From mboxrd@z Thu Jan  1 00:00:00 1970
From: Arnd Bergmann <arnd@arndb.de>
Subject: Re: [Ksummit-2010-discuss] [v2] Remaining BKL users, what to do
Date: Tue, 19 Oct 2010 09:26:54 +0200
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To: Dave Airlie <airlied@gmail.com>
Cc: Theodore Kilgore <kilgota@banach.math.auburn.edu>, Steven Rostedt <rostedt@goodmis.org>, Greg KH <greg@kroah.com>, codalist@telemann.coda.cs.cmu.edu, autofs@linux.kernel.org, Samuel Ortiz <samuel@sortiz.org>, Jan Kara <jack@suse.cz>, Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>, Jan Harkes <jaharkes@cs.cmu.edu>, netdev@vger.kernel.org, Anders Larsen <al@alarsen.net>, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Bryan Schumaker <bjschuma@netapp.com>, Christoph Hellwig <hch@infradead.org>, ksummit-2010-discuss@lists.linux-foundation.org, Petr Vandrovec <vandrove@vc.cvut.cz>, Arnaldo Carvalho de Melo <acme@ghostprotocols.net>, linux-fsdevel@vger.kernel.org, Evgeniy Dushistov <dushistov@mail.ru>, Ingo Molnar <mingo@elte.hu>, Andrew Hendry <andrew.hendry@gmail.com>, linux-media@vger.kernel.org

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.

	Arnd