Re: [KVM-RFC PATCH 1/2] eventfd: add an explicit srcu based notifierinterface

From: Davide Libenzi
Date: Wed Jun 17 2009 - 12:45:22 EST

On Tue, 16 Jun 2009, Gregory Haskins wrote:

> Davide Libenzi wrote:
> > On Tue, 16 Jun 2009, Gregory Haskins wrote:
> >
> >
> >> Does this all make sense?
> >>
> >
> > This conversation has been *really* long, and I haven't had time to look
> > at the patch yet. But looking at the amount of changes, and the amount of
> > even more changes talked in this thread, there's a very slim chance that
> > I'll ACK the eventfd code.
> > You may want to consider a solution that does not litter eventfd code that
> > much.
> >
> >
> > - Davide
> >
> >
> >
> Hi Davide,
> I understand your position and value your time/insight into looking at
> this things.
> Despite the current ongoing discussion, I still stand that the current
> patch is my proposed solution (though I have yet to convince Michael).
> But in any case, if you have the time, please look it over because I
> still think its the right direction to head in.

I don't think so. You basically upload a bunch of stuff it could have been
inside your irqfd into eventfd. Now the eventfd_signal() can magically
sleep, or not, depending on what the signal functions do. This makes up a
pretty aweful interface if you ask me.
A lot simpler and cleaner if eventfd_signal(), like all the wake up
functions inside the kernel, can be called from atomic context. Always,
not sometimes.

- Davide

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