Message-ID: <3d53b7120703141444k6484ccfeyd08cf60ecbbb894a@mail.gmail.com>
Date:	Thu, 15 Mar 2007 03:14:54 +0530
From:	"Syed Ahemed" <kingkhan@...il.com>
To:	"Willy Tarreau" <w@....eu>
Cc:	linux-kernel@...r.kernel.org, msnyder@...hat.com,
	jjohnstn@...hat.com
Subject: Re: NPTL patch for linux 2.4.28

 Thanks for the answer , I have already checked the core files size
diff which was surprising in a way.The corefile on linux 2.4.28 (which
actually shows less information than redhat) is bigger than redhat's
2.4.20-8 system core file.
Which brings me to the point that it has to be the generation of
corefiles and as a result lack of debugging support in 2.4.28 that is
causing the problem ( With or without NPTL is what i am out to find
out.

Getting RHEL's source ( http://lkml.org/lkml/2005/3/21/380 ) was an
idea i thought about but then a download of the RHEL source from the
following location was denied .
http://download.fedora.redhat.com/pub/fedora/linux/core/1/SRPMS/  and
the rpmfind site.
(Guess need to be a paid subscriber for that right ?)

Apart from the fact that am relying on a "free " patch (even if that
means i have to spend time forward porting it to 2.4.28 ) .I cannot go
the RHEL way for fear of having to port or debug custom applications
written on 2.4.28 .

I totally understand the fact that 2.4.28 does rarely have support for
patches and updates relative to the more active 2.4.20 or 2.6 kernel
,I still wonder why there aren't any NPTL patches available in the
non-redhat sites for kernels like 2.4.21 or more .
Please point me to NPTL patch location or the kernel SRPM if you could.

Regards
Azhar



On 3/14/07, Willy Tarreau <w@....eu> wrote:
> On Wed, Mar 14, 2007 at 05:49:22AM +0530, Syed Ahemed wrote:
> > Hello all.
> > I have a tricky problem on  hand and a straight forward question.
> >
> > Tricky problem:
> > ---------------------
> > While debugging a simple multithreaded application using gdb linux
> > 2.4.28 , i noticed the thread that has crashed after sigsegv has
> > complete information on the gdb (both  address and function at the
> > time of crash ) .But the other threads that are in wait state (
> > executing glibc functions at the time of crash ) just has the address
> > but not the function name as shown below.
> >
> >
> > sh-2.05b# ./gdb a.out /mnt/cf/engg_files/core_files/
> > a.out.1173437318.core.5312   a.out.1173453940.core.9829
> > a.out.1173438125.core.16016  lost+found
> > a.out.1173438881.core.18721
> > <f/engg_files/core_files/a.out.1173453940.core.9829
> > GNU gdb 6.3
> > Copyright 2004 Free Software Foundation, Inc.
> > GDB is free software, covered by the GNU General Public License, and you are
> > welcome to change it and/or distribute copies of it under certain
> > conditions.
> > Type "show copying" to see the conditions.
> > There is absolutely no warranty for GDB.  Type "show warranty" for details.
> > This GDB was configured as "i686-pc-linux-gnu"...Using host libthread_db
> > library
> > "/lib/libthread_db.so.1".
> >
> > warning: exec file is newer than core file.
> > Core was generated by `./a.out'.
> > Program terminated with signal 11, Segmentation fault.
> > Reading symbols from /lib/libpthread.so.0...done.
> > Loaded symbols for /lib/libpthread.so.0
> > Reading symbols from /lib/libc.so.6...done.
> > Loaded symbols for /lib/libc.so.6
> > Reading symbols from /opt/lib/ld-linux.so.2...done.
> > Loaded symbols for /opt//lib/ld-linux.so.2
> > #0  0x080485df in a (p=0x0) at threadcore.c:34
> > 34      threadcore.c: No such file or directory.
> >        in threadcore.c
> > (gdb) info threads
> >  3 process 10993  0x08053840 in ?? ()
> >  2 process 1267  0xbf5ff9d0 in ?? ()
> > * 1 process 9829  0x080485df in a (p=0x0) at threadcore.c:34
> > (gdb) thread 3
> > [Switching to thread 3 (process 10993)]#0  0x08053840 in ?? ()
> > (gdb) bt
> > #0  0x08053840 in ?? ()
> > Cannot access memory at address 0x2b
> > (gdb)
> > #0  0x08053840 in ?? ()
> > Cannot access memory at address 0x2b
> > (gdb) thread 1
> > [Switching to thread 1 (process 9829)]#0  0x080485df in a (p=0x0)
> >    at threadcore.c:34
> > 34      in threadcore.c
> > (gdb) bt
> > #0  0x080485df in a (p=0x0) at threadcore.c:34
> > #1  0x080485bc in main () at threadcore.c:21
> > (gdb) thread 2
> > [Switching to thread 2 (process 1267)]#0  0xbf5ff9d0 in ?? ()
> > (gdb) bt
> > #0  0xbf5ff9d0 in ?? ()
> > Cannot access memory at address 0x2b
> > (gdb) q
> > sh-2.05b#
> >
> >
> > The problem is with the same glibc and gdb , Redhat 9 linux 2.4.20-8
> > does  give me complete information of all the threads in the "info
> > threads" command.
> > Having read similar problems on various mailing lists , i believe the
> > only difference is redhat 9 has patched its kernel with NTPL or
> > debugging support for linux in the kernel.
> >
> > Wanted to confirm if it this correct .
>
> I really have no idea about this problem.
>
> > My question
> > ------------------
> >
> > Someone would say move to 2.6 kernel and a different glibc,But with
> > custom applications at stake .I can't take that risk as yet .So i
> > would want an NTPL patch for 2.4.28 kernel
> > Where do i get it ? Please do respond .
>
> Last time I saw an NPTL patch, it was for something like 2.4.21 patched
> with O(1) scheduler. I bet you'll have a hard time merging those together
> in 2.4.28. It is also possible that core dumps don't look the same. I
> have in mind some old changes about thread core dumps, but that's too
> far away to say anything reliable on the subject. Check that your core
> files are of the same sizes between NPTL and no-NPTL kernels.
>
> Alternatively, you could try RHEL3's kernel (2.4.21) which has all those
> things and which is still supported.
>
> Regards,
> Willy
>
>


-- 
Azhar khan

I'm afraid that I've seen too many people fix bugs by looking at
debugger output, and that almost inevitably leads to fixing the
symptoms rather than the underlying problems.
	
--Linus
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