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

From: Avi Kivity
Date: Mon Aug 24 2009 - 14:31:33 EST

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.

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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