From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752310AbcGROck (ORCPT ); Mon, 18 Jul 2016 10:32:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42814 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752016AbcGROch (ORCPT ); Mon, 18 Jul 2016 10:32:37 -0400 Date: Mon, 18 Jul 2016 16:32:27 +0200 From: Jiri Olsa To: Mark Rutland Cc: linux-kernel@vger.kernel.org, acme@kernel.org, adrian.hunter@intel.com, alexander.shishkin@linux.intel.com, hekuang@huawei.com, jolsa@kernel.org, kan.liang@intel.com, mingo@redhat.com, peterz@infradead.org, wangnan0@huawei.com Subject: Re: [RFCv2 1/4] perf stat: balance opening and reading events Message-ID: <20160718143227.GB4813@krava> References: <1468577293-19667-1-git-send-email-mark.rutland@arm.com> <1468577293-19667-2-git-send-email-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1468577293-19667-2-git-send-email-mark.rutland@arm.com> User-Agent: Mutt/1.6.2 (2016-07-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 18 Jul 2016 14:32:33 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 15, 2016 at 11:08:10AM +0100, Mark Rutland wrote: > In create_perf_stat_counter, when a target CPU has not been provided, we > call __perf_evsel__open with empty_cpu_map, and open a single FD per > thread. However, in read_counter we assume that we opened events for > the product of threads and CPUs described in the evsel's cpu_map. > > Thus, if an evsel has a cpu_map with more than one entry, we will > attempt to access FDs that we didn't open. This could result in a number > of problems (e.g. blocking while reading from STDIN if the fd memory > happened to be initialised to zero). > > This is problematic for systems were a logical CPU PMU covers some > arbitrary subset of CPUs. The cpu_map of any evsel for that PMU will be > initialised based on the cpumask exposed through sysfs, even if the user > requests per-thread events. > > Signed-off-by: Mark Rutland > Cc: Alexander Shishkin > Cc: Arnaldo Carvalho de Melo > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: linux-kernel@vger.kernel.org Acked-by: Jiri Olsa thanks, jirka > --- > tools/perf/builtin-stat.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index ee7ada7..f3e21a2 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -276,8 +276,12 @@ perf_evsel__write_stat_event(struct perf_evsel *counter, u32 cpu, u32 thread, > static int read_counter(struct perf_evsel *counter) > { > int nthreads = thread_map__nr(evsel_list->threads); > - int ncpus = perf_evsel__nr_cpus(counter); > - int cpu, thread; > + int ncpus, cpu, thread; > + > + if (target__has_cpu(&target)) > + ncpus = perf_evsel__nr_cpus(counter); > + else > + ncpus = 1; > > if (!counter->supported) > return -ENOENT; > -- > 1.9.1 >