Date: Mon, 30 May 2011 13:30:36 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Theodore Tso <tytso@MIT.EDU>
Cc: David Woodhouse <dwmw2@infradead.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix corruption of CONFIG_X86_32 in 'make oldconfig'
Message-ID: <20110530113036.GA22324@elte.hu>
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 <20110530104231.GF17821@elte.hu>
 <20110530104656.GA19532@elte.hu>
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* Theodore Tso <tytso@MIT.EDU> wrote:

> 
> On May 30, 2011, at 6:58 AM, Ingo Molnar wrote:
> 
> > 
> > * Theodore Tso <tytso@MIT.EDU> wrote:
> > 
> >> I'd think that "make ARCH=x86_64 oldconfig"
> >> 
> >> ... where the old configuration contained CONFIG_X86_32
> >> should trigger a warning, if not an outright error that 
> >> stops the build....
> > 
> > That would be a rather sad regression for me: i use that command 
> > regularly to transform .configs that came in bugreports into a config 
> > suitable for a testbox that has a different bitness userspace 
> > installed.
> 
> OK, so to clarify, what you want is for ARCH=xxx to always override 
> whatever is in .config? [...]

If 'xxx' clearly signals both architecture and bitness then it should 
override both the architecture and the bitness of the .config - 
that's both common-sense and currently implemented (and relied on) 
behavior.

'ARCH=x86 oldconfig' should maintain bitness in the .config like it 
does today, because the 'xxx' only specifies the architecture.

[ Btw., 'override the architecture' usecase is not just theoretical: 
  i sometimes use this form to convert existing .config's *between* 
  architectures, not just from 32-bit to 64-bit. So if i get an ARM 
  bugreport that gives me the appearance of a core kernel bug i will 
  often start by converting that to an x86 .config via 'make 
  ARCH=x86_64 oldconfig'. ]

>  Are we all on the same page here? [...]

I think this thread makes it rather clear that David and me are not 
on the same page. Not sure about you :)

> [...]  I thought David was arguing that what was in .config should 
> always be more important, since he regards "ARCH=xxxx" as "legacy".

Well i (and current behavior) argue that what the user types actually 
has a meaning and a purpose and provides an override to other 
environmental data.

> Or maybe I'm missing something here.... since people seem to be 
> slinging around examples what should or should not work, as opposed 
> to simply saying, "ARCH=xxx" must always override all else, even in 
> cases like "oldconfig", "randconfig", etc.  Is that what the patch 
> is going to do?

I said it from mail #1 on that "ARCH=xxx" must override the .config 
[except in cases like ARCH=x86 where 'xxx' does not imply bitness] 
and must modify/filter other typed arguments 
(randconfig/allnoconfig/allyesconfig, etc.) in an intuitive and 
common-sense fashion.

> All this talk of how it's OK for randconfig to give you i386 50% of 
> the time even when ARCH=x86_64 is specified is confusing me?  Maybe 
> that was just intended to be sarcasm?

That was the original regression i reported to David. So yes, i do 
argue, and argued from day 1 on (which was 2 years ago) that 
'ARCH=i386' and 'ARCH=x86_64' should override secondary sources of 
environment.

It's just that David has not accepted my reasoning and has given a 
changelog that describes the topic in a rather one-sided fashion.

Thanks,

	Ingo
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