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From Olivier Berger <>
Subject [users@httpd] Why subprocess won't dump cores on segmentation fault (prefork MPM) ?
Date Tue, 08 Jan 2013 13:04:08 GMT

(Please CC: me of any followup)

I'm running apache2 and experience a crash of (probably mod-php) some
apache child process, with the prefork MPM Debian package (see more
details in [0]).

I've had no luck in trying to get cores dumped when the child process

I've set ulimit -c unlimited, set /proc/sys/fs/suid_dumpable to 2,
managed to set CoreDumpDirectory to a dir writable by www-data user (the
one the subprocess are run under on Debian), etc.

Only the master apache2 process will dump a core on kill -11, but not
its children spawned subprocess.

Any idea how to get a backtrace of the culprit code ?

Something is trapped by PHP maybe and prevents the core dump ?

Oh, and no, running with -X seems no option : the reproducibility
involves a POST to PHP code right after an apachectl graceful
(i.e. /etc/init.d/apache2 reload) (see details in [1], a likely
duplicate of [0]).

Many thanks in advance.

Best regards,

Olivier BERGER - OpenPGP-Id: 2048R/5819D7E8
Ingenieur Recherche - Dept INF
Institut Mines-Telecom, Telecom SudParis, Evry (France)

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