1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index d36619ead3ba..00e46376e28f 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -157,6 +157,24 @@ struct lockdep_map {
 #endif
 };
 
+static inline void lockdep_copy_map(struct lockdep_map *to,
+                                    struct lockdep_map *from)
+{
+        int i;
+
+        *to = *from;
+        /*
+         * Since the class cache can be modified concurrently we could observe
+         * half pointers (64bit arch using 32bit copy insns). Therefore clear
+         * the caches and take the performance hit.
+         *
+         * XXX it doesn't work well with lockdep_set_class_and_subclass(), since
+         *     that relies on cache abuse.
+         */
+        for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
+                to->class_cache[i] = NULL;
+}
+
 /*
  * Every lock has a list of other locks that were taken after it.
  * We only grow the list, never remove from it: