From owner-freebsd-ports@FreeBSD.ORG  Wed May 17 12:38:05 2006
Return-Path: <owner-freebsd-ports@FreeBSD.ORG>
X-Original-To: ports@freebsd.org
Delivered-To: freebsd-ports@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 1DB4416A53A;
	Wed, 17 May 2006 12:38:05 +0000 (UTC)
	(envelope-from wxs@atarininja.org)
Received: from syn.atarininja.org (syn.csh.rit.edu [129.21.60.158])
	by mx1.FreeBSD.org (Postfix) with ESMTP id BD1F243D6B;
	Wed, 17 May 2006 12:38:04 +0000 (GMT)
	(envelope-from wxs@atarininja.org)
Received: by syn.atarininja.org (Postfix, from userid 1001)
	id BE3CE5C2F; Wed, 17 May 2006 08:39:44 -0500 (EST)
Date: Wed, 17 May 2006 08:39:44 -0500
From: Wesley Shields <wxs@atarininja.org>
To: Edwin Groothuis <edwin@mavetju.org>, Vasil Dimov <vd@freebsd.org>,
	ports@freebsd.org, Paul Koch <paul.koch@statseeker.com>
Message-ID: <20060517133944.GA39615@atarininja.org>
References: <200605171353.37745.paul.koch@statseeker.com>
	<20060517045403.GI1113@k7.mavetju>
	<200605171508.07228.paul.koch@statseeker.com>
	<20060517060026.GA40653@qlovarnika.bg.datamax>
	<20060517061302.GR1116@k7.mavetju>
	<20060517121337.GA50791@iib.unsam.edu.ar>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20060517121337.GA50791@iib.unsam.edu.ar>
User-Agent: Mutt/1.5.11
Cc: 
Subject: Re: Is it safe to compile multiple ports at the same time ?
X-BeenThere: freebsd-ports@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Porting software to FreeBSD <freebsd-ports.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-ports>,
	<mailto:freebsd-ports-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-ports>
List-Post: <mailto:freebsd-ports@freebsd.org>
List-Help: <mailto:freebsd-ports-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-ports>,
	<mailto:freebsd-ports-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 17 May 2006 12:38:15 -0000

On Wed, May 17, 2006 at 09:13:37AM -0300, Fernan Aguero wrote:
> +----[ Edwin Groothuis <edwin@mavetju.org> (17.May.2006 03:16):
> |
> | You have to obtain a lock on the X's Makefile before you are doing
> | to check if you have this port installed.
> | 
> | For example, a dependcy on pkg-config in the directory devel/pkgconfig:
> | 
> | - obtain lock on devel/pkgconfig/Makefile
> | - check if pkg-config exists, and if not, build and install it.
> | - release lock on devel/pkgconfig/Makefile
> | 
> |
> +----]
> 
> Why not
> 
> - check if pkg-config exists and only if it doesn't exist,
>   try to obtain lock on the lock target.

Because at that point aren't you in a race condition?

Port A finds out pkg-config doesn't exist.
Port B finds out pkg-config doesn't exist.

At this point both ports determine they need to build and install the
port.

Port B manages to obtain the lock first, and builds and installs
pkgconfig.
Port A waits on Port B to finish.
Upon finishing Port A obtains the lock and builds and attempts to
install an already installed port.

You must obtain the lock early on, like Edwin has stated.

-- WXS