rcu: check for entering dyntick-idle mode while in read-side critical section

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>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e86bc28233ea2222fe44ee3a3338ffc45169b9ec..8d7efc8a062f34fa980e777a49e7a12501e0a4ad 100644 (file)
--- 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 72b5385716baceeed57d135f1a33c56eca7bd147..29e26107c4968647935bcba16d077165c01969c4 100644 (file)
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1790,6 +1790,9 @@ 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 ||