From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932557AbcGOKIf (ORCPT ); Fri, 15 Jul 2016 06:08:35 -0400 Received: from foss.arm.com ([217.140.101.70]:48125 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932518AbcGOKIb (ORCPT ); Fri, 15 Jul 2016 06:08:31 -0400 From: Mark Rutland To: linux-kernel@vger.kernel.org Cc: acme@kernel.org, adrian.hunter@intel.com, alexander.shishkin@linux.intel.com, hekuang@huawei.com, jolsa@kernel.org, kan.liang@intel.com, mark.rutland@arm.com, mingo@redhat.com, peterz@infradead.org, wangnan0@huawei.com Subject: [RFCv2 1/4] perf stat: balance opening and reading events Date: Fri, 15 Jul 2016 11:08:10 +0100 Message-Id: <1468577293-19667-2-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1468577293-19667-1-git-send-email-mark.rutland@arm.com> References: <1468577293-19667-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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