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 <[email protected]>
Signed-off-by: Dmitry Torokhov <[email protected]>

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)

kernel/lockdep.c

@@ -1177,7 +1177,7 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
  * itself, so actual lookup of the hash should be once per lock object.
  */
 static inline struct lock_class *
-register_lock_class(struct lockdep_map *lock, unsigned int subclass)
+register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 {
 	struct lockdep_subclass_key *key;
 	struct list_head *hash_head;
@@ -1249,7 +1249,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass)
 out_unlock_set:
 	__raw_spin_unlock(&hash_lock);
 
-	if (!subclass)
+	if (!subclass || force)
 		lock->class_cache = class;
 
 	DEBUG_LOCKS_WARN_ON(class->subclass != subclass);
@@ -1937,7 +1937,7 @@ void trace_softirqs_off(unsigned long ip)
  * Initialize a lock instance's lock-class mapping info:
  */
 void lockdep_init_map(struct lockdep_map *lock, const char *name,
-		      struct lock_class_key *key)
+		      struct lock_class_key *key, int subclass)
 {
 	if (unlikely(!debug_locks))
 		return;
@@ -1957,6 +1957,8 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name,
 	lock->name = name;
 	lock->key = key;
 	lock->class_cache = NULL;
+	if (subclass)
+		register_lock_class(lock, subclass, 1);
 }
 
 EXPORT_SYMBOL_GPL(lockdep_init_map);
@@ -1995,7 +1997,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	 * Not cached yet or subclass?
 	 */
 	if (unlikely(!class)) {
-		class = register_lock_class(lock, subclass);
+		class = register_lock_class(lock, subclass, 0);
 		if (!class)
 			return 0;
 	}

kernel/mutex-debug.c

@@ -91,7 +91,7 @@ void debug_mutex_init(struct mutex *lock, const char *name,
 	 * Make sure we are not reinitializing a held lock:
 	 */
 	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
-	lockdep_init_map(&lock->dep_map, name, key);
+	lockdep_init_map(&lock->dep_map, name, key, 0);
 #endif
 	lock->owner = NULL;
 	lock->magic = lock;

lib/rwsem-spinlock.c

@@ -28,7 +28,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
 	 * Make sure we are not reinitializing a held semaphore:
 	 */
 	debug_check_no_locks_freed((void *)sem, sizeof(*sem));
-	lockdep_init_map(&sem->dep_map, name, key);
+	lockdep_init_map(&sem->dep_map, name, key, 0);
 #endif
 	sem->activity = 0;
 	spin_lock_init(&sem->wait_lock);

lib/rwsem.c

@@ -19,7 +19,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
 	 * Make sure we are not reinitializing a held semaphore:
 	 */
 	debug_check_no_locks_freed((void *)sem, sizeof(*sem));
-	lockdep_init_map(&sem->dep_map, name, key);
+	lockdep_init_map(&sem->dep_map, name, key, 0);
 #endif
 	sem->count = RWSEM_UNLOCKED_VALUE;
 	spin_lock_init(&sem->wait_lock);

lib/spinlock_debug.c

@@ -20,7 +20,7 @@ void __spin_lock_init(spinlock_t *lock, const char *name,
 	 * Make sure we are not reinitializing a held lock:
 	 */
 	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
-	lockdep_init_map(&lock->dep_map, name, key);
+	lockdep_init_map(&lock->dep_map, name, key, 0);
 #endif
 	lock->raw_lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
 	lock->magic = SPINLOCK_MAGIC;
@@ -38,7 +38,7 @@ void __rwlock_init(rwlock_t *lock, const char *name,
 	 * Make sure we are not reinitializing a held lock:
 	 */
 	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
-	lockdep_init_map(&lock->dep_map, name, key);
+	lockdep_init_map(&lock->dep_map, name, key, 0);
 #endif
 	lock->raw_lock = (raw_rwlock_t) __RAW_RW_LOCK_UNLOCKED;
 	lock->magic = RWLOCK_MAGIC;

net/core/sock.c

@@ -823,7 +823,7 @@ static void inline sock_lock_init(struct sock *sk)
 				   af_family_slock_key_strings[sk->sk_family]);
 	lockdep_init_map(&sk->sk_lock.dep_map,
 			 af_family_key_strings[sk->sk_family],
-			 af_family_keys + sk->sk_family);
+			 af_family_keys + sk->sk_family, 0);
 }
 
 /**