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segfault error 4 in libpthread-2.13.so X86_64

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Dallas Clement

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Oct 29, 2011, 3:40:01 PM10/29/11
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Hi All,

I've got a multi-threaded C++ program that has been working for years
that is segfaulting in the pthread library at exit after upgrading to
squeeze.  It litters my kernel log with the following message:

segfault at 67eaf9d0 ip 00007f4568e87d7c sp 00007fff4571fe00 error 4
in libpthread-2.13.so[7f4568e80000+17000

I can produce a core file, but unfortunately I can't see the symbols
inside the pthread lib to determine where it is crashing.  Is there a
pthread library source package or debug version of libc / pthreads
that I can try?

# uname -a
Linux bertha 2.6.32-5-amd64 #1 SMP Mon Oct 3 03:59:20 UTC 2011 x86_64 GNU/Linux

Thanks,

Dallas


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Chow Loong Jin

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Oct 29, 2011, 3:50:02 PM10/29/11
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On 30/10/2011 03:34, Dallas Clement wrote:
>
> I can produce a core file, but unfortunately I can't see the symbols
> inside the pthread lib to determine where it is crashing. Is there a
> pthread library source package or debug version of libc / pthreads
> that I can try?

Debugging symbols can be found in the libc6-dbg package.

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Adrian Knoth

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Oct 29, 2011, 4:00:02 PM10/29/11
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On 10/29/11 21:34, Dallas Clement wrote:

> Hi All,

Hi!

> I've got a multi-threaded C++ program that has been working for years
> that is segfaulting in the pthread library at exit after upgrading to

The "at exit" bit reminds me of a bug the FFADO team has been hunting
for months.

Feel free to have a rather lengthy read of

http://subversion.ffado.org/ticket/329

If you're using custom exit functions, this might give you some
directions.

> squeeze. It litters my kernel log with the following message:
>
> segfault at 67eaf9d0 ip 00007f4568e87d7c sp 00007fff4571fe00 error 4
> in libpthread-2.13.so[7f4568e80000+17000
>
> I can produce a core file, but unfortunately I can't see the symbols
> inside the pthread lib to determine where it is crashing.

I don't think it's really something in the pthread library, but this
mailing list clearly is the wrong place to discuss.

> Is there a pthread library source package or debug version of libc /
> pthreads that I can try?

libc6-dbg?


HTH


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Dallas Clement

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Oct 29, 2011, 4:00:02 PM10/29/11
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How can I link with libc6-dbg instead of regular libc6? Thanks.
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Bernd Zeimetz

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Oct 29, 2011, 5:30:02 PM10/29/11
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Do not use TOFU on Debian lists. It just makes a mess.

On 10/29/2011 09:55 PM, Dallas Clement wrote:
> How can I link with libc6-dbg instead of regular libc6? Thanks.

http://wiki.debian.org/HowToGetABacktrace

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Dallas Clement

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Oct 29, 2011, 5:40:01 PM10/29/11
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I can see that I've got a debug version of the pthreads library
installed on my system. Just don't know how to link with it vs the
non-debug version.

/usr/lib/debug/lib/x86_64-linux-gnu# ls
libpthread-2.13.so
Archive: http://lists.debian.org/CAE9DZUSvGDk131Xii9Xj0BgD...@mail.gmail.com

brian m. carlson

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Oct 29, 2011, 5:50:01 PM10/29/11
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On Sat, Oct 29, 2011 at 02:55:54PM -0500, Dallas Clement wrote:
> How can I link with libc6-dbg instead of regular libc6? Thanks.

You don't. The files in /usr/lib/debug contain only debugging symbols
that have been stripped from the normal binary. You simply link against
libc6 as normal and gdb (and other programs) will find the debugging
symbols automatically.

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Dallas Clement

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Oct 29, 2011, 6:30:02 PM10/29/11
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That certainly makes sense. I'm still not seeing the symbols though.
My kernel log show that the segfault came from the pthreads library,
yet when I load the core file into gdb, I'm not seeing any symbols.

(gdb) bt
#0 0x00007f04e3102d7c in ?? ()
#1 0x00007f04e3e73a60 in ?? ()
#2 0x00007f04e47db695 in ?? ()
#3 0xffffffffe212a700 in ?? ()
#4 0x00007f04e3e73a60 in ?? ()
#5 0x0000000000000000 in ?? ()

Got any other ideas for me to try?
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Chow Loong Jin

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Oct 30, 2011, 3:00:02 AM10/30/11
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On 30/10/2011 06:22, Dallas Clement wrote:
> That certainly makes sense. I'm still not seeing the symbols though.
> My kernel log show that the segfault came from the pthreads library,
> yet when I load the core file into gdb, I'm not seeing any symbols.
>
> (gdb) bt
> #0 0x00007f04e3102d7c in ?? ()
> #1 0x00007f04e3e73a60 in ?? ()
> #2 0x00007f04e47db695 in ?? ()
> #3 0xffffffffe212a700 in ?? ()
> #4 0x00007f04e3e73a60 in ?? ()
> #5 0x0000000000000000 in ?? ()
>
> Got any other ideas for me to try?

You need to load the core file, *and* the program. Something like...
$ gdb -c $corefile $path_to_program
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Dallas Clement

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Oct 31, 2011, 1:20:02 AM10/31/11
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The symbols are definitely present on my system. When I step through
the execution, I can see where it is crashing inside the pthread
library. The last thing it does is join with one thread that was
previously spawned.

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7f650debe720 (LWP 3784)]
0x00007f650c5f7d7c in pthread_join (threadid=190969600,
thread_return=0x0) at pthread_join.c:46
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Chow Loong Jin

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Oct 31, 2011, 3:00:01 AM10/31/11
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On 31/10/2011 13:13, Dallas Clement wrote:
> The symbols are definitely present on my system. When I step through
> the execution, I can see where it is crashing inside the pthread
> library. The last thing it does is join with one thread that was
> previously spawned.

And so?
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Dallas Clement

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Oct 31, 2011, 3:10:02 PM10/31/11
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Just pointing out that I'm seeing a segfault inside pthread_join of
libpthread-2.13.so. I need to look at the pthread source before I can
tell why it crashed. I will also try to roll back to an older version
of this library to confirm that I was not seeing this crash earlier.
Will report back what I find.
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Jonathan Nieder

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Oct 31, 2011, 3:50:01 PM10/31/11
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Dallas Clement wrote:

> Will report back what I find.

Please don't. This is the wrong list --- it is about development _of_
Debian, not development _on_ Debian.

You might find the libc-help list[1] to be more helpful. Or if your
questions are Debian-specific, debian-user[2] can be a great help.

Hope that helps,
Jonathan

[1] see http://sourceware.org/glibc/
[2] http://lists.debian.org/debian-user/


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Ben Hutchings

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Oct 31, 2011, 5:00:01 PM10/31/11
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On Mon, Oct 31, 2011 at 02:05:03PM -0500, Dallas Clement wrote:
> Just pointing out that I'm seeing a segfault inside pthread_join of
> libpthread-2.13.so. I need to look at the pthread source before I can
> tell why it crashed. I will also try to roll back to an older version
> of this library to confirm that I was not seeing this crash earlier.

This thread is off-topic for debian-devel. And this crash is almost
certainly not a bug in libpthread. Most likely your program has
corrupted the thread state in some way. You may find that valgrind or
helgrind (both in the valgrind package) can find the bug. Please do
not ask for further help on this list.

Ben.

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