By: dmcq (dmcq.delete@this.fano.co.uk), April 6, 2021 7:05 am
Room: Moderated Discussions
NoSpammer (no.delete@this.spam.com) on April 5, 2021 9:38 pm wrote:
> Aspect of Anonimity (aoa.delete@this.ddugjjihjvj.com) on April 5, 2021 7:57 pm wrote:
> > As I say in my previous comment to sr: even in theory TM instructions that can fail are terrible (if
> > I was unclear, see anon above). I attempted to end with the question "why bother with TM?", but I guess
> > it came off as a rebuke and I got no reply. I stopped caring for an answer at this point anyway...
> >
> > So lets forget practice and current TM and lets try to come up with a "nice" theoretical
> > TM feature, one that never aborts. If that's infeasable then forget TM forever.
>
> Have you ever actually studied the relevant theory?
>
> So how can hardware assume, a priori, that software cannot cause a deadly
> embrace under any circumstances? And how would you resolve it?
If all the control is done via HTM rather than locks then deadly embraces can be avoided if the oldest transaction can always cause a newer one to restart. There's a lot more problems besides that though which I think means it should be restricted to small things where one can assume a successful execution can defer an interrupt till it finishes.
> Aspect of Anonimity (aoa.delete@this.ddugjjihjvj.com) on April 5, 2021 7:57 pm wrote:
> > As I say in my previous comment to sr: even in theory TM instructions that can fail are terrible (if
> > I was unclear, see anon above). I attempted to end with the question "why bother with TM?", but I guess
> > it came off as a rebuke and I got no reply. I stopped caring for an answer at this point anyway...
> >
> > So lets forget practice and current TM and lets try to come up with a "nice" theoretical
> > TM feature, one that never aborts. If that's infeasable then forget TM forever.
>
> Have you ever actually studied the relevant theory?
>
> So how can hardware assume, a priori, that software cannot cause a deadly
> embrace under any circumstances? And how would you resolve it?
If all the control is done via HTM rather than locks then deadly embraces can be avoided if the oldest transaction can always cause a newer one to restart. There's a lot more problems besides that though which I think means it should be restricted to small things where one can assume a successful execution can defer an interrupt till it finishes.