Commit cdb7d2d6 authored by Waiman Long's avatar Waiman Long Committed by Ingo Molnar
Browse files

locking/lockdep: Add number of dynamic keys to /proc/lockdep_stats 



There have been recent reports about running out of lockdep keys:

	MAX_LOCKDEP_KEYS too low!

One possible reason is that too many dynamic keys have been registered.
A possible culprit is the lockdep_register_key() call in qdisc_alloc()
of net/sched/sch_generic.c.

Currently, there is no way to find out how many dynamic keys have been
registered. Add such a stat to the /proc/lockdep_stats to get better
clarity.

Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/20250506042049.50060-4-boqun.feng@gmail.com
parent 6a1a219f

kernel/locking/lockdep.c

+3 −0
Original line number Diff line number Diff line
@@ -219,6 +219,7 @@ static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES); 
static struct hlist_head lock_keys_hash[KEYHASH_SIZE];

unsigned long nr_lock_classes;

unsigned long nr_zapped_classes;

unsigned long nr_dynamic_keys;

unsigned long max_lock_class_idx;

struct lock_class lock_classes[MAX_LOCKDEP_KEYS];

DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
@@ -1238,6 +1239,7 @@ void lockdep_register_key(struct lock_class_key *key) 
			goto out_unlock;

	}

	hlist_add_head_rcu(&key->hash_entry, hash_head);

	nr_dynamic_keys++;

out_unlock:

	graph_unlock();

restore_irqs:
@@ -6609,6 +6611,7 @@ void lockdep_unregister_key(struct lock_class_key *key) 
		pf = get_pending_free();

		__lockdep_free_key_range(pf, key, 1);

		need_callback = prepare_call_rcu_zapped(pf);

		nr_dynamic_keys--;

	}

	lockdep_unlock();

	raw_local_irq_restore(flags);

kernel/locking/lockdep_internals.h

+1 −0
Original line number Diff line number Diff line
@@ -138,6 +138,7 @@ extern unsigned long nr_lock_classes; 
extern unsigned long nr_zapped_classes;

extern unsigned long nr_zapped_lock_chains;

extern unsigned long nr_list_entries;

extern unsigned long nr_dynamic_keys;

long lockdep_next_lockchain(long i);

unsigned long lock_chain_count(void);

extern unsigned long nr_stack_trace_entries;

kernel/locking/lockdep_proc.c

+2 −0
Original line number Diff line number Diff line
@@ -286,6 +286,8 @@ static int lockdep_stats_show(struct seq_file *m, void *v) 
#endif

	seq_printf(m, " lock-classes:                  %11lu [max: %lu]\n",

			nr_lock_classes, MAX_LOCKDEP_KEYS);

	seq_printf(m, " dynamic-keys:                  %11lu\n",

			nr_dynamic_keys);

	seq_printf(m, " direct dependencies:           %11lu [max: %lu]\n",

			nr_list_entries, MAX_LOCKDEP_ENTRIES);

	seq_printf(m, " indirect dependencies:         %11lu\n",