From owner-freebsd-hackers@FreeBSD.ORG  Tue Jun 21 14:50:30 2005
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
X-Original-To: hackers@freebsd.org
Delivered-To: freebsd-hackers@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 87D6416A41C
	for <hackers@freebsd.org>; Tue, 21 Jun 2005 14:50:30 +0000 (GMT)
	(envelope-from peadar.edwards@gmail.com)
Received: from zproxy.gmail.com (zproxy.gmail.com [64.233.162.197])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 3144543D1F
	for <hackers@freebsd.org>; Tue, 21 Jun 2005 14:50:30 +0000 (GMT)
	(envelope-from peadar.edwards@gmail.com)
Received: by zproxy.gmail.com with SMTP id 12so1005260nzp
	for <hackers@freebsd.org>; Tue, 21 Jun 2005 07:50:29 -0700 (PDT)
DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com;
	h=received:message-id:date:from:reply-to:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references;
	b=q5RNsbXVeRu1Dy78k9sGjJaQwuQcTsoyyIirUi1AEEjIEjIr+/CgmWkjfnKMhP0vVvPDej2XRw4EqsPOhYo5iFKb/S5WcbTz9K8ftKyIuBAVPZBIKMcgSgCUsU9YO6yEk/9zJ1t+hWAM7PK9L/99uLd7NNHoa/hlvKh1OndZAHc=
Received: by 10.36.59.12 with SMTP id h12mr1924246nza;
	Tue, 21 Jun 2005 07:50:29 -0700 (PDT)
Received: by 10.36.68.15 with HTTP; Tue, 21 Jun 2005 07:50:29 -0700 (PDT)
Message-ID: <34cb7c840506210750f7458cf@mail.gmail.com>
Date: Tue, 21 Jun 2005 15:50:29 +0100
From: Peter Edwards <peadar.edwards@gmail.com>
To: Charles Sprickman <spork@fasttrackmonkey.com>
In-Reply-To: <Pine.OSX.4.61.0506201654400.374@gee5.nat.fasttrackmonkey.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
References: <Pine.OSX.4.61.0506201654400.374@gee5.nat.fasttrackmonkey.com>
X-Mailman-Approved-At: Wed, 22 Jun 2005 11:46:38 +0000
Cc: hackers@freebsd.org
Subject: Re: Nagios and threads
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: Peter Edwards <peadar.edwards@gmail.com>
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>, 
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 21 Jun 2005 14:50:30 -0000

On 6/20/05, Charles Sprickman <spork@fasttrackmonkey.com> wrote:
> Hello,
>=20
> Just curious if there's any regulars here who would like to help Ethan
> out:
>=20
[snip]
>=20
> ... It happens when the main thread forks to execute an active
> check. On the second fork to create the grandchild, the grandchild is
> created by fork, but never returns from liblthread's fork wrapper, becaus=
e
> it's stuck in __pthread_acquire(). Maybe some FreeBSD users can help out
> with this problem."
>=20

IIRC, doing any significant work in a forked child of a multithreaded
process is somewhat ill defined. From SusV3's description of "fork()"

> ... Consequently, to avoid errors, the child process may only execute=20
> async-signal-safe operations until such time as one of the exec
> functions is called.

(This behaviour would extend to a grandchild.)

A comment in libpthread/thr_kern.c refers to this, so I think there's
at least some assumptions that the child won't be doing much before
execing or exiting. (But Im sure one of the implementors will pipe up
if I'm wrong :-))