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Date:      Mon, 29 Jan 2007 20:32:05 +0100
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Scott Long <scottl@samsco.org>
Cc:        cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org, Nate Lawson <nate@root.org>
Subject:   Re: cvs commit: src/sys/geom/eli g_eli.c
Message-ID:  <20070129193205.GE87767@garage.freebsd.pl>
In-Reply-To: <45BE46B7.8000406@samsco.org>
References:  <20070128202917.5B67916A5A6@hub.freebsd.org> <45BD82D2.20301@root.org> <20070129175222.GA87767@garage.freebsd.pl> <45BE37DC.6080509@root.org> <20070129184522.GD87767@garage.freebsd.pl> <45BE46B7.8000406@samsco.org>

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On Mon, Jan 29, 2007 at 12:10:47PM -0700, Scott Long wrote:
> Pawel Jakub Dawidek wrote:
> >On Mon, Jan 29, 2007 at 10:07:24AM -0800, Nate Lawson wrote:
> >>Pawel Jakub Dawidek wrote:
> >>>Hmm, I thought that cold is zeroed before smp_started is set?
> >>I don't think that's guaranteed.  Besides, there's an easier way to fix=
 your problem.  Instead of calling kthread_create() from your geom create r=
outine directly, queue a=20
> >>stub request on the thread taskqueue to call kthread_create().
> >>
> >>For example, see sys/dev/acpica/acpi_acad.c.  We call this from attach(=
)    and then the system thread only runs and then calls acpi_acad_init() o=
nce all CPUs are=20
> >>initialized.  See sys/sys/taskqueue.h for how to add a task to the syst=
em thread taskqueue:
> >>
> >>taskqueue_enqueue(taskqueue_thread, &task);
> >If we want to fix it better, I think GEOM should start (tasting at
> >least) after all CPUs are online.
>=20
> Why?  You're proposing yet another intrusive change to the kernel to
> handle yet another one-off requirement of your code.  Why not do what I
> suggested before with hooking the appropriate SYSINIT in your module?
> Or why not follow Robert's suggestion and implement a simple event
> mechanism so that any module can know when a CPU has come online or
> offline.  Heck, you probably don't even need to implement a new
> mechanism, just hook the existing EVENTHANLER mechanism.  That's what
> it's designed for!!

I'm afraid Scott that your proposals are hacks. As a GEOM class I should
not use SYSINIT, EVENTHANDLER, etc. I shouldn't bother if CPUs are
online or not. All events I need to implement a GEOM class I should
receive from the infrastructure. Also I shouldn't be called by the
infrastructure when the system is not yet ready for my activity, that's
why I proposed to implement this functionality in the infrastructure
(ie. delay GEOM tasting machanism), that hack SYSINITs in every single
GEOM class that need to bind to a CPU.

--=20
Pawel Jakub Dawidek                       http://www.wheel.pl
pjd@FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!

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