Date: Wed, 31 Mar 2010 23:33:30 -0400
From: Andrew Morton <akpm@linux-foundation.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
       Christoph Lameter <cl@linux-foundation.org>,
       Matthew Wilcox <matthew@wil.cx>, Yinghai Lu <yinghai@kernel.org>,
       Rabin Vincent <rabin@rab.in>, lkml <linux-kernel@vger.kernel.org>,
       penberg@cs.helsinki.fi, linux-arch@vger.kernel.org
Subject: Re: start_kernel(): bug: interrupts were enabled early
Message-Id: <20100331233330.1a7357e4.akpm@linux-foundation.org>
In-Reply-To: <4BB43CAC.3080102@zytor.com>
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	<4BB3C540.9000405@zytor.com>
	<1270075071.7101.79.camel@pasglop>
	<20100331154955.54176e5e.akpm@linux-foundation.org>
	<1270084631.7101.81.camel@pasglop>
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On Wed, 31 Mar 2010 23:26:52 -0700 "H. Peter Anvin" <hpa@zytor.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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