srcu: Make Tiny synchronize_srcu() check for readers

This commit adds lockdep checks for illegal use of synchronize_srcu()
within same-type SRCU read-side critical sections and within normal
RCU read-side critical sections.  It also makes synchronize_srcu()
be a no-op during early boot.

These changes bring Tiny synchronize_srcu() into line with both Tree
synchronize_srcu() and Tiny synchronize_rcu().

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: John Ogness <john.ogness@linutronix.de>

diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 33adafdad26138906557fa78ee024d4bef11965e..b12fb0cec44d61708302ebf388e2fdbcd2d58399 100644 (file)
--- 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);