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

[Paolo Bonzini]

> > > 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.
> >
> > It actually seems as close to a condition variable as an eventfd can be.
>
> A pthread condition typical code usage maps to eventfd like:
>
> 	while (read(efd, ...)>  0)
> 		if (CONDITION)
> 			break;
>
> So a pthread condition is really a wakeup gate like eventfd is.
> EFD_STATE has nothing to do with a pthread condition.

No, your code does not work for pthread_cond_broadcast (which arguably 
is the common case) because all the eventfd readers after the first 
would block.

Paolo
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