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Date: Mon, 24 Aug 2009 11:25:01 -0700 (PDT) From: Davide Libenzi <davidel@...ilserver.org> To: "Michael S. Tsirkin" <mst@...hat.com> cc: Avi Kivity <avi@...hat.com>, gleb@...hat.com, kvm@...r.kernel.org, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 0/2] eventfd: new EFD_STATE flag 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@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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