netdev - Re: [Ksummit-2010-discuss] [v2] Remaining BKL users, what to do

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Message-ID: <AANLkTinw=Wzh2Ucj6zKSoqC8J3Yq9xDr3mKMUB7K6Yyo@mail.gmail.com>
Date:	Wed, 20 Oct 2010 06:50:58 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Theodore Kilgore <kilgota@...ach.math.auburn.edu>,
	Steven Rostedt <rostedt@...dmis.org>, Greg KH <greg@...ah.com>,
	codalist@...emann.coda.cs.cmu.edu, autofs@...ux.kernel.org,
	Samuel Ortiz <samuel@...tiz.org>, Jan Kara <jack@...e.cz>,
	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>,
	Jan Harkes <jaharkes@...cmu.edu>, netdev@...r.kernel.org,
	Anders Larsen <al@...rsen.net>, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Bryan Schumaker <bjschuma@...app.com>,
	Christoph Hellwig <hch@...radead.org>,
	ksummit-2010-discuss@...ts.linux-foundation.org,
	Petr Vandrovec <vandrove@...cvut.cz>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-fsdevel@...r.kernel.org,
	Evgeniy Dushistov <dushistov@...l.ru>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Hendry <andrew.hendry@...il.com>,
	linux-media@...r.kernel.org
Subject: Re: [Ksummit-2010-discuss] [v2] Remaining BKL users, what to do

On Tue, Oct 19, 2010 at 11:26 PM, Arnd Bergmann <arnd@...db.de> wrote:
> On Tuesday 19 October 2010, Arnd Bergmann wrote:
>> On Tuesday 19 October 2010 06:52:32 Dave Airlie wrote:
>> > > I might be able to find some hardware still lying around here that uses an
>> > > i810. Not sure unless I go hunting it. But I get the impression that if
>> > > the kernel is a single-CPU kernel there is not any problem anyway? Don't
>> > > distros offer a non-smp kernel as an installation option in case the user
>> > > needs it? So in reality how big a problem is this?
>> >
>> > Not anymore, which is my old point of making a fuss. Nowadays in the
>> > modern distro world, we supply a single kernel that can at runtime
>> > decide if its running on SMP or UP and rewrite the text section
>> > appropriately with locks etc. Its like magic, and something like
>> > marking drivers as BROKEN_ON_SMP at compile time is really wrong when
>> > what you want now is a runtime warning if someone tries to hotplug a
>> > CPU with a known iffy driver loaded or if someone tries to load the
>> > driver when we are already in SMP mode.
>>
>> We could make the driver run-time non-SMP by adding
>>
>>       if (num_present_cpus() > 1) {
>>               pr_err("i810 no longer supports SMP\n");
>>               return -EINVAL;
>>       }
>>
>> to the init function. That would cover the vast majority of the
>> users of i810 hardware, I guess.
>
> Some research showed that Intel never support i810/i815 SMP setups,
> but there was indeed one company (http://www.acorpusa.com at the time,
> now owned by a domain squatter) that made i815E based dual Pentium-III
> boards like this one: http://cgi.ebay.com/280319795096

Also that board has no on-board GPU enabled i815EP (P means no on-board GPU).

So I think i810 is fine.
>
> The first person that can send me an authentic log file showing the
> use of X.org with DRM on a 2.6.35 kernel with two processors on that
> mainboard dated today or earlier gets a free upgrade to an AGP graphics
> card of comparable or better 3D performance from me. Please include
> the story how why you are running this machine with a new kernel.
>
> i830 is harder, apparently some i865G boards support Pentium 4 with HT
> and even later dual-core processors.

Also hyper-threaded 845G boards, however I'm happy to start a proper
deprecation procedure on the i830 ABI,
Its been a few years since a distro shipped with it, I think even
RHEL5 has the i915 driver enabled, so we are
probably talking RHEL4 era.

Dave.
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