linux-kernel - [tip: locking/core] locking/lockdep: Add number of dynamic keys to /proc/lockdep

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Message-ID: <174655391949.406.15401244848537848279.tip-bot2@tip-bot2>
Date: Tue, 06 May 2025 17:51:59 -0000
From: "tip-bot2 for Waiman Long" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>,
 Ingo Molnar <mingo@...nel.org>, Bill Wendling <morbo@...gle.com>,
 Justin Stitt <justinstitt@...gle.com>, Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
 Peter Zijlstra <peterz@...radead.org>, Will Deacon <will@...nel.org>,
 llvm@...ts.linux.dev, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/lockdep: Add number of dynamic keys to
 /proc/lockdep_stats

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     cdb7d2d68cde6145a06a56c9d5d5d917297501c6
Gitweb:        https://git.kernel.org/tip/cdb7d2d68cde6145a06a56c9d5d5d917297501c6
Author:        Waiman Long <longman@...hat.com>
AuthorDate:    Mon, 05 May 2025 21:20:49 -07:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 06 May 2025 18:34:43 +02:00

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: Waiman Long <longman@...hat.com>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Bill Wendling <morbo@...gle.com>
Cc: Justin Stitt <justinstitt@...gle.com>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <nick.desaulniers+lkml@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will@...nel.org>
Cc: llvm@...ts.linux.dev
Link: https://lore.kernel.org/r/20250506042049.50060-4-boqun.feng@gmail.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 050dbe9..dd2bbf7 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:
@@ -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);
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 20f9ef5..82156ca 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 6db0f43..b52c07c 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",