From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031011Ab2CUOFY (ORCPT ); Wed, 21 Mar 2012 10:05:24 -0400 Received: from mail-wi0-f170.google.com ([209.85.212.170]:48256 "EHLO mail-wi0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030943Ab2CUN7a (ORCPT ); Wed, 21 Mar 2012 09:59:30 -0400 From: Frederic Weisbecker To: LKML , linaro-sched-sig@lists.linaro.org Cc: Frederic Weisbecker , Alessio Igor Bogani , Andrew Morton , Avi Kivity , Chris Metcalf , Christoph Lameter , Daniel Lezcano , Geoff Levand , Gilad Ben Yossef , Ingo Molnar , Max Krasnyansky , "Paul E. McKenney" , Peter Zijlstra , Stephen Hemminger , Steven Rostedt , Sven-Thorsten Dietrich , Thomas Gleixner , Zen Lin Subject: [PATCH 11/32] nohz/cpuset: Don't turn off the tick if rcu needs it Date: Wed, 21 Mar 2012 14:58:17 +0100 Message-Id: <1332338318-5958-13-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1332338318-5958-1-git-send-email-fweisbec@gmail.com> References: <1332338318-5958-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If RCU is waiting for the current CPU to complete a grace period, don't turn off the tick. Unlike dynctik-idle, we are not necessarily going to enter into rcu extended quiescent state, so we may need to keep the tick to note current CPU's quiescent states. [added build fix from Zen Lin] Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Daniel Lezcano Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Ingo Molnar Cc: Max Krasnyansky Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner Cc: Zen Lin --- include/linux/rcupdate.h | 1 + kernel/rcutree.c | 3 +-- kernel/time/tick-sched.c | 22 ++++++++++++++++++---- 3 files changed, 20 insertions(+), 6 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 81c04f4..e06639e 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -184,6 +184,7 @@ static inline int rcu_preempt_depth(void) extern void rcu_sched_qs(int cpu); extern void rcu_bh_qs(int cpu); extern void rcu_check_callbacks(int cpu, int user); +extern int rcu_pending(int cpu); struct notifier_block; extern void rcu_idle_enter(void); extern void rcu_idle_exit(void); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 6c4a672..e141c7e 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -212,7 +212,6 @@ int rcu_cpu_stall_suppress __read_mostly; module_param(rcu_cpu_stall_suppress, int, 0644); static void force_quiescent_state(struct rcu_state *rsp, int relaxed); -static int rcu_pending(int cpu); /* * Return the number of RCU-sched batches processed thus far for debug & stats. @@ -1915,7 +1914,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) * by the current CPU, returning 1 if so. This function is part of the * RCU implementation; it is -not- an exported member of the RCU API. */ -static int rcu_pending(int cpu) +int rcu_pending(int cpu) { return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 43fa7ac..4f99766 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -506,9 +506,21 @@ void tick_nohz_idle_enter(void) local_irq_enable(); } +#ifdef CONFIG_CPUSETS_NO_HZ +static bool can_stop_adaptive_tick(void) +{ + if (!sched_can_stop_tick()) + return false; + + /* Is there a grace period to complete ? */ + if (rcu_pending(smp_processor_id())) + return false; + + return true; +} + static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) { -#ifdef CONFIG_CPUSETS_NO_HZ int cpu = smp_processor_id(); if (!cpuset_adaptive_nohz() || is_idle_task(current)) @@ -517,12 +529,14 @@ static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) return; - if (!sched_can_stop_tick()) + if (!can_stop_adaptive_tick()) return; tick_nohz_stop_sched_tick(ts, ktime_get(), cpu); -#endif } +#else +static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) { } +#endif /** * tick_nohz_irq_exit - update next tick event from interrupt exit @@ -852,7 +866,7 @@ void tick_nohz_check_adaptive(void) struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); if (ts->tick_stopped && !is_idle_task(current)) { - if (!sched_can_stop_tick()) + if (!can_stop_adaptive_tick()) tick_nohz_restart_sched_tick(); } } -- 1.7.5.4