rcu: Apply ACCESS_ONCE() to rcu_boost() return value

Both TINY_RCU's and TREE_RCU's implementations of rcu_boost() access
the ->boost_tasks and ->exp_tasks fields without preventing concurrent
changes to these fields.  This commit therefore applies ACCESS_ONCE in
order to prevent compiler mischief.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index dfa97cbb3910..9cb1ae4aabdd 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -312,8 +312,8 @@ static int rcu_boost(void)
         rt_mutex_lock(&mtx);
         rt_mutex_unlock(&mtx);  /* Keep lockdep happy. */
 
-        return rcu_preempt_ctrlblk.boost_tasks != NULL ||
-               rcu_preempt_ctrlblk.exp_tasks != NULL;
+        return ACCESS_ONCE(rcu_preempt_ctrlblk.boost_tasks) != NULL ||
+               ACCESS_ONCE(rcu_preempt_ctrlblk.exp_tasks) != NULL;
 }
 
 /*