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Subject[PATCH v6 12/16] locking/lockdep: Check data structure consistency
Date
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@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 | 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
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