From 36131fdc87c847b498d82808dd5ac88443dc8cf5 Mon Sep 17 00:00:00 2001 From: Kaushal Kumar Date: Thu, 15 May 2014 19:19:04 +0530 Subject: [PATCH] sched: Remove synchronize rcu/sched calls from _cpu_down There is no need for sync_sched() in _cpu_down as stop_machine() provides that barrier implicitly. Removing it also helps improve hot-unplug latency. The sync_sched/rcu were earlier removed for the same reason by the commit 9ee349ad6d326df3633 ("sched: Fix set_cpu_active() in cpu_down()"), but recently got added as part of commit <6acce3ef84520537> ("sched: Remove get_online_cpus() usage."). CRs-Fixed: 1048941 Change-Id: I97763004454d082d3cc2d9d9dbef7da923608600 Signed-off-by: Kaushal Kumar Signed-off-by: Matt Wagantall Signed-off-by: Runmin Wang --- kernel/cpu.c | 15 --------------- 1 file changed, 15 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 37731292f8a1..1cfd381642da 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -365,21 +365,6 @@ static int _cpu_down(unsigned int cpu, int tasks_frozen) goto out_release; } - /* - * 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(); - smpboot_park_threads(cpu); /* -- 2.11.0