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Subject[PATCH v3 19/24] locking/lockdep: Check data structure consistency
Date
Debugging lockdep data structure inconsistencies is challenging. Add
disabled code that verifies data structure consistency at runtime.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
kernel/locking/lockdep.c | 146 +++++++++++++++++++++++++++++++++++++++
1 file changed, 146 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 6f338f852f7e..78f14c151407 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -72,6 +72,8 @@ 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.
@@ -744,6 +746,148 @@ 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 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 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 (test_bit(i, list_entries_being_freed))
+ 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)) {
+ e = list_entries + i;
+ if (WARN_ON_ONCE(test_bit(i, list_entries_being_freed)))
+ return false;
+ 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;
+ }
+ }
+
+ /* Check whether all classes have valid lock lists. */
+ for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
+ class = &lock_classes[i];
+ if (!class->locks_before.next)
+ continue;
+ 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;
+ }
+ }
+
+ return true;
+}
+
/*
* Initialize the lock_classes[] array elements and also the free_lock_classes
* list.
@@ -4309,6 +4453,8 @@ static void free_zapped_classes(struct callback_head *ch)
raw_local_irq_save(flags);
locked = graph_lock();
rcu_callback_scheduled = false;
+ if (check_data_structure_consistency)
+ WARN_ON_ONCE(!check_data_structures());
list_for_each_entry(class, &zapped_classes, lock_entry) {
reinit_class(class);
nr_lock_classes--;
--
2.20.0.rc2.403.gdbc3b29805-goog
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