rcu: Add lockdep-RCU checks for simple self-deadlock

It is illegal to have a grace period within a same-flavor RCU read-side
critical section, so this commit adds lockdep-RCU checks to splat when
such abuse is encountered.  This commit does not detect more elaborate
RCU deadlock situations.  These situations might be a job for lockdep
enhancements.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 6c4a6722abfd..3cf713a724c1 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1816,6 +1816,10 @@ EXPORT_SYMBOL_GPL(call_rcu_bh);
  */
 void synchronize_sched(void)
 {
+        rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                           !lock_is_held(&rcu_lock_map) &&
+                           !lock_is_held(&rcu_sched_lock_map),
+                           "Illegal synchronize_sched() in RCU-sched read-side critical section");
         if (rcu_blocking_is_gp())
                 return;
         wait_rcu_gp(call_rcu_sched);
@@ -1833,6 +1837,10 @@ EXPORT_SYMBOL_GPL(synchronize_sched);
  */
 void synchronize_rcu_bh(void)
 {
+        rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+                           !lock_is_held(&rcu_lock_map) &&
+                           !lock_is_held(&rcu_sched_lock_map),
+                           "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
         if (rcu_blocking_is_gp())
                 return;
         wait_rcu_gp(call_rcu_bh);