linux-kernel - Re: [PATCH 2/2] perf metricgroup: Return error code from metricgroup__add_metric_sys_event

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Date:   Mon, 14 Jun 2021 11:56:47 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     John Garry <john.garry@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        kajoljain <kjain@...ux.ibm.com>,
        linux-perf-users <linux-perf-users@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] perf metricgroup: Return error code from
 metricgroup__add_metric_sys_event_iter()

Em Thu, Jun 10, 2021 at 11:45:17AM -0700, Ian Rogers escreveu:
> On Thu, Jun 10, 2021 at 7:37 AM John Garry <john.garry@...wei.com> wrote:
> >
> > The error code is not set at all in the sys event iter function.
> >
> > This may lead to an uninitialized value of "ret" in
> > metricgroup__add_metric() when no CPU metric is added.
> >
> > Fix by properly setting the error code.
> >
> > It is not necessary to init "ret" to 0 in metricgroup__add_metric(), as
> > if we have no CPU or sys event metric matching, then "has_match" should
> > be 0 and "ret" is set to -EINVAL.
> >
> > However gcc cannot detect that it may not have been set after the
> > map_for_each_metric() loop for CPU metrics, which is strange.
> >
> > Fixes: be335ec28efa8 ("perf metricgroup: Support adding metrics for system PMUs")
> > Signed-off-by: John Garry <john.garry@...wei.com>
> 
> Acked-by: Ian Rogers <irogers@...gle.com>

Do your Acked-by applies to both patches? Or just 2/2?  I reproduced the
problem fixed by 1/2 on a Thinkpad T450S (broadwell) and after applying
the patch it doesn't segfaults.

Please clarify,

- Arnaldo

 
> Thanks,
> Ian
> 
> > ---
> >  tools/perf/util/metricgroup.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
> > index c456fdeae06a..d3cf2dee36c8 100644
> > --- a/tools/perf/util/metricgroup.c
> > +++ b/tools/perf/util/metricgroup.c
> > @@ -1073,16 +1073,18 @@ static int metricgroup__add_metric_sys_event_iter(struct pmu_event *pe,
> >
> >         ret = add_metric(d->metric_list, pe, d->metric_no_group, &m, NULL, d->ids);
> >         if (ret)
> > -               return ret;
> > +               goto out;
> >
> >         ret = resolve_metric(d->metric_no_group,
> >                                      d->metric_list, NULL, d->ids);
> >         if (ret)
> > -               return ret;
> > +               goto out;
> >
> >         *(d->has_match) = true;
> >
> > -       return *d->ret;
> > +out:
> > +       *(d->ret) = ret;
> > +       return ret;
> >  }
> >
> >  static int metricgroup__add_metric(const char *metric, bool metric_no_group,
> > --
> > 2.26.2
> >

-- 

- Arnaldo