linux-kernel - Re: [PATCH] fix maxcpus=N parsing

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Message-Id: <1188323896.5531.63.camel@localhost.localdomain>
Date:	Wed, 29 Aug 2007 03:58:16 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Hugh Dickins <hugh@...itas.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <len.brown@...el.com>, Andi Kleen <ak@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix maxcpus=N parsing

On Mon, 2007-08-27 at 16:02 +0100, Hugh Dickins wrote:
> Fix 61ec7567db103d537329b0db9a887db570431ff4: maxcpus=N is now having no
> effect on x86_64, and freezing bootup on i386 (because of inconsistency
> with the separate maxcpus parsing down in arch/i386, I guess).  That's
> because early_param parsing is a little different from __setup parsing,
> and needs the "=" omitted: then it seems to work as the original commit
> intended (no mention of IO-APIC in /proc/interrupts when maxcpus=0).
> 
> Signed-off-by: Hugh Dickins <hugh@...itas.com>
> ---
> Sorry, I noticed this back in -mm, but got diverted by deeper mysteries.
> Cc'ed Rusty: I presume there's a good reason why early_param parsing is
> confusingly different, but he may know better and want to change it.

Yeah, early_param is modelled on module_param which does more than the
naive substring match of __setup.  There's a warning in the header IIRC.

The original intention wass that everything would move to
module_param-style parameters.  However __setup is still useful for
trivial core stuff.

> It's odd that i386 treats maxcpus=N differently from other architectures:
> on i386 it limits cpu_possible_map, on others it just limits what boots
> (then powersaved is liable to bring up the others on x86_64 - hmmm).

Indeed, it'd be nice to see this made uniform.

But this patch is fine.

Cheers,
Rusty.

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