[PATCH tip/core/rcu 45/55] rcu: check for entering dyntick-idle mode while in read-side critical section

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

CONFIG_RCU_FAST_NO_HZ assumes that all calls to rcu_needs_cpu() are
outside of all RCU read-side critical sections.  This patch adds diagnostic
checks to verify this assumption.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/rcupdate.h |    3 +++
 kernel/rcutree.c         |    3 +++
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e86bc28..8d7efc8 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -233,6 +233,8 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head)
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
+#define PROVE_RCU(a) a
+
 extern struct lockdep_map rcu_lock_map;
 # define rcu_read_acquire() \
 		lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
@@ -311,6 +313,7 @@ static inline int rcu_read_lock_sched_held(void)
 
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+# define PROVE_RCU(a)			do { } while (0)
 # define rcu_read_acquire()		do { } while (0)
 # define rcu_read_release()		do { } while (0)
 # define rcu_read_acquire_bh()		do { } while (0)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 8455043..743a658 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1786,6 +1786,9 @@ static int rcu_pending(int cpu)
  */
 static int rcu_needs_cpu_quick_check(int cpu)
 {
+	PROVE_RCU(WARN_ON_ONCE(lock_is_held(&rcu_lock_map)));
+	PROVE_RCU(WARN_ON_ONCE(lock_is_held(&rcu_bh_lock_map)));
+	PROVE_RCU(WARN_ON_ONCE(lock_is_held(&rcu_sched_lock_map)));
 	/* RCU callbacks either ready or pending? */
 	return per_cpu(rcu_sched_data, cpu).nxtlist ||
 	       per_cpu(rcu_bh_data, cpu).nxtlist ||
-- 
1.7.3.2