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Date: Wed, 28 Nov 2018 15:43:21 -0800
From: Bart Van Assche <bvanassche@....org>
To: mingo@...hat.com
Cc: peterz@...radead.org, tj@...nel.org, johannes.berg@...el.com,
linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>
Subject: [PATCH 23/27] locking/lockdep: Check data structure consistency
Debugging lockdep data structure inconsistencies is challenging. Add
disabled code that verifies data structure consistency at runtime.
Signed-off-by: Bart Van Assche <bvanassche@....org>
---
kernel/locking/lockdep.c | 142 +++++++++++++++++++++++++++++++++++++++
1 file changed, 142 insertions(+)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 288a2f6fd0ef..141bb0662ff5 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.
@@ -736,6 +738,135 @@ 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, lock_order_entry) {
+ if (e->links_to != c) {
+ printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
+ c->name ? : "(?)", 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)
+{
+ 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;
+}
+
+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.
+ */
+ list_for_each_entry(e, &all_list_entries, alloc_entry) {
+ if (!in_any_class_list(&e->lock_order_entry)) {
+ printk(KERN_INFO "list entry %ld is not in any class list; class %s <> %s\n",
+ 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.
+ */
+ list_for_each_entry(e, &free_list_entries, alloc_entry) {
+ if (in_any_class_list(&e->lock_order_entry)) {
+ printk(KERN_INFO "list entry %ld occurs in a class list; class %s <> %s\n",
+ 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;
+}
+
static void init_lists(void)
{
int i;
@@ -4294,6 +4425,14 @@ static void free_zapped_classes(struct list_head *zapped_classes)
unsigned long flags;
int locked;
+ raw_local_irq_save(flags);
+ locked = graph_lock();
+ if (check_data_structure_consistency)
+ WARN_ON_ONCE(!check_data_structures());
+ if (locked)
+ graph_unlock();
+ raw_local_irq_restore(flags);
+
if (list_empty(zapped_classes))
return;
@@ -4314,6 +4453,9 @@ static void free_zapped_classes(struct list_head *zapped_classes)
if (locked)
graph_unlock();
raw_local_irq_restore(flags);
+
+ if (check_data_structure_consistency)
+ WARN_ON_ONCE(!check_data_structures());
}
/*
--
2.20.0.rc0.387.gc7a69e6b6c-goog
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