Subject: gdb: Cannot find new threads: generic error
From: Markus Fischer <markus@fischer.name>
Date: Mon, 28 Apr 2008 18:15:51 +0200

Hi,

I'm not sure if this is related at all to the vserver, but I can't 
figure out what's going on/wrong.

I'm running

# vserver-info
Versions:
                    Kernel: 2.6.22.19-vs2.2.0.7
                    VS-API: 0x00020200
              util-vserver: 0.30.212; Dec  9 2006, 12:26:51

Features:
                        CC: gcc, gcc (GCC) 4.1.2 20061115 (prerelease) 
(Debian 4.1.1-20)
                       CXX: g++, g++ (GCC) 4.1.2 20061115 (prerelease) 
(Debian 4.1.1-20)
                  CPPFLAGS: ''
                    CFLAGS: '-Wall -g  -O2 -std=c99 -Wall -pedantic -W 
-funit-at-a-time'
                  CXXFLAGS: '-g -O2 -ansi -Wall -pedantic -W 
-fmessage-length=0 -funit-at-a-time'
                build/host: i486-pc-linux-gnu/i486-pc-linux-gnu
              Use dietlibc: yes
        Build C++ programs: yes
        Build C99 programs: yes
            Available APIs: compat,v11,fscompat,v13,net,v21,oldproc,olduts
             ext2fs Source: e2fsprogs
     syscall(2) invocation: alternative
       vserver(2) syscall#: 273/glibc

Paths:
                    prefix: /usr
         sysconf-Directory: /etc
             cfg-Directory: /etc/vservers
          initrd-Directory: $(sysconfdir)/init.d
        pkgstate-Directory: /var/run/vservers
           vserver-Rootdir: /var/lib/vservers

In a vserver I'm running debian testing with

# gdb --version
GNU gdb 6.7.1-debian

trying to debug php

# php -c . -v
PHP 5.2.3-1+lenny1 (cli) (built: Oct  3 2007 19:22:40)
Copyright (c) 1997-2007 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies

However I always get this:

qa01:~# gdb php
GNU gdb 6.7.1-debian
Copyright (C) 2007 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
<http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "i486-linux-gnu"...
(no debugging symbols found)
Using host libthread_db library "/lib/libthread_db.so.1".
(gdb) r
Starting program: /usr/bin/php
(no debugging symbols found)
[repeated a lot of times]
[Thread debugging using libthread_db enabled]
Error while reading shared library symbols:
Cannot find new threads: generic error
Cannot find new threads: generic error

I'm pretty sure I've debugged this way in the past, but now it doesn't 
work anymore because of this "generic errors".

Does anyone have a clue if this is possibly related to vserver somehow? 
Or am I on the complete wrong track?

thanks,
- Markus