Re: [PATCH v2 2/6] perf test: Handle metric reuse in pmu-events parsing test

[John Garry]

On 06/04/2021 13:17, Jiri Olsa wrote:
> > > > +			ref = &metric->metric_ref;
> > > > +			ref->metric_name = pe->metric_name;
> > > > +			ref->metric_expr = pe->metric_expr;
> > > > +			list_add_tail(&metric->list, compound_list);
> > > > +
> > > > +			rc = expr__find_other(pe->metric_expr, NULL, pctx, 0);
> > Hi Jirka,
> >
> > > so this might add new items to pctx->ids, I think you need
> > > to restart the iteration as we do it in __resolve_metric
> > > otherwise you could miss some new keys
> > I thought that I was doing this. Indeed, this code is very much like
> > __resolve_metric();)
> >
> > So expr__find_other() may add a new item to pctx->ids, and we always iterate
> > again, and try to lookup any pmu_events, *, above. If none exist, then we
> hm, I don't see that.. so, what you do is:
>
> 	hashmap__for_each_entry_safe((&pctx->ids) ....) {
>
> 		rc = expr__find_other(pe->metric_expr, NULL, pctx, 0);
> 	}
>
> and what I think we need to do is:
>
> 	hashmap__for_each_entry_safe((&pctx->ids) ....) {
>
> 		rc = expr__find_other(pe->metric_expr, NULL, pctx, 0);
>
> 		break;	
> 	}
>
> each time you resolve another metric, you need to restart
> the pctx->ids iteration, because there will be new items,
> and we are in the middle of it

Sure, but we will restart anyway.

Regardless of this, I don't think what I am doing is safe, i.e. adding 
new items in the middle of the iter, so I will change in the way you 
suggest.

Thanks,
John