From patchwork Thu Jul 7 16:04:32 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mark Rutland X-Patchwork-Id: 71594 Delivered-To: patch@linaro.org Received: by 10.140.28.4 with SMTP id 4csp1489126qgy; Thu, 7 Jul 2016 09:05:07 -0700 (PDT) X-Received: by 10.98.10.25 with SMTP id s25mr1645758pfi.44.1467907507006; Thu, 07 Jul 2016 09:05:07 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id c16si4681288pae.6.2016.07.07.09.05.06; Thu, 07 Jul 2016 09:05:06 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752895AbcGGQE7 (ORCPT + 30 others); Thu, 7 Jul 2016 12:04:59 -0400 Received: from foss.arm.com ([217.140.101.70]:37352 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751854AbcGGQEw (ORCPT ); Thu, 7 Jul 2016 12:04:52 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3574C318; Thu, 7 Jul 2016 09:05:51 -0700 (PDT) Received: from leverpostej.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 8CF313F41F; Thu, 7 Jul 2016 09:04:49 -0700 (PDT) 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: [RFC PATCH 1/3] perf stat: balance opening and reading events Date: Thu, 7 Jul 2016 17:04:32 +0100 Message-Id: <1467907474-3290-2-git-send-email-mark.rutland@arm.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1467907474-3290-1-git-send-email-mark.rutland@arm.com> References: <1467907474-3290-1-git-send-email-mark.rutland@arm.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk 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(-) -- 1.9.1 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;