Re: [PATCH v6 8/8] nouveau/svm: Implement atomic SVM access

[Alistair Popple]

On Monday, 15 March 2021 6:51:13 PM AEDT Christoph Hellwig wrote:
> > -   /*XXX: atomic? */
> > -   return (fa->access == 0 || fa->access == 3) -
> > -          (fb->access == 0 || fb->access == 3);
> > +   /* Atomic access (2) has highest priority */
> > +   return (-1*(fa->access == 2) + (fa->access == 0 || fa->access == 3)) -
> > +          (-1*(fb->access == 2) + (fb->access == 0 || fb->access == 3));
> 
> This looks really unreabable.  If the magic values 0, 2 and 3 had names
> it might become a little more understadable, then factor the duplicated
> calculation of the priority value into a helper and we'll have code that
> mere humans can understand..

Fair enough, will add some definitions for the magic values.

> > +           mutex_lock(&svmm->mutex);
> > +           if (mmu_interval_read_retry(&notifier->notifier,
> > +                                       notifier_seq)) {
> > +                   mutex_unlock(&svmm->mutex);
> > +                   continue;
> > +           }
> > +           break;
> > +   }
> 
> This looks good, why not:
> 
>               mutex_lock(&svmm->mutex);
>               if (!mmu_interval_read_retry(&notifier->notifier,
>                                            notifier_seq))
>                       break;
>               mutex_unlock(&svmm->mutex);
>       }

I had copied that from nouveau_range_fault() but this suggestion is better. 
Will update, thanks for looking.



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