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

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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: Waiman Long <longman@redhat.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Ingo 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
This commit is contained in:
Waiman Long 2025-05-05 21:20:49 -07:00 committed by Ingo Molnar
parent 6a1a219f53
commit cdb7d2d68c
3 changed files with 6 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
kernel/locking/lockdep.c
View File

@ -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);

1
kernel/locking/lockdep_internals.h
View File

@ -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;

2
kernel/locking/lockdep_proc.c
View File

@ -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",