Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking updates from Ingo Molnar:
 "The main changes relate to making lock_is_held() et al (and external
  wrappers of them) work on const data types - this requires const
  propagation through the depths of lockdep.

  This removes a number of ugly type hacks the external helpers used"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  lockdep: Convert some users to const
  lockdep: Make lockdep checking constant
  lockdep: Assign lock keys on registration

Author: torvalds

include/linux/backing-dev.h

@@ -332,7 +332,7 @@ static inline bool inode_to_wb_is_valid(struct inode *inode)
  * holding either @inode->i_lock, @inode->i_mapping->tree_lock, or the
  * associated wb's list_lock.
  */
-static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
+static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
 {
 #ifdef CONFIG_LOCKDEP
 	WARN_ON_ONCE(debug_locks &&

include/linux/lockdep.h

@@ -337,9 +337,9 @@ extern void lock_release(struct lockdep_map *lock, int nested,
 /*
  * Same "read" as for lock_acquire(), except -1 means any.
  */
-extern int lock_is_held_type(struct lockdep_map *lock, int read);
+extern int lock_is_held_type(const struct lockdep_map *lock, int read);
 
-static inline int lock_is_held(struct lockdep_map *lock)
+static inline int lock_is_held(const struct lockdep_map *lock)
 {
 	return lock_is_held_type(lock, -1);
 }

include/linux/srcu.h

@@ -92,7 +92,7 @@ void synchronize_srcu(struct srcu_struct *sp);
  * relies on normal RCU, it can be called from the CPU which
  * is in the idle loop from an RCU point of view or offline.
  */
-static inline int srcu_read_lock_held(struct srcu_struct *sp)
+static inline int srcu_read_lock_held(const struct srcu_struct *sp)
 {
 	if (!debug_lockdep_rcu_enabled())
 		return 1;
@@ -101,7 +101,7 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp)
 
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
-static inline int srcu_read_lock_held(struct srcu_struct *sp)
+static inline int srcu_read_lock_held(const struct srcu_struct *sp)
 {
 	return 1;
 }

include/net/sock.h

@@ -1445,10 +1445,8 @@ do {									\
 } while (0)
 
 #ifdef CONFIG_LOCKDEP
-static inline bool lockdep_sock_is_held(const struct sock *csk)
+static inline bool lockdep_sock_is_held(const struct sock *sk)
 {
-	struct sock *sk = (struct sock *)csk;
-
 	return lockdep_is_held(&sk->sk_lock) ||
 	       lockdep_is_held(&sk->sk_lock.slock);
 }

kernel/locking/lockdep.c

@@ -648,18 +648,12 @@ static int count_matching_names(struct lock_class *new_class)
 	return count + 1;
 }
 
-/*
- * Register a lock's class in the hash-table, if the class is not present
- * yet. Otherwise we look it up. We cache the result in the lock object
- * itself, so actual lookup of the hash should be once per lock object.
- */
 static inline struct lock_class *
-look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
+look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 {
 	struct lockdep_subclass_key *key;
 	struct hlist_head *hash_head;
 	struct lock_class *class;
-	bool is_static = false;
 
 	if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
 		debug_locks_off();
@@ -672,24 +666,11 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 	}
 
 	/*
-	 * Static locks do not have their class-keys yet - for them the key
-	 * is the lock object itself. If the lock is in the per cpu area,
-	 * the canonical address of the lock (per cpu offset removed) is
-	 * used.
+	 * If it is not initialised then it has never been locked,
+	 * so it won't be present in the hash table.
 	 */
-	if (unlikely(!lock->key)) {
-		unsigned long can_addr, addr = (unsigned long)lock;
-
-		if (__is_kernel_percpu_address(addr, &can_addr))
-			lock->key = (void *)can_addr;
-		else if (__is_module_percpu_address(addr, &can_addr))
-			lock->key = (void *)can_addr;
-		else if (static_obj(lock))
-			lock->key = (void *)lock;
-		else
-			return ERR_PTR(-EINVAL);
-		is_static = true;
-	}
+	if (unlikely(!lock->key))
+		return NULL;
 
 	/*
 	 * NOTE: the class-key must be unique. For dynamic locks, a static
@@ -721,7 +702,35 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 		}
 	}
 
-	return is_static || static_obj(lock->key) ? NULL : ERR_PTR(-EINVAL);
+	return NULL;
+}
+
+/*
+ * Static locks do not have their class-keys yet - for them the key is
+ * the lock object itself. If the lock is in the per cpu area, the
+ * canonical address of the lock (per cpu offset removed) is used.
+ */
+static bool assign_lock_key(struct lockdep_map *lock)
+{
+	unsigned long can_addr, addr = (unsigned long)lock;
+
+	if (__is_kernel_percpu_address(addr, &can_addr))
+		lock->key = (void *)can_addr;
+	else if (__is_module_percpu_address(addr, &can_addr))
+		lock->key = (void *)can_addr;
+	else if (static_obj(lock))
+		lock->key = (void *)lock;
+	else {
+		/* Debug-check: all keys must be persistent! */
+		debug_locks_off();
+		pr_err("INFO: trying to register non-static key.\n");
+		pr_err("the code is fine but needs lockdep annotation.\n");
+		pr_err("turning off the locking correctness validator.\n");
+		dump_stack();
+		return false;
+	}
+
+	return true;
 }
 
 /*
@@ -739,18 +748,13 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 	DEBUG_LOCKS_WARN_ON(!irqs_disabled());
 
 	class = look_up_lock_class(lock, subclass);
-	if (likely(!IS_ERR_OR_NULL(class)))
+	if (likely(class))
 		goto out_set_class_cache;
 
-	/*
-	 * Debug-check: all keys must be persistent!
-	 */
-	if (IS_ERR(class)) {
-		debug_locks_off();
-		printk("INFO: trying to register non-static key.\n");
-		printk("the code is fine but needs lockdep annotation.\n");
-		printk("turning off the locking correctness validator.\n");
-		dump_stack();
+	if (!lock->key) {
+		if (!assign_lock_key(lock))
+			return NULL;
+	} else if (!static_obj(lock->key)) {
 		return NULL;
 	}
 
@@ -3273,7 +3277,7 @@ print_lock_nested_lock_not_held(struct task_struct *curr,
 	return 0;
 }
 
-static int __lock_is_held(struct lockdep_map *lock, int read);
+static int __lock_is_held(const struct lockdep_map *lock, int read);
 
 /*
  * This gets called for every mutex_lock*()/spin_lock*() operation.
@@ -3482,13 +3486,14 @@ print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
 	return 0;
 }
 
-static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
+static int match_held_lock(const struct held_lock *hlock,
+					const struct lockdep_map *lock)
 {
 	if (hlock->instance == lock)
 		return 1;
 
 	if (hlock->references) {
-		struct lock_class *class = lock->class_cache[0];
+		const struct lock_class *class = lock->class_cache[0];
 
 		if (!class)
 			class = look_up_lock_class(lock, 0);
@@ -3499,7 +3504,7 @@ static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
 		 * Clearly if the lock hasn't been acquired _ever_, we're not
 		 * holding it either, so report failure.
 		 */
-		if (IS_ERR_OR_NULL(class))
+		if (!class)
 			return 0;
 
 		/*
@@ -3724,7 +3729,7 @@ __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
 	return 1;
 }
 
-static int __lock_is_held(struct lockdep_map *lock, int read)
+static int __lock_is_held(const struct lockdep_map *lock, int read)
 {
 	struct task_struct *curr = current;
 	int i;
@@ -3938,7 +3943,7 @@ void lock_release(struct lockdep_map *lock, int nested,
 }
 EXPORT_SYMBOL_GPL(lock_release);
 
-int lock_is_held_type(struct lockdep_map *lock, int read)
+int lock_is_held_type(const struct lockdep_map *lock, int read)
 {
 	unsigned long flags;
 	int ret = 0;
@@ -4295,7 +4300,7 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 		 * If the class exists we look it up and zap it:
 		 */
 		class = look_up_lock_class(lock, j);
-		if (!IS_ERR_OR_NULL(class))
+		if (class)
 			zap_class(class);
 	}
 	/*