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

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 23 Jun 2009 13:59:07 -0700 (PDT)
Davide Libenzi <davidel@xmailserver.org> wrote:

> On Tue, 23 Jun 2009, Andrew Morton wrote:
> 
> > On Tue, 23 Jun 2009 12:25:36 -0700 (PDT)
> > Davide Libenzi <davidel@xmailserver.org> 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.

That isn't for us to decide. Entire syscalls can be disabled in config.