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Message-Id: <20250506042049.50060-4-boqun.feng@gmail.com>
Date: Mon, 5 May 2025 21:20:49 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>,
Will Deacon <will@...nel.org>,
Boqun Feng <boqun.feng@...il.com>,
Waiman Long <longman@...hat.com>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
Bill Wendling <morbo@...gle.com>,
Justin Stitt <justinstitt@...gle.com>,
linux-kernel@...r.kernel.org,
llvm@...ts.linux.dev
Subject: [PATCH 3/3] locking/lockdep: Add # of dynamic keys stat to /proc/lockdep_stats
From: Waiman Long <longman@...hat.com>
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@...hat.com>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
Link: https://lore.kernel.org/r/20250425001155.775458-1-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 58883c8375d1..e7166ff64681 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",
--
2.39.5 (Apple Git-154)
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