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SubjectRe: [patch 05/11] syslets: core code


On Wed, 14 Feb 2007, Ingo Molnar wrote:
>
> hm, there must be some misunderstanding here. That mlock is /only/ once
> per the lifetime of the whole 'head' - i.e. per sys_async_register().
> (And you can even forget i ever did it - it's 5 lines of code to turn
> the completion ring into a swappable entity.)

But the whole point is that the notion of a "register" is wrong in the
first place. It's wrong because:

- it assumes we are going to make these complex state machines (which I
don't believe for a second that a real program will do)

- it assumes that we're going to make many async system calls that go
together (which breaks the whole notion of having different libraries
using this for their own internal reasons - they may not even *know*
about other libraries that _also_ do async IO for *their* reasons)

- it fundamentally is based on a broken notion that everything would use
this "AIO atom" in the first place, WHICH WE KNOW IS INCORRECT, since
current users use "aio_read()" that simply doesn't have that and
doesn't build up any such data structures.

So please answer my questions. The problem wasn't the mlock(), even though
that was just STUPID. The problem was much deeper. This is not a "prepare
to do a lot of very boutique linked list operations" problem. This is a
"people already use 'aio_read()' and want to extend on it" problem.

You didn't at all react to that fundamental issue: you have an overly
complex and clever thing that doesn't actually *match* what people do.

Linus
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