From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751618AbeDDIxz (ORCPT ); Wed, 4 Apr 2018 04:53:55 -0400 Received: from cloudserver094114.home.pl ([79.96.170.134]:57472 "EHLO cloudserver094114.home.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017AbeDDIxG (ORCPT ); Wed, 4 Apr 2018 04:53:06 -0400 From: "Rafael J. Wysocki" To: Linux PM Cc: Peter Zijlstra , Frederic Weisbecker , Thomas Gleixner , Paul McKenney , Thomas Ilsche , Doug Smythies , Rik van Riel , Aubrey Li , Mike Galbraith , LKML , Len Brown Subject: [PATCH v9 03/10] sched: idle: Do not stop the tick before cpuidle_idle_call() Date: Wed, 04 Apr 2018 10:36:20 +0200 Message-ID: <49129842.FegiqWMPcW@aspire.rjw.lan> In-Reply-To: <1736751.LdhZHb50jq@aspire.rjw.lan> References: <1736751.LdhZHb50jq@aspire.rjw.lan> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Rafael J. Wysocki Make cpuidle_idle_call() decide whether or not to stop the tick. First, the cpuidle_enter_s2idle() path deals with the tick (and with the entire timekeeping for that matter) by itself and it doesn't need the tick to be stopped beforehand. Second, to address the issue with short idle duration predictions by the idle governor after the tick has been stopped, it will be necessary to change the ordering of cpuidle_select() with respect to tick_nohz_idle_stop_tick(). To prepare for that, put a tick_nohz_idle_stop_tick() call in the same branch in which cpuidle_select() is called. Signed-off-by: Rafael J. Wysocki Reviewed-by: Frederic Weisbecker --- v8 -> v9: * No changes in the patch. * Tag from Frederic. --- kernel/sched/idle.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) Index: linux-pm/kernel/sched/idle.c =================================================================== --- linux-pm.orig/kernel/sched/idle.c +++ linux-pm/kernel/sched/idle.c @@ -146,13 +146,15 @@ static void cpuidle_idle_call(void) } /* - * Tell the RCU framework we are entering an idle section, - * so no more rcu read side critical sections and one more + * The RCU framework needs to be told that we are entering an idle + * section, so no more rcu read side critical sections and one more * step to the grace period */ - rcu_idle_enter(); if (cpuidle_not_available(drv, dev)) { + tick_nohz_idle_stop_tick(); + rcu_idle_enter(); + default_idle_call(); goto exit_idle; } @@ -169,16 +171,26 @@ static void cpuidle_idle_call(void) if (idle_should_enter_s2idle() || dev->use_deepest_state) { if (idle_should_enter_s2idle()) { + rcu_idle_enter(); + entered_state = cpuidle_enter_s2idle(drv, dev); if (entered_state > 0) { local_irq_enable(); goto exit_idle; } + + rcu_idle_exit(); } + tick_nohz_idle_stop_tick(); + rcu_idle_enter(); + next_state = cpuidle_find_deepest_state(drv, dev); call_cpuidle(drv, dev, next_state); } else { + tick_nohz_idle_stop_tick(); + rcu_idle_enter(); + /* * Ask the cpuidle framework to choose a convenient idle state. */ @@ -245,7 +257,6 @@ static void do_idle(void) tick_nohz_idle_restart_tick(); cpu_idle_poll(); } else { - tick_nohz_idle_stop_tick(); cpuidle_idle_call(); } arch_cpu_idle_exit();