[PATCH] lockdep: constify usage of struct lock_class_key where possible

[Heiner Kallweit <hkallweit1@gmail.com>]

Constify usage of struct lock_class_key where possible. This requires
to constify also usage of struct lockdep_subclass_key in two places.

Especially relevant is constification of lockdep_map.key, as it makes
clear that the key isn't changed during lifetime of struct lockdep_map.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 include/linux/lockdep.h       | 18 ++++++++++--------
 include/linux/lockdep_types.h |  2 +-
 kernel/locking/lockdep.c      | 12 ++++++------
 3 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 621566345..3fa2b62f2 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -125,25 +125,27 @@ extern void lockdep_unregister_key(struct lock_class_key *key);
  * to lockdep:
  */
 
-extern void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
-	struct lock_class_key *key, int subclass, u8 inner, u8 outer, u8 lock_type);
+void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
+			   const struct lock_class_key *key, int subclass,
+			   u8 inner, u8 outer, u8 lock_type);
 
 static inline void
 lockdep_init_map_waits(struct lockdep_map *lock, const char *name,
-		       struct lock_class_key *key, int subclass, u8 inner, u8 outer)
+		       const struct lock_class_key *key, int subclass,
+		       u8 inner, u8 outer)
 {
 	lockdep_init_map_type(lock, name, key, subclass, inner, outer, LD_LOCK_NORMAL);
 }
 
 static inline void
 lockdep_init_map_wait(struct lockdep_map *lock, const char *name,
-		      struct lock_class_key *key, int subclass, u8 inner)
+		      const struct lock_class_key *key, int subclass, u8 inner)
 {
 	lockdep_init_map_waits(lock, name, key, subclass, inner, LD_WAIT_INV);
 }
 
 static inline void lockdep_init_map(struct lockdep_map *lock, const char *name,
-			     struct lock_class_key *key, int subclass)
+				    const struct lock_class_key *key, int subclass)
 {
 	lockdep_init_map_wait(lock, name, key, subclass, LD_WAIT_INV);
 }
@@ -252,9 +254,9 @@ static inline int lock_is_held(const struct lockdep_map *lock)
 #define lockdep_is_held(lock)		lock_is_held(&(lock)->dep_map)
 #define lockdep_is_held_type(lock, r)	lock_is_held_type(&(lock)->dep_map, (r))
 
-extern void lock_set_class(struct lockdep_map *lock, const char *name,
-			   struct lock_class_key *key, unsigned int subclass,
-			   unsigned long ip);
+void lock_set_class(struct lockdep_map *lock, const char *name,
+		    const struct lock_class_key *key, unsigned int subclass,
+		    unsigned long ip);
 
 #define lock_set_novalidate_class(l, n, i) \
 	lock_set_class(l, n, &__lockdep_no_validate__, 0, i)
diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index eae115a26..0d3df9019 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -184,7 +184,7 @@ void clear_lock_stats(struct lock_class *class);
  * This is embedded into specific lock instances:
  */
 struct lockdep_map {
-	struct lock_class_key		*key;
+	const struct lock_class_key		*key;
 	struct lock_class		*class_cache[NR_LOCKDEP_CACHING_CLASSES];
 	const char			*name;
 	u8				wait_type_outer; /* can be taken in this context */
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index f13883162..fe1415260 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -888,7 +888,7 @@ static int count_matching_names(struct lock_class *new_class)
 static noinstr struct lock_class *
 look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 {
-	struct lockdep_subclass_key *key;
+	const struct lockdep_subclass_key *key;
 	struct hlist_head *hash_head;
 	struct lock_class *class;
 
@@ -1286,7 +1286,7 @@ static bool is_dynamic_key(const struct lock_class_key *key)
 static struct lock_class *
 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 {
-	struct lockdep_subclass_key *key;
+	const struct lockdep_subclass_key *key;
 	struct hlist_head *hash_head;
 	struct lock_class *class;
 	int idx;
@@ -4937,8 +4937,8 @@ static inline int check_wait_context(struct task_struct *curr,
  * Initialize a lock instance's lock-class mapping info:
  */
 void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
-			    struct lock_class_key *key, int subclass,
-			    u8 inner, u8 outer, u8 lock_type)
+			   const struct lock_class_key *key, int subclass,
+			   u8 inner, u8 outer, u8 lock_type)
 {
 	int i;
 
@@ -5408,7 +5408,7 @@ static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
 
 static int
 __lock_set_class(struct lockdep_map *lock, const char *name,
-		 struct lock_class_key *key, unsigned int subclass,
+		 const struct lock_class_key *key, unsigned int subclass,
 		 unsigned long ip)
 {
 	struct task_struct *curr = current;
@@ -5733,7 +5733,7 @@ static noinstr void check_flags(unsigned long flags)
 }
 
 void lock_set_class(struct lockdep_map *lock, const char *name,
-		    struct lock_class_key *key, unsigned int subclass,
+		    const struct lock_class_key *key, unsigned int subclass,
 		    unsigned long ip)
 {
 	unsigned long flags;
-- 
2.54.0