Lockdep: add lockdep_set_class_and_subclass() and lockdep_set_subclass()

This annotation makes it possible to assign a subclass on lock init. This
annotation is meant to reduce the _nested() annotations by assigning a
default subclass.

One could do without this annotation and rely on lockdep_set_class()
exclusively, but that would require a manual stack of struct lock_class_key
objects.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

1 files changed, 11 insertions, 4 deletions

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 1314ca0f29be..14fec2a23b2e 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -202,7 +202,7 @@ extern int lockdep_internal(void);
  */
 
 extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
-                             struct lock_class_key *key);
+                             struct lock_class_key *key, int subclass);
 
 /*
  * Reinitialize a lock key - for cases where there is special locking or
@@ -211,9 +211,14 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
  * or they are too narrow (they suffer from a false class-split):
  */
 #define lockdep_set_class(lock, key) \
-                lockdep_init_map(&(lock)->dep_map, #key, key)
+                lockdep_init_map(&(lock)->dep_map, #key, key, 0)
 #define lockdep_set_class_and_name(lock, key, name) \
-                lockdep_init_map(&(lock)->dep_map, name, key)
+                lockdep_init_map(&(lock)->dep_map, name, key, 0)
+#define lockdep_set_class_and_subclass(lock, key, sub) \
+                lockdep_init_map(&(lock)->dep_map, #key, key, sub)
+#define lockdep_set_subclass(lock, sub) \
+                lockdep_init_map(&(lock)->dep_map, #lock, \
+                                 (lock)->dep_map.key, sub)
 
 /*
  * Acquire a lock.
@@ -257,10 +262,12 @@ static inline int lockdep_internal(void)
 # define lock_release(l, n, i)                  do { } while (0)
 # define lockdep_init()                         do { } while (0)
 # define lockdep_info()                         do { } while (0)
-# define lockdep_init_map(lock, name, key)      do { (void)(key); } while (0)
+# define lockdep_init_map(lock, name, key, sub) do { (void)(key); } while (0)
 # define lockdep_set_class(lock, key)           do { (void)(key); } while (0)
 # define lockdep_set_class_and_name(lock, key, name) \
                 do { (void)(key); } while (0)
+#define lockdep_set_class_and_subclass(lock, key, sub) \
+                do { (void)(key); } while (0)
 # define INIT_LOCKDEP
 # define lockdep_reset()                do { debug_locks = 1; } while (0)
 # define lockdep_free_key_range(start, size)    do { } while (0)