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-rw-r--r--include/linux/lockdep.h13
1 files changed, 12 insertions, 1 deletions
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 06aed8305bf3..2186a64ee4b5 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;
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