[PATCH] srcu: Make Tiny SRCU synchronize_srcu() more complete

[Zqiang]

This commit add lockdep detection for illegal use synchronize_srcu()
in same-type SRCU (or in RCU) read-side critical section and support
early boot operations.

Signed-off-by: Zqiang <qiang1.zhang@xxxxxxxxx>
---
 kernel/rcu/srcutiny.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 33adafdad261..b12fb0cec44d 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -197,6 +197,16 @@ void synchronize_srcu(struct srcu_struct *ssp)
 {
 	struct rcu_synchronize rs;
 
+	RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
+			lock_is_held(&rcu_bh_lock_map) ||
+			lock_is_held(&rcu_lock_map) ||
+			lock_is_held(&rcu_sched_lock_map),
+			"Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section");
+
+	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
+		return;
+
+	might_sleep();
 	init_rcu_head_on_stack(&rs.head);
 	init_completion(&rs.completion);
 	call_srcu(ssp, &rs.head, wakeme_after_rcu);
-- 
2.25.1