[tip:core/urgent] rcu: Make rcu_enter_nohz() pay attention to nesting

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Commit-ID:  4305ce7894dd38b0633bfc8978437320119223bd
Gitweb:     http://git.kernel.org/tip/4305ce7894dd38b0633bfc8978437320119223bd
Author:     Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 16 May 2011 14:27:31 -0700
Committer:  Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 26 May 2011 09:42:22 -0700

rcu: Make rcu_enter_nohz() pay attention to nesting

The old version of rcu_enter_nohz() forced RCU into nohz mode even if
the nesting count was non-zero.  This change causes rcu_enter_nohz()
to hold off for non-zero nesting counts.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
---
 kernel/rcutree.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 195b3a3..99c6038 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -324,8 +324,8 @@ void rcu_enter_nohz(void)
 	smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */
 	local_irq_save(flags);
 	rdtp = &__get_cpu_var(rcu_dynticks);
-	rdtp->dynticks++;
-	rdtp->dynticks_nesting--;
+	if (--rdtp->dynticks_nesting == 0)
+		rdtp->dynticks++;
 	WARN_ON_ONCE(rdtp->dynticks & 0x1);
 	local_irq_restore(flags);
 }
--
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