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

[Davide Libenzi]

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.



- Davide


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/