Re: [Xen-devel] ring.h notification hold-off question

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 10/11/07 05:37, "Daniel Stodden" <stodden@xxxxxxxxxx> wrote:

> b) if __old were UINT_MAX, then the consumer side might/would
>    set req_event to 0 after catching up right? (req_cons(== req_prod)+1)
>    now assume __new  ==  __old + 2 then we had
> 
> req_event [0] < __new [1] < __old [INT_MAX]
> 
>    i.e.
> __new - req_event [1] > __new - __old [-1]
> 
>    i.e. _notify=false, which i believe skips a wanted notification.

No. req_event==0, new==1, old==UINT_MAX. Then new-req_event==1, new-old==2.
Hence a notification will be sent.

Case (c) you are also wrong because after the subtractions we cast to an
unsigned integer. Hence in the case old<new<req_event, new-req_event will be
a large +ve integer, not a small -ve one.

 -- Keir



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