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Subject[PATCH-tip v2] locking/lockdep: Cleanup reinit_class()
Date
Replace the duplicated WARN_ON_ONCE() tests in reinit_class() with
BUILD_BUG_ON() which have the same effect of making sure that those
lists aren't cleared accidentally because of their placements in the
lock_class structure.

Signed-off-by: Waiman Long <longman@redhat.com>
---
include/linux/lockdep_types.h | 4 ++++
kernel/locking/lockdep.c | 8 +++++---
2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index d22430840b53..446d981ae3a2 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -108,6 +108,10 @@ struct lock_class {
*/
struct list_head locks_after, locks_before;

+ /*
+ * All the fields that require re-initialization after being zapped
+ * must be put after "key".
+ */
const struct lockdep_subclass_key *key;
unsigned int subclass;
unsigned int dep_gen_id;
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 2e6892ec3756..5fb015dc1686 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -6011,13 +6011,15 @@ static void zap_class(struct pending_free *pf, struct lock_class *class)

static void reinit_class(struct lock_class *class)
{
+ const unsigned int key_offset = offsetof(struct lock_class, key);
+
WARN_ON_ONCE(!class->lock_entry.next);
WARN_ON_ONCE(!list_empty(&class->locks_after));
WARN_ON_ONCE(!list_empty(&class->locks_before));
+ BUILD_BUG_ON(offsetof(struct lock_class, lock_entry) > key_offset);
+ BUILD_BUG_ON(offsetof(struct lock_class, locks_after) > key_offset);
+ BUILD_BUG_ON(offsetof(struct lock_class, locks_before) > key_offset);
memset_startat(class, 0, key);
- WARN_ON_ONCE(!class->lock_entry.next);
- WARN_ON_ONCE(!list_empty(&class->locks_after));
- WARN_ON_ONCE(!list_empty(&class->locks_before));
}

static inline int within(const void *addr, void *start, unsigned long size)
--
2.27.0
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