Re: Slow DOWN, please!!!

Andrew Morton
2008-05-01T19:59:17Z

On Thu, 1 May 2008 20:37:14 +0100
Al Viro <viro@ZenIV.linux.org.uk> wrote:

> * patches should be visible *when* *they* *can* *be* *changed*.
> If it's "Linus had pulled from linux-foo.git and that included a merge
> from linux-foobar.git, which is developed on foobar-wank@hell.knows.where",
> it's too late. It's not just that you don't revert; it's that you _can't_
> realistically revert in such situation - not without very massive work.
> And I don't know what _can_ be done about that, other than making it
> socially discouraged. To some extent it's OK, but my impression is that
> some areas are as bad as CVS-based "communities" had been and switch to
> git has simply hidden the obvious signs of trouble...

Yup. I think the only sane+scalable way of making this happen is to
prevail upon the 100-odd subsystem maintainers to keep an eye out for code
which should be exposed to additional eyes.

There are of course many reasons _why_ such code needs the attention of
others, and those reasons have varying strengths. Off the top of my head:

- modifies stuff outside the designated subsystem (eg: lib/pcounter.c -
thanks Pavel)

- (having just spent an hour looking at drivers/net/sfc/ and having
boggled at its bitmap.h): adds generic-looking infrastructure which
should be in core kernel. Or already _is_ in core kernel.

- Adds any kernel<->user interface which is not of the the most
trivial&standard form

- Futzes with memory management internals, adds pagefault handlers, etc.

- Ditto vfs things, I guess

- In any way attempts to work around _any_ shortcoming of any other part
of the kernel!

- Does anything RCU related. Every time I cc Paul on an rcu-using patch,
he finds holes in it.

- add your own here.

But we won't find such code by going out and looking for it - we do need
the recipients of that code to say "hey, others might want to see this".
That's very low-effort for the hey-sayer, so I expect we can do better here
quite easily.