Re: [PATCH v2 10/19] tools/xenstore: change per-domain node accounting interface

[Julien Grall <julien@xxxxxxx>]

Hi Juergen,

On 11/01/2023 08:59, Juergen Gross wrote:
> > ... to make sure domain_nbentry_add() is not returning a negative 
> > value. Then it would not work.
> > A good example imagine you have a transaction removing nodes from tree 
> > but not adding any. Then the "ret" would be negative.
> > Meanwhile the nodes are also removed outside of the transaction. So 
> > the sum of "d->nbentry + ret" would be negative resulting to a failure 
> > here.
> Thanks for catching this.
>
> I think the correct way to handle this is to return max(d->nbentry + 
> ret, 0) in
> domain_nbentry_add(). The value might be imprecise, but always >= 0 and 
> never
> wrong outside of a transaction collision.
I am bit confused with your proposal. If the return value is imprecise, 
then what's the point of returning max(...) instead of simply 0?
Cheers,

--
Julien Grall