Re: seg fault in modperl_perl_global_request_save

On 09-12-30 16:28 , Alex Aminoff wrote:
> 
> 1. Problem Description:
> 
> Our production apache22/mod_perl2 web server segfaults regularly. I
> have tracked down this problem as much as I can, and could use some
> help. This is running on FreeBSD; the same problem occurs on FreeBSD
> 7.0, 7.2, and 8.0. apache22 is installed from ports, with WITH_DEBUG
> and WITH_EXECPTION_HOOK; mod_perl2 is installed from ports, my
> attempts to compile it with debug flags appear so far to be
> unsuccessful. (detailed version info below)
> 
> For no reason I can fathom, I can not seem to get apache to dump core
> when it seg faults. I've set CoreDumpDirectory, I've set ulimit
> coredumpsize, nothing.  No matter; I was able to install
> mod_whatkilledus and mod_backtrace.
> 
> mod_whatkilledus shows that the segfaults happen on a wide variety of
> requests; most requests to our main web server are handled by
> mod_perl, either with a ResponseHandler or a FilterHandler.
> 
> mod_backtrace shows that the seg fault is always happening in
> modperl_perl_global_request_save:
> 
> [Wed Dec 30 15:05:41 2009] pid 6955 mod_backtrace backtrace for sig 11
> (thread "pid" 6955)
> [Wed Dec 30 15:05:41 2009] pid 6955 mod_backtrace main() is at 8063880
> 0x8085a26 <ap_run_fatal_exception+70> at /usr/local/sbin/httpd
> 0x808752e <ap_mpm_set_exception_hook+238> at /usr/local/sbin/httpd
> 0x8087569 <ap_mpm_set_exception_hook+297> at /usr/local/sbin/httpd
> 0xbfbfffb4
> 0x287a83c5 <modperl_perl_global_request_save+213> at
> /usr/local/libexec/apache22/mod_perl.so
> 0x2879982d <modperl_response_handler_cgi+141> at
> /usr/local/libexec/apache22/mod_perl.so
> 0x807bc66 <ap_run_handler+70> at /usr/local/sbin/httpd
> ...
> 
> So, any general pointers for what direction to go next would be
> appreciated. I would like to have mod_backtrace tell me what in my
> perl code is triggering the error, in which case I could work around
> it. Should I continue to pursue recompiling mod_perl2 and possibly
> perl itself with more debugging turned on?

Most certainly, yes.  A stack trace without debugging symbols is not
very useful in trying to pin down the source of a segfault bug.

-- 
Philippe M. Chiasson     GPG: F9BFE0C2480E7680 1AE53631CB32A107 88C3A5A5
http://gozer.ectoplasm.org/       m/gozer\@(apache|cpan|ectoplasm)\.org/

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