[PATCH v6 12/16] locking/lockdep: Check data structure consistency

[Bart Van Assche]

Debugging lockdep data structure inconsistencies is challenging. Add
code that verifies data structure consistency at runtime. That code is
disabled by default because it is very CPU intensive.

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 | 170 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index a8ea03bfc944..acf61dbb8b30 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -74,6 +74,8 @@ module_param(lock_stat, int, 0644);
 #define lock_stat 0
 #endif
 
+static bool check_data_structure_consistency;
+
 /*
  * lockdep_lock: protects the lockdep graph, the hashes and the
  *               class/list/hash allocators.
@@ -760,6 +762,81 @@ static bool assign_lock_key(struct lockdep_map *lock)
 	return true;
 }
 
+/* Check whether element @e occurs in list @h */
+static bool in_list(struct list_head *e, struct list_head *h)
+{
+	struct list_head *f;
+
+	list_for_each(f, h) {
+		if (e == f)
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * Check whether entry @e occurs in any of the locks_after or locks_before
+ * lists.
+ */
+static bool in_any_class_list(struct list_head *e)
+{
+	struct lock_class *class;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		class = &lock_classes[i];
+		if (in_list(e, &class->locks_after) ||
+		    in_list(e, &class->locks_before))
+			return true;
+	}
+	return false;
+}
+
+static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
+{
+	struct lock_list *e;
+
+	list_for_each_entry(e, h, entry) {
+		if (e->links_to != c) {
+			printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
+			       c->name ? : "(?)",
+			       (unsigned long)(e - list_entries),
+			       e->links_to && e->links_to->name ?
+			       e->links_to->name : "(?)",
+			       e->class && e->class->name ? e->class->name :
+			       "(?)");
+			return false;
+		}
+	}
+	return true;
+}
+
+static u16 chain_hlocks[];
+
+static bool check_lock_chain_key(struct lock_chain *chain)
+{
+#ifdef CONFIG_PROVE_LOCKING
+	u64 chain_key = 0;
+	int i;
+
+	for (i = chain->base; i < chain->base + chain->depth; i++)
+		chain_key = iterate_chain_key(chain_key, chain_hlocks[i] + 1);
+	/*
+	 * The 'unsigned long long' casts avoid that a compiler warning
+	 * is reported when building tools/lib/lockdep.
+	 */
+	if (chain->chain_key != chain_key)
+		printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
+		       (unsigned long long)(chain - lock_chains),
+		       (unsigned long long)chain->chain_key,
+		       (unsigned long long)chain_key);
+	return chain->chain_key == chain_key;
+#else
+	return true;
+#endif
+}
+
 static bool list_entry_being_freed(int list_entry_idx)
 {
 	struct pending_free *pf;
@@ -773,6 +850,97 @@ static bool list_entry_being_freed(int list_entry_idx)
 	return false;
 }
 
+static bool in_any_zapped_class_list(struct lock_class *class)
+{
+	struct pending_free *pf;
+	int i;
+
+	for (i = 0, pf = pending_free; i < ARRAY_SIZE(pending_free);
+	     i++, pf++)
+		if (in_list(&class->lock_entry, &pf->zapped_classes))
+			return true;
+
+	return false;
+}
+
+static bool check_data_structures(void)
+{
+	struct lock_class *class;
+	struct lock_chain *chain;
+	struct hlist_head *head;
+	struct lock_list *e;
+	int i;
+
+	/* Check whether all classes occur in a lock list. */
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		class = &lock_classes[i];
+		if (!in_list(&class->lock_entry, &all_lock_classes) &&
+		    !in_list(&class->lock_entry, &free_lock_classes) &&
+		    !in_any_zapped_class_list(class)) {
+			printk(KERN_INFO "class %px/%s is not in any class list\n",
+			       class, class->name ? : "(?)");
+			return false;
+			return false;
+		}
+	}
+
+	/* Check whether all classes have valid lock lists. */
+	for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+		class = &lock_classes[i];
+		if (!class_lock_list_valid(class, &class->locks_before))
+			return false;
+		if (!class_lock_list_valid(class, &class->locks_after))
+			return false;
+	}
+
+	/* Check the chain_key of all lock chains. */
+	for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
+		head = chainhash_table + i;
+		hlist_for_each_entry_rcu(chain, head, entry) {
+			if (!check_lock_chain_key(chain))
+				return false;
+		}
+	}
+
+	/*
+	 * Check whether all list entries that are in use occur in a class
+	 * lock list.
+	 */
+	for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
+		if (list_entry_being_freed(i))
+			continue;
+		e = list_entries + i;
+		if (!in_any_class_list(&e->entry)) {
+			printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
+			       (unsigned int)(e - list_entries),
+			       e->class->name ? : "(?)",
+			       e->links_to->name ? : "(?)");
+			return false;
+		}
+	}
+
+	/*
+	 * Check whether all list entries that are not in use do not occur in
+	 * a class lock list.
+	 */
+	for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
+		if (WARN_ON_ONCE(list_entry_being_freed(i)))
+			return false;
+		e = list_entries + i;
+		if (in_any_class_list(&e->entry)) {
+			printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
+			       (unsigned int)(e - list_entries),
+			       e->class && e->class->name ? e->class->name :
+			       "(?)",
+			       e->links_to && e->links_to->name ?
+			       e->links_to->name : "(?)");
+			return false;
+		}
+	}
+
+	return true;
+}
+
 /*
  * Initialize the lock_classes[] array elements, the free_lock_classes list
  * and also the pending_free[] array.
@@ -4376,6 +4544,8 @@ static void free_zapped_classes(struct rcu_head *ch)
 	if (!graph_lock())
 		goto restore_irqs;
 	pf->scheduled = false;
+	if (check_data_structure_consistency)
+		WARN_ON_ONCE(!check_data_structures());
 	list_for_each_entry(class, &pf->zapped_classes, lock_entry) {
 		reinit_class(class);
 	}
-- 
2.20.1.97.g81188d93c3-goog