Re: [patch] eventfd - revised interface and cleanups (2nd rev)

From: Davide Libenzi
Date: Tue Jun 23 2009 - 17:06:09 EST

On Tue, 23 Jun 2009, Andrew Morton wrote:

> On Tue, 23 Jun 2009 12:25:36 -0700 (PDT)
> Davide Libenzi <davidel@xxxxxxxxxxxxxxx> wrote:
> > Another cleanup this patch does, is making AIO select EVENTFD, instead of
> > adding a bunch of empty function stubs inside eventfd.h in order to
> > handle the (AIO && !EVENTFD) case.
> Given that we're trying to squeak this patch into 2.6.31, it's quite
> unfortunate to include unrelated changes. Especially ones which
> involve the always-problematic "select". Although this one looks less
> than usually deadly due to the simple dependencies of AIO and eventfd.
> However...
> Is this a good way of fixing the (AIO && !EVENTFD) case? Surely if the
> developer selected this combination, he doesn't want to carry the
> overhead of including eventfd. IOW, if AIO can work acceptably without
> eventfd being compiled into the kernel then adding the stubs is a
> superior solution.

IMO when someone says "AIO included in the kernel", should get the whole
AIO functionality and not part of it.
People already started using KAIO+eventfd, and a (AIO && !EVENTFD) config
will make their code fail.

- Davide

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