On 6/30/24 01:10, Kent Overstreet wrote:
Add a new helper to disable lockdep tracking entirely for a given class.
This is needed for bcachefs, which takes too many btree node locks for
lockdep to track. Instead, we have a single lockdep_map for "btree_trans
has any btree nodes locked", which makes more since given that we have
centralized lock management and a cycle detector.
Could you explain a bit more what the current novalidate_class is
lacking WRT to the bcachefs lock? Is it excessive performance overhead
or some bogus lockdep warning?
Cheers,
Longman
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Waiman Long <[email protected]>
Cc: Boqun Feng <[email protected]>
Signed-off-by: Kent Overstreet <[email protected]>
---
fs/bcachefs/btree_locking.c | 2 +-
include/linux/lockdep.h | 4 ++++
include/linux/lockdep_types.h | 1 +
kernel/locking/lockdep.c | 9 ++++++++-
4 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/fs/bcachefs/btree_locking.c b/fs/bcachefs/btree_locking.c
index 79057cde4c41..16834a6b4c3d 100644
--- a/fs/bcachefs/btree_locking.c
+++ b/fs/bcachefs/btree_locking.c
@@ -10,7 +10,7 @@ void bch2_btree_lock_init(struct btree_bkey_cached_common *b,
enum six_lock_init_flags flags)
{
__six_lock_init(&b->lock, "b->c.lock", &bch2_btree_node_lock_key,
flags);
- lockdep_set_novalidate_class(&b->lock);
+ lockdep_set_notrack_class(&b->lock);
}
#ifdef CONFIG_LOCKDEP
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 08b0d1d9d78b..b76f1bcd2f7f 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -181,6 +181,9 @@ static inline void lockdep_init_map(struct lockdep_map
*lock, const char *name,
#define lockdep_set_novalidate_class(lock) \
lockdep_set_class_and_name(lock, &__lockdep_no_validate__, #lock)
+#define lockdep_set_notrack_class(lock) \
+ lockdep_set_class_and_name(lock, &__lockdep_no_track__, #lock)
+
/*
* Compare locking classes
*/
@@ -338,6 +341,7 @@ static inline void lockdep_set_selftest_task(struct
task_struct *task)
#define lockdep_set_subclass(lock, sub) do { } while (0)
#define lockdep_set_novalidate_class(lock) do { } while (0)
+#define lockdep_set_notrack_class(lock) do { } while (0)
/*
* We don't define lockdep_match_class() and lockdep_match_key() for !LOCKDEP
diff --git a/include/linux/lockdep_types.h b/include/linux/lockdep_types.h
index 70d30d40ea4a..9f361d3ab9d9 100644
--- a/include/linux/lockdep_types.h
+++ b/include/linux/lockdep_types.h
@@ -80,6 +80,7 @@ struct lock_class_key {
};
extern struct lock_class_key __lockdep_no_validate__;
+extern struct lock_class_key __lockdep_no_track__;
struct lock_trace;
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 151bd3de5936..b6bb9fcd992a 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4918,6 +4918,9 @@ EXPORT_SYMBOL_GPL(lockdep_init_map_type);
struct lock_class_key __lockdep_no_validate__;
EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
+struct lock_class_key __lockdep_no_track__;
+EXPORT_SYMBOL_GPL(__lockdep_no_track__);
+
#ifdef CONFIG_PROVE_LOCKING
void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn cmp_fn,
lock_print_fn print_fn)
@@ -5002,6 +5005,9 @@ static int __lock_acquire(struct lockdep_map *lock,
unsigned int subclass,
if (unlikely(!debug_locks))
return 0;
+ if (unlikely(lock->key == &__lockdep_no_track__))
+ return 0;
+
if (!prove_locking || lock->key == &__lockdep_no_validate__)
check = 0;
@@ -5764,7 +5770,8 @@ void lock_release(struct lockdep_map *lock, unsigned long ip)
trace_lock_release(lock, ip);
- if (unlikely(!lockdep_enabled()))
+ if (unlikely(!lockdep_enabled() ||
+ lock->key == &__lockdep_no_track__))
return;
raw_local_irq_save(flags);
