linux-kernel - Re: start_kernel(): bug: interrupts were enabled early

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Date:	Wed, 31 Mar 2010 23:33:30 -0400
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Matthew Wilcox <matthew@....cx>,
	Yinghai Lu <yinghai@...nel.org>, Rabin Vincent <rabin@....in>,
	lkml <linux-kernel@...r.kernel.org>, penberg@...helsinki.fi,
	linux-arch@...r.kernel.org
Subject: Re: start_kernel(): bug: interrupts were enabled early

On Wed, 31 Mar 2010 23:26:52 -0700 "H. Peter Anvin" <hpa@...or.com> wrote:

> On 03/31/2010 03:26 PM, Andrew Morton wrote:
> > 
> > Not by adding overhead to every single down_read()/down_write() just to
> > fix a once-off startup problem - that's taking laziness way too far.
> > 
> 
> How much overhead is this on non-x86 architectures (keep in mind x86
> doesn't use this?)
> 

Just a few instructions, I guess.   But we can do it with zero.

And from a design POV, pretending that down_read()/down_write() can be
called with interrupts disabled is daft - they cannot!  Why muck up the
usual code paths with this startup-specific hack?

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