Re: [PATCH 0/2] eventfd: new EFD_STATE flag

From: Davide Libenzi
Date: Mon Aug 24 2009 - 18:08:25 EST

On Mon, 24 Aug 2009, Avi Kivity wrote:

> On 08/24/2009 09:25 PM, Davide Libenzi wrote:
> > Indeed, the default eventfd behaviour is like, well, an event. Signaling
> > (kernel side) or writing (userspace side), signals the event.
> > Waiting (reading) it, will reset the event.
> > If you use EFD_SEMAPHORE, you get a semaphore-like behavior.
> > Events and sempahores are two widely known and used abstractions.
> > The EFD_STATE proposed one, well, no. Not at all.
> >
> There are libraries that provide notifications (or fire watches) when some
> value changes. They're much less frequently used than events or semaphores,
> though.

There are userspace libraries that do almost everything, but you hardly
see things like pthread_(EFD_STATE-like)_create() or similar system
interfaces based on such abstraction.
Is that really difficult to understand where I'm standing, leaving the KVM
hat off for a moment?

- Davide

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