Commit-ID: f0f2e7d307fff226e0c1df5a07101a1216a46d8a Gitweb: http://git.kernel.org/tip/f0f2e7d307fff226e0c1df5a07101a1216a46d8a Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Tue, 29 Sep 2015 08:59:32 -0700 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Fri, 4 Dec 2015 12:27:31 -0800 rcu: Avoid tick_nohz_active checks on NOCBs CPUs Currently, rcu_prepare_for_idle() checks for tick_nohz_active, even on individual NOCBs CPUs, unless all CPUs are marked as NOCBs CPUs at build time. This check is pointless on NOCBs CPUs because they never have any callbacks posted, given that all of their callbacks are handed off to the corresponding rcuo kthread. There is a check for individually designated NOCBs CPUs, but it pointelessly follows the check for tick_nohz_active. This commit therefore moves the check for individually designated NOCBs CPUs up with the check for CONFIG_RCU_NOCB_CPU_ALL. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- kernel/rcu/tree_plugin.h | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 42df937..8e9d4a4 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1513,7 +1513,8 @@ static void rcu_prepare_for_idle(void) struct rcu_state *rsp; int tne; - if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL)) + if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) || + rcu_is_nocb_cpu(smp_processor_id())) return; /* Handle nohz enablement switches conservatively. */ @@ -1527,10 +1528,6 @@ static void rcu_prepare_for_idle(void) if (!tne) return; - /* If this is a no-CBs CPU, no callbacks, just return. */ - if (rcu_is_nocb_cpu(smp_processor_id())) - return; - /* * If a non-lazy callback arrived at a CPU having only lazy * callbacks, invoke RCU core for the side-effect of recalculating -- 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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