glibc-cvs/2005-q1/msg00206.html
http://sources.redhat.com/bugzilla/show_bug.cgi?id=737

we arent supporting anything older than 2.3.6 now

as for adding -mno-tls-direct-seg-refs to all glibc CFLAGS, the answer is no

Comment 3 Daniel Webert 2006-06-05 08:41:45 UTC

ups - spank me - i explained the issue inadequate :( 
as mentioned in comment #1 we can use 'no-tls-direct' in the cflags - so what a about a einfo in the xen-ebuild howto ...

Comment 4 Chris Bainbridge (RETIRED) gentoo-dev

2006-06-05 11:54:43 UTC

It's already mentioned in the xen gentoo wiki which you ebuild points you to.

Comment 5 Chris Bainbridge (RETIRED) gentoo-dev

2006-07-30 03:24:06 UTC

Perhaps something like the following could be added to the glibc ebuild?

if [[ -e /proc/xen ]] && ! is-flag -mno-tls-direct-seg-refs; then ewarn "You are using Xen but don't have -mno-tls-direct-seg-refs in your CFLAGS. This will result in a 50% performance penalty, which is probably not what you want."; fi

Some people are obviously still tripping over this bug, maybe this would help.

Comment 6 SpanKY gentoo-dev

2006-07-30 10:31:01 UTC

post a diff

Comment 7 SpanKY gentoo-dev

2006-09-24 02:56:25 UTC

added warning to cvs