* [PATCH] locking/lockdep: Add # of dynamic keys stat to /proc/lockdep_stats
@ 2025-04-25 0:11 Waiman Long
2025-05-04 18:04 ` Boqun Feng
0 siblings, 1 reply; 2+ messages in thread
From: Waiman Long @ 2025-04-25 0:11 UTC (permalink / raw)
To: Peter Zijlstra, Ingo Molnar, Will Deacon, Boqun Feng
Cc: linux-kernel, Waiman Long
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>
---
kernel/locking/lockdep.c | 3 +++
kernel/locking/lockdep_internals.h | 1 +
kernel/locking/lockdep_proc.c | 2 ++
3 files changed, 6 insertions(+)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 58d78a33ac65..aeedaaaa403c 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -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:
@@ -6606,6 +6608,7 @@ 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);
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 20f9ef58d3d0..82156caf77d1 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -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;
diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
index 6db0f43fc4df..b52c07c4707c 100644
--- a/kernel/locking/lockdep_proc.c
+++ b/kernel/locking/lockdep_proc.c
@@ -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",
--
2.49.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] locking/lockdep: Add # of dynamic keys stat to /proc/lockdep_stats
2025-04-25 0:11 [PATCH] locking/lockdep: Add # of dynamic keys stat to /proc/lockdep_stats Waiman Long
@ 2025-05-04 18:04 ` Boqun Feng
0 siblings, 0 replies; 2+ messages in thread
From: Boqun Feng @ 2025-05-04 18:04 UTC (permalink / raw)
To: Waiman Long; +Cc: Peter Zijlstra, Ingo Molnar, Will Deacon, linux-kernel
On Thu, Apr 24, 2025 at 08:11:55PM -0400, Waiman Long wrote:
> 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>
Queued for 6.16.
Regards,
Boqun
> ---
> kernel/locking/lockdep.c | 3 +++
> kernel/locking/lockdep_internals.h | 1 +
> kernel/locking/lockdep_proc.c | 2 ++
> 3 files changed, 6 insertions(+)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index 58d78a33ac65..aeedaaaa403c 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -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:
> @@ -6606,6 +6608,7 @@ 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);
> diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
> index 20f9ef58d3d0..82156caf77d1 100644
> --- a/kernel/locking/lockdep_internals.h
> +++ b/kernel/locking/lockdep_internals.h
> @@ -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;
> diff --git a/kernel/locking/lockdep_proc.c b/kernel/locking/lockdep_proc.c
> index 6db0f43fc4df..b52c07c4707c 100644
> --- a/kernel/locking/lockdep_proc.c
> +++ b/kernel/locking/lockdep_proc.c
> @@ -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",
> --
> 2.49.0
>
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