rcu: Make RCU_FAST_NO_HZ respect nohz= boot parameter

If the nohz= boot parameter disables nohz, then RCU_FAST_NO_HZ needs to
also disable itself.  This commit therefore checks for tick_nohz_enabled
being zero, disabling rcu_prepare_for_idle() if so.  This commit assumes
that tick_nohz_enabled can change at runtime: If this is not the case,
then a simpler approach suffices.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 19b61ac1079f..e978845c6800 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -97,6 +97,7 @@ struct rcu_dynticks {
                                     /* # times non-lazy CBs posted to CPU. */
         unsigned long nonlazy_posted_snap;
                                     /* idle-period nonlazy_posted snapshot. */
+        int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 };