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Date:      Tue, 18 Oct 2011 19:59:22 +0200
From:      Fabian Keil <freebsd-listen@fabiankeil.de>
To:        freebsd-stable@freebsd.org
Subject:   Re: Setting coredumpsize on a running process?
Message-ID:  <20111018195922.747d239f@fabiankeil.de>
In-Reply-To: <CAF-QHFWX3zFjskA4WOhgh%2B9E5Ap139_E3gvE5vkM_b2xgoQfjQ@mail.gmail.com>
References:  <j7k2lb$k85$1@dough.gmane.org> <20111018144312.GA17496@icarus.home.lan> <CAF-QHFWX3zFjskA4WOhgh%2B9E5Ap139_E3gvE5vkM_b2xgoQfjQ@mail.gmail.com>

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Ivan Voras <ivoras@freebsd.org> wrote:

> On 18 October 2011 16:43, Jeremy Chadwick <freebsd@jdc.parodius.com> wrot=
e:
> > On Tue, Oct 18, 2011 at 04:32:11PM +0200, Ivan Voras wrote:
> >> I have PHP executing as fastcgi via the mod_fcgid module in Apache. I
> >> suspect there is a bug in PHP or one of its extensions which causes it
> >> to crash with sigsegv, but I cannot get any coredumps. I suspect
> >> something is setting coredumpsize to 0 - either Apache, mod_fcgid or P=
HP.
> >>
> >> So the question is: is there a way to set coredumpsize on a running
> >> process, with the intention of getting a core dump when it crashes? I
> >> already tried setting CoreDumpDirectory in Apache and also configuring
> >> apache22limits_args in /etc/rc.conf but without effect.
> >
> > I ended up solving this on a machine where coredumps with Apache + PHP
> > were highly common by setting sysctl kern.corefile to
> > /var/cores/%P.%N.core, then made sure the /var/cores directory was
> > root:wheel, perms 1777. =A0Otherwise I could not get a coredump.
> > apache22limits_enable did not help either, nor did CoreDumpDirectory.
>=20
> > Having fun yet?
>=20
> Oh, I have years and years of fun debugging PHP, in one way or the other =
:)
>=20
> Your suggestion for setting core dump directory explicitely helped;
> now it looks like I've hit an infinite recursion / stack eating bug
> somewhere in PCRE...
>=20
> #1703 0x0000000805d5c72e in match () from /usr/local/lib/libpcre.so.0
> #1704 0x0000000805d5b4f0 in match () from /usr/local/lib/libpcre.so.0
> #1705 0x0000000805d5c72e in match () from /usr/local/lib/libpcre.so.0
> #1706 0x0000000805d5b4f0 in match () from /usr/local/lib/libpcre.so.0
>=20
> However, I'm drawing the line at debugging PCRE, this will go into the
> "don't do that" category.

There's a fair chance that this isn't a bug in pcre,
but the result of a poorly written expression.

You may want to have a look at pcrestack(3).

Fabian

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