[PATCH v2] rcu: Make call_rcu() lazy only when CONFIG_RCU_LAZY is enabled

[Zqiang]

Currently, regardless of whether the CONFIG_RCU_LAZY is enabled,
invoke the call_rcu() is always lazy, it also means that when
CONFIG_RCU_LAZY is disabled, invoke the call_rcu_flush() is also
lazy. therefore, this commit make call_rcu() lazy only when
CONFIG_RCU_LAZY is enabled.

Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
---
 v1->v2: 
 Use IS_ENABLED(CONFIG_RCU_LAZY) to the existing function of the same name.

 kernel/rcu/tree.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index abc615808b6e..ecf42b0d3726 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2887,7 +2887,10 @@ EXPORT_SYMBOL_GPL(call_rcu_flush);
  */
 void call_rcu(struct rcu_head *head, rcu_callback_t func)
 {
-	return __call_rcu_common(head, func, true);
+	if (IS_ENABLED(CONFIG_RCU_LAZY))
+		return __call_rcu_common(head, func, true);
+	else
+		return __call_rcu_common(head, func, false);
 }
 EXPORT_SYMBOL_GPL(call_rcu);
 
-- 
2.25.1