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Date:      Mon, 29 Jan 2007 12:10:47 -0700
From:      Scott Long <scottl@samsco.org>
To:        Pawel Jakub Dawidek <pjd@FreeBSD.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:  <45BE46B7.8000406@samsco.org>
In-Reply-To: <20070129184522.GD87767@garage.freebsd.pl>
References:  <20070128202917.5B67916A5A6@hub.freebsd.org> <45BD82D2.20301@root.org> <20070129175222.GA87767@garage.freebsd.pl> <45BE37DC.6080509@root.org> <20070129184522.GD87767@garage.freebsd.pl>

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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 routine directly, queue a 
>> 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() once all CPUs are 
>> initialized.  See sys/sys/taskqueue.h for how to add a task to the system 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.
> 

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!!

Scott




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