Re: [PATCH 4/5] perf stat: Avoid segv if core.user_cpus isn't set.

From: Ian Rogers <irogers@google.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	 Mark Rutland <mark.rutland@arm.com>,
	 Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	 Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mike Leach <mike.leach@linaro.org>,  Leo Yan <leo.yan@linaro.org>,
	John Garry <john.garry@huawei.com>,
	 Will Deacon <will@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	 Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	 Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,  Kajol Jain <kjain@linux.ibm.com>,
	James Clark <james.clark@arm.com>,
	 German Gomez <german.gomez@arm.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	 Riccardo Mancini <rickyman7@gmail.com>,
	Andi Kleen <ak@linux.intel.com>,
	 Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>,
	 Alexander Antonov <alexander.antonov@linux.intel.com>,
	linux-perf-users@vger.kernel.org,  linux-kernel@vger.kernel.org,
	coresight@lists.linaro.org,
	 linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
	 bpf@vger.kernel.org, Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 4/5] perf stat: Avoid segv if core.user_cpus isn't set.
Date: Mon, 28 Mar 2022 13:46:29 -0700	[thread overview]
Message-ID: <CAP-5=fXUPTPgKE1TAtBxx4hBNYQJwDbHf+ZNq7AKkaYabYC+KA@mail.gmail.com> (raw)
In-Reply-To: <YkIbXzCYEutqxQRE@kernel.org>

On Mon, Mar 28, 2022 at 1:32 PM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Em Sun, Mar 27, 2022 at 11:24:13PM -0700, Ian Rogers escreveu:
> > Passing null to perf_cpu_map__max doesn't make sense as there is no
> > valid max. Avoid this problem by null checking in
> > perf_stat_init_aggr_mode.
>
> Applying this one after changing user_cpus back to cpus as this is a fix
> independent of this patchset.
>
> In the future, please try to have such patches at the beginning of the
> series, so that  they can get cherry-picked more easily.

Ack. The problem is best exhibited when the intersect happens, without
it getting a reproducer wasn't something I was able to do.

Thanks,
Ian

> - Arnaldo
>
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >  tools/perf/builtin-stat.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > index 5bee529f7656..ecd5cf4fd872 100644
> > --- a/tools/perf/builtin-stat.c
> > +++ b/tools/perf/builtin-stat.c
> > @@ -1472,7 +1472,10 @@ static int perf_stat_init_aggr_mode(void)
> >        * taking the highest cpu number to be the size of
> >        * the aggregation translate cpumap.
> >        */
> > -     nr = perf_cpu_map__max(evsel_list->core.user_cpus).cpu;
> > +     if (evsel_list->core.user_cpus)
> > +             nr = perf_cpu_map__max(evsel_list->core.user_cpus).cpu;
> > +     else
> > +             nr = 0;
> >       stat_config.cpus_aggr_map = cpu_aggr_map__empty_new(nr + 1);
> >       return stat_config.cpus_aggr_map ? 0 : -ENOMEM;
> >  }
> > --
> > 2.35.1.1021.g381101b075-goog
>
> --
>
> - Arnaldo

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