обратная трассировка — ошибка 6-го сегмента PHP-FPM

У меня проблема с php5-fpm. Очень часто он получает segfault и блокирует всю обработку php, поэтому ответ клиенту не предоставляется.
Для меня обратная трассировка выглядит как бесконечный цикл, но я не вижу, вызвана ли она скриптом или внутренним модулем php.

Есть ли шанс увидеть, какой скрипт / модуль задействован?

Segfault всегда выглядит так (вывод dmesg):

php5-fpm[1858]: segfault at 7fffa4de4fa0 ip 0000000000691515 sp 00007fffa4de4f90 error 6 in php5-fpm[400000+800000]

Версия PHP:

php -v
PHP 5.5.9-1ubuntu4.11 (cli) (built: Jul  2 2015 15:23:08)
Copyright (c) 1997-2014 The PHP Group
Zend Engine v2.5.0, Copyright (c) 1998-2014 Zend Technologies
with Zend OPcache v7.0.3, Copyright (c) 1999-2014, by Zend Technologies

Обратный след Coredump:

(gdb) bt
#0  0x0000000000691515 in ?? ()
#1  0x0000000000692a64 in vspprintf ()
#2  0x0000000000707359 in zend_spprintf ()
#3  0x00000000006e4a46 in _convert_to_string ()
#4  0x0000000000725859 in ?? ()
#5  0x0000000000717668 in execute_ex ()
#6  0x00000000006dd7c9 in dtrace_execute_ex ()
#7  0x000000000079df80 in ?? ()
#8  0x0000000000717668 in execute_ex ()
#9  0x00000000006dd7c9 in dtrace_execute_ex ()
#10 0x000000000079df80 in ?? ()
#11 0x0000000000717668 in execute_ex ()
#12 0x00000000006dd7c9 in dtrace_execute_ex ()
#13 0x000000000079df80 in ?? ()
#14 0x0000000000717668 in execute_ex ()
#15 0x00000000006dd7c9 in dtrace_execute_ex ()
#16 0x000000000079df80 in ?? ()
#17 0x0000000000717668 in execute_ex ()
#18 0x00000000006dd7c9 in dtrace_execute_ex ()
#19 0x000000000079df80 in ?? ()
#20 0x0000000000717668 in execute_ex ()
#21 0x00000000006dd7c9 in dtrace_execute_ex ()
#22 0x000000000079df80 in ?? ()
#23 0x0000000000717668 in execute_ex ()
#24 0x00000000006dd7c9 in dtrace_execute_ex ()
#25 0x000000000079df80 in ?? ()
#26 0x0000000000717668 in execute_ex ()
#27 0x00000000006dd7c9 in dtrace_execute_ex ()
#28 0x000000000079df80 in ?? ()
#29 0x0000000000717668 in execute_ex ()
#30 0x00000000006dd7c9 in dtrace_execute_ex ()
#31 0x000000000079df80 in ?? ()
#32 0x0000000000717668 in execute_ex ()
#33 0x00000000006dd7c9 in dtrace_execute_ex ()
#34 0x000000000079df80 in ?? ()
#35 0x0000000000717668 in execute_ex ()
#36 0x00000000006dd7c9 in dtrace_execute_ex ()
#37 0x000000000079df80 in ?? ()
#38 0x0000000000717668 in execute_ex ()
#39 0x00000000006dd7c9 in dtrace_execute_ex ()
#40 0x000000000079df80 in ?? ()
#41 0x0000000000717668 in execute_ex ()
#42 0x00000000006dd7c9 in dtrace_execute_ex ()
#43 0x000000000079df80 in ?? ()
#44 0x0000000000717668 in execute_ex ()
#45 0x00000000006dd7c9 in dtrace_execute_ex ()
#46 0x000000000079df80 in ?? ()
(...)
#68150 0x0000000000717668 in execute_ex ()
#68151 0x00000000006dd7c9 in dtrace_execute_ex ()
#68152 0x000000000079df80 in ?? ()
#68153 0x0000000000717668 in execute_ex ()
#68154 0x00000000006dd7c9 in dtrace_execute_ex ()
#68155 0x000000000079df80 in ?? ()
#68156 0x0000000000717668 in execute_ex ()
#68157 0x00000000006dd7c9 in dtrace_execute_ex ()
#68158 0x000000000079cec1 in ?? ()
#68159 0x0000000000717668 in execute_ex ()
#68160 0x00000000006dd7c9 in dtrace_execute_ex ()
#68161 0x00000000006ef250 in zend_execute_scripts ()
#68162 0x000000000068f065 in php_execute_script ()
#68163 0x0000000000463b00 in main ()

Backtrace получить имя файла:

(gdb) print (char *)executor_globals.active_op_array->filename
Attempt to extract a component of a value that is not a structure.

Установленные пакеты:

dpkg -l | grep php
ii  php5-apcu                           4.0.2-2build1                       amd64        APC User Cache for PHP 5
ii  php5-cli                            5.5.9+dfsg-1ubuntu4.11              amd64        command-line interpreter for the php5 scripting language
ii  php5-common                         5.5.9+dfsg-1ubuntu4.11              amd64        Common files for packages built from the php5 source
ii  php5-curl                           5.5.9+dfsg-1ubuntu4.11              amd64        CURL module for php5
ii  php5-fpm                            5.5.9+dfsg-1ubuntu4.11              amd64        server-side, HTML-embedded scripting language (FPM-CGI binary)
ii  php5-gd                             5.5.9+dfsg-1ubuntu4.11              amd64        GD module for php5
ii  php5-json                           1.3.2-2build1                       amd64        JSON module for php5
ii  php5-mcrypt                         5.4.6-0ubuntu5                      amd64        MCrypt module for php5
ii  php5-mysqlnd                        5.5.9+dfsg-1ubuntu4.11              amd64        MySQL module for php5 (Native Driver)
ii  php5-readline                       5.5.9+dfsg-1ubuntu4.11              amd64        Readline module for php5