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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-09-29 08:59:32 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-12-04 12:27:31 -0800
commitf0f2e7d307fff226e0c1df5a07101a1216a46d8a (patch)
tree4f7f567e4e2518b9110e41af338d154aa9c30046
parent699d40352059e64a4d993af170272585c41988d0 (diff)
downloadlinux-sh-f0f2e7d307fff226e0c1df5a07101a1216a46d8a.tar.gz
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@linux.vnet.ibm.com>
-rw-r--r--kernel/rcu/tree_plugin.h7
1 files changed, 2 insertions, 5 deletions
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 42df93721e6f..8e9d4a4d0326 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