Messages in this thread | | | Subject | Re: [PATCH] perf metricgroup: Fix for metrics containing duration_time | From | John Garry <> | Date | Wed, 20 Jan 2021 17:08:36 +0000 |
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On 20/01/2021 16:40, Ian Rogers wrote: > On Wed, Jan 20, 2021 at 8:23 AM John Garry <john.garry@huawei.com > <mailto:john.garry@huawei.com>> 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. > > > Thanks for this, it should be fairly easy to add a test. Could we do this?
I don't mind following up with that.
> > Fixes: c2337d67199a ("perf metricgroup: Fix metrics using aliases > covering multiple PMUs") > Reported-by: Joakim Zhang <qiangqing.zhang@nxp.com > <mailto:qiangqing.zhang@nxp.com>> > Signed-off-by: John Garry <john.garry@huawei.com > <mailto:john.garry@huawei.com>> > > 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; > > > What about the case of "!ev1->pmu_name && !ev2->pmu_name" ?
As far as I know, it should not happen, since duration_time is a special event. More below.
> > Thanks, > Ian > > + > + 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))
ev->leader->pmu_name == NULL for only duration_time event. And we don't get here for ev == metric_events[i] == duration_time event (as we use evlist__for_each_entry_continue() and duration_time is always last in metric_events[]), so both event arguments should not have pmu_name == NULL. Indeed, I could just check metric_events[i]->leader->pmu_name != NULL, but thought it better to check both for safety.
Cheers, John
> break; > if (!strcmp(metric_events[i]->name, > ev->name)) { > set_bit(ev->idx, evlist_used); > -- > 2.26.2 >
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