From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934006AbcKPIhb (ORCPT ); Wed, 16 Nov 2016 03:37:31 -0500 Received: from terminus.zytor.com ([198.137.202.10]:57892 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751335AbcKPIh2 (ORCPT ); Wed, 16 Nov 2016 03:37:28 -0500 Date: Wed, 16 Nov 2016 00:36:49 -0800 From: tip-bot for David Carrillo-Cisneros Message-ID: Cc: kan.liang@intel.com, jolsa@redhat.com, pjt@google.com, linux-kernel@vger.kernel.org, acme@redhat.com, hpa@zytor.com, peterz@infradead.org, alexander.shishkin@linux.intel.com, eranian@google.com, torvalds@linux-foundation.org, nilayvaish@gmail.com, vegard.nossum@gmail.com, mingo@kernel.org, tglx@linutronix.de, davidcc@google.com Reply-To: acme@redhat.com, linux-kernel@vger.kernel.org, jolsa@redhat.com, kan.liang@intel.com, pjt@google.com, tglx@linutronix.de, mingo@kernel.org, davidcc@google.com, nilayvaish@gmail.com, vegard.nossum@gmail.com, peterz@infradead.org, alexander.shishkin@linux.intel.com, torvalds@linux-foundation.org, eranian@google.com, hpa@zytor.com In-Reply-To: <1478026378-86083-1-git-send-email-davidcc@google.com> References: <1478026378-86083-1-git-send-email-davidcc@google.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] perf/core: Do not set cpuctx->cgrp for unscheduled cgroups Git-Commit-ID: 864c2357ca898c6171fe5284f5ecc795c8ce27a8 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 864c2357ca898c6171fe5284f5ecc795c8ce27a8 Gitweb: http://git.kernel.org/tip/864c2357ca898c6171fe5284f5ecc795c8ce27a8 Author: David Carrillo-Cisneros AuthorDate: Tue, 1 Nov 2016 11:52:58 -0700 Committer: Ingo Molnar CommitDate: Tue, 15 Nov 2016 14:18:22 +0100 perf/core: Do not set cpuctx->cgrp for unscheduled cgroups Commit: db4a835601b7 ("perf/core: Set cgroup in CPU contexts for new cgroup events") failed to verify that event->cgrp is actually the scheduled cgroup in a CPU before setting cpuctx->cgrp. This patch fixes that. Now that there is a different path for scheduled and unscheduled cgroup, add a warning to catch when cpuctx->cgrp is still set after the last cgroup event has been unsheduled. To verify the bug: # Create 2 cgroups. mkdir /dev/cgroups/devices/g1 mkdir /dev/cgroups/devices/g2 # launch a task, bind it to a cpu and move it to g1 CPU=2 while :; do : ; done & P=$! taskset -pc $CPU $P echo $P > /dev/cgroups/devices/g1/tasks # monitor g2 (it runs no tasks) and observe output perf stat -e cycles -I 1000 -C $CPU -G g2 # time counts unit events 1.000091408 7,579,527 cycles g2 2.000350111 cycles g2 3.000589181 cycles g2 4.000771428 cycles g2 # note first line that displays that a task run in g2, despite # g2 having no tasks. This is because cpuctx->cgrp was wrongly # set when context of new event was installed. # After applying the fix we obtain the right output: perf stat -e cycles -I 1000 -C $CPU -G g2 # time counts unit events 1.000119615 cycles g2 2.000389430 cycles g2 3.000590962 cycles g2 Signed-off-by: David Carrillo-Cisneros Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Kan Liang Cc: Linus Torvalds Cc: Nilay Vaish Cc: Paul Turner Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vegard Nossum Link: http://lkml.kernel.org/r/1478026378-86083-1-git-send-email-davidcc@google.com Signed-off-by: Ingo Molnar --- kernel/events/core.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 0e29213..ff230bb 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -902,6 +902,17 @@ list_update_cgroup_event(struct perf_event *event, * this will always be called from the right CPU. */ cpuctx = __get_cpu_context(ctx); + + /* Only set/clear cpuctx->cgrp if current task uses event->cgrp. */ + if (perf_cgroup_from_task(current, ctx) != event->cgrp) { + /* + * We are removing the last cpu event in this context. + * If that event is not active in this cpu, cpuctx->cgrp + * should've been cleared by perf_cgroup_switch. + */ + WARN_ON_ONCE(!add && cpuctx->cgrp); + return; + } cpuctx->cgrp = add ? event->cgrp : NULL; }