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first time debugging apache/mod_perl Seg fault

Alan McKay

2009-07-13

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Hey folks,

I'm running CentOS 5.2 with a custom built apache not from Yum.

I am following instructions here
http://perl.apache.org/docs/2.0/devel/debug/c.html#Getting_the_core_File_Dumped

and here :
http://perl.apache.org/docs/2.0/devel/debug/c.html#Analyzing_Dumped_Core_Files

I have mod_perl built with symbols and reproduce my problem, but I'm
not having much luck with gdb. I really have no experience with this
aspect of Linux so am shooting in the dark a bit here.

I also have no idea whether I'm "threaded" or "unthreaded", so I tried
both of the "curinfo" macros with no luck.

Here is the output of "bt full" which clearly shows a few "my_perl"
entries.  But I'm just not clear how to find out what part of our
Perl code is causing the issue.

(gdb) bt full
#0 0x0044e172 in Perl_cv_const_sv () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#1 0x00442a7c in Perl_yylex () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#2 0x0044b295 in Perl_yyparse () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#3 0x004b8200 in Perl_pp_range () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#4 0x004ba0b2 in Perl_pp_require () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#5 0x004ba7ad in Perl_pp_dofile () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#6 0x0048488f in Perl_runops_standard () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#7 0x00424ffe in Perl_magicname () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#8 0x00429806 in Perl_call_sv () from
/usr/lib/perl5/5.8.8/i386-linux-thread-multi/CORE/libperl.so
No symbol table info available.
#9 0x00140a7f in modperl_callback (my_perl=0x9476458,
handler=0xaccc268, p=0xaf2a840, r=0xaf2a880, s=0xad0bad0,
args=0xbd473e8) at modperl_callback.c:101
    items = <value optimized out>
    cv = <value optimized out>
    sp = (SV **) 0xafead24
    status = 0
#10 0x0014117a in modperl_callback_run_handlers (idx=6, type=4,
r=0xaf2a880, c=0x0, s=0xad0bad0, pconf=0x0, plog=0x0, ptemp=0x0,
run_mode=MP_HOOK_RUN_FIRST)
  at modperl_callback.c:262
    my_perl = (PerlInterpreter *) 0x9476458
    interp = (modperl_interp_t *) 0xa965888
    scfg = (modperl_config_srv_t *) 0x8d437b8
    dcfg = (modperl_config_dir_t *) 0xaf2a2e0
    rcfg = (modperl_config_req_t *) 0xaf2b5f0
    handlers = (modperl_handler_t **) 0xaccc298
    p = (apr_pool_t *) 0xaf2a840
    av = (MpAV *) 0xaccc280
    avp = <value optimized out>
    i = 0
    status = 0
    desc = 0x158cd3 "PerlResponseHandler"
    av_args = (AV *) 0xbd473e8
#11 0x0014180a in modperl_callback_per_dir (idx=6, r=0xaf2a880,
run_mode=MP_HOOK_RUN_FIRST) at modperl_callback.c:369
No locals.
#12 0x0013a79f in modperl_response_handler_run (r=0xaf2a880, finish=0)
at mod_perl.c:1000
    retval = <value optimized out>
#13 0x0013a96b in modperl_response_handler_cgi (r=0xaf2a880) at mod_perl.c:1100
    dcfg = (modperl_config_dir_t *) 0xaf2a2e0
    h_stdin = (GV *) 0xc2d7a20
    h_stdout = (GV *) 0xb4ba144
    retval = -1
    rc = <value optimized out>
    rcfg = (modperl_config_req_t *) 0xaf2b5f0
    my_perl = (PerlInterpreter *) 0x9476458
    interp = (modperl_interp_t *) 0xa965888
#14 0x08076a79 in ap_run_handler (r=0xaf2a880) at config.c:157
    n = 6
    rv = 40
#15 0x08079be7 in ap_invoke_handler (r=0xaf2a880) at config.c:372
    handler = 0x0
    result = <value optimized out>
    old_handler = 0xaccbe38 "perl-script"
    ignore = <value optimized out>
#16 0x08090798 in ap_process_request (r=0xaf2a880) at http_request.c:258
---Type <return> to continue, or q <return> to quit---
    access_status = 0
#17 0x0808da3b in ap_process_http_connection (c=0xaf1a9d8) at http_core.c:190
    r = (request_rec *) 0xaf2a880
    csd = (apr_socket_t *) 0x0
#18 0x0807dab9 in ap_run_process_connection (c=0xaf1a9d8) at connection.c:43
    n = 1
    rv = 40
#19 0x080a3dc5 in child_main (child_num_arg=<value optimized out>) at
prefork.c:650
    numdesc = 0
    pdesc = (const apr_pollfd_t *) 0x0
    current_conn = (conn_rec *) 0xaf1a9d8
    csd = (void *) 0xaf1a840
    ptrans = (apr_pool_t *) 0xaf1a800
    allocator = (apr_allocator_t *) 0x9301738
    status = <value optimized out>
    i = <value optimized out>
    lr = <value optimized out>
    pollset = (apr_pollset_t *) 0xaf18850
    sbh = (ap_sb_handle_t *) 0xaf18848
    bucket_alloc = (apr_bucket_alloc_t *) 0xaf1c808
    last_poll_idx = 0
#20 0x080a4087 in make_child (s=0x8d2fd70, slot=28) at prefork.c:746
    pid = 0
#21 0x080a49e0 in ap_mpm_run (_pconf=0x8d070a8, plog=0x8d451a0,
s=0x8d2fd70) at prefork.c:881
    status = 0
    pid = {pid = -1, in = 0x8d01250, out = 0x2, err = 0xd070a8}
    child_slot = <value optimized out>
    exitwhy = APR_PROC_EXIT
    processed_status = <value optimized out>
    index = <value optimized out>
    remaining_children_to_start = 0
    rv = <value optimized out>
#22 0x08064645 in main (argc=147869856, argv=0xaf187f8) at main.c:740
    c = 0 '\0'
    configtestonly = 0
    confname = 0x80ae357 "conf/httpd.conf"
    def_server_root = 0x80ae367 "/usr/local/apache2"
    temp_error_log = 0x0
    error = <value optimized out>
    process = (process_rec *) 0x8d05130
    server_conf = <value optimized out>
    pglobal = (apr_pool_t *) 0x8d050a0
    pconf = (apr_pool_t *) 0x8d070a8
    plog = (apr_pool_t *) 0x8d451a0
    ptemp = (apr_pool_t *) 0x8d491b0
    pcommands = (apr_pool_t *) 0x8d090b0
    opt = (apr_getopt_t *) 0x8d09150
    rv = 0
    optarg = 0x3b6ff4 "\234m;"
(gdb)


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