Re: [Intel-wired-lan] [PATCH net-next 1/2] stmmac: xsk: fix underflow of budget in zerocopy mode

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Jason Xing wrote:
> On Tue, Jul 22, 2025 at 10:16 PM Willem de Bruijn
> <willemdebruijn.kernel@gmail.com> wrote:
> >
> > Jason Xing wrote:
> > > Hi Paul,
> > >
> > > On Mon, Jul 21, 2025 at 4:56 PM Paul Menzel <pmenzel@molgen.mpg.de> wrote:
> > > >
> > > > Dear Jason,
> > > >
> > > >
> > > > Thank you for your patch.
> > >
> > > Thanks for your quick response and review :)
> > >
> > > >
> > > > Am 21.07.25 um 10:33 schrieb Jason Xing:
> > > > > From: Jason Xing <kernelxing@tencent.com>
> > > > >
> > > > > The issue can happen when the budget number of descs are consumed. As
> > > >
> > > > Instead of “The issue”, I’d use “An underflow …”.
> > >
> > > Will change it.
> > >
> > > >
> > > > > long as the budget is decreased to zero, it will again go into
> > > > > while (budget-- > 0) statement and get decreased by one, so the
> > > > > underflow issue can happen. It will lead to returning true whereas the
> > > > > expected value should be false.
> > > >
> > > > What is “it”?
> > >
> > > It means 'underflow of budget' behavior.
> >
> > A technicality, but this is (negative) overflow.
> >
> > Underflow is a computation that results in a value that is too small
> > to be represented by the given type.
> 
> Interesting. Thanks for sharing this with me:)
> 
> I just checked the wikipedia[1] that says " Underflow can in part be
> regarded as negative overflow of the exponent of the floating-point
> value.". I assume this rule can also be applied in this case? I'm
> hesitant to send the v3 patch tomorrow with this 'negative overflow'
> term included.

My point is very pedantic. I think these cases are not underflow.

But it is often called that, understandably. So choose as you see fit.