From: Jiri Olsa <jolsa@redhat.com>
To: Stephane Eranian <eranian@google.com>
Cc: Numfor Mbiziwo-Tiapo <nums@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Song Liu <songliubraving@fb.com>,
mbd@fb.com, LKML <linux-kernel@vger.kernel.org>,
Ian Rogers <irogers@google.com>
Subject: Re: [PATCH] Fix perf stat repeat segfault
Date: Mon, 15 Jul 2019 10:31:05 +0200 [thread overview]
Message-ID: <20190715083105.GB2821@krava> (raw)
In-Reply-To: <CABPqkBR=arE==2H2H0t1uAU2aTgPOr6Yucgh16J0rKughf_=CQ@mail.gmail.com>
On Mon, Jul 15, 2019 at 01:14:59AM -0700, Stephane Eranian wrote:
> On Mon, Jul 15, 2019 at 12:59 AM Jiri Olsa <jolsa@redhat.com> wrote:
> >
> > On Sun, Jul 14, 2019 at 02:36:42PM -0700, Stephane Eranian wrote:
> > > On Sun, Jul 14, 2019 at 1:55 PM Jiri Olsa <jolsa@redhat.com> wrote:
> > > >
> > > > On Sun, Jul 14, 2019 at 10:44:36PM +0200, Jiri Olsa wrote:
> > > > > On Wed, Jul 10, 2019 at 01:45:40PM -0700, Numfor Mbiziwo-Tiapo wrote:
> > > > > > When perf stat is called with event groups and the repeat option,
> > > > > > a segfault occurs because the cpu ids are stored on each iteration
> > > > > > of the repeat, when they should only be stored on the first iteration,
> > > > > > which causes a buffer overflow.
> > > > > >
> > > > > > This can be replicated by running (from the tip directory):
> > > > > >
> > > > > > make -C tools/perf
> > > > > >
> > > > > > then running:
> > > > > >
> > > > > > tools/perf/perf stat -e '{cycles,instructions}' -r 10 ls
> > > > > >
> > > > > > Since run_idx keeps track of the current iteration of the repeat,
> > > > > > only storing the cpu ids on the first iteration (when run_idx < 1)
> > > > > > fixes this issue.
> > > > > >
> > > > > > Signed-off-by: Numfor Mbiziwo-Tiapo <nums@google.com>
> > > > > > ---
> > > > > > tools/perf/builtin-stat.c | 7 ++++---
> > > > > > 1 file changed, 4 insertions(+), 3 deletions(-)
> > > > > >
> > > > > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
> > > > > > index 63a3afc7f32b..92d6694367e4 100644
> > > > > > --- a/tools/perf/builtin-stat.c
> > > > > > +++ b/tools/perf/builtin-stat.c
> > > > > > @@ -378,9 +378,10 @@ static void workload_exec_failed_signal(int signo __maybe_unused, siginfo_t *inf
> > > > > > workload_exec_errno = info->si_value.sival_int;
> > > > > > }
> > > > > >
> > > > > > -static bool perf_evsel__should_store_id(struct perf_evsel *counter)
> > > > > > +static bool perf_evsel__should_store_id(struct perf_evsel *counter, int run_idx)
> > > > > > {
> > > > > > - return STAT_RECORD || counter->attr.read_format & PERF_FORMAT_ID;
> > > > > > + return STAT_RECORD || counter->attr.read_format & PERF_FORMAT_ID
> > > > > > + && run_idx < 1;
> > > > >
> > > > > we create counters for every iteration, so this can't be
> > > > > based on iteration
> > > > >
> > > > > I think that's just a workaround for memory corruption,
> > > > > that's happening for repeating groupped events stats,
> > > > > I'll check on this
> > > >
> > > > how about something like this? we did not cleanup
> > > > ids on evlist close, so it kept on raising and
> > > > causing corruption in next iterations
> > > >
> > > not sure, that would realloc on each iteration of the repeats.
> >
> > well, we need new ids, because we create new events every iteration
> >
> If you recreate them, then agreed.
> It is not clear to me why you need ids when not running is STAT_RECORD mode.
it's for faster reading of group events, see:
82bf311e15d2 perf stat: Use group read for event groups
jirka
next prev parent reply other threads:[~2019-07-15 8:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-10 20:45 [PATCH] Fix perf stat repeat segfault Numfor Mbiziwo-Tiapo
2019-07-11 4:44 ` Ravi Bangoria
2019-07-14 20:44 ` Jiri Olsa
2019-07-14 20:55 ` Jiri Olsa
2019-07-14 21:36 ` Stephane Eranian
2019-07-15 7:59 ` Jiri Olsa
2019-07-15 8:14 ` Stephane Eranian
2019-07-15 8:31 ` Jiri Olsa [this message]
2019-07-15 14:21 ` [PATCH] perf stat: Fix segfault for event group in repeat mode Jiri Olsa
2019-07-16 18:48 ` Arnaldo Carvalho de Melo
2019-07-23 21:49 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2019-07-11 17:21 [PATCH] Fix perf stat repeat segfault Numfor Mbiziwo-Tiapo
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