From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754293AbcCJMIN (ORCPT ); Thu, 10 Mar 2016 07:08:13 -0500 Received: from www.linutronix.de ([62.245.132.108]:60797 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753760AbcCJMGD (ORCPT ); Thu, 10 Mar 2016 07:06:03 -0500 Message-Id: <20160310120025.169219710@linutronix.de> User-Agent: quilt/0.63-1 Date: Thu, 10 Mar 2016 12:04:40 -0000 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Ingo Molnar , rt@linutronix.de Subject: [patch 08/15] sched, hotplug: Move sync_rcu to be with set_cpu_active(false) References: <20160310115406.940706476@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=peterz-cpuhp-stuff-1.patch X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra The sync_rcu stuff is specificically for clearing bits in the active mask, such that everybody will observe the bit cleared and will not consider the cleared CPU for load-balancing etc. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner --- kernel/cpu.c | 15 --------------- kernel/sched/core.c | 14 ++++++++++++++ 2 files changed, 14 insertions(+), 15 deletions(-) --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -691,21 +691,6 @@ static int takedown_cpu(unsigned int cpu struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu); int err; - /* - * By now we've cleared cpu_active_mask, wait for all preempt-disabled - * and RCU users of this state to go away such that all new such users - * will observe it. - * - * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might - * not imply sync_sched(), so wait for both. - * - * Do sync before park smpboot threads to take care the rcu boost case. - */ - if (IS_ENABLED(CONFIG_PREEMPT)) - synchronize_rcu_mult(call_rcu, call_rcu_sched); - else - synchronize_rcu(); - /* Park the hotplug thread */ kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread); --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7345,6 +7345,20 @@ int sched_cpu_deactivate(unsigned int cp int ret; set_cpu_active(cpu, false); + /* + * We've cleared cpu_active_mask, wait for all preempt-disabled and RCU + * users of this state to go away such that all new such users will + * observe it. + * + * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might + * not imply sync_sched(), so wait for both. + * + * Do sync before park smpboot threads to take care the rcu boost case. + */ + if (IS_ENABLED(CONFIG_PREEMPT)) + synchronize_rcu_mult(call_rcu, call_rcu_sched); + else + synchronize_rcu(); if (!sched_smp_initialized) return 0;