Commit-ID: 779de6ce54f627f955d4a3d0c5b3dcfaab74fea8 Gitweb: http://git.kernel.org/tip/779de6ce54f627f955d4a3d0c5b3dcfaab74fea8 Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Wed, 10 Jun 2015 13:34:41 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Wed, 22 Jul 2015 15:27:30 -0700 cpu: Wait for RCU grace periods concurrently In kernels built with CONFIG_PREEMPT, _cpu_down() waits for RCU and RCU-sched grace periods back-to-back, incurring quite a bit more latency than required. This commit therefore uses the new synchronize_rcu_mult() to allow waiting for both grace periods concurrently. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- kernel/cpu.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 9c9c9fa..d63b062 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -380,14 +380,14 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) * will observe it. * * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might - * not imply sync_sched(), so explicitly call both. + * not imply sync_sched(), so wait for both. * * Do sync before park smpboot threads to take care the rcu boost case. */ -#ifdef CONFIG_PREEMPT - synchronize_sched(); -#endif - synchronize_rcu(); + if (IS_ENABLED(CONFIG_PREEMPT)) + synchronize_rcu_mult(call_rcu, call_rcu_sched); + else + synchronize_rcu(); smpboot_park_threads(cpu); -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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