Tag Archives: ubuntu

Ubuntu 10.10, modperl and Apache segfaulting fixed

Last month, before moving to Melbourne, where I am now, to work in the Opera Australia office for a few months, I had to setup a laptop for all the development work I normally do. So I chose Ubuntu 10.10 amd64. I have to say I'm quite happy with it. Everything works out of the box for me, including a Quickcam 9000 USB camera I used to shoot this poor time-lapse video from my new office window. Woot!

Anyway, the development environment for one particular project consists of Apache and mod_perl. So I setup the usual list of dependencies, but when I tried to start Apache to run the test suite, it would always stop right away with a segmentation fault.

Didn't really dig into the problem. Just straced the apache process, and that's what I got:

[apache starts up, reads a bunch of Perl modules, and opens the access  
brk(0x7f342adbd000)                     = 0x7f342adbd000
brk(0x7f342adde000)                     = 0x7f342adde000
brk(0x7f342adff000)                     = 0x7f342adff000
brk(0x7f342ae20000)                     = 0x7f342ae20000
brk(0x7f342ae41000)                     = 0x7f342ae41000
stat("/usr/lib/perl5/auto/DBI/DESTROY.al", 0x7f341e8459b0) = -1 ENOENT (No  
such file or directory)
stat("/home/cosimo/src/auth-svn/lib/auto/DBI/DESTROY.al", 0x7fffc4e2d520)  
= -1 ENOENT (No such file or directory)
0x7fffc4e2d520) = -1 ENOENT (No such file or directory)
stat("/etc/perl/auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1 ENOENT (No such  
file or directory)
stat("/usr/local/lib/perl/5.10.1/auto/DBI/DESTROY.al", 0x7fffc4e2d520) =  
-1 ENOENT (No such file or directory)
stat("/usr/local/share/perl/5.10.1/auto/DBI/DESTROY.al", 0x7fffc4e2d520) =  
-1 ENOENT (No such file or directory)
stat("/usr/lib/perl5/auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1 ENOENT (No  
such file or directory)
stat("/usr/share/perl5/auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1 ENOENT  
(No such file or directory)
stat("/usr/lib/perl/5.10/auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1 ENOENT  
(No such file or directory)
stat("/usr/share/perl/5.10/auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1  
ENOENT (No such file or directory)
stat("/usr/local/lib/site_perl/auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1  
ENOENT (No such file or directory)
stat("./auto/DBI/DESTROY.al", 0x7fffc4e2d520) = -1 ENOENT (No such file or  
stat("/var/tmp/test_cosimo_22931/auto/DBI/DESTROY.al", 0x7fffc4e2d520) =  
-1 ENOENT (No such file or directory)
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++

I thought it would be wiser to ask for advice on the DBI and mod_perl mailing lists. Tim Bunce suggested to try and get a stack trace of Apache. Why didn't I think of that in the first place? A few days later, I got my stack trace:

# gdb -c ./core /usr/sbin/apache2 
Reading symbols from ... 
Core was generated by `/usr/sbin/apache2 -d /var/tmp/test_cosimo_9727 -k 
start -C User cosimo -C Group ...'. 

Program terminated with signal 11, Segmentation fault. 
#0 0x00007fdaedfed858 in XS_Class__XSAccessor_END () 
from /usr/lib/perl5/auto/Class/XSAccessor/XSAccessor.so 
(gdb) backtrace 
#0 0x00007fdaedfed858 in XS_Class__XSAccessor_END () 
from /usr/lib/perl5/auto/Class/XSAccessor/XSAccessor.so 
#1 0x00007fdaf83cf845 in Perl_pp_entersub () from /usr/lib/libperl.so.5.10 
#2 0x00007fdaf83752c6 in Perl_call_sv () from /usr/lib/libperl.so.5.10 
#3 0x00007fdaf86ad40b in modperl_perl_call_list () 
from /usr/lib/apache2/modules/mod_perl.so 
#4 0x00007fdaf86b5786 in modperl_perl_destruct () 
from /usr/lib/apache2/modules/mod_perl.so 
#5 0x00007fdaf86a6256 in modperl_interp_destroy () 
from /usr/lib/apache2/modules/mod_perl.so 
#6 0x00007fdaf86a6715 in modperl_tipool_destroy () 
from /usr/lib/apache2/modules/mod_perl.so 
#7 0x00007fdaf86a62b2 in modperl_interp_pool_destroy () 
from /usr/lib/apache2/modules/mod_perl.so 
#8 0x00007fdaf98fd4e3 in ?? () from /usr/lib/libapr-1.so.0 
#9 0x00007fdaf98fc3b1 in apr_pool_destroy () from /usr/lib/libapr-1.so.0 
#10 0x00007fdaf98fc27f in apr_pool_clear () from /usr/lib/libapr-1.so.0 
#11 0x00007fdafa1b960d in main (argc=11, argv=0x7fff93b50ef8) 
at /build/buildd/apache2-2.2.16/server/main.c:692

Even if you don't know anything about stack traces, this output gently points to Class::XSAccessor. Perrin Harkins on the mod_perl list suggested to update Class::XSAccessor to the latest CPAN version, since its changelog mentioned some segmentation faults fixed in 0.10.

And that did it. No more segfaults on Ubuntu 10.10. Solution: upgrade Class::XSAccessor to 0.10+. Thanks to Class::XSAccessor maintainer(s)!

Ubuntu 8.04 and Perl OpenGL extension

Recently, I was trying to install the perl OpenGL module for a fun hack I'm trying to write at home.

There was no way of getting it installed. The compilation didn't succeed. The error message from the compiler was something along the line of:

... /usr/lib/xorg/extensions/glx.so: Undefined symbol GetTimeInMillis ...

Searching on the web held the following result (just 1):

Perl and OpenGL: http://ubuntuforums.org/showthread.php?t=948812

Reading the thread, from last October, it was clear that the author found no solution to this problem. A look at the OpenGL extension, and in particular, to its build script revealed that you can compile and link the OpenGL extension with different GL libraries.

Turns out that Ubuntu works with the FREEGLUT library. Thus, doing:

$ wget http://cpan.perl.org/modules/by-module/OpenGL/OpenGL-0.57.tar.gz
$ tar xzvf OpenGL-0.57.tar.gz
$ cd OpenGL-0.57
$ perl Makefile.PL interface=FREEGLUT
$ make
$ make test
(a small demo application should run...)
$ sudo make install

should build and install the OpenGL extension.
More about my fun project later… It's going to be presented at the Nordic Perl Workshop next April…