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-rw-r--r--kernel/rcu/tree.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 0412030..2e991f8 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -653,3 +653,15 @@ static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
}
#endif /* #ifdef CONFIG_RCU_TRACE */
+
+/*
+ * Place this after a lock-acquisition primitive to guarantee that
+ * an UNLOCK+LOCK pair act as a full barrier. This guarantee applies
+ * if the UNLOCK and LOCK are executed by the same CPU or if the
+ * UNLOCK and LOCK operate on the same lock variable.
+ */
+#ifdef CONFIG_PPC
+#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */
+#else /* #ifdef CONFIG_PPC */
+#define smp_mb__after_unlock_lock() do { } while (0)
+#endif /* #else #ifdef CONFIG_PPC */