From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754988Ab1HOPxs (ORCPT ); Mon, 15 Aug 2011 11:53:48 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:46598 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754964Ab1HOPxq (ORCPT ); Mon, 15 Aug 2011 11:53:46 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Andrew Morton , Anton Blanchard , Avi Kivity , Ingo Molnar , Lai Jiangshan , "Paul E . McKenney" , Paul Menage , Peter Zijlstra , Stephen Hemminger , Thomas Gleixner , Tim Pepper Subject: [PATCH 19/32] nohz/cpuset: Restart tick when nohz flag is cleared on cpuset Date: Mon, 15 Aug 2011 17:52:16 +0200 Message-Id: <1313423549-27093-20-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1313423549-27093-1-git-send-email-fweisbec@gmail.com> References: <1313423549-27093-1-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: Andrew Morton Cc: Anton Blanchard Cc: Avi Kivity Cc: Ingo Molnar Cc: Lai Jiangshan Cc: Paul E . McKenney Cc: Paul Menage Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Thomas Gleixner Cc: Tim Pepper --- include/linux/cpuset.h | 1 + kernel/cpuset.c | 21 +++++++++++++++++++++ kernel/sched.c | 8 ++++++++ 3 files changed, 30 insertions(+), 0 deletions(-) diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h index 799b9a4..7f9d78d 100644 --- a/include/linux/cpuset.h +++ b/include/linux/cpuset.h @@ -265,6 +265,7 @@ static inline bool cpuset_adaptive_nohz(void) } extern void cpuset_update_nohz(void); +extern void cpuset_exit_nohz_interrupt(void *unused); #else static inline void cpuset_update_nohz(void) { } diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 3135096..ee3b0d0 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -1199,6 +1199,14 @@ 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; @@ -1212,6 +1220,19 @@ 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. + */ + smp_mb(); + cpu_exit_nohz(cpu); + } } } #else diff --git a/kernel/sched.c b/kernel/sched.c index 78ea0a5..75378be 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2513,6 +2513,14 @@ void cpuset_update_nohz(void) cpuset_nohz_restart_tick(); } +void cpuset_exit_nohz_interrupt(void *unused) +{ + if (!tick_nohz_adaptive_mode()) + return; + + cpuset_nohz_restart_tick(); +} + static void cpuset_nohz_task_switch(struct task_struct *next) { int cpu = smp_processor_id(); -- 1.7.5.4