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    SubjectRe: [PATCH 0/2] eventfd: new EFD_STATE flag
    On Mon, Aug 24, 2009 at 11:25:01AM -0700, Davide Libenzi wrote:
    > On Sun, 23 Aug 2009, Michael S. Tsirkin wrote:
    >
    > > On Sun, Aug 23, 2009 at 04:40:51PM +0300, Avi Kivity wrote:
    > > > On 08/23/2009 04:36 PM, Michael S. Tsirkin wrote:
    > > >> More important here is realization that eventfd is a mutex/semaphore
    > > >> implementation, not a generic event reporting interface as we are trying
    > > >> to use it.
    > > >>
    > > >
    > > > Well it is a generic event reporting interface (for example, aio uses it).
    > >
    > > Davide, I think it's a valid point. For example, what read on eventfd
    > > does (zero a counter and return) is not like any semaphore I saw.
    >
    >
    > 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.

    Hmm. All we try to do is, associate a small key with the event
    that we signal. Is it really that uncommon/KVM specific?

    >
    >
    > - Davide
    >
    >
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