+
+/*
+ * Wrappers for the rcu_node::lock acquire.
+ *
+ * Because the rcu_nodes form a tree, the tree traversal locking will observe
+ * different lock values, this in turn means that an UNLOCK of one level
+ * followed by a LOCK of another level does not imply a full memory barrier;
+ * and most importantly transitivity is lost.
+ *
+ * In order to restore full ordering between tree levels, augment the regular
+ * lock acquire functions with smp_mb__after_unlock_lock().
+ */
+static inline void raw_spin_lock_rcu_node(struct rcu_node *rnp)
+{
+ raw_spin_lock(&rnp->lock);
+ smp_mb__after_unlock_lock();
+}
+
+static inline void raw_spin_lock_irq_rcu_node(struct rcu_node *rnp)
+{
+ raw_spin_lock_irq(&rnp->lock);
+ smp_mb__after_unlock_lock();
+}
+
+#define raw_spin_lock_irqsave_rcu_node(rnp, flags) \
+do { \
+ typecheck(unsigned long, flags); \
+ raw_spin_lock_irqsave(&(rnp)->lock, flags); \
+ smp_mb__after_unlock_lock(); \
+} while (0)
+
+static inline bool raw_spin_trylock_rcu_node(struct rcu_node *rnp)
+{
+ bool locked = raw_spin_trylock(&rnp->lock);
+
+ if (locked)
+ smp_mb__after_unlock_lock();
+ return locked;
+}