1 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 06aed8305bf..2186a64ee4b 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -32,6 +32,17 @@ extern int lock_stat;
 #define MAX_LOCKDEP_SUBCLASSES          8UL
 
 /*
+ * NR_LOCKDEP_CACHING_CLASSES ... Number of classes
+ * cached in the instance of lockdep_map
+ *
+ * Currently main class (subclass == 0) and signle depth subclass
+ * are cached in lockdep_map. This optimization is mainly targeting
+ * on rq->lock. double_rq_lock() acquires this highly competitive with
+ * single depth.
+ */
+#define NR_LOCKDEP_CACHING_CLASSES      2
+
+/*
  * Lock-classes are keyed via unique addresses, by embedding the
  * lockclass-key into the kernel (or module) .data section. (For
  * static locks we use the lock address itself as the key.)
@@ -138,7 +149,7 @@ void clear_lock_stats(struct lock_class *class);
  */
 struct lockdep_map {
         struct lock_class_key           *key;
-        struct lock_class               *class_cache;
+        struct lock_class               *class_cache[NR_LOCKDEP_CACHING_CLASSES];
         const char                      *name;
 #ifdef CONFIG_LOCK_STAT
         int                             cpu;