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

John Garry
2021-04-06T12:45:52Z

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