Date: Wed, 17 May 2006 15:53:09 +0300 From: Vasil Dimov <vd@FreeBSD.org> To: Wesley Shields <wxs@atarininja.org> Cc: ports@freebsd.org, Edwin Groothuis <edwin@mavetju.org>, Paul Koch <paul.koch@statseeker.com> Subject: Re: Is it safe to compile multiple ports at the same time ? Message-ID: <20060517125309.GA1265@qlovarnika.bg.datamax> In-Reply-To: <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> <20060517133944.GA39615@atarininja.org>
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On Wed, May 17, 2006 at 08:39:44AM -0500, Wesley Shields wrote:
> 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.
> > |=20
> > | For example, a dependcy on pkg-config in the directory devel/pkgconfi=
g:
> > |=20
> > | - obtain lock on devel/pkgconfig/Makefile
> > | - check if pkg-config exists, and if not, build and install it.
> > | - release lock on devel/pkgconfig/Makefile
> > |=20
> > |
> > +----]
> >=20
> > Why not
> >=20
> > - check if pkg-config exists and only if it doesn't exist,
> > try to obtain lock on the lock target.
>=20
> Because at that point aren't you in a race condition?
>=20
> Port A finds out pkg-config doesn't exist.
> Port B finds out pkg-config doesn't exist.
>=20
> At this point both ports determine they need to build and install the
> port.
>=20
> 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.
>=20
> You must obtain the lock early on, like Edwin has stated.
>=20
Maybe he meant
- check if pkg-config exists and only if it doesn't exist,
try to obtain lock on the lock target.
- check if pkg-config exists, and if not, build and install it.
- release lock on devel/pkgconfig/Makefile
this will eventually save unnecessary locking with the cost of checking
twice if the port is installed.
--=20
Vasil Dimov
gro.DSBeerF@dv
Testing can show the presence of bugs, but not their absence.
-- Edsger W. Dijkstra
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