Date: Tue, 14 Sep 2004 07:59:46 +0200
From: Roger Luethi <rl@hellgate.ch>
To: Albert Cahalan <albert@users.sf.net>
Cc: William Lee Irwin III <wli@holomorphy.com>,
       Andrew Morton OSDL <akpm@osdl.org>,
       linux-kernel mailing list <linux-kernel@vger.kernel.org>,
       Paul Jackson <pj@sgi.com>
Subject: Re: [1/1][PATCH] nproc v2: netlink access to /proc information
Message-ID: <20040914055946.GA20929@k3.hellgate.ch>
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	William Lee Irwin III <wli@holomorphy.com>,
	Andrew Morton OSDL <akpm@osdl.org>,
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	Paul Jackson <pj@sgi.com>
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On Sat, 11 Sep 2004 18:25:56 -0400, Albert Cahalan wrote:
> > One nitpick: As vmexe and vmlib are always 0 for !CONFIG_MMU, we should
> > ifdef them out of the list of offered fields for that configuration (and
> > maybe in nproc_ps_field as well).
> 
> No. First of all, I think they can be offered. Until proven
> otherwise, I'll assume that the !CONFIG_MMU case is buggy.

I agree with you that those specific fields should be offered for
!CONFIG_MMU. However, if for some reason they cannot carry a value
that fits the field description, they should not be offered at all. The
ambiguity of having 0 mean either "0" or "this field is not available"
is bad. Trying to read a specific field _can_ fail, and applications
had better handle that case (it's still trivial compared to having to
parse different /proc file layouts depending on the configuration).

> mean that fewer apps can run on !CONFIG_MMU boxes. It's
> same problem as "All the world's a VAX". It's better that
> the apps work; an author working on a Pentium 4 Xeon is
> likely to write code that relies on the fields and might
> not really understand what "no MMU" is all about.

The presumed wrong assumptions underlying broken tools of the future
are not a good base for designing a new interface. My interest is in
making it easy to write correct applications (or in fixing broken apps
that won't work, say, on !CONFIG_MMU systems).

Roger
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