From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031091Ab2CUOEa (ORCPT ); Wed, 21 Mar 2012 10:04:30 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:34760 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030997Ab2CUN7j (ORCPT ); Wed, 21 Mar 2012 09:59:39 -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 14/32] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset Date: Wed, 21 Mar 2012 14:58:20 +0100 Message-Id: <1332338318-5958-16-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 Issue an IPI to restart the tick on a CPU that belongs to a cpuset when its nohz flag gets cleared. 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/cpuset.h | 2 ++ kernel/cpuset.c | 23 +++++++++++++++++++++++ kernel/time/tick-sched.c | 8 ++++++++ 3 files changed, 33 insertions(+), 0 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 5510708..89ef5f3 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -263,6 +263,8 @@ static inline bool cpuset_adaptive_nohz(void) return false; } + +extern void cpuset_exit_nohz_interrupt(void *unused); #else static inline bool cpuset_cpu_adaptive_nohz(int cpu) { return false; } static inline bool cpuset_adaptive_nohz(void) { return false; } diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 5a28cf8..00864a0 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1221,6 +1221,14 @@ static void cpuset_change_flag(struct task_struct *tsk, DEFINE_PER_CPU(int, cpu_adaptive_nohz_ref); +static void cpu_exit_nohz(int cpu) +{ + preempt_disable(); + smp_call_function_single(cpu, cpuset_exit_nohz_interrupt, + NULL, true); + preempt_enable(); +} + static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) { int cpu; @@ -1234,6 +1242,21 @@ static void update_nohz_cpus(struct cpuset *old_cs, struct cpuset *cs) per_cpu(cpu_adaptive_nohz_ref, cpu) += 1; else per_cpu(cpu_adaptive_nohz_ref, cpu) -= 1; + + val = per_cpu(cpu_adaptive_nohz_ref, cpu); + + if (!val) { + /* + * The update to cpu_adaptive_nohz_ref must be + * visible right away. So that once we restart the tick + * from the IPI, it won't be stopped again due to cache + * update lag. + * FIXME: We probably need more to ensure this value is really + * visible right away. + */ + smp_mb(); + cpu_exit_nohz(cpu); + } } } #else diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index fc35d41..fe31add 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -875,6 +875,14 @@ void tick_nohz_check_adaptive(void) } } +void cpuset_exit_nohz_interrupt(void *unused) +{ + struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + + if (ts->tick_stopped && !is_idle_task(current)) + tick_nohz_restart_adaptive(); +} + void tick_nohz_post_schedule(void) { struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); -- 1.7.5.4