[PATCH tip/core/rcu 1/2] rcu: fix holdoff for accelerated GPs for last non-dynticked CPU

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

Make the holdoff only happen when the full number of attempts have been
made.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcutree_plugin.h |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 464ad2c..79b53bd 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1010,6 +1010,10 @@ int rcu_needs_cpu(int cpu)
 	int c = 0;
 	int thatcpu;
 
+	/* Check for being in the holdoff period. */
+	if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies)
+		return rcu_needs_cpu_quick_check(cpu);
+
 	/* Don't bother unless we are the last non-dyntick-idle CPU. */
 	for_each_cpu_not(thatcpu, nohz_cpu_mask)
 		if (thatcpu != cpu) {
@@ -1041,10 +1045,8 @@ int rcu_needs_cpu(int cpu)
 	}
 
 	/* If RCU callbacks are still pending, RCU still needs this CPU. */
-	if (c) {
+	if (c)
 		raise_softirq(RCU_SOFTIRQ);
-		per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
-	}
 	return c;
 }
 
-- 
1.6.6