From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758165AbbJHSgc (ORCPT ); Thu, 8 Oct 2015 14:36:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48545 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753062AbbJHSgb (ORCPT ); Thu, 8 Oct 2015 14:36:31 -0400 From: Daniel Bristot de Oliveira To: Peter Zijlstra , Ingo Molnar , Steven Rostedt Cc: LKML , "Luis Claudio R. Goncalves" Subject: [PATCH] trace: stop critical timings before idle loop on idle=poll Date: Thu, 8 Oct 2015 15:36:06 -0300 Message-Id: <10fc3705874aef11dbe152a068b591a7be1899b4.1444314899.git.bristot@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When using idle=poll, the preemptoff tracer is always showing the idle task as the culprit for long latencies. That happens because critical timings are not stopped before idle loop. This patch stops critical timings before entering the idle loop, starting it again after the idle loop. This problem does not affect the irqsoff tracer because interruptions are enabled before entering the idle loop. Signed-off-by: Daniel Bristot de Oliveira Reviewed-by: Luis Claudio R. Goncalves --- kernel/sched/idle.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 8f177c7..4a2ef5a 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -57,9 +57,11 @@ static inline int cpu_idle_poll(void) rcu_idle_enter(); trace_cpu_idle_rcuidle(0, smp_processor_id()); local_irq_enable(); + stop_critical_timings(); while (!tif_need_resched() && (cpu_idle_force_poll || tick_check_broadcast_expired())) cpu_relax(); + start_critical_timings(); trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id()); rcu_idle_exit(); return 1; -- 2.4.3