[PATCH 1/6] locking/lockdep: lock_class_is_held()

[Kent Overstreet <kent.overstreet@linux.dev>]

This patch adds lock_class_is_held(), which can be used to assert that a
particular type of lock is not held.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
---
 include/linux/lockdep.h  |  4 ++++
 kernel/locking/lockdep.c | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index dc2844b071c2..fc86557d2a21 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -344,6 +344,8 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 #define lockdep_repin_lock(l,c)	lock_repin_lock(&(l)->dep_map, (c))
 #define lockdep_unpin_lock(l,c)	lock_unpin_lock(&(l)->dep_map, (c))
 
+int lock_class_is_held(struct lock_class_key *key);
+
 /*
  * Must use lock_map_aquire_try() with override maps to avoid
  * lockdep thinking they participate in the block chain.
@@ -442,6 +444,8 @@ extern int lockdep_is_held(const void *);
 #define lockdep_repin_lock(l, c)		do { (void)(l); (void)(c); } while (0)
 #define lockdep_unpin_lock(l, c)		do { (void)(l); (void)(c); } while (0)
 
+static inline int lock_class_is_held(struct lock_class_key *key) { return 0; }
+
 #define DEFINE_WAIT_OVERRIDE_MAP(_name, _wait_type)	\
 	struct lockdep_map __maybe_unused _name = {}
 
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index e85b5ad3e206..38924d90da85 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -6599,6 +6599,26 @@ void debug_check_no_locks_held(void)
 }
 EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
 
+#ifdef CONFIG_LOCKDEP
+int lock_class_is_held(struct lock_class_key *key)
+{
+	struct task_struct *curr = current;
+	struct held_lock *hlock;
+
+	if (unlikely(!debug_locks))
+		return 0;
+
+	for (hlock = curr->held_locks;
+	     hlock < curr->held_locks + curr->lockdep_depth;
+	     hlock++)
+		if (hlock->instance->key == key)
+			return 1;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(lock_class_is_held);
+#endif
+
 #ifdef __KERNEL__
 void debug_show_all_locks(void)
 {
-- 
2.42.0