From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751419AbdIAHVj (ORCPT ); Fri, 1 Sep 2017 03:21:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54188 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751000AbdIAHVi (ORCPT ); Fri, 1 Sep 2017 03:21:38 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 41985356FC Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx06.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=jolsa@redhat.com Date: Fri, 1 Sep 2017 09:21:33 +0200 From: Jiri Olsa To: Peter Zijlstra Cc: Jiri Olsa , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Alexander Shishkin , Namhyung Kim , David Ahern , Andi Kleen , Mark Rutland Subject: Re: [PATCH 03/10] perf: Make sure we read only scheduled events Message-ID: <20170901072133.GA14815@krava> References: <20170824162737.7813-1-jolsa@kernel.org> <20170824162737.7813-4-jolsa@kernel.org> <20170828192359.jfcb55q5remlhfbw@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170828192359.jfcb55q5remlhfbw@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.8.3 (2017-05-23) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Fri, 01 Sep 2017 07:21:38 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 28, 2017 at 09:23:59PM +0200, Peter Zijlstra wrote: > On Thu, Aug 24, 2017 at 06:27:30PM +0200, Jiri Olsa wrote: > > Adding leader's state check into perf_output_read_group > > to ensure we read only leader, which is scheduled in. > > > > Similar check is already there for siblings. > > > > Signed-off-by: Jiri Olsa > > --- > > kernel/events/core.c | 10 +++++++--- > > 1 file changed, 7 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index 30e30e94ea32..9a2791afe051 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -5760,6 +5760,11 @@ void perf_event__output_id_sample(struct perf_event *event, > > __perf_event__output_id_sample(handle, sample); > > } > > > > +static bool can_read(struct perf_event *event) > > +{ > > + return event->state == PERF_EVENT_STATE_ACTIVE; > > +} > > + > > static void perf_output_read_one(struct perf_output_handle *handle, > > struct perf_event *event, > > u64 enabled, u64 running) > > @@ -5800,7 +5805,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, > > if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) > > values[n++] = running; > > > > - if (leader != event) > > + if ((leader != event) && can_read(leader)) > > leader->pmu->read(leader); > > > > values[n++] = perf_event_count(leader); > > @@ -5812,8 +5817,7 @@ static void perf_output_read_group(struct perf_output_handle *handle, > > list_for_each_entry(sub, &leader->sibling_list, group_entry) { > > n = 0; > > > > - if ((sub != event) && > > - (sub->state == PERF_EVENT_STATE_ACTIVE)) > > + if ((sub != event) && can_read(sub)) > > sub->pmu->read(sub); > > > > values[n++] = perf_event_count(sub); > > I'm not seeing how this makes sense. Groups should either _all_ be > scheduled or not at all. Please explain. so this could be called for event which is already scheduled out: perf_event_exit_task_context task_ctx_sched_out <- unschedules event perf_event_exit_event sync_child_event perf_event_read_event perf_output_read if leader != events (which is, if you don't have Mark's fix), we'll call leader->pmu->read(leader) even if it's not scheduled in jirka