Re: [1/1][PATCH] nproc v2: netlink access to /proc information

From: William Lee Irwin III (wli_at_holomorphy.com)
Date: 09/14/04

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    Date:	Mon, 13 Sep 2004 23:18:00 -0700
To: Roger Luethi <rl@hellgate.ch>

    On Sat, 11 Sep 2004 18:25:56 -0400, Albert Cahalan wrote:
    >> No. First of all, I think they can be offered. Until proven
    >> otherwise, I'll assume that the !CONFIG_MMU case is buggy.

    On Tue, Sep 14, 2004 at 07:59:46AM +0200, Roger Luethi wrote:
    > 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).

    Apart from doing something it's supposed to for !CONFIG_MMU and using
    the internal kernel accounting I set up for the CONFIG_MMU=y case I'm
    not very concerned about this. I have a vague notion there should
    probably be some consistency with the /proc/ precedent but am not
    particularly tied to it. We should probably ask Greg Ungerer (the
    maintainer of the external MMU-less patches) about what he prefers
    since it's likely we can't anticipate all of the !CONFIG_MMU concerns.

    On Sat, 11 Sep 2004 18:25:56 -0400, Albert Cahalan wrote:
    >> 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.

    On Tue, Sep 14, 2004 at 07:59:46AM +0200, Roger Luethi wrote:
    > 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).

    I don't really know what the approach to app compatibility used by
    userspace for !CONFIG_MMU is; I'll refer you to Greg Ungerer as my
    knowledge of the CONFIG_MMU usage models and/or whatever userspace
    is used in tandem with it outside the VM's internals is rather scant.

    -- wli
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