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

William Lee Irwin III
2004-09-14T06:20:08Z

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