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>

7 files changed, 23 insertions, 14 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)
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 4c0553461000..ba7156ac70c1 100644
--- a/kernel/lockdep.c
+++ b/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;
         }
diff --git a/kernel/mutex-debug.c b/kernel/mutex-debug.c
index e3203c654dda..18651641a7b5 100644
--- a/kernel/mutex-debug.c
+++ b/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;
diff --git a/lib/rwsem-spinlock.c b/lib/rwsem-spinlock.c
index db4fed74b940..c4cfd6c0342f 100644
--- a/lib/rwsem-spinlock.c
+++ b/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);
diff --git a/lib/rwsem.c b/lib/rwsem.c
index 901d0e7da892..cdb4e3d05607 100644
--- a/lib/rwsem.c
+++ b/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);
diff --git a/lib/spinlock_debug.c b/lib/spinlock_debug.c
index dafaf1de2491..b6c4f898197c 100644
--- a/lib/spinlock_debug.c
+++ b/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;
diff --git a/net/core/sock.c b/net/core/sock.c
index b77e155cbe6c..d472db4776c3 100644
--- a/net/core/sock.c
+++ b/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);
 }
 
 /**