Re: [PATCH-RFC 2/2] eventfd: EFD_STATE flag

[Avi Kivity]

On 08/04/2009 11:54 AM, Michael S. Tsirkin wrote:
> On Tue, Aug 04, 2009 at 11:53:03AM +0300, Avi Kivity wrote:
>    
> > On 08/03/2009 07:57 PM, Michael S. Tsirkin wrote:
> >      
> > > > Why not do it at the point of the write?
> > > >
> > > >       if (value != ctx->count) {
> > > >           ctx->count = value;
> > > >           wake_things_up();
> > > >       }
> > > >
> > > >          
> > > What if write comes before read?
> > >
> > >        
> > The read will get the new value.
> >      
>
> Yes :) But how does read know it should not block?
>    

If a different read comes after the write but after our read, it will 
have transferred the value, resulting in the same situation.

I think reads should never block with a state based mechanism.

--
error compiling committee.c: too many arguments to function

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