Re: [PATCH] perf metricgroup: Fix for metrics containing duration_time

[Jiri Olsa]

On Thu, Jan 21, 2021 at 12:18:38AM +0800, John Garry wrote:
> Metrics containing duration_time cause a segfault:
> 
> $./perf stat -v -M L1D_Cache_Fill_BW sleep 1
> Using CPUID GenuineIntel-6-3D-4
> metric expr 64 * l1d.replacement / 1000000000 / duration_time for L1D_Cache_Fill_BW
> found event duration_time
> found event l1d.replacement
> adding {l1d.replacement}:W,duration_time
> l1d.replacement -> cpu/umask=0x1,(null)=0x1e8483,event=0x51/
> Segmentation fault
> 
> In commit c2337d67199a ("perf metricgroup: Fix metrics using aliases
> covering multiple PMUs"), the logic in find_evsel_group() when iter'ing
> events was changed to not only select events in same group, but also for
> aliased PMUs.
> 
> Checking whether events were for aliased PMUs was done by comparing the
> event PMU name. This was not safe for duration_time event, which has no
> associated PMU (and no PMU name), so fix by checking if the event PMU name
> is set also.
> 
> Fixes: c2337d67199a ("perf metricgroup: Fix metrics using aliases covering multiple PMUs")
> Reported-by: Joakim Zhang <qiangqing.zhang@xxxxxxx>
> Signed-off-by: John Garry <john.garry@xxxxxxxxxx>

Tested/Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>

thanks,
jirka

> 
> diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> index 2e60ee170abc..e6d3452031e5 100644
> --- a/tools/perf/util/metricgroup.c
> +++ b/tools/perf/util/metricgroup.c
> @@ -162,6 +162,14 @@ static bool contains_event(struct evsel **metric_events, int num_events,
>  	return false;
>  }
>  
> +static bool evsel_same_pmu(struct evsel *ev1, struct evsel *ev2)
> +{
> +	if (!ev1->pmu_name || !ev2->pmu_name)
> +		return false;
> +
> +	return !strcmp(ev1->pmu_name, ev2->pmu_name);
> +}
> +
>  /**
>   * Find a group of events in perf_evlist that correspond to those from a parsed
>   * metric expression. Note, as find_evsel_group is called in the same order as
> @@ -280,8 +288,7 @@ static struct evsel *find_evsel_group(struct evlist *perf_evlist,
>  			 */
>  			if (!has_constraint &&
>  			    ev->leader != metric_events[i]->leader &&
> -			    !strcmp(ev->leader->pmu_name,
> -				    metric_events[i]->leader->pmu_name))
> +			    evsel_same_pmu(ev->leader, metric_events[i]->leader))
>  				break;
>  			if (!strcmp(metric_events[i]->name, ev->name)) {
>  				set_bit(ev->idx, evlist_used);
> -- 
> 2.26.2
>