[PATCH v4 04/15] locking/lockdep: Initialize the locks_before and locks_after lists earlier

[Bart Van Assche]

This patch does not change any functionality. A later patch will reuse
lock classes that have been freed. In combination with that patch this
patch wil have the effect of initializing lock class order lists once
instead of every time a lock class structure is reinitialized.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Waiman Long <longman@xxxxxxxxxx>
Cc: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 kernel/locking/lockdep.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7ca9ac392dde..9ab782378b3b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -735,6 +735,25 @@ static bool assign_lock_key(struct lockdep_map *lock)
 	return true;
 }
 
+/*
+ * Initialize the lock_classes[] array elements.
+ */
+static void init_data_structures_once(void)
+{
+	static bool initialization_happened;
+	int i;
+
+	if (likely(initialization_happened))
+		return;
+
+	initialization_happened = true;
+
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		INIT_LIST_HEAD(&lock_classes[i].locks_after);
+		INIT_LIST_HEAD(&lock_classes[i].locks_before);
+	}
+}
+
 /*
  * 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
@@ -775,6 +794,8 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 			goto out_unlock_set;
 	}
 
+	init_data_structures_once();
+
 	/*
 	 * Allocate a new key from the static array, and add it to
 	 * the hash:
@@ -793,8 +814,8 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 	class->key = key;
 	class->name = lock->name;
 	class->subclass = subclass;
-	INIT_LIST_HEAD(&class->locks_before);
-	INIT_LIST_HEAD(&class->locks_after);
+	WARN_ON_ONCE(!list_empty(&class->locks_before));
+	WARN_ON_ONCE(!list_empty(&class->locks_after));
 	class->name_version = count_matching_names(class);
 	/*
 	 * We use RCU's safe list-add method to make
@@ -4176,6 +4197,8 @@ void lockdep_free_key_range(void *start, unsigned long size)
 	int i;
 	int locked;
 
+	init_data_structures_once();
+
 	raw_local_irq_save(flags);
 	locked = graph_lock();
 
@@ -4239,6 +4262,8 @@ void lockdep_reset_lock(struct lockdep_map *lock)
 	unsigned long flags;
 	int j, locked;
 
+	init_data_structures_once();
+
 	raw_local_irq_save(flags);
 	locked = graph_lock();
 
-- 
2.20.0.rc2.403.gdbc3b29805-goog