linux-kernel - Re: [PATCH 1/2] perf stat: Fix segfault when counting armv8

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Message-ID: <CAM9d7cgT4qLH0mPM1nTRa-FYwjMOc4LOCUD_X0r21hdUUVLpRA@mail.gmail.com>
Date:   Wed, 23 Sep 2020 23:15:06 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Wei Li <liwei391@...wei.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Li Bin <huawei.libin@...wei.com>
Subject: Re: [PATCH 1/2] perf stat: Fix segfault when counting armv8_pmu events

On Wed, Sep 23, 2020 at 11:08 PM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Wed, Sep 23, 2020 at 10:49:52PM +0900, Namhyung Kim wrote:
> > On Wed, Sep 23, 2020 at 2:44 PM Jiri Olsa <jolsa@...hat.com> wrote:
> > >
> > > On Tue, Sep 22, 2020 at 11:13:45AM +0800, Wei Li wrote:
> > > > When executing perf stat with armv8_pmu events with a workload, it will
> > > > report a segfault as result.
> > >
> > > please share the perf stat command line you see that segfault for
> >
> > It seems the description in the patch 0/2 already has it:
> >
> >   [root@...alhost hulk]# tools/perf/perf stat  -e
> > armv8_pmuv3_0/ll_cache_rd/,armv8_pmuv3_0/ll_cache_miss_rd/ ls >
> > /dev/null
> >   Segmentation fault
>
> yea I found it, but can't reproduce it.. I see the issue from
> patch 2, but not sure what's the problem so far

I think the problem is that armv8_pmu has a cpumask,
and the user requested per-task events.

The code tried to open the event with a dummy cpu map
since it's not a cpu event, but the pmu has cpu map and
it's passed to evsel.  So there's confusion somewhere
whether it should use evsel->cpus or a dummy map.

Thanks
Namhyung